US2675477A - Modulator for pulse transmitters - Google Patents

Description

April 13, 1954 2,675,477

$- TESZNER MODULATOR FOR PULSE TRANSMITTERS Filed Jan. 21, 1948 2 Sheets-Sheet l LOAD VOLTAGE F 2 Av TIM 7 LOAD PuLsEo 0s144r04 Fig. 4

vaL TAbE coma/r INVENTOR 5'f'anLs/as Teszner April 13, 1954 s. TESZNER 2,675,477

MODULATOR FOR PULSE TRANSMITTERS Filed Jan. 21, 1948 '2 Sheets-Sheet 2 Fig.6 Fig. 7

- VUL TAGE CUR/Pf/VT T/ME Fig. 8

o w P I2\ I i BRANULAR 1 L i 7 .s'EMI- aollm'rms Y k BODY g g 4 L J H. F'-

Pmasea Oscn-AAmR Fly. 9 I Fig, 10 v01 T465 TIME CURRENT IN V E N T0 R STanLslas Tszner Affofnej Patented Apr. 13, 1954 UNITED STATES PATENT OFFICE Claims priority, application France January 27-, 1947 10 Claims. 1

My invention relates to new devices for the producing of high-voltage electric pulses of substantially rectangular wave-shape, having a steep wave-front.

To achieve the desired result, the invention takes advantage of the special properties of granular semi-conducting bodies and, more particularly, of that particular one of the properties which is sometimes called electric hysteresis, but is better designated electric residual effect.

It is a known fact that for various applications of modulators and more particularly for the feeding of magnetrons, it is of interest to produce pips assuming a shape that is as near as possible a rectangular shape. My invention has for its object improvements in modulators allowing the production of such a shape in a very simple and advantageous manner, its principle being applicable if desired to the production of pips of other predetermined shapes.

The. invention is based on the application to this purpose ofv compound systems of electronic semi-conductors and more particularly on a suitable application in view of the object sought for of the hysteresis of the material used for such e elements. It should be remembered that compound electronic semi-conductors are constituted by semi-conductive grains such for instance'as silicon carbide, commercially available as Carborundum that are generally agglomerated by means of an auxiliary component such as clay, the resultant material being baked in such a case at high temperature. Such compound material is characterized inter alia by a more or less considerable variation of its conductivity as a function of the voltage applied to the terminals. This variation occurs with a certain lag with reference to voltage variation and said lag is obviously all the more important when, under conditions remaining otherwise similar, said variation is to be more rapid; these hysteresis phenomena appear both for the rising part and the sinking part of the voltage curve- Now, in the applications generally known of such compound electronic semi-conductors, it has .empted through a suitable structure or application of the material, to reduce as much as possible the hysteresis effect that has been considered heretofore as always prejudicial.

The chief feature of my invention consists on the contrary in making use of the hysteresis phenomenon in order to produce the desired shape of pip.

The features and advantages of my invention will appear more readily in the reading of the 2 following description with reference to accompanying drawings that show by way of mere exemplification diagrams for the construction of the modulator; of the following figures.

Fig. l is a wiring diagram of a modulator of a recent known type.

Fig. 2 shows the usual shape of the pip provided by such a modulator.

Fig. 3 is the diagram of a modulator according to this invention with a compound electronic semi-conductors inserted in series in the circuit.

Figs. 4, 6 and 10 show the volt-ampere curves of the compound of electronic conductors.

Figs. 5, 7 and 9 show diiierent shapes of the pips that can be obtained.

Fig. 8 is a diagram of a modulator according to invention with a compound electronic semiconductor inserted in parallel in the circuit as a modification of Fig. 3.

The known modulator, the diagram of which appears in Fig. 1, is particularly suitable for the feeding of high power magnetrons.

Its chief components are constituted by the network I surrounded by a chain line in the drawing. Said network includes condensers 2 and induction coils 3, and cooperates with the transformer l and the spark gap 5 which as here shown may be constituted by a three electrode spark gap. An induction coil 6 adapted to limit the intensity of the current which is fed by the source of energy T to the spark gap and is tuned for resonance with the equivalent capacity of the network I and the induction coil of the transformer 4 to the frequency of said source 1 feeding the modulator.

When the capacity of the network, I is loaded, the spark-gap 5 is caused to strike or else it strikes automatically and the discharge of the network I through the spark gap produces across the terminals of the transformer a pip that is very near in shape the rectangular shape as illustrated in Fig. 2. As the transformer is designedina manner such as to transform with an excellent yield even pips having a very steep front, it raises the voltage of said pips to the value required for feeding the magnetrons.

Said modulator that is remarkable through its simplicity shows a considerable improvement with reference to the older modulators including thermo-ionic tubes. However, it shows certain drawbacks, and inparticular the network 1 generating the pulses forms a comparatively intricate system and further more the peak or crest of. the pip that is generated thereby is detrimentally affected by parasitic oscillations. Now

as will be shown hereinafter the application of a compound electronic semi-conductor allows removing such drawbacks.

Such an application may be effected according to two typical embodiments corresponding to series and to parallel connections.

Fig. 3 is a diagram of a modulator incorporating a semi-conductor in series connections. It includes as in the case of Fig. 1 a source 1 and a transformer of pips 4 termed the second inductive impedance hereinafter but instead of the other parts, there is provided a system including an impedance 8 termed the first inductive impedance hereinafter and a simple capacity 5 tuned for resonance to the frequency of the source and a system including a spark gap In and an electronic semi-conductor ll inserted in series. The semi-conductor I I may also be located on the other side of the transformer 4 and the latter may in fact be omitted.

The operation of such a modulator is easy to understand. When the capacity 9 is loaded, the spark gap ID is caused to strike, said spark gap being if required incorporated in the semi-conductors, and the pip is modulated to the desired shape by means of the compound semi-conductor ll.

However, if the latter shows the features that are generally sought for and corresponding to a volt-ampere curve of the type shown in Fig. 4, the shape of the pip obtained at the terminals of the transformer 4 will approximate rather a triangular shape (Fig. 5) than the desired rectangular shape. On the contrary, a rectangular shape will be obtained if the hysteresis of the semi-conductor is increased both for the rising and sinking parts of the volt-ampere curve as in the case illustrated in Fig. 6, for which the arrows show the direction of variation of the voltage. In this case, the modulated pip is shown correspondingly by Fig. '7. The increase of the hysteresis phenomenon that depends obviously in the first place on the suitable constitution of the compound electronic semi-conductors, will be made easier by reason of the sudden application of voltage to the terminals through the striking of the spark gap. It should be mentioned furthermore that the hysteresis phenomenon provides in the present case a supplementary parameter in addition to the circuit constants, which allows an adjustment of the breadth of the pip.

Fig. 8 shows a modification according to wh ch the modulating diagram includes a compound semi-conductor connected in parallel with the transformer. It includes the same elements as the diagram illustrated in Fig. 3, except for the fact that the compound semi-conductors I 2 show different features both from the standpoint of specific resistance as of hysteresis when compared to the compound semi-conductor ll of Fig. 3. It should be noticed furthermore that the compound semi-conductor l2 may be located as well ahead of or beyond the transformer, which latter may also be omitted if required. In the present case also, the features generally required for compound semi-conductors are hardly suitable and the difference between the shape of the pip obtained in the case of Fig. 9 and the shape desired for said pip as shown in Fig. 7 is much more marked than in the case of the above disclosed series connection.

Consequently, in order to obtain the desired shape of pip it is necessary to increase still further the hysteresis in a manner corresponding to the volt-ampere curve in Fig. 10. The supp mentary parameter provided by the possibility of controlling the value of hysteresis in the preceding case would no longer exist in this case and moreover the energy performance would be less. However in this last case the use of electronic semi-conductors applied according to the teachings of my invention affords a solution of the problem.

Lastly. it should be well understood that, generally speaking, the application of compound of electronic semi-conductors is by no means limited to cooperation with spark gap modulators and the execution of the diagrams may also vary within wide limits, for instance the feed may be provided by means of a direct current supply; furthermore my invention is applicable to all kinds of modulators in particular to those incorporatin thermo-ionic tubes. The diagrams disclosed are provided solely by way of example and any other form'of execution of the modulator associated with a compound arrangement of electronic semi-conductors and resorting to the hysteresis of said element for obtaining a modulator pip of a predetermined shape falls within the scope of the present invention as defined in accompanying claims.

What I claim is:

1. A modulator for generating high-voltage pulses of substantially rectangular wave-shape for a pulse transmitter, comprising a high-voltage electric source, a first inductive impedance in series connection with said source, a condenser r having two terminals, said terminals being respectively connected to the terminals of the series assembly formed by said source and said first inductive impedance, and a circuit connected across the terminals of said condenser, said circuit comprising a series-connected spark gap and second inductive impedance and having a granular semi-conducting body made of grains of silicon carbide agglomerated with an insulating material operatively connected to said second inductive impedance, and means for applying to a load circuit voltage derived from said second inductive impedance.

2. A modulator as claimed in claim 1, wherein said granular semi-conducting body and said second inductive impedance are both connected in series with said spark-gap.

3. A modulator as claimed in claim 1, wherein said granular semi-conducting body is connected in parallel with said second inductive impedance, the assembly of said semi-conductin body and second inductive impedance being connected in series with said spark-gap.

4. A modulator as claimed in claim 1, wherein the means for applying the voltage developed across said second inductive impedance to said load circuit consists of a transformer having at least two windings one of which constitutes said second inductive impedance.

5. A modulator as claimed in claim 1, the load circuit of which is constituted by a high-frequency pulsed oscillator.

6. A modulator for generating high-voltage pulses of substantially rectangular wave shape for a pulse transmitter, comprising a high-voltage electric source, a firstinductive impedance in series connection with said source, a condenser having two terminals, said terminals bein respectively connected to the terminals of the series assembly formed by said source and said first inductive impedance, and a circuit connected across the terminals of said condenser, said circuit comprising a series-connected spark gap and second inductive impedance and having a body operatively connected comprising a composition of matterf'having a volt-ampere characteristic, a part of the shape of which is a substantially rectangular loop, said composition being granular and containing a semi-conductor and an agglomerating insulating substance, and means for applying; to a load circuit voltage derived from said second inductive impedance.

7. A'modulator as claimed in claim 6, wherein said bod; and said second inductive impedance are both'flconnected in series with said spark-gap.

8. A modulator as claimed in claim 6, wherein said body is connected in parallel with said second inductive impedance, the assembly of said semi-conducting body and said second inductive impedance being connected in series with said spark-gap.

9. A modulator as claimed in claim 6, wherein the means for applying the voltage developed across said second inductive-impedance to said load circuit consists of a transformer having at least two windings one of which constitutes said second inductive impedance.

10. A modulator as claimed in claim 6, the load circuit of which is constituted by a high frequency pulsed oscillator.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,246,626 McCaa Nov. 13, 1917 1,822,742 McEachron Sept. 8, 1931 2,000,719 Siepian et al. May 7, 1935 2,181,568 Kotowski et al. Nov. 28, 1939 2,206,792 Stalhane July 2, 1940 2,369,030 Edwards Feb. 6, 1945 2,462,918 Stiefel Mar. 1, 1949 2,484,209 Dufiy Oct. 11, 1949 2,487,279 Stalhane Nov. 8, 1949 2,546,952 Spencer Mar. 27, 1951

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