US2106821A - Piezoelectric crystal controlled oscillator circuits - Google Patents

Description

H. TUNlcK PIEZiOELECTRIC CRYSTAL CONTROLLED OSCILLATOR CIRCUITS oniginal Filed Feb. 6, 1932 v l Eg j INVENTOR HARRY TuNlcK Bfr/5 ATTORNEY patentedv F eb. 1, 1938 UNITED STATES PIEZOELECTRIC CRYSTAL CONTROLLED' OSCILLATOR. CIRCUITS Harry Tuniek, Rye, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Original application February 6, 19.32, Serial No.

L' 591,365. Patent No. 2,044,137, dated June 16, f 1936. Divided and this application October 19, 1933, Serial No. 694,229. In Great Britain February 6, 1933A 4 Claims.

My present invention is a division of my copending application, Serial Number 591,365, filed February 6, 1932, Patent No. 2,044,137, granted June 16, 1936. .g5 Piezo-electric crystal controlled oscillation generators are usually coupled to some load circuit as a result of which variations in load, reacting back upon the crystal controlled oscillator, cause undesired variations in frequency. The .l0 principal object of my present invention is to provide crystal controlled multi-electrode tube oscillator circuits wherein the crystal is loaded lightly and wherein variations in load cannot cause appreciable reaction, with the concomitant 1l-,5 evil of frequency drift, upon the crystal. In fulfilling this object, I associate the crystal with an electron discharge device such that certain elec- `trodes within the device together with the crystal, form a complete oscillating circuit. Then, I couple another electrode to the oscillating system, this coupling taking place only through the electron stream within the electron discharge device. 'I'his coupling is of such a nature that despite variations in load, there is very little effect or reaction upon the crystal whereby the system oscillates at a frequency widely independent of load variations and of a constancy heretofore unobtainable with known systems.

A further object of my present invention is to provide a symmetrical, balanced, or pushpull oscillator `arrangement utilizing the features outlined above.

Turning to the accompanying drawing, which are given solely by way of illustration and in no way are limitative of my present invention,

Figures 1, la, 2 and 3 are preferred embodiments of my present invention.

In Figure 1 I have shown the crystal 2 connected between the control grids 4 of a pair of 40 electron discharge device oscillatorsvI, 3. Grid bias is accomplished by means of resistors I6 which, however, may be replaced by other biasing means. The oscillatory system of Figure l is formed by the screen grid 8, control grids 4,

cathodes 6 and crystal 2." The anodes I0 are coupled through the electron streams within the tubes to the oscillatory system. Also, in Figure 1 impedances, preferably in the form of tunable circuits I2, I4, are connected between the screen grids and anodes respectively. To prevent spurious oscillation generation due to, for example, the inherent capacity between the crystal electrodes, neutralizing condensers 46, 48 are provided. These are suitably adjusted so that with- 55 out the crystal in circuit the system fails to oscillate. However, it will be found that when the crystal is placed into circuit the circuit will go into oscillation at a frequency corresponding to that of a natural frequency of the crystal.

Circuit I4 is 1tuned to the fundamental fre- `5 quency of the crystal, or, should odd harmonics be desired it should be tuned to some odd harmonic of the crystal 2 because of its pushpull relation with respect to the anodes of the devices. Should it be desired to obtain even harmonics the anodes l() Ill as shown in Figure la should be connected in parallel and the tunable circuit I4 connected in series with the parallel connection, the circuit ifi being tuned to some even harmonic. Thus, as indicated, either odd harmonic or even har- .15 monic energy may be built up in the output circuit I4 which, of course, is only coupled by virtue of the electron streams within the tubes to the crystal oscillating system.

As shown in Figure 2 the tuned circuit I2 20 and crystal 2 may be reversed in position, the circuit I2 being preferably tuned to a natural oscillating frequency. The circuit I2 as shown in Figure 2, may of course be replaced vby a resistance or inductance. The crystal 2 is shunted 25 in the arrangement shown in Figure 2 by a resistor 5U allowing polarizing potentials to pass unidirectionally to the screen grids of the electron discharge devices I, 3. By way of example, the output circuit I4 is coupled inductively to the 30 input of `a frequency multiplier modulator cir-t cuit diagrammatically indicated at 52 supplied with modulating potentials from a suitable source 54. Modulated output from the arrangement 52 is fed to some power amplifying device indicated 35 at 56 and in turn transmitted either by wire line or Vpreferably-througll the air by electromagnetic waves by the action of antenna 58.

Another pushpull modification is illustrated in Figure 3 wherein the crystal 2 is provided with 40 two pairs of electrodes 60, 62. These electrodes are connected to the control grids 4 and screen grids 8 as indicated, of electron discharge devices I, 3. To prevent capacitive coupling betweenv the leads to the crystal electrodes, shielding 64 45 grounded at point 'Ill or several points is provided. Polarizing potential is applied to the screen grids through shunting resistor 14, and, biasing potential is applied to the control grids to the shunting choke 76. In this arrangement, the screen grids act as plates in the crystal controlled oscillating system, and the plates or anodes I0 of the electron discharge devices I, 3 are coupled to the frequency control oscillating system formed by the crystal, screen grids, cathodes and control grids only by "fio virtue of the electron streams Within the tubes.

Oscillations are set up by virtue of the fact that variations in screen grid voltages at a natural frequency of the crystal are fed to the crystal 2 which in turn generates voltages which are applied to the electrodes 62 in such phase that the electron streams are varied to cause continuous oscillation generation at a very constant frequency.

Various modifications of my present invention may of course be made as will be apparent from even a. casual reading of the specification. Accordingly, I do not intend to be limited by the exact modifications illustrated and described, -but my invention should be given the full scope indicated by the breadth of the appended claims.

Having thus described my invention, what I claim is: A

1. An oscillation generator comprising a pair of electron dischargel devices each having an anode, a cathode, ay control grid radjacent the cathode, and a screen grid adjacent the anode, a piezo-electric crystal having only two electrodes connected to like grids of said devices, said crystal electrodes being-y electrically isolated from said anodes, a resonant circuit having inductance and capacity connected between other like gridsv of said devices whereby oscillations corresponding to a predetermined frequency of said crystal are s'et up between said cathodes, crystal and grids, means including a circuit having inductance and capacity connected between the anodes of said devices, the electrical constants of the last said circuit being such as to render said circuit resonant at an even harmonic frequency with respect to the vibrational frequency of said crystal and means including a source of direct current potential applied negatively to said cathode and positively to said anodes for sustaining useful oscillations in said discharge devices at said harmonically related frequency, the oscillations being produced by virtue of electron coupling of said anodes to said grids and cathodes.

2. In an oscillation generator, a push-pull network comprising two electron discharge tubes, each tube having a cathode, an anode and at least two intermediate electrodes, including a control grid and a. screen grid, a piezo-electricV device having at most two electrodes and circuit connections therefrom to said control grids, a. resonant vcircuit tuned to a natural frequency of said piezo-electric device and symmetrically disposed in conductive association with said screen grids, a resonant output circuit tuned to an even harmonic of the vibrational frequency of said piezoelectric device and symmetrically connectedto tron discharge tubes and a piezo-electric device having at most two electrodes and circuit connections therefrom to similarly disposed electrodes in said tubes, the method of deriving oscillatory energyfin a utilization .circuit connected thereto, which comprises the steps of resonating said push-pull network at a natural frequency of said Apiezo-electric device, neutralizing the interlelectrode capacitive feed-back of energy in said tubes by mutual interchange of electrostatic charges externally of said1tubes,'and as between unlike electrodes ,-of Asaid tubes, causing pulsations of electronic flow to take place contraphasally in one of said tubes with respect to the other, resonating said utilization vcircuit at an even harmonic of the natural frequency of said piezo-electric device, and utilizingr said pulsations as the sole and entire control of the output energy in said utilization circuit;

4. An oscillation' generator having two electron discharge tubes, each tube having acathode, an anode, a control grid and at least one grid intervening between the control grid and the anode, a piezo-electric device having twov electrodes at most, said electrodes being connected respectively to corresponding grids of the respective tubes, a. resonant circuit interconnecting two other corresponding gridsof the rrespective tubes, another resonant circuit having parallel-connected capacitive and inductive elements interconnecting the anodes, a source of direct current anode potential connected between a mid-tap onwrtheinductive element of the last Y said resonant` circuit and ground, said'cathodes being grounded, 'an adjustable capacitor fconnectedfrom the control,

grid of a first tube to a. different grid of--a lsecond tube, another adjustable capacitor connected between the control `grid of saidl second tube and a different'grid of said first tube, a 'grid'leak resistor connected between ther control grid rand thecath- `ode of each-tube, and means for so adjusting the sok

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