US2197124A - Oscillator with amplifier coupling - Google Patents

Description

April 16, 1940.

J. w. CONKLIN OSCILLATOR WITH AMPLIFIER COUPLING Filed April 30, 1937 OSC/LLWTOH HMP.

12 Zmnentor James W Conlil in (Ittorneg LINE ' I1, the cathodes being connected to the grounded Patented Apr. 16, 1940 James W. Conklin, Audubon, N. J., assignor to Radio Corporation of- America, a corporation of Delaware Application April 30, 1937, Serial No. 139,839

3 Claims.

This invention relates to radio transmitting and receiving systems which involve the use of a resonant concentric circuit for controlling the operating frequency of an oscillation generator, and hasfor its, principal object the provision of an improved arrangement and method of operation whereby the generator frequency is rendered independent of variations or adjustments in the amplifiers to which the generator is coupled. More particularly, the invention involves the use of a resonant concentric circuit for the-dual purpose of stabilizing the generator frequency and coupling the generatorto the amplifier into which it feeds. Prior to the present invention, it was customary to couple the concentric circuit or line to the oscillator input circuit and to provide the oscillator output with a tank circuit through which the oscillator was coupled to the amplifier. The present invention is based on the discovery that utilization of the concentric line in the'oscillator output as'a means of stabilizing the oscillator frequency and coupling the oscillator to, the amplifier has the advantages of (1) improving the frequency stability for a given line, (2) permitting the oscillator controls to be fixed so that there are no operating controls having an im.- portant'efiect on frequency, (3) ermitting greater flexibility in design due to the fact that the oscillator tube is not required to perform a dual function, and (4)- generally'improving the performance of the system. v I

The invention will be better understood from the following description when considered in connection with the accompanying drawing, and its scopeis indicated by the appended claims. Referring to the drawing, a Figure 1 is 'a wiring diagram of the "conventional combined oscillator and amplifier circuit heretofore utilized,

Figure 2, is a wiring diagram of the'improved oscillator-amplifier system as applied'to a generator of the negative transconductance type, and

Figures 3 and .4 are similar diagrams of modified embodiments of the invention.

The well known system of Fig. 1 includes a cross-neutralized oscillator H], which is provided with an input circuit including concentric con ductors l l and i2 between which is interposed an input winding l3, and with an output circuit including a tank circuit composed of aparallel connected capacitor l4 and winding 15'. Suitable potentials are applied to the oscillator input and output circuits,respectively, through leads l6 and side of'the powersupply line. ln the oscillator devices. power ultra-high frequency oscillators of the resthe neutralizing condensers are used for regeneration control..

Coupled to the winding l5, through coupling capacitors l8 and I9, is a cross-neutralized tuned push-pull amplifier 20 which is provided 'with an I.

output winding 2!.

The primary function of the oscillator tank circuit formed by capacitor l4 and inductor I5 is toprovide a storage circuit of oscillatory power at the operating frequency for supplying the load requirements, the driving power for the succeeding amplifier in the present illustration. 'A secondary function of the tank circuit isto provide a plate circuit impedance incidental to the operaculating energy in the oscillator tank circuit be large compared to the load supplied, in order that the load variations shall not greatly affect'the' 1 frequency and/or .the oscillation stability of-th e, oscillatorm It. is well known to the art that in oscillator circuits employing frequency stabilizing or con.-

'trol means of the low power factor type, such as a piezo-electric crystal or a concentric resonant line, it is desirable that the circulating or stored energy be confined primarily to: the stabilizing In -the prior art, particularly" in high onant line controlled type, it has been necessary, for reasons explained the foregoing description', to have considerable circulating energy in the oscillator tank circuit, represented by, ele- 1 r at) ments l4 and I5 of Fig. 1, which result s'in an undesired division of the primary frequency determination between line II and tank circuit l4 and I5. To confine the primary oscillator frequency control to line I l, the tank circuit hi and I5 Would preferably have low energy storage'and be of the broadlytuning type. 1 I v As indicated above, this system leaves some thing to be desired in that operationof the generator l 0 is not altogether independent of changes in the operating conditions or adjustments of the amplifier 20. Thepresent invention avoids this difliculty by transferring the concentric line Il-I2 vtothe oscillator output circuit, where it functions both as the oscillator tankcircuit and as a coupling between theoscillator output and amplifier input circuits.

In the priorart practice, it has been considered of prime importance to minimizetheloadcoupled to the control line, in order to obtain a high Q circuit with maximum. frequency stability, and the method of my invention would have been considered improper, asit couples several devices, including the load'circuit, to the control line.

To prove the merit'of my invention, let E1 and E2 represent the total circulating energy present in the control line H--l2 and the oscillator tank circuit |4l5, respectively, referring to Fig. 1. Also let W1 and W2 rep-resent the coupled load to these respective circuits, W1 representing the oscillator grid losses and line losses, and W2 representing the output load or amplifier. grid excitation power. Now it is a fact that the virtue of the line in controlling frequency is in one sense Now in the case of a high power ultra-high fre- "quency oscillator, where the oscillator and ampliher will likely be similar, W2 will probably'equal W1 and E2 will necessarily be of the same order as E1; therefore,

and

will be of the same order. Thus, we have two low power factor circuits associated with the oscillator, both capable of having a primary effect on cases of the same order of magnitude respectively.

Therefore, the power factor of the co'ntrol circuit will be of the same order as fier 23 and which may be provided with relatively adjustable plates 24 and 25 for adjustingitsca- 'pacity. The oscillator 22 is of the negativetransconductance type which is characterized bythe tuning type.

factthat its output current varies inversely as the input voltages. It includes an inner grid 26 which functions as a suppressor grid, a second grid 27 which is subjected to a potential higher than that of the plate and functions as an anode,

and an outer grid 28 which functions as the control grid of the oscillator. .It will be noted that a resistor 29 is provided for reducing the plate voltage and limiting the plate current, that choke coils 3i! and 3| are provided in the input and output circuits, that a resistor 32 is inter-U a capacitor 35 or altogether by the interelectrode capacity of the oscillator tube which may be of the RCA-954 type.

Whensuch a pentode tube is used as a negative-transconductance tube, the grid 26 isoperated at zero or slightly negative potential, the grid 21 at high positive potential, the grid 28 at negative potential, and the-plate at low positive potential. Under these conditions, the grids! functions as the primary anode, but, it being a mesh structure, part of the electrons pass through and are attracted to the slightly positive plate. If the interposed grid 28 be given a suiiicientiy negative charge to overcome the velocity of the electrons, they will return to the screen grid, re-

Considering the grid 2? as the anode and the grid 28 sulting in an increased screen current.

as the control electrode, the resulting transcon- Coupling between the input. and output circuits may be effected in part by ductance is negative, 1. e., within the range of operation, the anode current decreases when the control electrode is made more positive. Utilized grid 27 through the capacitor 35.

It will be observed that the negative-transconductance action consists'largely of an interchange of current between the plate and the grid 21. This interchange is not complete, however, as part of the returning electrons again made more negative. Further, while the control grid 26 plays no part in the normal action, it.

may be used to control the spacecurrentpwith a resulting great effect on the negative resistance and amplitude of oscillations produced by the tube.

The oscillator output potential is applied to the concentric circuit Hl2, which is tuned to the sions or by adjustment of the plates 2 i,25 and which also functions to couple the oscillator output circuit to the input circuit of the amplifier 23, with the advantages previously discussed.

The system of Fig. 3 differs from thatofFig. 2 in that it includes a cross-neutralized oscillator 35 of the push-pull triode ,type,-provided with an output winding 3% interposed in the oscillator grid circuits and located between the concentric conductors H and [2. The oscillator tank circuit M--i5 is of the low-energy storage, broadly Coupling between the oscillator 35 and the'amplifier 2D is effected by means of an amplifier input winding which is immersed in the field induced between the conductors II and l2 by the. current of the oscillator-output coil 36. The system of Fig. .4 differs from that of Fig. 3-

later is connected. between the concentric con in that the output circuit of asingle tube 05011,

.ductors II and I2 and coupling between the oscil- I lator input and output circuits is effected by means of a capacitor 39 and a. coil located between the conductors II and I2.

It will, of course, be apparent that theinvenamplifier tuned to the frequency of said oscillations, and means coupling said amplifier directly to said line so that the concentration of circulat ing energy in said stabilizer provides energyto drive said amplifier and to'control the frequency of said oscillations in the presence of changes in the load presented by said amplifier to said oscillator.

2. In a stabilized oscillator-amplifier, a concentric line resonator, a thermionic discharge and reduces the effect of changes in tube, means coupling said discharge tube and said line so that sustained oscillations are produced Whose frequency is maintained at a predetermined valuecorresponding to the resonant frequency of said line, a load device comprising a radio frequency amplifier tuned to the frequency of said oscillations, means directly coupling said load device to said concentric line resonator so that the concentration of circulating currents in said resonator provides frequency stabilization said load on said oscillations.

3. In a stabilized oscillator-amplifier, a thermionic tube having grid cathode and anode electrodes, a resonant line stabilizer, means coupling said stabilizer to said grid electrode, means ineluding said tube and stabilizer for generating ultra high frequency oscillations whose frequency is determined by said stabilizer, an amplifier tuned to said high frequency oscillations provided with input and output circuits, and means coupling said amplifier input circuits directly to said stabilizer for impressing oscillations on said amplifier.

JAMES w. com.

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