WO2022064285A1

WO2022064285A1 - Electronic system for powering machines or apparatus with radio frequency comprising a step up transformator and an oscillator using a solid state amplifier

Info

Publication number: WO2022064285A1
Application number: PCT/IB2021/055871
Authority: WO
Inventors: Alessandro Tonello; Fulvio PERRI
Original assignee: Stalam S.P.A.
Priority date: 2020-09-25
Filing date: 2021-06-30
Publication date: 2022-03-31
Also published as: EP4218365A1; IT202000022726A1

Abstract

The present invention refers to a Solid State (SS) Radio Frequency (RF) electronic system for use mainly, but not exclusively, in I.S.M. (ISM - Industrial Scientific Medical) with high load impedances, and in particular to a Radio Frequency (RF) equipment for drying and heat treatments of raw materials, semi-finished and finished industrial products that implements this system.

Description

ELECTRONIC SYSTEM FOR POWERING MACHINES OR APPARATUS WITH RADIO FREQUENCY

COMPRISING A STEP UP TRANSFORMATOR AND AN OSCILLATOR USING A SOLID STATE AMPLIFIER.

TECHNICAL FIELD OF THE INVENTION

The present invention refers to a Solid State (SS) Radio Frequency (RF) electronic system for use mainly, but not exclusively, in I.S.M. (ISM - Industrial Scientific Medical) with high load impedances, and in particular to a Radio Frequency (RF) apparatus for drying and heat treatments of raw materials, semi-finished and finished industrial products that implements this system.

STATE OF THE PRIOR ART

As known, Radio Frequency (RF) electronic systems suitable for use in I.S.M. (ISM - Industrial Scientific Medical) with high load impedances, in the past always and currently almost always, are made using traditional "triodes" or even, although not frequently, "tetrodes" or "pentodes", or vacuum thermionic valves such as active components that generate RF.

This technology, once widely used both for use with low load impedances and with high load impedances, over the years has been, and even now increasingly is, progressively replaced by Solid State (SS) electronic technology, for the known considerable intrinsic advantages of this technique, also thanks to the progressive technological development of active RF semiconductor components. In particular, RF electronic systems for use in ISM fields with low load impedances, typically 50 Q, have been progressively replaced over the years by SS electronics, especially for flexibility, modularity and lower overall costs of the latter, but this is rarely done at high load impedances, due to objective technical difficulties in adapting the low output impedances typical of SS systems to the high, variable impedances and often with high reactive components, as is almost always required by uses in ISM fields.

For these substantial reasons, in addition to various others, such as for example the delicacy and susceptibility of active semiconductor components when subject to load imbalances or when typically operating in highly disturbed environments, the current uses of RF electronic systems that employ the traditional triode or other types of thermionic valves, have remained relegated to typical or special applications in ISM fields, and in particular in high impedance dielectric heating, as well as in various others specific fields such as, for example, defense, aerospace, research, etc., characterized by uses that require very intense electromagnetic fields and/or RF voltages.

Clearly, this has contributed to drastically reduce the production of thermionic valves worldwide, causing the conspicuous reduction of their availability and consequently supply, becoming concentrated on very few suppliers. Thus, a constant increase in their prices has been generated, so much so as to make them significantly incident on the costs of RF technology for the aforementioned uses compared to other techniques, including non-thermoelectric ones, although the latter are much less efficient but have installation and maintenance management costs for the components subject to less wear. For example, this type of RF electronic systems is widely used in dielectric heating for drying and heat treatments of raw materials, semi-finished and finished industrial products, or in all those RF machines designed for sectors such as food, agro-industrial, officinal, pharmaceutical, nutraceutical, textile, technical textiles, latex, glass and basalt fibers, wood and paper, bricks and technical ceramic products, expanded technopolymers, and many others, etc., and more generally to treat products where the volumetric or endogenous heating turns out to be convenient and decisive in technological processes compared to exogenous heating systems, such as traditional thermal ones.

The effectiveness of said technological processes through heating by dielectric losses, considering the chemical-physical-electrical characteristics of the products to be treated, require the application of high RF electromagnetic fields to transfer sufficient, or volumetrically generate, high powers in them.

For this reason, said products are electrically comparable to high and even variable impedances, since their chemical-physical-electrical characteristics vary during the processes to which they are subjected.

Referring now by way of example to a drying and/or pre-cooking machine for industrial and/or food products with dielectric heating, it is equipped with an RF electronic system, or RF generator, generally based on a single self-excited oscillator with thermionic valve, (also called "thermionic tube"), able to shift frequency, with respect to the natural oscillation frequency dictated by its resonant circuit, depending on many factors, mainly related to the high and variable load impedance, moreover if characterized from important reactive components. The thermionic tube is powered at very high voltages and, consequently, operates with relatively moderate currents, essentially behaving like a constant voltage generator. The output circuit of the thermionic tube is substantially characterized by a resonant LC circuit with a high quality factor (Q), tuned for example to about 27.12 MHz, which transfers the power to the load through a coupling and/or adaptation network equipped with inductive/capacitive elements and/or through a variable capacitance and mechanically controlled divider.

From this first resonant/oscillating circuit, the RF energy transits into a secondary paired/tuned circuit, with a lower quality factor (Q), which substantially represents the use or load circuit, electrically similar to a L/C resonance passive circuit. This second parallel resonant circuit, in the preliminary phase, can be tuned by means of mobile short circuits applied to tuning inductances placed in parallel to the RF applicator, or between the sides of the "distributed" capacitor, which constitutes the element that applies RF to the product to be treated.

The product flows through a tunnel, made with metal surfaces to confine the RF electromagnetic field radiated inside, on a conveyor belt (this in the case of a continuous machine, but from the point of view of operation the considerations are similar also in the case of a static machine also called "batch") adjacent to the electrode connected to ground, which therefore constitutes the "cold armature" of the resonance capacitor. This second resonance circuit, for reasons related to managing the impedance adaptation to the RF generator or to the first resonance circuit, is tuned to a slightly different frequency than that used to tune the thermionic tube circuit, for example to about 28 MHz or even about 26 MHz. The dielectric variation with respect to air caused by the product passing between the plates of the RF applicator, since it is always characterized by a complex permittivity that is variable and very different from vacuum, is the cause of the "slipping" of the tuning of the secondary circuit, affecting only moderately also on the primary circuit due to the low coupling coefficient between the resonance levels of the two circuits. The primary circuit therefore allows a greater quantity of RF energy to pass through (highlighted by the voltage present between the armatures of the RF applicator) and the required function of dielectric heating of the product can thus be performed.

In other words, the transfer of RF energy between the generator and the load is substantially linked to the differentiation of the oscillation frequencies between the two resonant circuits of the generator and the load, an operation which in any case always involves a variation in the overall oscillation frequency of the system, depending on the variation of the load or of the power supplied, also resulting from the coupling and/or adaptation network interposed between them.

Clearly, the proper functioning of this RF equipment is closely linked to the skills and abilities of the designer specialized in RF settings and of the operator adequately trained in the management of technological processes. For example, it is the task of the designer specialized in RF settings, based not only on circuit simulations with dedicated software but also on specific empirical experiences, to adjust the oscillation frequency of the RF generator, the quality factor (Q) of the output circuits, the percentage of "slipping" of the overall system frequency as a function of the coupling and/or adaptation of the load and of the previously chosen quality factor (Q).

In addition, it is always a task of the designer specialized in RF settings to adjust the distribution of the intensity of the RF field between the electrodes, transversely and longitudinally along the path of the conveyor belt or of the area provided for irradiation to the products by means of localized adaptations, acting on the geometry of the RF applicator as well as on the reactive compensation elements connected to it.

Even if the addition of specific automatic electronic control systems to the RF equipment can facilitate the operator in the management of the machine in order to obtain the expected results on the technological processes carried out, his intervention and supervision is still necessary for constant checks on the correctness of the settings and operation.

As can be understood, a considerable experience of the designer specialized in RF settings and dedicated training of the operator is therefore required, before the latter can move on to the effective and efficient use of the machine.

Figure 1 shows a typical simplified circuit diagram, but not exclusive or limiting, representative of an RF apparatus for drying and heat treatments of raw materials, semifinished and finished industrial products that uses a thermionic valve, in this case a triode, as an active component for the generation of RF.

The apparatus essentially has a DC High-Voltage power supply (also called "HVDC") which supplies the high voltage to the RF system, also known as the "RF generator", and a thermionic valve for generating the RF connected to a tuned LC plate circuit, which also sets the frequency of the power oscillator.

A triode grid feedback network determines the reaction for controlling the thermionic valve in percentage terms and also, within certain limits, affects the overall oscillation frequency of the RF system. The plate power of the triode, through the tuned LC circuit, is applied to the use group or circuit indicated in figure 1, through a coupling and/or adaptation network (also called "Matching Network") which, in addition to adapting the impedances of the load circuit to those of the RF generator output, it also allows to perform a precise control of the delivered power.

Said coupling and/or adaptation network is generally made by means of passive resistive and/or reactive components suitably interconnected, adjustable in fixed and/or continuous mode, which allow the technician specialized in RF settings to be able to partially compensate any high reactive components of the downstream impedances as well as to adjust their values in the upstream module, so that the power transfer between the RF generator and the use group or circuit can be adjusted in a controlled manner.

Said use group or circuit, can be electrically comparable to a tunable network, adjustable by the technician specialized in RF settings, which interacts, as for the previously indicated circuit elements, with the overall oscillation frequency of the RF apparatus and with the displacement of the same according to the applied load.

Also in this circumstance, the experience of the technician specialized in RF settings in adequately tuning the coupling and/or adaptation network according to the circuit of use, turns out to be fundamental both for the correct operation of the RF apparatus and for the control and success of the technological process.

In the lower part of the diagram in figure 1, one of the many possible circuits of use, also called "RF applicator", consisting of cylindrical metal bars, equipped with concentric cylindrical insulators, interconnected by conducting elements, is represented as an indication, but not for this reason exclusive or limiting. Such a circuit is in fact electrically similar to a capacitor "C", which can be represented in a "concentrated" way since in first approximation it consists of two conductive plates, of which the upper one connected to the high RF voltage and the lower one to ground, spaced and separated from a dielectric material. Said RF applicator, has the function of applying the RF to the product or products that are inserted between the plates (i.e. between the conductive plates) of the capacitor, also known as "RF electrodes", and by means of them drying and/or thermally treating the dielectric products subjected to the RF field.

Among the RF electrodes, in this exemplary case, there is also an inductive component "L" electrically connected between the ends of the capacitor plates and equipped with a movable conductor terminal (called "shunt") which makes it possible to make the inductance value adjustable in such a way that by conveniently detuning the resonant frequency of the use circuit with respect to that generated by the oscillating circuit of the triode, and also with the interaction of the coupling and/or adaptation network, it is possible to obtain the desired RF electromagnetic field intensity between the plates of the RF applicator, necessary for the desired technological process. The positioning of the inductive component "L" with respect to the longitudinal development of the RF applicator also makes it possible to modulate the amplitude of the field intensity between the electrodes, thus subjecting the products to be treated to distribution profiles of the RF power delivered according to specific technological treatment needs.

Clearly, each of the aforementioned operations requires a long and careful tuning by a very specialized technician, based on numerous experiences and technical validations carried out "in the field", since in addition to the type of process, the adjustments must be made according to the type of RF applicator, the type of product and the chemical- physical-electrical features of the same.

From the description made, many disadvantages emerge that characterize the current RF electronic systems for use in ISM fields with high load impedances made using thermionic valves, the main ones of which, by way of example, but not for this reason limited or exclusive, are reported below:

- periodic replacement of the thermionic valve is required since by its own nature and operating characteristics it has a life span of its own like all filament components (for example, such as old incandescent bulbs), causing a programmed machine stop at each event, or even unexpected in case of sudden failure, as well as the use of expert personnel to correctly carry out the replacement;

- the costs of the thermionic valve in continuous growth, given the ever smaller number of world producers due to the reduction of their uses as they are replaced with other systems and technologies, is becoming increasingly important, so much so as to affect the operating cost of RF apparatus and their use especially in the typical uses in ISM fields;

- in the event of sudden failure of any RF component, since it can also be frequent considering that all the circuits are subjected to high voltages, the operation of the RF equipment is completely blocked and the intervention of a specialized technician is therefore required for repair;

- to preserve a good life span of the thermionic valves and at the same time guarantee a good operating stability of the RF equipment, the cooling system must be optimal in terms of thermo-hygrometric characteristics in the case of air, and thermochemical -physical in the case of water, conditions that require dedicated and expensive systems, moreover due to their interaction with high voltage parts, which also require frequent checks and maintenance, actively involving user customers, especially if the environments are harsh (dusts, mists, acids, etc.);

- the electromagnetic spectrum generated by thermionic valves, due to their intrinsic characteristics of non-linearity, is very perturbed, i.e. manifests multiple frequencies of the fundamental one, especially in class C operation (almost always adopted in order to obtain a sufficiently high efficiency of the RF generator), involving the use of complicated electromagnetic filtering systems both for compliance with the regulations on electromagnetic compatibility, and to avoid coupling and adaptation problems to the load, as well as additional losses in circuits and RF applicators, even with the risk of unwanted corona effects and spurious oscillation frequencies that can cause bums of products and components;

- the high voltages involved, typical of RF generation circuits applied to thermionic valves, can produce and emit unwanted ionizing radiations caused by natural physical phenomena of the system which, even if partially shielded by the casings of the active components and by the metal cabinets, can be a problem if the apparatus should be very close to operators and technicians;

- the high specialization required of technicians with highly focused and dedicated skills to design and manufacture specific RF components for high operating voltages, as well as to make appropriate RF settings according to the products to be treated and technological processes to be implemented, by combining ad hoc the use circuits with those of the RF generation system;

- the complicated but necessary control management of the RF electromagnetic field applied to the products for the various processes, which must also be consistent with the operating needs of the RF generation system circuits;

- the volumetric dimensions and the weights involved in circuits and RF generation systems which, especially for medium-low powers, cannot be physically reduced since they operate at high voltages and therefore require spaces and distances between the important components, make the equipment expensive and impractical especially for sectors where compactness and lightness are required;

- the volumetric dimensions of the RF generation circuits for high powers, since they are limited to the maximum ones available for the thermionic valves, require modular constructions that must be physically spaced to avoid electromagnetic interference between them, with the consequence of requiring large spaces if the productions requests from processes and applications in ISM fields are high, as is often required by the market;

- the rigidity and, albeit wide, insufficient flexibility in the development of the RF settings, or in controlling the load impedance adaptations according to the products to be treated and technological processes to be carried out, makes it difficult to manage and mass-produce suitable RF apparatus for any type of use in ISM fields, affecting the difficulties and costs of design, production, development and testing, making each machine almost unique for each customer and type of use;

- the rigidity of construction and realization, substantially based on the development of the interaction between RF generation circuits and RF use circuits and with the coupling and/or adaptation network interposed between them, does not allow to easily modify the frequencies of use of the RF field indispensable for use in ISM fields, thus entailing the need to completely redesign the entire RF equipment;

- substantially everything else that is disadvantageous is linked to and due to the necessary high operating voltages of the RF generation apparatus (e.g. risks for maintenance operations, degradation of passive RF components, high sensitivity to mains voltage peaks or gaps, etc. ).

On the one hand, therefore, the current electronic RF generation system with thermionic valves, despite the difficulties of designing and setting up with the load (since in fact generation, coupling and/or adaptation and use must be "functionally integrated" circuits), being powered at high voltages, that is, already having a high output impedance, it lends itself well to operating circuits with high load impedances, even considerably variable, and with important reactive components.

On the other hand, the advancement of the Solid State (SS) technique in many areas with the intrinsic advantages typical of this technology already widely proven in many sectors (thanks above all to the continuous important technological developments on semiconductor power components) and that in this specific case in addition to being innovative, they overcome many limitations and disadvantages of thermionic valve systems, make the objectives of the present invention clear.

An invention which, in order to be fully and adequately applicable for typical uses in ISM fields with high load impedances, requires that it is possible to emulate the electronic behavior and the typical operation of thermionic valves for these applications, thus exploiting the advantages that still make them very widespread in these specific sectors, but at the same time using the considerable intrinsic advantages of the Solid State (SS) technique.

Further disadvantages that characterize the current RF electronic systems for use in ISM fields with high load impedances made with thermionic valves overcome by the SS technique according to the present invention, are evident and deducible in the descriptions of objects, drawings and examples of embodiment of the new invention shown below.

OBJECTS OF THE INVENTION

An object of the present invention is to improve the state of the prior art in the terms and aspects clearly highlighted above, in particular with reference to an SS RF electronic system for use in ISM fields with high load impedances that emulate the typical operation of thermionic valves for similar uses, and in particular to an RF apparatus, for drying and heat treatments of raw materials, semi-finished products and finished industrial products, which implements this system.

A further object of the present invention is to provide an SS RF electronic system for use in ISM fields with high load impedances that allows the use of the same broadband, thus eliminating the need for an accurate and customized setup for any specific impedance value or variation range around it.

A further object of the present invention is to provide an SS RF electronic system for use in ISM fields with high load impedances that allows for controllability of the power supplied with continuity, both in continuous and pulsed mode or in any case that can be modulated according to predefined signal trends, both in the time and frequency domain, even remotely.

Another object of the present invention is to provide an SS RF electronic system for use in ISM fields with high load impedances that is robust with respect to possible load mismatches, caused by considerable impedance variations and with important reactive components thereof.

A further object of the present invention is to provide an SS RF electronic system for use in ISM fields with high load impedances capable of preventing machine stops in the event of breakage or malfunction. Another object of the present invention is to provide an SS RF electronic system for use in ISM fields with high load impedances that does not emit ionizing radiation that is hazardous and harmful to human health.

Still another object of the present invention is to provide an SS RF electronic system for use in ISM fields with high load impedances which has a modular and low cost cooling system.

A further object of the present invention is to provide an SS RF electronic system for use in ISM fields with high load impedances that allows the use of interchangeable and modular groups.

Still another object of the present invention is to provide an SS RF electronic system for use in ISM fields with high load impedances whose operation is not affected by external agents, such as dust, humidity, aggressive atmospheres, etc.

A further object of the present invention is to provide an SS RF electronic system for use in ISM fields with high load impedances which allows a standardized and economical industrial construction.

Finally, a further object of the present invention is to provide an SS RF electronic system for use in ISM fields with high load impedances that is light and space-saving, consequently also allowing for ease of packaging and subsequent simpler and faster transport.

Last but not least, further important objects which characterize the present invention are evident and deducible in the descriptions of drawings and examples of embodiment of the new invention reported hereinafter.

According to an aspect of the present invention, a Solid State (SS) Radio Frequency (RF) electronic system is provided for use in ISM fields with high load impedances according to claim 1.

According to a further aspect of the present invention, a Radio Frequency (RF) apparatus is provided for drying and heat treatments of raw materials, semi-finished products and finished industrial products which implements said system according to claim 48.

The dependent claims refer to preferred and advantageous embodiment of the invention, without thereby delimiting the protective fields strictly related to them.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will become more evident from the detailed description of a preferred, but not exclusive, embodiment of a Solid State (SS) Radio Frequency (RF) electronic system for use in ISM fields with high load impedances illustrated as an example, but not limitative, in the accompanying drawings in which:

- figure 1 shows the simplified circuit diagram typical of an RF apparatus for drying and heat treatments of raw materials, semi-finished and finished industrial products that uses a thermionic valve as an active component for the generation of RF, that is, made according to the state of the prior art;

- figure 2 shows the circuit diagram of an SS RF electronic system for use in ISM fields with high load impedances according to the present invention;

- figure 3 shows an enlarged scale view of the final power group of the SS RF system of figure 2;

- figure 4 shows the basic circuit diagram used for the realization of the first stage of RF output transformation of the final power group of the SS RF electronic system of figure 2;

- figure 5 shows the circuit diagram used for the realization of the second stage of RF transformation of the voltage/impedance booster group of the SS RF electronic system of figure 2.

EXAMPLES OF EMBODIMENT OF THE INVENTION

With reference to the attached figures, the number 1 indicates an SS RF electronic system for powering machines or equipment, typically but not exclusively for use in ISM fields, with RF signals at high load impedances according to the present invention. Said system essentially comprises at least one power supply group 2, at least one RF signal generation group 3, at least one logic interface and RF signal control group 4 and, preferably, at least one power pre-amplification group 5 and/or at least one power division group 6 as well as at least one transmission line la designed to be powered by at least one power division group 6 or by at least one power pre-amplification group 5 or by at least one RF signals generation group 3 with a respective percentage of power. Clearly, the percentage could be 100% in the case of a single transmission line la.

The transmission line la comprises at least one final power group 7 and at least one voltage/impedance booster group 8.

The indication of a group that raises the voltage and the impedance at the same time is legitimized by the fact that in a circuit operating in a sinusoidal regime (as will be explained better later), the impedance is mathematically described by equation (1):

where V and I represent the voltage and current phasors, respectively.

Since the voltage phasor is directly proportional to the impedance, raising the latter will result in a consequent elevation of the voltage or vice versa.

As regards the power supply group 2, it can essentially comprise a first power supply 2a, for example a switching power supply, used to supply one or more previous stages to the power division group 6 of the electronic system 1.

The use of switching power supplies constitutes the current system of greatest use, as the operating logic and the components used allow to obtain high efficiencies, thus helping to maximize the overall energy efficiency of the electronic system where employees.

The first switching power supply 2a can then comprise one or more sub-power supplies 2b (figure 2 shows the sub-power supplies 2b detached from the first switching power supply 2a, but which are in fact included therein), for example switching sub-power supplies (or "POL", acronym for "Point of Load"), used to power one or more stages following the power division group 6 of the electronic system 1.

In the embodiment of the present invention shown in the figures, the power supply 2a constitutes what is usually defined "auxiliary power supply" whose function is substantially that of supplying all the elements of the system with the exception of the power stages, that is, with the exclusion of the at least one final power group 7. This power supply can be either a switching power supply, direct from the mains, with power proportional to what is absorbed by the auxiliary and low power stages (RF drivers), or a secondary power supply, scaled by the DC-DC switching power supplies 2b, previously defined POL.

In the non-limiting embodiment of the present invention shown in the figures, the first power supply 2a comprises three switching sub-power supplies 2b, each dedicated to the respective final power group 7, which can each supply a continuous supply voltage between about 24 V and about 60 V.

Conveniently, the first switching power supply 2a and consequently also the switching sub-power supplies 2b, are provided with means or components for stabilizing the voltage and limiting the current, and with means or components for remote control, so as to allow an external operator the variation of the supply voltage and consequently also of the power at least of the RF signal generation group 3.

This group 3 can comprise a waveform generator with high stability, "DDS" or stabilized by means of a quartz crystal, by way of non-limitation, for example exactly at 27.120 MHz (< ± 10'⁷ PPM of thermal variation per degree centigrade), but which could be indifferently at any frequency of the bands for use in ISM fields, such as, for example, from 12 to 82 MHz, and in particular at the typical frequencies for uses without limitations of restrictions in the radiated amplitudes established by the international ITU - CISPR standards that beyond at 27.12MHz ± 0.163MHz they are also 13.56MHz ± 0.07MHz and 40.68MHz ± 0.02MHz (and also 6.78MHz ± 0.015MHz and 433.92MHz ± 0.87MHz, albeit with limitations in some "regions "). This group 3 preferably comprises an oscillator, a circuit for controlling the duty cycle and for modulating the pulse width ("Pulse-Width Modulation"), as well as a low power amplification chain, for example an amplification chain up to a value between about 1W and about 5W, for example up to about 2W. The low power amplification chain is downstream and/or upstream of the oscillator and the circuit for controlling the duty cycle.

The choice of using an oscillator with a high frequency stability is due to the fact that the ITU ("International Telecommunication Union", an international organization that deals with defining standards in telecommunications and in the use of radio waves), resumed by the CISPR (Special International Committee for Radio Interference) and recalled by the IEC (International Electrotechnical Commission), are increasingly restrictive, given the developments and proliferation of telecommunications and signal transmission systems that occupy increasingly dense frequency bands, and therefore absolutely to be respected to avoid interference.

The use of a high frequency stability oscillator therefore allows the maintenance of the RF within the exact frequency band granted for use in ISM fields without limits in the irradiation amplitude.

However, it should be noted that the frequency bands listed above for use in ISM fields can also be envisaged outside those established by the ITU standards, in particular by choosing them on the basis of application technological needs, provided that in compliance with the limits of radiated emissions established by the CISPR regulations. The circuit for controlling the duty cycle and for modulating the pulse width allows, by means of an electric and/or electronic retroactive feedback circuit, to protect the internal electronic system 1 from any overloads. In practice, if the power circulating inside the electronic system 1 exceeds a certain threshold value, the circuit for controlling the duty cycle and for modulating the pulse width reduces the duty cycle, defined as the ratio between width and period of the pulse.

The reaction times of the reduction of the duty cycle on the electronic system 1 are very fast, in the order of about 100-800ns, for example 200ns; the reaction times of the retroactive feedback are also very fast, in the order of about 400-600ns, for example 500ns; the total reaction time of the system is attested to be in the range between approximately 500ns and 1400ns, and therefore fast enough to ensure complete protection for all the groups included in said system.

The same circuit for the control of the duty cycle and for the modulation of the pulse width which performs the protection function indicated above, can conveniently also constitute the fundamental element for regulating the power delivered to the load, both in continuous and pulsed mode or in any case it can be modulated according to predefined signal trends both in the time and frequency domain, even in remote mode. In particular, by working at constant peak power, maximum efficiency is achieved, since the RF apparatus and the adaptation networks have been studied and calculated for this power level. Preferably, therefore, an attempt will be made to maintain the power at the maximum peak level, as a function of the supply voltage supplied by the one or more sub-power supplies 2b, by acting on the duty cycle to modulate it. In fact, since the products heat treated by dielectric dissipation depend on the average power, an efficient method for controlling and varying the power is to divide the wave flow into variable cycle pulse packets. For example, with an "on/off impulsive cycle of 50%, the power applied to the product will be halved, while at the same time keeping the peak power value of the impulse high, thus ensuring high energy efficiency of the RF system. However, it should be noted that the power variation applied to the product can be carried out by adjusting the one or more sub-power supplies 2b, but combined with the previous one it has a purely coarse pre-setting function, while the subsequent fine tuning is obtained through the aforementioned duty cycle control.

Naturally, the control of all the functions just mentioned, for example power control, variation of the duty cycle and pulse width, etc., takes place by the operator or automatically by means of the logic interface and RF signal control group 4.

Said logic interface and RF signal control group 4 can essentially comprises a logic unit designed to manage the control of operating parameters of the electronic system 1, for example the interface with the operator, the screen, the network, the connectivity and, as already mentioned, the control of the parameters relating to the variation of the duty cycle and of the pulse width.

The logic interface and RF signal control group 4 also comprises hardware components for the logic unit, for example a luminous alphanumeric display, for example using "OLED" technology, a power supply, an alphanumeric keypad, a spare battery and a ventilated container.

Clearly, for the management of all the parameters and functions controlled by the logic unit, an adequate software program is provided that can allow a simple and intuitive interface with the operator.

After generating the RF at the desired frequency by means of the RF signal generation group 3, the output signal from this latter group enters the power pre-amplification group 5. In the preferred embodiment of the present invention, the group 5 helps to raise the power of the RF signal however, in other embodiments, this group 5 could be directly integrated within the RF signal generation group 3 or it could not be present.

Said group 5 essentially comprises a pre-driving sub-group 5a and a driving sub-group 5b.

The pre-driving sub-group 5a can comprise one or more power amplifiers which increase the power level of the output signal from the RF signal generation group 3, which must be specified that it has already been increased by the low power amplification chain present in the aforementioned group 3.

For example, the pre-driving group 5a can raise the power from about 2 W to a range between about 5 W and about 25 W, for example up to about 10 W.

As regards the driving sub-group 5b, it essentially comprises an input transformer, for example a 9: 1 input transformer, one or more power amplifiers used to further raise the power level of the output signal from the pre-driving sub-group 5a, and an output transformer, for example a 1 :4 output transformer.

The one or more power amplifiers of the driving sub-group 5b can raise the signal power level for example from about 10 W, also wanting from a range between about 5 W and about 25 W, up to about 100 W, and also up to about 150 W.

The one or more power amplifiers can be of any type suitable to reach the desired power level, for example they can be integrated and/or hybrid amplifiers.

Subsequently, as shown in the preferred embodiment of the present invention of figure 2, the output signal power from the driving sub-group 5b enters the power division group 6.

Said group 6 essentially comprises a power divider 6a ("splitter"). In particular, in the embodiment of the present invention shown in the figures, said power divider 6a is an isolated RF power divider with two, three or more ways which divides the power of the output signal from the driving sub-group 5b or from the RF signals generation group 3 in an equal or differentiated manner and almost independent of the load conditions between at least two, three or more transmission lines la of the electronic system 1.

As can be understood, if the electronic system 1 comprises the power divider group 6, it will also comprise at least two transmission lines la.

For example, if the signal power input to the isolated three-way power divider 6a is about 100 W transmitted through a transmission line having an impedance of about 50 , said divider will provide three power signals of approximately 33 W through three transmission lines each having approximately 50 of impedance.

The choice of using a system with three separate amplifiers, after the power division group 6, is dictated by the fact that, since the entire electronic system 1 must be able to manage high powers (as will be seen later), it will be possible to use a three-phase mains power supply and three single-phase 2b sub-power supplies, thus allowing to obtain an electrically powered system in a balanced way, with all the advantages that this entails compared to single-phase loads which instead unbalance the power supply network. Clearly, a solution with two, four or more sub-power supplies could also be envisaged.

Of course, in other embodiments of the present invention, the electronic system 1 could also not provide for the power division group 6, for example in the case where the electronic system 1 provides for a single transmission line la.

From a manufacturing point of view, the RF signal generation group 3, the logic interface and RF signal control group 4 and the pre-driving sub-group 5a, can be provided, for example, in a single printed circuit in order to simplify the construction of the complex section of the electronic system 1.

In other embodiments of the present invention, it would also be possible to have a separate configuration of the groups 3, 4 and 5a on the basis of any particular design requirements.

Again from a manufacturing point of view, for example, a dedicated printed circuit is provided both for the driving sub-group 5b and for the power division group 6.

In other embodiments of the present invention, it would also be possible to have a single printed circuit with the driving sub-group 5b and the power division group 6 combined. In the embodiment of the present invention shown in the figures, the three printed circuits (one for the groups 3, 4, 5a, one for the sub-group 5b and one for the group 6) are suitably housed on a sheet-like component, such as for example an aluminum plate having a thickness of about 2 mm and the indicative dimensions of about 160 mm in width and 168 mm in length, such as to also constitute an effective dissipative element of the local heat produced by these circuit sections.

Naturally, in other embodiments of the present invention, a different sizing of the sheetlike component can be provided on the basis of any particular design requirements, for example a smaller or greater number of printed circuits, or can be used a dissipating mechanical support with fins, to facilitate the dissipation of heat.

In the continuation of the discussion, the structure of the electronic system 1 will be described along a single transmission line la which, clearly, will also be equivalent for the other two lines present. It is therefore specified that the description which will be provided of the final power group 7 and of the voltage/impedance booster group 8 will be equivalent for all three transmission lines la of the electronic system 1.

In practice, in the non-limiting embodiment of the present invention shown in the figures, the electronic system 1 comprises three high-level amplification groups 7 and three voltage/impedance booster groups 8.

Of course, as already indicated above, an embodiment can also be provided in which the electronic system 1 comprises only a single transmission line la.

The final power group 7 essentially comprises a power amplification sub-group 7b.

The power amplification subgroup 7b comprises a Solid State (SS) power amplifier 7b 1. More in detail, the SS power amplifier 7b 1 advantageously comprises two transistors 7b 1 ', 7bl", for example two lateral diffusion transistors (called "LDMOS").

In the non-limiting embodiment shown in the figures, the two transistors 7b T, 7b 1" are suitably placed with the two sections available in parallel and with each other in a "Push-Pull" configuration.

The choice of using a push-pull configuration allows a doubling of the output power from the SS power amplifier and at the same time a favorable doubling of the input and output impedance of the same.

Naturally, in other embodiments of the present invention, different configurations can be provided, as long as it is possible to obtain the necessary output power value, according to the design specifications linked to the application requirements. For example, a configuration composed of two modules could be used, each comprising two "LDMOS" transistors in counterphase, added together with one of the known combiners or other configurations similar and equivalent in effects.

Similarly, in other embodiments of the present invention, it is possible to use an SS power component other than the "LDMOS" transistor, provided that it allows to obtain the necessary output power value, according to the design specifications in accordance with the intended uses. For example, it would be possible to use vertical diffusion transistors ("VDMOS") or similar or others based on Gallium Nitride ("GaN"), or still others based on new research and future advanced semiconductor technology developments.

The use of a SS power amplifier 7b 1 as described, has the advantage of allowing not only a broadband use of the electronic system 1, but also of obtaining energy efficiency values close to 80% and even more in the case of use in "high energy efficiency" operating classes (for example D and E), and gain values even higher than 20 dB per amplifier stage and/or transistor module.

The final power group 7 may then comprise an input transformer 7a, for example an 9: 1 input transformer, placed upstream of said power amplification sub-group 7b, and an output transformer 7c, for example a 1 :4 output transformer, located downstream of said power amplification sub-group 7b.

Advantageously, the final power group 7 can have an equalization/coupling network 7d, for example positioned before the input transformer 7a.

Said equalization/coupling network 7d comprises one or more electrical and/or electronic circuits whose main purpose is to improve the amplitude-frequency transfer function in the field of use, mainly for broadband applications of the electronic system 1, which, as seen previously, they can be, for example, included in the range from about 12 MHz to about 45 MHz, even up to 80 MHz and more.

Regarding the 9: 1 input transformer 7a, it is used to substantially perform the adaptation of the "Gate" impedance or of the input of said at least one SS power amplifier 7b 1.

By way of non-limiting example, the 9: 1 input transformer 7a can be made by means of a ferrite core, of adequate dimensions and magnetic permeability to treat the input power of the transmission line, with a primary winding of one turn and a secondary winding of three turns, i.e. with a 1 :3 turn ratio corresponding to a 1 :9 impedance ratio.

In other embodiments of the present invention, the input transformer 7a could also be made with a primary and secondary winding having a different number of turns and therefore a different impedance ratio.

The 9: 1 transformer 7a can for example transform the input impedance of about 50 into an output impedance from "Gate" to "Gate" of about 5.5 (being the two "LDMOS" transistors 7b 1', 7b2"arranged in counterphase).

The SS power amplifier 7b 1, allows a power amplification capable of reaching, for example, nominal values of about 1300 W per transistor.

In the embodiment of the present invention shown in the figures, since two transistors 7bl'and 7b 1 "are present, it is possible to reach values up to about 2600 W or more of RF power which, also considering any losses due to dissipative phenomena, can substantially reach up to about 2500 W.

It is reminded that the output power is related to the impedance according to the well- known simplified equation (2) below:

where V_d is the power supply voltage, Z is the impedance and P_outis the output power. Considering, for example, a power supply voltage V_d between about 46 V and 48 V which, due to loss due to voltage drop and parasitic capacitance, can drop by about 2 V, and an output power for each transistor 7b 1 ', 7bl" equal to about 1300 W (2600W/2), an output impedance value of the single transistor of about 0.75 is obtained. Therefore, considering, for example, the two transistors 7bl', 7bl” connected in counterphase, impedance values substantially in the order of 1.5 will be obtained at the output.

As can be deduced from the previous example, at the output of the power amplifier at SS 7b 1, there will be a very low impedance value, while the electronic system 1 must instead be suitable for working with high load impedances, even variable ones and with important reactive components, i.e. emulating the typical operation of thermionic valves with said loads. For this reason, immediately after the SS power amplifier 7bl, an output transformer 7c is provided, for example a 1 :4 balanced transformer for adapting the impedance of "Drain" or of the output of said SS power amplifier 7b 1.

This transformer, having to work with a high bandwidth in order to cover the wide ranges of the expected use frequencies and also for the needs of wide variability of the load impedances, must be designed in a very precise way and at the same time guarantee a high efficiency., for example higher than about 96%, considering the high powers involved in the system.

In the non-limiting embodiment shown in figures 2, 3 and 4, the 1 :4 balanced transformer 7c is made using two coaxial transmission lines according to the configuration, defined as "equal delay", with primary windings placed in parallel and secondary windings placed in series, as shown in figure 4. The use of coaxial transmission lines allows to save from the point of view of simplicity and manufacturing costs of the transformer, while at the same time extending the frequency transformation range.

Of course, in other embodiments of the present invention it would also be possible to use other methods for the construction of the output transformer 7c, for example by means of a multilayer printed circuit made of a specific material, such as polytetrafluoroethylene ("PTFE"), ceramic or the like.

Furthermore, it would be possible to use for the construction of the output transformer 7c a different number of coaxial transmission lines, or other configurations known in the literature.

In particular, the two coaxial transmission lines can each be made by means of four flexible cables insulated in PTFE having an impedance of approximately 12 Q which, when placed in parallel, give the resulting impedance values of approximately 3 Q. The arrangement of the two lines in series allows to reach nominal impedance values of the order of 6 Q and 1.5 Q, as required, from the parallel side.

The two coaxial transmission lines can also be coated with one or more sleeves in magnetic material, suitable for obtaining low losses. For example, each line is coated with three sleeves side by side made of ferrite, according to a Nickel-Zinc mixture, having magnetic permeability < 150.

Said mixture is able to work at quite high temperatures (>100°C), and has a high "Curie point".

Clearly, in other embodiments of the present invention, sleeves with different mixtures can be used, as long as they are able to guarantee low losses with the desired magnetic permeability.

From a manufacturing point of view, the output transformer 7c can be closed in a container, for example an aluminum container, which will contribute to its cooling. In addition, to obtain a better heat transfer to the outside, the transformer 7c can be embedded in a special resin, for example an epoxy or high temperature silicone resin. This resin, loaded with ceramic powders, such as Aluminum Nitride powders ("AIN"), will be used to transfer the generated heat to the outside and will irremovably block all parts, also ensuring a better mechanical resistance to vibrations.

Advantageously, the final power group 7 can also comprise elements placed downstream or subsequently to the output transformer 7c, for example capacitors and/or inductances and/or resistors and/or filters, adapted to compensate for low and/or high band frequencies in which the output transformer 7c must operate.

If desired, at the balanced output of the final power group 7 there are, therefore, about 6 of impedance and an effective voltage value already equal to about 123 V.

With such a voltage value, a suitable voltage/impedance booster group 8 can therefore be conveniently provided and inserted. The main objective of this group is to considerably raise the voltage/impedance, while at the same time guaranteeing solidity and robustness of the electronic system 1 when stressed, even considerably, by possible load mismatches, due to strong variations in impedances and also with important reactive components.

Said group 8 can comprise a first step-up transformer 8a, a power sensing sub-group 8b and finally a second step-up transformer 8c.

The first step-up transformer 8a, for example a 1 :9 balanced-balanced step-up transformer, is used for a first impedance boost. In particular, said 1 :9 balanced- balanced step-up transformer can, for example, raise the input impedance to group 8 from about 6 to about 54 .

From a manufacturing point of view, this 1 :9 balanced-balanced step-up transformer 8a can be built using techniques similar to those used for the construction of the 1 :4 balanced transformer 7c, i.e. by means of coaxial transmission lines coated with ferrite sleeves, with variable mixture and having magnetic permeability values /q included, for example, between about 100 and about 800, in order to widen the band of use. The particular method of connection of the coaxial lines of the transformer 8a also allows to obtain the galvanic separation of the final power group 7 from the load, that is the electrical isolation of the DC power supply voltage from the RF load.

Similarly to the 1 :4 balanced transformer 7c, the 1 :9 balanced-balanced step-up transformer 8a can also be closed inside a container, for example made of aluminum or other metal alloy.

In the embodiment shown in Figure 2, at the balanced output of the first step-up transformer 8a there will, therefore, be approximately 54 Q of impedance and an effective voltage value of approximately 362 V.

Conveniently, a power sensing sub-group 8b is subsequently provided.

Said group 8b mainly comprises one or more balanced directional couplers, for example a double balanced directional coupler 8b 1, 8b2 with opposite lines in phase and able to work with maximum rated input powers which can reach values up to about 3000 W.

Such balanced directional couplers 8b 1, 8b2 with opposite lines in phase, have the purpose of analyzing the load and monitoring the RF power levels transited without simultaneously suffering losses on the transmission line la and on the load. In particular, the balanced directional couplers 8b 1, 8b2 allow the measurement of the direct component of the RF power, i.e. the one that reaches the load from the source, and of the reflected component of the RF power, i.e. the one that is sent back from the load to the source since it is not absorbed from the dielectric load subjected to the treatment.

The knowledge of the direct and reflected components of the RF power therefore allows the calculation of the total RF power actually delivered to the product, of the reflection attenuation and of the standing wave ratio of the load. A further function is to use the RF power value reflected at the output either from the final power group 7 or from the transformer 8a, once transformed into a direct voltage inside or outside the one or more balanced directional couplers 8b 1, 8b2, to activate, for example by means of an activation signal sent by the logic interface and RF signal control group 4, in communication with the couplers 8b 1, 8b2, a special electronic "trigger" or threshold circuit (in communication with the output of the RF signal generation group 3). The electronic "trigger" circuit acts first by blocking, then reducing and subsequently increasing, according to a programmed ascent ramp, the output power from the RF signal generation group 3, for protecting the electronic system 1 from a mismatched load.

This voltage is therefore supplied for reading the reflected RF power not only to the electronic “trigger” or threshold circuit dedicated for protection, but also to the logic interface and RF signal control group 4 for software management of the system when overloaded.

The electronic "trigger" or threshold circuit can be conveniently placed upstream and/or downstream of the balanced directional couplers 8b 1, 8b2 of the power sensing subgroup 8b or integrated directly into the eventual printed circuit dedicated to groups 3, 4 and 5 a.

Conveniently, the balanced directional couplers 8b 1 and 8b2 with opposing lines in phase can be equipped with circuits and/or systems that detect and measure the direct and reflected components of both RF voltages and RF currents, allowing to obtain a very flexible and precise controllability of the RF power delivered by the electronic system 1 to the load, for example by means of the principles described above in relation to the electronic "trigger" or threshold circuit, which can be managed both in continuous and pulsed mode or in any case modulated according to predefined signal trends and in the domain of time and frequency. Furthermore, the knowledge of the single direct and reflected components of both the RF voltages and the RF currents allows to manage and control the operation of the electronic system 1 in such a way that it can be assimilated to a voltage generator or a current generator, and advantageously also to emulate the typical electronic operation of a thermionic valve as the load varies. Downstream of the power sensing sub-group 8b, a second step-up transformer 8c can be conveniently provided.

Said step-up transformer 8c, for example a 1 :9 balanced-balanced step-up transformer, allows a further increase or elevation of the output impedance and at the same time guarantees, in addition to the feature of its use at a wide frequency band, also a significant robustness and solidity with respect to possible load mismatches, caused for example by considerable variations in load impedances even with important reactive components.

In the non-limiting embodiment shown in the figures, the 1 :9 balanced-balanced step-up transformer 8c can be suitably designed following the known Guanella scheme, described for example in the document "Novel Matching Systems for High Frequencies", Brown-Boveri Review, Vol 31, September 1944, Pag. 327-329", which substantially consists of the configuration having primary windings placed in parallel and secondary windings placed in series shown in figure 5. Said 1 :9 balanced-balanced step-up transformer 8c, is capable of transform for example from about 54 Q of input impedance to about 486 Q of output impedance.

From a manufacturing point of view, the 1 :9 balanced-balanced step-up transformer 8c can be made by means of one or more transfer lines, for example bifilar lines insulated in PTFE, each wound on two coupled ferrite cores, for example according to a compound in Nickel-Zinc with a medium/low magnetic permeability, for example with magnetic permeability -t = 125.

In particular, to increase the insulation between the windings and for reasons of power and inductance, three pairs of coupled cores were used, each pair wound with a respective bifilar line.

In the non-limiting embodiment shown in Figures 2 and 5, the 1 :9 balanced-balanced step-up transformer 8c is therefore composed of three pairs of coupled cores, for example three pairs of coupled toroidal cores, each pair wound with a respective balanced bifilar line.

Conveniently, said bifilar lines can be spaced apart by means of a spacer element in order to maintain both a good parallelism between the wires and a stable and controlled distance. Said spacer element can be, for example, a bar made of silicone elastomer material.

These bifilar lines have an impedance which for a correct and good operation of the step-up transformer 8c must be approximately three times the low input impedance, therefore in this case said bifilar lines have an impedance value of approximately 162 . The output of the 1 :9 balanced-balanced step-up transformer 8c is isophase and balanced, for this reason, in order to obtain an even higher impedance, the secondary windings of each 1 :9 balanced-balanced step-up transformer 8c of each transmission line la of the electronic system 1 can be connected in series which, as previously mentioned, in the embodiment of the present invention shown in the figures, are equal to three.

In this way it is possible to obtain an output impedance from the electronic system 1 for example equal to approximately 1458 (486 multiplied by three step-up transformers 8c in series) corresponding to an effective voltage value of approximately 3201 V, and a consequent value peak-to-peak voltage of about 9053 V. The maximum final RF power that can be transferred to the load by the electronic system 1, also considering any losses along the three transmission lines, is between about 6500 W and about 7500 W, for example on average equal at approximately 7000 W.

In addition, the step-up transformer 8c can comprise one or more compensation elements of the parasitic capacitances and/or parasitic inductances or connection upstream and/or downstream thereof.

By way of non-limiting example, the step-up transformer 8c could include inductive and/or capacitive elements in parallel and/or in series at the output of said step-up transformer 8c, present or not selectively present in at least one of them.

Conveniently, the step-up transformer 8c can be connected to a supporting printed circuit and closed in a container, preferably made of plastic material in order to increase the degree of insulation in a simple way, but if desired also in metallic material, such as copper or aluminum, clearly sized to guarantee the necessary electrical insulation from parts with high RF voltages.

Advantageously, the step-up transformer 8c can also be immersed in a low-loss resin loaded with ceramic powders, for example Boron Nitride or Aluminum Nitride, in order to increase the dielectric strength of the insulation system and at the same time facilitate cooling for thermal conduction.

The electronic system 1 also comprises a suitable cooling group (not shown in the figures) for the disposal of the dissipated power, for example a liquid cooling group, for example with water, or by means of another suitable liquid.

The liquid cooling group, in addition to its high efficiency, since the heat can be selectively extracted from where it is generated, also allows a heat removal capacity that is from about five times up to about a hundred times better than a group of air cooling, on average about twenty times better, thanks to the considerable thermal capacity of liquids compared to gasses.

Furthermore, by using a liquid cooling group, the acoustic pollution in the working environment of the electronic system 1 is also improved, and it is easier to avoid unwanted overheating or unwanted movements of air in the environments where the apparatus is used, especially in applications where the thermo-hygrometric and purity conditions must be kept stable and controlled.

By way of non-limiting example, said liquid cooling group can comprise one or more recirculation pumps, one or more water tanks, one or more radiators, one or more fans for the water-air exchange and one or more feeders, to power one or more fans, as well as systems that use heat exchangers or heat pumps.

Advantageously, the cooling group can comprise one or more flexible connecting cables between said cooling group and the group(s) of the electronic system 1 which require(s) removal of the heat dissipated by the components which, kept at a controlled temperature, they allow to avoid drifts and system operation instability even in harsh environments.

Object of the present invention is also a Radio Frequency (RF) apparatus for drying and heat treatments of raw materials, semi-finished products and finished industrial products which uses one or more electronic systems 1.

As seen in the typical diagram of such an apparatus shown in Figure 1 and described in detail in the prior art, it is mainly composed of a thermionic valve that generates the RF, a coupling and/or adaptation network, and finally the RF applicator that applies the RF previously generated to the products placed therein, thus subjecting them to the RF electromagnetic field to obtain the desired heat treatments.

According to the present invention, in said RF apparatus, usable in all those RF machines typically but not exclusively used for use in ISM (Industrial Scientific Medical) fields with high load impedances, and particularly where volumetric or endogenous heating is convenient and decisive compared to traditional exogenous systems, the thermionic valve that generates the RF is replaced, based on specific application needs, with one or more electronic systems 1.

The modularity feature of the electronic system 1 allows to combine more than one electronic system 1 in order to reach higher powers, and at the same time to be able to distribute the power delivered to the load in a differentiated way and according to settable and defined profiles, unlike the thermionic valve systems where instead the volumes necessary for the RF generator and the non-fractionability of the RF applicator are such as not to allow it, except with complexity and in a very coarse, fixed and inflexible way.

In the case of several electronic systems 1 side by side, the modularity feature of the electronic system 1 avoids the complete blocking of the working cycle of the machine in the event of a fault, while at the same time allowing the replacement of the damaged electronic system 1, unlike thermionics valve systems where the uniqueness of the RF generator connected to the RF applicator does not make it possible, thus determining the complete stop of the manufacturing process and for the necessary repair time.

Furthermore, if an electronic system 1 fails, the RF powers supplied by the other electronic systems 1 can be remodeled in an appropriate manner, thus maintaining full operation of the machine and the working process, and only for the time necessary for its replacement, which can also be performed with the machine switched on ("hot swapping"). This replacement, given the conception of the electronic system 1, is designed to be carried out also by not highly qualified personnel, unlike the thermionic valve systems where their replacement requires specialization and, above all, a lot of attention due to the high voltages involved. With the modularity of the electronic system 1, a single logic unit can control many electronic systems 1 side by side by serial connection, making it easy to manage and set the profiles of the RF powers delivered in the time domain and in the space domain determined by the size of the RF applicator, also through intuitive operator interface systems, such as for example "touch screen" panels conveniently programmed with synoptic graphics and detailed in the individual iconic elements, for example with active graphics, which can be modulated or set in the process variables.

According to the peculiarities of the foregoing, said apparatus designed for machines for uses mainly, but not only, in ISM fields with high load impedances, essentially comprise one or more electronic systems 1 that emulate the operation of a thermionic valve, at least one network of coupling and/or adaptation downstream of said electronic system and at least one RF applicator arranged downstream of said at least one coupling and/or adaptation network.

The coupling and/or adaptation network can be tuned by the operator and includes one or more electrical and/or electronic circuits designed to filter and/or modulate and/or stabilize and/or modify and/or compensate the impedance connected to said electronic system 1 in a fixed or variable manner.

As regards the RF applicator, it can be as described in the state of the prior art, i.e. composed of a facing pair of a multiplicity of electrically interconnected cylindrical conductive tubes, electrically similar to two facing conductive plates between which the dielectric material to be treated is interposed, or composed of structures and geometries studied and created ad hoc according to the expected product and technological process through an appropriate method of application of the RF electromagnetic field, such as pairs of concentric cylindrical electrodes, or pairs of facing perforated plates, or sheets shaped according to specific geometric profiles, etc.

In any case, any other types of RF applicators or circuits suitable for use typically, but not exclusively, in ISM fields can be connected (for example probes or passive devices for thermo-medical treatments, or specific circuits for the excitation of ionized gases, or electrodes for the generation of electric arcs for particle treatments, etc.), which can be electrically represented by high load impedances, even considerably variable and/or with high reactive components.

The output RF voltage from the electronic system 1, after having been modified in amplitude and phase by the coupling and/or adaptation network whose function can also be to compensate for the higher reactive components of the load impedances, is applied to the element, for example to one of the plates of the RF applicator called "live", while the other element of the RF applicator, for example the other plate, is connected to ground. Following the insertion of the dielectric products to be dried and thermally treated that flow, for example by means of a conveyor belt, between the elements at differentiated RF voltages of the RF applicator, for example between the plates of the applicator, the dissipation due to dielectric losses which it is created allows to generate volumetric or endogenous energy in the same, thus allowing to obtain the expected treatment effects.

The SS RF electronic system for use in ISM fields with high load impedances just described at the conceptual and operating principle level allows, therefore, the replacement of the thermionic valve technology, managing to obtain output voltages/impedances that are comparable to the latter as they are completely similar in the typical values, while at the same time maintaining a good level of robustness and solidity with respect to possible load mismatches.

Furthermore, thanks to the modularity feature, the SS RF electronic system for use in ISM fields with high load impedances just described, in the case of using multiple systems, in the event of breakage, it allows to avoid total machine downtime and to replace the group that has failed simply by "removing" the broken group from its seat and inserting the new one, while avoiding the intervention of a specialized technician for the repair.

In addition, the SS RF electronic system for use in ISM fields with high load impedances just described, is suitable for broadband use, thus avoiding the need for complex circuit setup case by case, when application and uses require the use of differentiated RF frequencies, or such as to be convenient also for the success or optimization of technological processes. In fact, it is reiterated the important aspect that all the elements that make up the electronic system 1 are all designed and built to operate at broadband, thus making it possible to set different RF frequencies for the various systems used, thus allowing to easily create "multifrequency" apparatus and machines, a feature that greatly expands the areas of use for special applications and especially those of technical-scientific research. It is important to underline how these important features are very complicated and often technically not possible in systems that use thermionic valves, especially in self-oscillating circuits, which in any case require the technically adapting the RF applicators to the specific technical purpose, thus denaturing their suitable predisposition to the specific technological use.

It should also be highlighted how the broadband feature of the elements that make up the electronic system 1 allows, in addition to the more sophisticated systems provided, to mitigate any strong load mismatches with respect to the SS electronic system, since when they occur, considerable variations in the natural oscillation frequencies of the utilization circuit can occur.

Furthermore, the SS RF electronic system for use in ISM fields with high load impedances just described, allows a high purity of the electromagnetic spectrum and frequency stability, thus responding in the best way to the increasingly stringent regulations in the field of Electromagnetic Compatibility (ITU, CISPR, IEC, EU directives and specific regulations for areas or countries, such as the FCC in the USA, Canada and other countries of South East Asia). Not only that, but the purity of the RF signal generated, being without or with low amplitudes of harmonics or multiple frequencies, allows a simpler adaptation of load impedances, limits unwanted dissipations on high voltage components and prevents the application processes from being negatively affected by unwanted spurious electromagnetic fields. Furthermore, the SS RF electronic system for use in ISM fields with high load impedances just described, as well as perfect controllability, even remotely, of the RF power delivered to the load both in continuous and pulsed mode, also allows to exploit the considerable advantages of modularity, for example in the construction of complex machines such as to require differentiated treatments.

In addition, the SS RF electronic system for use in ISM fields with high load impedances just described, allows a simplified and economical industrial construction of machines and plants that use it since they are not strictly dependent on the type of process and features of the products/loads to be dealt with, with the consequence also of a considerable improvement in production management and in the optimization of delivery times.

Last but not least, the SS RF electronic system for use in ISM fields with high load impedances just described, allows savings in terms of transport and packaging costs thanks above all to the compactness and intrinsic lightness of the SS compared to the thermionic valves technology where, due to the natural use of electronic circuits, it is confirmed to involve considerable volumes, dimensions and weights.

It has thus been seen that the present invention fully achieves the proposed objects, as well as many others which are evident and deducible from everything described.

The invention thus conceived is susceptible of numerous modifications and variations, all of which fall within the scope of the inventive concept as defined in the claims.

Furthermore, all the details can be replaced by other technically equivalent elements. In practice, the materials and components used, as well as the contingent shapes and dimensions, may be any according to specific needs without thereby departing from the scope of the protection of the following claims. In the event that the technical features mentioned in the claims are followed by reference numbers, these reference numbers are introduced with the sole purpose of increasing the clarity of the claims, and consequently the aforementioned reference numbers do not have a limiting effect on the interpretation of each element identified as an example by such reference numbers.

Claims

1. Electronic system (1) for powering machines or apparatus with Radio Frequency (RF) signals at high load impedances, including at least one power supply group (2) for the voltage of the system components, at least one RF signal generation group (3), at least one logic interface and RF signal control group (4), and at least one transmission line (la) designed to be powered by said at least one RF signal generation group (3) or by another group of the system with a respective percentage of power, said at least one transmission line (la) comprising at least one final power group (7) and at least one voltage/impedance booster group (8), characterized in that said at least one final power group (7) comprises at least one power amplification sub-group (7b), said at least one power amplification sub-group (7b) including at least one Solid State (SS) power amplifier (7b 1).

2. Electronic system (1) according to claim 1, wherein said system (1) comprises at least one power pre-amplification group (5) and/or at least one power division group (6), said at least one transmission line (la) being designed to be powered by said at least one power pre-amplification group (5) and/or by said at least one power division group (6) with a respective power percentage.

3. Electronic system (1) according to claim 1 or 2, wherein said at least one power supply group (2) comprises at least a first power supply (2a) adapted to supply one or more previous stages to the at least one power division group (6) of the electronic system (1).

4. Electronic system (1) according to claim 3, wherein said at least one first power supply (2a) is a switching power supply.

5. Electronic system (1) according to claim 3 or 4, wherein said at least one first power supply (2a) comprises one or more sub-power supplies (2b) suitable for supplying one or more successive stages to the power division group (6) of the electronic system (1).

6. Electronic system (1) according to claim 5, wherein said one or more sub-power supplies (2b) comprise three switching sub-power supplies.

7. Electronic system (1) according to claim 5 or 6, wherein said at least one first

34 power supply (2a) and said one or more sub-power supplies (2b) are provided with means or components for stabilizing the voltage and limiting the current and with means or remote control components of the supply voltage and of the power of at least said at least one RF signal generation group (3).

8. Electronic system (1) according to any one of the preceding claims, wherein said RF signal generation group (3) comprises at least one high-stability waveform generator.

9. Electronic system (1) according to claim 8, wherein said high-stability waveform generator comprises at least one oscillator, at least one circuit for controlling the duty cycle and for modulating the pulse width.

10. Electronic system (1) according to claim 8 or 9, wherein said RF signal generation group (3) comprises a low power amplification chain downstream and/or upstream of said oscillator and of said circuit for controlling the duty cycle.

11. Electronic system (1) according to claim 9, wherein said oscillator is a crystal oscillator, optionally made of quartz.

12. Electronic system (1) according to any one of claims 9 to 11, wherein said at least one circuit for controlling the duty cycle and for modulating the pulse width comprises an electric and/or electronic circuit of retroactive feedback.

13. Electronic system (1) according to any one of the preceding claims, wherein said at least one logic interface and RF signal control group (4) comprises at least a logic unit designed to manage the control of operating parameters of the electronic system (1).

14. Electronic system (1) according to claims 9 and 13, wherein said parameters relate to the variation of the duty cycle and of the pulse width of the waveform generated by said high-stability waveform generator of said RF signal generation group (3).

15. Electronic system (1) according to any one of claims 2 to 14, wherein said power pre-amplification group (5) comprises a pre-driving sub-group (5a) and a driving sub-group (5b) both able to increase the power level of the output signal from the RF signal generation group (3).

35

16. Electronic system (1) according to claim 15, wherein said pre-driving sub-group (5a) comprises one or more power amplifiers which increase the power level of the output signal from the RF signal generation group (3).

17. Electronic system (1) according to claim 15 or 16, wherein said driving subgroup (5b) comprises an input transformer, one or more power amplifiers used to further raise the power level of the output signal from the pre-driving sub-group (5a) and an output transformer.

18. Electronic system (1) according to any one of claims 2 to 17, wherein said power division group (6) comprises a two, three or more-way RF isolated power divider (6a) which divides the signal power at the output of the driving sub-group (5b) or of the RF signal generation group (3) in equal or differentiated parts respectively along at least two, three or more transmission lines (la) of said electronic system (1).

19. Electronic system (1) according to any one of the preceding claims, wherein said final power group (7) comprises at least one input transformer (7a) upstream of said power amplification sub-group (7b) and at least one output transformer (7c) downstream of said power amplification sub-group (7b).

20. Electronic system (1) according to claim 19, wherein said final power group (7) comprises an equalization/coupling network (7d), said equalization/coupling network (7d) comprising one or more electrical and/or electronic circuits suitable for improving the amplitude-frequency transfer function in the field of use of the electronic system (1).

21. Electronic system (1) according to claim 19 or 20, wherein said at least one input transformer (7a) is a 9: 1 transformer for matching the Gate impedance or the input of said at least one SS power amplifier (7b 1).

22. Electronic system (1) according to any one of claims 20 to 21, wherein said output transformer (7c) is a 1 :4 transformer for matching the Drain impedance or the output of said at least one SS power amplifier (7b 1).

23. Electronic system (1) according to any one of claims 21 to 22, wherein said output transformer (7c) is made by means of at least two coaxial transmission lines according to a configuration having the primary windings placed in parallel and the secondary windings placed in series.

24. Electronic system (1) according to claim 23, in which said at least two coaxial transmission lines are each made by means of four flexible insulated cables placed in parallel.

25. Electronic system (1) according to any of the preceding claims, wherein said SS power amplifier (7bl) comprises at least two transistors (7b 1', 7bl") placed in parallel according to a push-pull configuration.

26. Electronic system (1) according to any one of the preceding claims, wherein said SS power amplifier (7bl) comprises at least two modules, each comprising at least two transistors (7b 1', 7b 1") in push-pull and added together with one or more of the known combiners or other configurations similar and equivalent for the effects.

27. Electronic system (1) according to claim 25 or 26, wherein said at least two transistors (7b 1', 7b 1") are LDMOS or VDMOS transistors.

28. Electronic system (1) according to any one of claims 21 to 27, wherein said final power group (7) comprises elements placed downstream of the output transformer (7c) and adapted to compensate for low and/or high frequencies of band in which the output transformer (7c) must operate.

29. Electronic system (1) according to any one of the preceding claims, wherein said voltage/impedance booster group (8) comprises a first step-up transformer (8a), a power sensing sub-group (8b) and a second step-up transformer (8c), these transformers (8a, 8c) being designed to raise the output voltage/impedance from said final power group (7).

30. Electronic system (1) according to claim 29, wherein said first step-up transformer (8a) is a balanced-balanced 1 :9 step-up transformer made by means of one or more coaxial transmission lines.

31. Electronic system (1) according to claim 30, wherein said one or more coaxial transmission lines are coated with one or more sleeves made of ferrite having magnetic permeability values /q comprised between about 100 and about 800.

32. Electronic system (1) according to any one of claims 29 to 31, wherein said power sensing sub-group (8b) comprises one or more balanced directional couplers (8b 1, 8b2) suitable for analyzing the load and monitoring, by means of said logic interface and RF signal control group (4), the power level of the electronic system (1).

33. Electronic system (1) according to claim 32, wherein said one or more balanced directional couplers are two balanced directional couplers (8b 1, 8b2) with opposite lines in phase.

34. Electronic system (1) according to claim 32 or 33, wherein said one or more balanced directional couplers (8b 1, 8b2) comprise circuits and/or systems that detect and measure the direct and reflected components of both the RF voltages and the RF currents of the transiting RF signals.

35. Electronic system (1) according to claim 32 or 33 or 34, wherein said power sensing sub-group (8b) comprises at least one electronic trigger or threshold circuit placed downstream and/or upstream of said one or more balanced directional couplers (8b 1, 8b2) adapted to be operated by means of an activation signal emitted by said logic interface and RF signal control group (4) on the basis of the reflected power value measured by said one or more balanced directional couplers (8b 1, 8b2) and designed to block and then reduce and subsequently increase, according to a programmed ascent ramp, the output power from said RF signal generation group (3).

36. Electronic system (1) according to any one of claims 32 to 35, wherein said power sensing sub-group (8b) comprises at least one electronic circuit placed downstream and/or upstream of said one or more balanced directional couplers (8b 1, 8b2) adapted to be operated by means of a driving signal emitted by said logic interface and RF signal control group (4) on the basis of the values of RF direct and reflected voltages and currents measured by said one or more balanced directional couplers (8b 1, 8b2).

37. Electronic system (1) according to claim 36, wherein said at least one electronic circuit located downstream and/or upstream of said one or more balanced directional couplers (8b 1, 8b2) is designed to control the RF power delivered to the load by managing it in continuous and/or pulsed and/or modulable mode according to trends of predefined driving signals variable in the time and/or frequency domain.

38. Electronic system (1) according to claim 36 or 37, wherein said at least one electronic circuit placed downstream and/or upstream of said one or more balanced

38 directional couplers (8b 1, 8b2) is designed to also control the components of the RF voltages and of the RF currents of the transiting RF signals, managing them in such a way as to assimilate the operation of the electronic system (1) to an RF voltage generator or an RF current generator, and/or to emulate the electronic operation typical of a thermionic valve as the load varies.

39. Electronic system (1) according to any one of claims 29 to 38, wherein said second step-up transformer (8c) is a 1 :9 balanced-balanced step-up transformer made through one or more transfer lines according to a configuration having primary windings placed in parallel and secondary windings placed in series.

40. Electronic system (1) according to claim 39, wherein said one or more transfer lines are insulated bifilar lines.

41. Electronic system (1) according to claim 40, in which each of said bifilar lines are spaced by means of a spacer element, said spacer element being able to maintain a substantial parallelism between the wires of the bifilar lines and a controlled distance between them.

42. Electronic system (1) according to any one of claims 38 to 41, wherein said second step-up transformer (8c) comprises one or more compensation elements of the parasitic capacitances and/or parasitic inductances or of the connections upstream and/or downstream thereof.

43. Electronic system (1) according to any one of claims 38 to 42, wherein said second step-up transformer (8c) comprises inductive and/or capacitive elements in parallel and/or in series with the output of said second step-up transformer (8c).

44. Electronic system (1) according to any one of claims 38 to 43, wherein said second step-up transformer (8c) of said transmission line (la) is placed in series with the other second step-up transformers (8c) of the other transmission line/s (la).

45. Electronic system (1) according to any one of the preceding claims, in which said at least one voltage/impedance booster group (8) is designed, at the output of the electronic system (1), to raise the voltage of signals received at the input to a value between about 3000 V_e^ and about 3500 V_e f, for example about 3201 V_e f-

39

46. Electronic system (1) according to any one of the preceding claims, wherein said at least one voltage/impedance booster group (8) is designed to raise the output impedance of the electronic system (1) to a value between about 1200 and about 1700 , for example about 1458 .

47. Electronic system (1) according to any one of the preceding claims, wherein said electronic system (1) comprises at least one cooling group adapted to selectively cool the groups of the electronic system (1) and wherein said at least one cooling group is a liquid cooling group.

48. Radio Frequency (RF) apparatus for drying and heat treatments of raw materials, semi-finished and finished industrial products, and/or usable in RF equipment and machines in ISM fields, comprising one or more electronic systems (1) according to any one of the previous claims, at least one coupling and/or adaptation network downstream of said electronic system and at least one RF applicator or any RF utilization circuit downstream of said at least one coupling and/or adaptation network.

49. RF apparatus according to claim 48, wherein said at least one coupling and/or adaptation network comprises one or more electrical and/or electronic circuits adapted to filter and/or modulate and/or stabilize and/or further raise the voltage level at the output of said electronic system (1) and/or modify and/or compensate the impedance connected to said electronic system (1) in a fixed or variable manner.

50. RF apparatus according to claim 48 or 49, wherein said at least one applicator or any RF utilization circuit comprises at least two or more conductive elements of any shape and size separated by a dielectric material in contact or not with them.

40