US2350171A

US2350171A - Reactance controlled generator

Info

Publication number: US2350171A
Application number: US447696A
Authority: US
Inventors: Howard C Lawrence
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1942-06-19
Filing date: 1942-06-19
Publication date: 1944-05-30
Anticipated expiration: 1961-05-30
Also published as: GB567585A

Description

y 1944. H. c. LAWRENCE I 35 5 REACTANCE CONTROLLED GENERATOR File d June 19, 1942 PEncrn E Coureol. FOTENT/fll.

flue o Maoazanow V01. 7065 INVENTOR A I'i'ORNEY Patented May 30, 1944 ."UNITED STATES PATENT OFFlCE REAOTANCE CONTROLLED GENERATOR 7 Howard C. Lawrence, Haddon Heights, N. 1., as-

signor to Radio poration of Delaware Application June 19, 1942, Serial No. 447,696

8 Claims.

v system involves. the useof a reactance tube connected across the oscillator tank circuit. The -u;ual reactance. -tube and oscillator circuit requires the useof two tubes. Compact design such as is necessary in mobile equipmentmakes it desirable to use a single tube for this Purpose. jjI n this application I. disclose anew and improved ,reactance tube and controlled oscillator includa ing a singletube.

. j'This. oscillation generator may also be used. as the generator and modulator in a wave length modulation system, in which case the variable ,jrea'ctance' efiect produced in the generator tube is'controlled by signals to correspondingly con trol thelength of the oscillations generated.

Corporation of America, a corradio frequency output voltage at the plate of the tube when the frequency control R4 is set at the maximum direct current voltage position. Too large a load resistor will cause lowoutput voltage because of the low direct current plate voltage present at th tube, while too small a resistor will cause low output voltage because of v the lowradio frequency impedance of the plate load. A tuned circuit or radio frequency choke may be substituted for this load although this will change the amount of frequency shift obtainable and introduce the possibility oscillation if the circuits are justed.

C3 is of such a value that a maximum reactive of ,a new mode of not properly adcomponent of the plate voltage is fed backto the resonant circuit l2. It should be made small to obtain maximum phase shift and yet large to obtain minimum attenuation. The optimum I In describing my invention reference will be made to the attached drawing wherein:

Figure '1 illustrate "by circuit diagram a con trolled oscillationgeneratorarranged in accordance with myinventi'om" Figure 2 is a vector diagram used to illustrate "the" operation of my'controlled generator; while Figures 3 and '4 are modifications of the arrangementof Flgurel. 1

Thecircuit shown in Figure l is an oscillator and reac'tance 'tubecontrol system using a single pentode tube; The frequency'range of the oscillator can be made controllable over a range of at least 2% direct current Of this tube.

by means of a variation in the potential applied to one element The absence of any radio frequency *voltagbn the controlled circuit makes it possible to use unshielded wires the control'leads. p 7

The; cathode" 4, grid 6 and screen grid"8 of tubejV are connected as a conventional triode groun'ded plate Hartley "oscillator having a tank H circuit'll l. The screen is bypassed to ground for radio frequency and direct current voltage applied through resistor R2 to give the proper within 'a power cable for screen voltage. Resistor R3 in the plate circuit of 'V is chosen to given the maximum a ailable phase with that across the conditions are most easily obtained from the vector diagrams, Figure 2. The plate voltage is vrepresented by the vector ER3 at zero degrees phase angle. The voltage drop,.Ec, across C3, and the voltage drop EL across the resonant circuit must add up to EH3. At resonance the parallel circuit Ll Cl appears as a resistance of magnitude QwLl or The voltage across LI Cl is therefore outof feedback capacitor C3. The reactive component of Ec has as its locus a semi-circle the diameter of which is ERS. It is evident that the maximum reactive com ponent of voltage is obtained whenEL=Ec and the maximum amplitude is one-half ERS. Then:

where Q is that of the resonant circuit Ll Cl. When-these conditions exist, a voltage is fed back from the plate of V to the resonant circuit 45 out of phase with that normally appearing at the grid 'of V. The plate circuit of the tube therefore appears to the resonant circuit as a capacity. The magnitude of this capacity depends upon the radio frequency voltage available across R3. This available radio frequency voltage is controlled by the plate voltage applied to the tube by noasses-m. The dotted lines in Figure 2 ply. 'Three different circuit gave a controllable frequency range of that this will vary tube. since this Gm determines the show conditions when the capacity C3 is of too small value.

assarri An adjustment of the potential on the anode It I of tube V! changes the magnitude of the complex impedance (which here is capacitive in character) applied by C3 across the resonant circuit Ll Cl. This variable reactance is part of the resonant circuit Ll Cl and determines in part the frequency of. the-generated, oscillations. The change in potential on the plate 'll' of'the tube may correspond to automatic frequency control potentials or to signals or other control potentials applied to the leads across condenser C in Fig e l marked "Control potentials" or to the transformer Tl of Figure 3. C5 isthen'small enough not to bypass the control or modulation potentials.

In Figure 3, as in Figure-,1, "LI and CI is thecircuit resonant at the oscillator frequency. Rl supplies proper bias to the grid. Condenser C2 Condenser C3 pro- C3 equals g;

where is that of the resonant circhitjLl-Cl.

R3 is the plate voltage supply resistance and also the radio frequency load. The transformer Tl secondary is bypassed for radio frequency by condenser C5. The potential on the screen electrode I is usually higher than that on the plate It.

. I have shown in Figure 4 a balanced oscillator using the principle used in Figures 1 and 3. In Figure 4 the various elements have been designated by the sar'nej numerals used in Figures 1 and 3. q

' Ll and Cl are of such values that they produce the desired oscillation frequency; Rl, B1, C2 and C2 provide proper grid bias and radio frequency bypass action respectively. Cl and C5 are radio frequency bypasses on the direct current voltage sources. R3 and R3 are load elements at the radio frequency. They may be resistors, tuned circuits or other type components.

C3 and C3 feed back radio frequency voltage developed across R3 and R3 and at the same time shift the phase of this voltage, causing the plate circuit to look like a capacity, the value of which depends on plate voltage. Frequency control is by variation or modulation of the plate voltage.

The operation thereof is in general as set forth in detail above. In Figure 4 the oscillator plate potential is never higher than the screen potential wherelinear control is desired. In this modification I where Q is that of the resonant circuit LI-Cl.

Plate modulation or control is used with the control or modulation potential applied between lead 20 and ground. The plate potential at 20 may be modulated at an audio rate for frequency modulation or controlled by a potentiometer from a local or remote point for generator frequency control.

The oscillator shown in Figure loperates at 200 kc. It has a controllablefrequency range of 4000 cycles when operated from a 200 volt B sup- 9001 tubes checked in this between 4000 and 5000 cycles. It-can be seen somewhat with the Gm of the radio rerange.

In an oscillator arranged as in Figure 1 to generate oscillations at 200 kc. the elements shown had the following values:

Cl ,.,.r coo C! V guf 500 C3 "prof" 17 c4 f 0.004 C5 if 0.1 RI ms 150,000 R2 do 33,000 R3 do 47,000 R4 do 100,000 V 7 Type 9001 tube B+ -.volts I 200 is possible to arrange v way that the frequency shift is slightly negative similarly stabilize the quency voltage availableat the plate. messenlator output voltage varied between 25 and 35 volts for one particular tube as the plate. voltage was varied between 0 and +200 volts. Screen current changed from 0.45 to 0.35 milliampere and the plate current changed from 0 to 0.3 milliampere.

Frequency stability of this oscillator is such that when the supply voltage to the complete receiver was dropped 25%, the oscillator frequency 'varied' .005% at'one extreme of the frequency control and .06

the oscillator in such a with a change in battery voltage at one extreme of the controllable range and slightly positive at the other extreme, giving a minimum frequency change for 'a change in battery voltage for all settingsof the frequency control. The choice of screen dropping resistor R2, grid resistorRl grid coupling capacitor C2 and the position of the tap on oscillator coil Ll, as well as the LC ratio of the resonant circuit will determinethe stability of the oscillator. These values should be carefully considered to obtain best stability.

The output voltage of the oscillator may be maintained within closer limits by reducing the range over which the plate voltage of VI may be varied. It is suggested that this range always start at 0 volts plate since this is the condition of minimum effect of battery voltage due to change in Gm of the tube upon the frequency of the oscillator. A small capacity across R3 will output voltage but at the same time will reduce the controllable frequency The output voltage is taken from Ll through either a small capacitor, tap .on winding, or, as shown,- by an auxiliary winding coupled to Ll.

'- I claim: r

1. In means for supplying a controllable reacti've effect across a resonant circuit in which alternatingcurrent flows, an electron discharge device having electrodes including a control electrode coupled with said resonant circuit and an additional electron receiving electrode coupled to the aforesaid electrodes by the electron stream of the device, a phase shifting reactance coupling said electron receiving electrode to said control electrode for feeding thereto alternating voltage a component of which is displaced in phase substantially 90? with respect to the alternating voltage appearing on said control electrode due to its connection to said resonant circuit, whereby a reactive effect is added to said resonant circuit, and connections for adjusting the potential on said additional electrode to vary the voltage fed to the control electrode and thereby vary said reactiveeffect.

2. In means for supplying a controllablereactive effect across a resonant circuit in which at the other extreme. It

alternating current flows, an electron discharge device having an anode-like electrode, a cathode and a control electrode coupled with said reso- I nant circuit and an additional electron receiving phase substantially 90 with respect to the alternating voltage appearing on said control electrode due to its connection to said resonant circuit, whereby a reactive effect is added to said resonant circuit, and connections for varying the direct current potential applied to said additional 7 electrode to vary the voltage fed to the control electrode and thereby vary said reactive effect.

3. In means for supplying a controllable reactive effect across a resonant circuit in which alternating current flows, a pair of electron discharge systems having electrodes including a control .electrode coupled with said resonant circuit and an additional electron receiving electrode coupled to the aforesaid electrodes by the electron stream of, thedevice, a phase shifting reactance coupling the electron receiving electrode of one of said systems to the control electrode of said one of said systems, a phase shifting reactance coupling the electron receiving electrode of the other system to the control electrode of the other system, said phase shifting reactances feeding back to said control electrodes alternating voltages displaced in phase with respect to the alternating voltages appearing on said control electrodes due to their coupling to said resonant circuit, and means for applying variable direct current potentials in phase to said electron receiving electrodes.

4. In a controllable frequency generator, an electron discharge device having oscillation generating electrodes including a control electrode in an oscillation generating circuit, and an additional electron receiving electrode coupled to the generating electrodes by the electron stream of the device, a phase shifting reactance coupling said electron receiving electrode to said generating circuit for feeding thereto a voltage of the generated frequency a component of which is displaced in phase about 90 with respect to the generated voltage, whereby a reactive effect is added to said resonant circuit and connections for applying a variable potential to said addi tional electrode to vary said reactive effect.

5. In a system for generating waves of controllable frequency, an electron discharge device having oscillation generation electrodes including a control grid in an oscillation generating circuit and an additional electron receiving electrode coupled to the generating electrodes by the electron stream of the device, a phase shifting reactance coupling said electron receiving electrode to said control electrode for feeding thereto a voltage of the generated frequency a component of which is displaced in phase about 90 with respect to the generated voltage on said control electrode, whereby a reactive effect is produced by said device in said generating circuit to determine in part the frequency of the oscillations generated, and means for varying the potential on an electrode of said device to vary said reactive etl'ect and thereby vary the frequency of the oscillations generated.

6. In a wave length modulation system, an electron discharge device having oscillation generation electrodes including a control grid in an oscillation generating circuit and an additional electron receiving electrode coupled to the generating electrodes by the electron stream of the device, a phase shifting reactance coupling said electron receiving electrode to said control elec- Ill trode for feeding thereto a voltage having a component displaced about in phase with respect to the generated voltage on said control electrode, whereby a reactive effect is produced in the generating circuit to control the frequency of the oscillations generated, and connections for varying the potential on said electron receiving electrode of said device in accordance with signals to vary said reactive effect and thereby vary the frequency of the oscillations generated in accordance with signals.

7. In a wave length modulation system, an electron discharge device having oscillation generating electrodes including an anode-like elec trode, a control electrode and a cathode in an oscillation generating circuit including reactance and an additional electron receiving electrode coupled to the generating electrodes by the electron stream of the device, a connection for applying positive potential to said anode-like electrode, a load impedance for applying direct current potential of less valueto said additional electrode, a phase shifting reactance coupling said electron receiving electrode to said control electrode for feeding thereto a voltage of the generated frequency displaced in phase with respect to the generated voltage on said control electrode, whereby a reactive effect is produced which supplements the reactance of said generating circuit and influences the frequency of operation of said oscillation generating circuit, a source of signal potentials, and means coupling said source of signal potentials to said additional electrode in said device to control the voltage thereof and thereby correspondingly control said reactive effect and the frequency of the oscillations generated.

8. In a wave length modulation system, a pair of electron discharge systems each having oscillation generatingelectrodes including a control electrode coupled in an oscillation generating circuit and each having an additional electron receiving electrode coupled to the generating electrodes by the electron streams of the system, a load impedance connecting to each of said additional electrodes, separate phase shifting reactances coupling the electron receiving electrode of each system to the control electrode of eachsystem for feeding to said control electrode voltages of the generated frequency displaced in phase with respect to the generated voltage on said control electrodes whereby reactive effects are produced across said reactances and supplied to said generating circuit to influence the frequency of operation of said oscillation generating circuit, a source of control potentials, and means coupling said source of control potentials to the electron receiving electrodes in said systems to control the voltage thereof and thereby correspondingly control said reactive effects and the frequency of the oscillations generated.

HOWARD C. LAWRENCE.