WO2010001337A2

WO2010001337A2 - Quad antenna

Info

Publication number: WO2010001337A2
Application number: PCT/IB2009/052833
Authority: WO
Inventors: Maurizio Stasolla
Original assignee: Maurizio Stasolla
Priority date: 2008-06-30
Filing date: 2009-06-30
Publication date: 2010-01-07
Also published as: WO2010001337A3; ITMI20081206A1

Abstract

A Quad antenna defining a flat surface formed by a plurality of loops arranged in a chequerboard fashion. The antenna reveals a good omnidirectionality while also ensuring a high gain. Moreover, even when the antenna is tuned according to a preset wavelength, the passband is wide enough to enable the use of said antenna for energy conversion from an electromagnetic wave into electrical energy.

Description

QUAD ANTENNA

Field of the invention

The present invention refers to a Quad antenna. State of the art The state of the art comprises a large number of types of antenna. Very few have an optimal performance and, in any case, if they are optimised, this applies to certain characteristics, while the remainder still have shortcomings due mainly to the technological limits achieved by the known art. For instance, in frequency bands higher than the gigahertz, solutions exist that have a very high gain, but that also introduce a very high level of directivity, so that in order to communicate with a mobile correspondent it becomes necessary to rely on the use of tracking systems. This problem is common to parabolic dishes and to Yagi antennas. In fact, in order to achieve a high gain in one direction, strongly directional antennas are obtained that are suitable for use mainly in fixed point-to-point connections, as in the case of radio relay systems.

At the opposite extreme of such directional antennas, there are omnidirectional antennas, again for fixed stations, such as the well-known 'Ground-Plain' or 'biconical' or 'V-inverted' antennas, that have a limited gain, while still enabling multi-point connections, but they generally radiate only along one, vertical plane. These antennas are normally placed at the top of pylons and, being electrically open-ended, they are not suitable for use in places infested by storms because they often attract lightning.

Among the best technological solutions, it is worth mentioning those based on a so-called "array of antennas", in which a series of identical antennas with a high gain in different directions are coupled together; each of them has a limited radiation lobe, but combined together (if properly designed), they cover an almost omnidirectional radiation lobe, although there will in fact be some lobes facing more in certain directions, which can be calculated as the vector sum of the lobes forming each pair of consecutive antennas involved. This technology overcomes the known attenuation problems experienced in very high frequency transmissions.

A Quad antenna is a folded-dipole antenna with four straight arms placed in series with one another, each sized to coincide with a quarter of the wavelength (λ/4) and arranged to form a square or an open rhombus, see figures 1a and 1b of the prior art, for instance. In other words, taking a geometrically closed conductive rhombus, if it is opened at one corner and a radio-frequency (RF) generator is connected at the two ends obtained thereby, the rhombus resonates, thus creating a highly inductive load, exactly like a turn in a solenoid substantially pressed on four edges and it offers a characteristic impedance of 150 ohm at its working frequency, with a wide, almost totally omnidirectional, radiation lobe. Some arrays are known by the English names Hybrid Quad, or BiQuad or Double- Quad antennas, which include a pair of Quad antennas connected together at the open ends, i.e. juxtaposed so that they are coplanar and they both have one diagonal or one axis lying on the same straight line, see figures 1c and 1d of the prior art. There are consequently known applications with two Quad antennas in parallel. This solution enables a low output impedance (approximately 75 ohm) to be achieved, but the total power applied at the centre is halved in each of the two antennas. The typical gain of this type of antenna, when there is a reflector panel, equates to that of a 10-element Yagi and is consequently of the order of 8-9 dB, but its very wide radiation lobe is halved, becoming intensified in only one direction, unlike the version without a reflector. Another known solution consists in placing two pairs of mutually parallel Quad antennas in series, thereby achieving a double-eight, i.e. all the rhombi are juxtaposed with one diagonal lying on the same straight line, as shown in figures 1e and 1f of the prior art. The connection to an RF generator is achieved in the central area, in line with the parallel of the two pairs of Quad antennas, in much the same way as in the case of BiQuad antennas. We know from the known art that the construction of similar Quad antennas, in which the different rhombi are arranged one after the other to form a double-eight, generates a typical narrow, elongated configuration because each rhombus has one vertex in common with another rhombus. In particular, two consecutive rhombi show a insulated crossing of the conductors coinciding with said common vertex. This aspect is better clarified in figures 1e and 1f. In this configuration, the gain is of the order of 11.5 dB and this makes it easy to imagine that increasing the number of Quads included in an antenna leads to an increase on the corresponding gain. The radiation lobe narrows, however, in relation to the plane perpendicular to the one in which the rhombi lie and passing through the axis that passes through the various vertices.

Thus, a BiQuad or double Quad, or double-eight antenna is not flat in relation to said conductor crossings. It is worth adding that the circulation of the current in double and double-eight Quad antennas is inverted between two consecutive rhombi. As shown in figure 2, we know that axial directors are used with a Quad antenna, i.e. the one to which the power supply cable is connected and a reflector element that is the oversized last director. The directors simultaneously increase the gain and the directivity of the antenna, while the reflector element reduces the rear radiation lobe in favour of a greater gain of the front lobe.

Again according to the known art, the last element that acts as a reflector (WR) may be of larger size than the radiator, giving rise to a very small Front-Rear (F/R) signal ratio. On the other hand, optimal reflectors, with a high F/R signal ratio, are elements that consist of solid metal surfaces, or with a close-knit mesh, that are consequently preferable to the reflector shown.

It is clear from the known art that it has to be paid attention, in double-eight antennas, to ensure that the conductors do not touch each other at the crossings in order to avoid short-circuiting the path of the current inside the various rhombi. Thus, by doubling the number of Quad antennas, the gain is increased by 3 dB, but if the directivity is increased, then it becomes of well worth the while to maximise the gain of the antenna but not to increase its directivity excessively, and particularly to contain the dimensions of the antenna in order to be able to integrate it more easily in other equipment. The use of rectangular elements with sides, or portions of sides, in common and powered from the centre of one side, as shown in the example on the left in fig.1a, was described in an article on 'Curtain Quads', published by Ross Arderson in the journal QST in November 1984, entitled 'Meet the Curtain Quad Antenna'. This article describes a layout as shown in figure 1i of the prior art. This document explains that an antenna can be extended in a plane rather than along an axis. Here again, it is worth noting that the circulation of the current in adjacent loops is inverted in one with respect to the next, but the active elements are only the horizontal ones, i.e. λ/4 in length. In operation, the antenna thus tends to have a good radiation only along one plane, which coincides with the horizontal in the case of figures 1 i and 1j. In fact, only the horizontal stretches of the elements radiate at the wavelength, since their length is a quarter of the tuning wavelength, while the vertical stretches serve as couplers and their length must be calculated so as to guarantee the best performance in terms of gain, i.e. greater than a quarter-wavelength. Thus, a loop defining an antenna according to said article is longer than the tuning wavelength. The general behaviour of these antennas is confirmed, in that increasing their gain makes their directivity increase too. Summary of the invention The object of the present invention is to produce a Quad antenna suitable for solving the above-described problem of the increment in directivity with an increase in gain, by producing an antenna that, for a given increase in gain, has a more limited increase in directivity than in the case of the known antennas. As explained in claim 1 , the present invention relates to a Quad antenna comprising a plurality of coplanar circuits (loops) of a length corresponding to a predetermined tuning wavelength, characterised in that at least one first loop is juxtaposed with at least one second loop in a first direction, and at least one third loop is juxtaposed with the second loop in a second direction perpendicular to said first direction, so that said first and second juxtaposed directions intersect each other at the gravity center of said second loop.

An antenna according to the present invention consequently comprises a plurality of loops arranged for form a chequerboard pattern.

An antenna according to the present invention comprises a plurality of transceiver loops, such as rhombi or circles, or the like, juxtaposed to form a surface resonating to electromagnetic waves; moreover, the number of loops having a first same sense of circulation of the current is greater than the number of loops having a second same sense of circulation opposite to said first sense. Said rhombi or circles may be open or closed, juxtaposed but galvanically separated or even connected to one another, as explained in more detail below in the examples described, inducing a short circuit of all the sides defining the loops, or of only a portion thereof.

In the case of rhombi, if we continue indefinitely to juxtapose first rhombi along directions perpendicular to one another, further rhombi are formed by the sides of the first rhombi, in exactly the same way as for the white squares on a chequerboard. In particular, if the diagonals of two adjacent rhombi lie two by two along said perpendicular juxtaposed directions, the juxtaposition of four rhombi defines a fifth rhombus formed by the sides of the first four facing towards the other rhombi.

According to another aspect of the invention, a Quad antenna forming the object of the present invention can advantageously comprise at least one straight element sized to resonate at a given frequency, made of a conductor material connected galvanically to a vertex of a rhombus defining the antenna; said straight element lying on the surface on which the antenna lies, along a line that bisects the supplementary angle with respect to the vertex to which it is connected.

An antenna prepared according to the present invention advantageously possesses a high gain while retaining a wider radiation lobe than antennas prepared according to the known art. According to another aspect of the invention, the characteristics of the antenna forming the object of the present invention enable another use in addition to the reception/transmission of electromagnetic signals.

Another object of the present invention is a method for converting electromagnetic waves into electrical energy according to claim 13. The dependant claims describe preferred embodiments of the invention and form an integral part of the present description.

Brief description of the figures

Further characteristics and advantages of the invention will emerge more clearly from the detailed description of a preferred but not exclusive embodiment of a Quad antenna illustrated herein as a nonlimiting example with the aid of the attached drawings, wherein:

Figs. 1a and 1b respectively show examples of square and rhombus shaped Quad antennas according to the known art (Prior Art);

Figs. 1c and 1d show, according to the known art (Prior Art): BiQuad or Double-Quad (Prior Art), examples of antennas arranged in parallel to form an eight according to the examples of figs.1a and 1b, respectively;

Fig. 1e shows a front view of the extended version of the previous fig. 1d: a - . double-eight with a reflector panel, while fig. 1f shows a side view of the same antenna and serves to emphasise the electrically insulated crossings (Prior Art);

Fig.ig - 1j show the so-called Curtain Quad antennas according to the known art (Prior Art);

Fig. 2 shows the use of directors and reflectors according to the known art in a Quad antenna (Prior Art);

Fig. 3a shows a base drawing of an antenna according to the present invention, based on Quad antennas, comprising a plurality of rhombi. A detail is highlighted, shown in figure 3b, that shows two opposite vertices of corresponding consecutive rhombi that have one vertex in common, being juxtaposed along a first direction without mutual contact, while figure 3c shows a detail wherein two opposite vertices of two adjacent rhombi are juxtaposed without mutual contact along a second direction perpendicular with respect to said first direction;

Fig. 4a shows a left portion of the antenna of figure 3a, highlighting the sense in which the current circulating in the antenna flows, while Fig. 4b is a schematic representation of a sinusoidal wave of current propagated in the antenna; the two figures 4a and 4b are associated, where the letters a, b, c, d, show the propagation of the quarter-waves along the sides defining each rhombus, delineating the perfect completeness of all the quarter-waves (a,b,c,d) in each rhombus; Fig. 4c shows an example of different deactivation, by means of conductive material, of a given polarised loop in relation to all the others, i.e. with a current circulation opposite to the others;

Fig. 5a shows a design variant obtained from the portion of antenna in figure 4a, wherein the vertices along which two adjacent rhombi are juxtaposed are completely short-circuited with one another, so as to obtain a better rephasing of the current/voltage signals circulating in the various loops defining the antenna, making any structural imperfections of the antenna non-critical and considerably amplifying the band of frequencies in which the antenna resonates. The same figure also shows the planes of polarisation inscribed in the rhombi; Fig. 5b shows the current circulation in the loops of an antenna comparable with the antenna of the previous figure, while figure 5c shows the detail of the short circuit of the vertices;

Figs. 5d, 5e and 5f show alternative variants of the antenna in fig. 4c, designed to avoid having any current circulating in the rhombi polarised inversely with respect to all the others;

Fig. 6a shows a variant of antenna with each loop resonating at 10λ, which makes the antenna particularly extensive along an axis of symmetry α, showing the planes of polarisation of said rhombi inscribed in said rhombi;

Fig. 6b shows a variant of antenna that is particularly extensive along an axis of symmetry perpendicular to said axis α, showing the planes of polarisation of said rhombi inscribed in said rhombi;

Fig. 6c shows a detail relating to the rhombi lying along said axis of symmetry α;

Figs. 6d and 6e show a variant that also enables the activation of the rhombi lying along said axis of symmetry α by means of a single jumper;

Fig. 6f shows a variant of a hybrid antenna in which a Biconical antenna of known type is integrated in order to create an equally-distributed greater capacity at the centre and to further flatten the vertical radiation lobe, while leaving the almost completely omnidirectional horizontal lobe unaltered, given that it lacks a reflector element. The detail in figure 6g shows that all the vertices of adjacent rhombi are short-circuited two by two, so that in figure 6f we can see rhombi of multiple dimensions with respect to the rhombi indicated by the letters A, B, etc., i.e. that are capable of resonating at different frequencies with respect to said rhombi A, B, etc., in order to guarantee a broader pass-band for the antenna;

Fig. 6i, with the details shown in figures 6h and 6j, shows a further variant of antenna according to which the antenna has a square shape and all the vertices of rhombi facing along a main diagonal are disconnected from one another two by two, while all the other vertices are short-circuited two by two; here again, rhombi of multiple dimensions with respect to said rhombi A, B, etc. are highlighted;

Fig. 7a shows a double-eight antenna with at least one straight element connected to a peripheral vertex of the antenna, coplanar with the antenna and lying along a bisecting line relative to said vertex;

Fig. 7b shows a schematic representation, as in figures 4a and 4b, of a sinusoidal wave of current propagating through the antenna; the two figures are associated, the letters a, b, c, d, showing the propagation of the quarter-waves along the sides that define each rhombus and said straight elements;

Fig. 8 shows a front view of the antenna in figure 7a comprising directors and reflectors;

Figs. 9 show the radiation lobe obtained from a 3-D simulation using the known '4nec2' software, where the antenna is as illustrated in fig. 5b, where figure 9a shows the radiation lobe with a reflector panel and figure 9b without the reflector panel and with a substantially uniform and omnidirectional lobe;

Figs. 10 show an example, in front and side views respectively, of an antenna according to figure 3a comprising director elements; Fig. 11a shows a variant of antenna according to the present invention wherein said loops defining the antenna are circular, so as to achieve a circular polarisation;

Fig. 11 b shows a variant of fig. 11a with the addition of axial directors compatible with the antenna; Fig. 12a shows an example of an embodiment of an energy generator/converter from radio waves, comprising a plurality of antennas according to the present invention;

Figs. 12b and 12c show another example of an embodiment of an energy generator/converter from electromagnetic waves, also achievable using nanotechnology and comprising a plurality of antennas according to the present invention; inside, in parallel with each loop, another known antenna (preferably broadband, of the rectangular Archimedean type) has been inserted, as shown in fig.12d;

Fig 12e is another example of an embodiment of a generator/converter achievable in nanotechnology, with the rhombus-shaped loops equivalent to those in figures 12a - 12d, among which some rhombi are made of solid material;

Fig. 12f shows another method for producing a photovoltaic converter using nanotechnology, which is also more straightforward than as shown in fig. 12b, and which is also suitable for functioning with solar light, but receiving energy in both a rightward and a leftward circular polarisation, very similar to the spiral polarisation with which photons are propagated, enabling a greater efficiency to be achieved even in the presence of hollow interspaces.

The same reference numbers and letters are used in the figures to identify the same elements or components.

Detailed description of a preferred embodiment of the invention One variant of antenna according to the present invention is illustrated in figure 3a, which shows that any rhombus among a plurality of coplanar rhombi, with the sole exception of those at the perimeter, are juxtaposed with other rhombi at their vertices, thereby defining a flat antenna. Two juxtaposed rhombi for a corresponding vertex according to the design described in the present invention may be not only juxtaposed but also galvanically interconnected, as shown in figures 3b and 3c. According to another preferred embodiment, moreover, additional rhombi are juxtaposed or galvanically connected to a given rhombus, e.g. 11 , at all the vertices.

An elementary portion of the antenna comprises a first rhombus 11 and at least one second rhombus 12, juxtaposed with the rhombus 11 along a first direction so that said first direction coincides with a diagonal of the rhombus 11 and with a diagonal of the rhombus 12. Identifying a second direction and a third direction of juxtaposition parallel to one another and perpendicular to said first direction of juxtaposition, there are the rhombus 13 juxtaposed with the rhombus 12 and the rhombus 14 juxtaposed with the rhombus 11 , so that the diagonals of said four rhombi lie two by two on said straight lines of juxtaposition, and thereby define the rhombus 15 formed by the sides of the rhombi 11 , 12, 13, 14, that face towards the other rhombi. The rhombi can be directly or indirectly galvanically connected to one another. As shown in figures 3b and 3c, the galvanic connection between the vertices of the rhombi is partial and it is achieved so as to form a single general loop comprising said loops 11 , 12, 13, 14.

In particular, as shown in figure 3a, it is clear that an antenna according to the present invention comprises two symmetrical and parallel, general loops, of which the first extends to the right of an axis of symmetry α and the second to the left of said axis α. Each of said two general loops, without crossings over itself or other loops, defines said plurality of loops or rhombi juxtaposed with one another and tuned to the wavelength of a signal being transmitted. The length of each general loop, and consequently the number of loops or rhombi defined thereby, is sized in relation to a predetermined impedance value.

In order to understand the characteristics of an antenna according to the present invention, it is important to note that, at the centroid of the antenna, in line with the terminals 20 and 21 , a cable 40 is connected for the transmission of an RF signal being received or transmitted. In particular, an antenna according to the present invention is also symmetrical in relation to a second axis of symmetry β perpendicular to said first axis of symmetry α. It should be noted that, here again, two further independent loops are formed, each of which defines a plurality of loops or rhombi that are in mutual contact at two points on their corners 22 and 23.

The portion of the conductor 100 defining the antenna, which includes the terminal 20, extends entirely along a first semi-plane with respect to the axis β, while the portion of the conductor 100 including the terminal 21 extends entirely along a second semi-plane with respect to the axis of symmetry β. The details in figures 3b and 3c show enlargements of two rhombi whose vertices come head-to-head with no mutual contact.

Thus, the conductor 100 that constitutes the antenna is folded without overlapping, meaning that antennas can be made on flat printed circuit boards without any need to prepare complicated jumpers. As shown in figure 4a, the circulation of the current within the rhombi juxtaposed at the corners of the rhombus 11' is inverted with respect to the case of the rhombus 13', as it has to be consistent with the direction in which the current circulates at the corner in common defined by the conductor 100. This aspect determines an improvement in the antenna's performance because the flow generated by any given rhombus is concatenated, giving rise to a vector sum with the flows generated by adjacent rhombi in which the current circulates in the opposite direction.

As a result, in a sufficiently extensive antenna according to the present invention, we see that the circulation of the current in each rhombus corresponds to the layout of a chequerboard.

The vector composition of the magnetic flow that is concatenated to the rhombi is such that an antenna thus designed has a higher gain for the same surface area because it is optimised as far as possible, and also a wide angle of radiation, parameters that are difficult to reconcile in the known antennas. Since said antenna is also symmetrical in relation to a second axis Ct, it can be advantageously analysed considering only one half, e.g. the left-hand half shown in figure 3a, it being granted that an antenna comprising only one half can also be made, with the need to subsequently adapt the impedance of the antenna by means of a balun transformer, of known type.

Because, in structural terms, the length of each side of each rhombus corresponds to a quarter of the wavelength, λ/4, the portion of antenna represented in figure 4a will consequently resonate at 6λ, and the whole antenna will continue to resonate at 6λ, but representing the coupling of two identical portions prompts the adaptation of the impedance, which is halved while the gain is doubled, i.e. it is increased by 3 dB, while the transmission lobe is slightly flattened laterally, thereby increasing its directivity. This is easy to perceive if we count the number of sides needed to connect the two poles of the antenna and the multiply it by the length of each side, corresponding to λ/4, thus obtaining (with reference to figure 4a) 24^* λ/4 = 6^*λ.

Figure 4b, on the right, shows a sinusoidal wave divided into quarter-waves, each associated with one side of a rhombus. This association is identified by means of the lowercase letters a, b, c, d. The planes of radiation or polarisation are perpendicular to the plane on which the antenna lies and pass through each pair of vertices of each rhombus associated with the antinodes of the sinusoidal wave.

It is immediately easy to see from fig. 4a, that the rhombi 11' and 16' are inversely polarised with respect to all the others. For the sake of simplicity, we define the rhombi polarised like the rhombi 11' and 16' as minority rhombi and all the others as majority rhombi.

To improve transmission efficiency, the minority rhombi can be efficiently inactivated by placing an inscribed metal surface in each one, e.g. 24' and 28', preferably compatible with the shape of the loop so that the sides of the inscribed metal surface lie parallel to the sides of the rhombus, as shown in figure 4c, without any contact between them. This solution prevents the generation of a magnetic flux by the minority rhombi. Said metal surfaces inscribed in the rhombi can be further connected to earth to ensure a better deactivation of the minority rhombi.

According to the variant shown in figure 5b and in detail in figure 5c, the vertices of each adjacent rhombus are short-circuited and the rhombi 18' and 14' and those symmetrical to them with respect to the axis α, represent the shortest loops for the circulation of the current and determine its impedance, while the other loops, although they contribute to signal transmission/reception, in terms of impedance they contribute very little.

According to another variant shown in figures 5d, 5e and 5f, there is no need to use metal surfaces to inhibit the functioning of the minority loops by selectively preparing crossings of the metal conductor 100, so that at some points the vertices are only juxtaposed, while at others they are obtained with the crossing of the conductor 100. In particular, it is only necessary to prepare one jumper or insulated crossing, i.e. two antenna branches that do not cross over each other without mutual contact, of the conductor 100 defining the antenna, at the point where the two rhombi in which we wish to prevent the current from circulating are juxtaposed, or by adding other jumpers or insulated crossings to the previous jumper or insulated crossing at the points of juxtaposition immediately surrounding the loops in which we wish to prevent the current from circulating. In this way, the electromagnetic flux in said minority rhombi is nil because the current circulation therein is nil.

Figure 6a shows a complete antenna resonating at 10 λ, in which it is clear that there are eight minority rhombi out of a total number of twenty-eight. This means that their ratio is 8:28 or, in other words, 2:7. Looking at figure 6c, as in the antenna 3a, it is clear that there are four minority rhombi out of sixteen, meaning a ratio of 1 :4.

Finally, if we look at the version extending along the axis β in figure 6b, there are eight minority rhombi out of twenty-six, with a ratio of 4:13.

It is therefore clear that flat antennas that extend further along the axis of symmetry α have a stronger polarisation and are consequently more efficient. Moreover, we can see from figure 6b that the two rhombi that extend along the axis α behind the terminals 20' and 21' for connecting to the RF cable are not polarised, so they are not active. To optimise the functioning of the antenna, we can make them active by creating a single jumper in line with the RF cable connection point, so that a first side of a first of said two rhombi leading up to one of said terminals 20' or 21', is galvanically connected to a second side of a second rhombus symmetrical to said terminals. Clearly, one of the two galvanic connections deriving therefrom must be made by means of a jumper, as shown in figure 6e.

A Quad antenna, like the antennas in figure 1 , for instance, or in figures 3 to 6, can be further improved when it comprises straight elements 2 a quarter wave in length, again lying on the plane defined by the antenna and extending externally to a rhombus at the perimeter along the line bisecting the supplementary angle defined by a vertex at the perimeter, as shown in figures 7a and 8.

Said straight elements 2 come to be positioned in line with the vertices and virtually extend the points where the antinodes, of the current for instance, occur along the same transmission plane, i.e. at the points where the sinusoidal wave shown in figure 7b acquires its maximum or minimum value. The present invention advantageously tends to increase the gain of an antenna made according to the invention by approximately 1-2 dB with respect to a double- eight antenna of known type. Surprisingly, a wider radiation angle is achieved at the same time along the plane parallel to said straight elements 2 and perpendicular to the plane on which the antenna lies. To facilitate its description, said double-eight antenna, like the antenna 1 too, defines or lies on a plane, but it can be spread over any surface, such as a portion of a cylindrical surface for instance, in which case its characteristic omnidirectionality could be further enhanced. In addition, the antenna can comprise passive director and reflector elements 3 according to the known art on the directors and reflectors of Quad antennas, according to which they must be arranged parallel to the arms defining each Quad, as shown in figures 8 and 10.

Figures 9 show the radiation diagrams for an antenna according to the present invention. In particular, figure 9a shows the use of a rear reflector, while figure 9b shows the same antenna without the rear reflector.

In particular, we can see from figure 9b that it has a marked omnidirectionality, in despite of a high gain. These characteristics are much appreciated, especially in cities, where the use of very high frequencies leads to many signal reflections being produced, so a very wide radiation lobe with a high gain enables a continuous and reliable connection to be assured even in the presence of obstacles.

The present invention thus enables the preparation of a panel antenna 1 and the use of straight elements 2 capable of offering a high gain and a good omnidirectionality. Moreover, panel antennas made in this way are easy to integrate in the circuitry of transmission equipment because they contain no jumpers, i.e. they have no crossings of the conductor defining the antenna. The antenna can also be adapted to function with the circular polarisation shown in figures 11 , in which case there is an open or closed circular-shaped loop instead of each rhombus, the physical length of which corresponds to λ. Here again, compatible axial directors may be inserted, which may also be circular in shape, to give the antenna a greater directivity and a higher gain. A variant of an antenna according to the present invention may be sized so as to be capable of converting an electromagnetic wave into a direct current, thanks to the addition of rectifier and filter circuits. Said antenna is particularly suitable for such a use because its large bandwidth enables it to absorb a great deal of energy, be it sized for radio wave bands or for nanometric bands of solar light. It is also advantageously unnecessary for the antenna to be perfectly tuned to a predetermined wavelength because its characteristically extremely wide bandwidth enables electromagnetic energy to be converted into electrical energy, although the dimensions of the loops are greater than the dimension obtained analytically. Figure 12a shows an example of an embodiment of a radio wave generator energy converter into electrical energy comprising a plurality of antennas according to the present invention. Rectifier and filter circuits are connected at the ends of the central terminals on each antenna used, equating to points 20 and 21 in figure 3a, using diodes that have a very low working threshold, e.g. of the Schottky type (in order to reduce losses and avoid detuning the antenna), according to known direct current conversion techniques. The base diagram shown comprises at least two antennas in parallel, subsequently placed in series with other identical antennas to double or further multiply the total current and voltage. A Schottky diode is inserted in line with said connection terminals, placed in series with an output branch, to rectify the alternating resonating oscillation. To avoid the signal picked up by the antenna being dispersed on the non-resonant outer conductors, an inductor is inserted immediately downstream from the diode to filter the alternating components of the signals being picked up and converted by the antenna. Further filtering can be done by means of high-capacity earthed capacitors. Each earthing connection or negative pole is represented by the metal panel, if any, or more generally by the other central output branch of the antenna. According to the variant in figures 12b and 12c, an Archimedean antenna of known type is connected inside each rhombus or loop to give the antenna in question characteristics more of the broadband type - not in the form of a spiralling circle, however, but in a rectangular shape, as shown in the detail in figure12d, to reduce the surface cavities. The connection of the ends of each Archimedean antenna inside each loop is not binding and can preferably be completed between two opposite vertices of a rhombus. Fig. 12e shows another variant for achieving an electrical energy generator using nanotechnology according to the present invention wherein, in order to pick up a larger number of photons, solid and hollow rhombi are juxtaposed alternately, starting from the solid central connecting rhombi whose vertices define said terminals equivalent to those in figure 3a, towards the periphery. Physically, a smaller surface area is available for picking up the photons, i.e. approximately half the one in figure12b, but it is substantially more straightforward to produce. Another nanometric implementation, shown in figure 12f, involves the same application in the photovoltaic field of an antenna defined by circular loops, such as the one shown in figure 11 , but - given the corpuscular behaviour of photons - they must necessarily be solid. Its particular feature lies in that it receives energy with a rightward or leftward circular polarisation in much the same way as the vortex polarisation with which photons are propagated.

In the examples in figures 12b,12e and 12f, there may also be a reflector element to the rear to retrieve the photons that pass through the hollow interspaces, i.e. the more limited lumen that is created in the rear part obtained by diffusion.

Advantageously, the antennas in figs. 12b, 12e and 12f, sized so as to function as energy absorbers or converters, offer such a very high efficiency and high angle of absorption that no solar tracking systems are necessary. These antennas can be made using known nanotechnological processes. It is also possible to implement other variants of energy converters/generators, not shown in the figures, for instance by also inserting Archimedean antennas inside each of the circular loops shown in fig. 11a. There may be several layers defining an antenna according to the present invention, and characterised by a different tuning to cover different frequency bands, or there may be identical structures in different planes, possibly of the same size but with complementary solid rhombi so that a second structure picks up the photons passing through the hollow rhombi of a first structure. Such uses do not rule out a promiscuous use of an antenna according to the present invention, of a converter of radio waves and of a photovoltaic solar panel, based on silicon, for instance.

The elements and characteristics illustrated in the various preferred embodiments can be combined without departing from the scope of the invention protected by this application.

Claims

1. A Quad antenna comprising a plurality of coplanar loops of a length corresponding to a preset tuning wavelength (λ), characterised in that at least one first loop (11)(12) is juxtaposed with at least one second loop (12)(11) in a first direction, and at least one third loop (13)(14) is juxtaposed with said second loop in a second direction perpendicular to said first direction, so that said first and second directions of juxtapositions intersect each other at the gravity center of said second loop.

2. An antenna according to claim 1 , wherein said plurality of loops forms a chequerboard pattern.

3. An antenna according to one of the previous claims, wherein each juxtaposed loop may comprise the galvanic separation of the loops or the short-circuiting of all, or only a portion of the sides defining the loops.

4. An antenna according to one of the previous claims, wherein the juxtaposition of two loops in which only one portion of each of the conductors are galvanically connected to the other, involves a crossing of a conductor (100) that defines the antenna.

5. An antenna according to the previous claims, wherein said loops (11)(12)(13)(14) may be in the form of open or closed rhombi or circles.

6. An antenna according to claim 5, wherein - when said loop is in the shape of a rhombus - the length of each of its sides corresponds to a quarter of the tuning wavelength of the rhombus.

7. An antenna according to claim 6, comprising a first portion and a second portion, mutually symmetrical with respect to a first axis (β) and connected mutually at two points (22,23) defined by a corresponding number of vertices of two rhombi; said first portion comprises a first terminal (20) and said second portion comprises a second terminal (21); said terminals are suitable for connecting to a signal generator/receiver.

8. An antenna according to one of the previous claims, comprising at least one screening element (24')(28'), comprising a metallic surface inscribed in one of said plurality of loops (11')(16') and connected to ground to prevent the loop from functioning.

9. An antenna according to one of the previous claims, wherein the current circulation in two adjacent loops is prevented by providing a jumper or a crossing of said conductor (100) at the point where they are juxtaposed.

10. An antenna according to one of the previous claims, further comprising at least one straight element (2) of conductor material (100), connected galvanically to a point on the perimeter of a peripheral loop, said straight element (2) being of a length at least equating to or greater than a quarter of the tuning wavelength of the loop; said element extending along the surface defined by the antenna and towards the outer edge thereof.

11. An antenna according to the claims 1 or 2 or 5 or 6 or 7 or 8 or 9 or 10, wherein said loops are defined by said conductor (100) connecting said terminals

(20, 21) without the conductor crossing over itself.

12. An antenna according to claims from 1 to 10, wherein, at each point where two loops are juxtaposed, all the juxtaposed sides defining the two loops are short-circuited.

13. A method for converting an electromagnetic wave into electrical energy comprising the use of a Quad antenna according to any of the previous claims.

14. A method according to claim 13, wherein each at said loops defining the antenna can be alternately filled or an Archimedean antenna can be inscribed therein.

15. A method according to claims 13 or 14, wherein filter elements are associated with each antenna to obtain a rectified electrical energy.