US2076168A - Quenching oscillator for superregenerative receivers - Google Patents

Description

A ril 6, 1937. n A. H. TURN ER I 2,076,168

QUENCHING OSCILLATOR FOR SUFERREGENERATIVE RECEIVERS Filed Oct. '31, 1935 Patented Apr. 6, 1937 r 2,07

UNITED STATES PATENT OFFICE QUENCHING OSCILLATOR FOR SUPER- REGENERATIVE RECEIVERS Alfred H. Turner, Collingswood, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application October 31, 1935, Serial No. 47,665 10 Claims. (01. 250-) The present invention relates to a quenching variable tuning capacitor I! connected between oscillator for super-regenerative receivers and the cathode l by a ground lead i 9, and the conhas for its primary object to provide means for trol grid 9 through a grid leak and condenser quenching the radio frequency oscillations of a means 2l-23. The antenna for applying resuper-regenerative receiver at a very rapid rate ceived signals to the circuit I3 is indicated at a without lgsing receiver sensitivity, and is coupled to the high potential side 0f The sensitivity of a super-regenerative rehe c rcuit throu h a coupl g p t r 1 of ceiver is a function of the ability of the local tive y low capacity. oscillator to vary its amplitude in accordance with Feed back control for the anode I I is provided 1 the modulation of an incoming signal. If the through an anode circuit 29 connected with a To 0 positive portion of t quenching cycle is t feed back winding 3| forming a continuation ofshort the radio frequency oscillator will not have the Winding l5 d anode po e a s pplied time to build up oscillations of sumcient amplithereto from a pp y ead 33 and a choke coil tude, and if too long the oscillations will reach a 35 to a Ital) Point 37 between the windings 5 and steady state and will not be able to reproduce 3L h ground lead I9 is isolated from the the signal modulation. It is, therefore, a furthen anodeui rough a block capacitor 39.

object of the present invention to provide a Signal Output terminals 4| a e p ovided in the quenching oscillator for a super-regenerative repp y a to Which ay e o e d a y ceiver which will provide optimum duration for Suitable Output device Such a pair of head'- the positive portion of the quenching cycle for Phones The up e enerative circuit debest sensitivity. This has been found to depend seribed represents any s itable super-re eneraupon the rate at which the radio fr qu ncy two receiver to which a quenching frequency is cillator can build up oscillations and upon the to be appliedthe P n example the decrement of the radio frequency oscillator quenching frequency s Supplied from an oscillacircum tor 45 through connection with the grid 9 as indi- As the frequency of the usual sine-wave Gated at 25 quenching oscillator is increased much beyond y-p videdln connection audibility, the duration of the positive half-cycle Wlth such Circuits s usually satisfactory when is not sufficient to permit the radio frequency the Signal frequency i hi f mpl about oscillations to build up sufiiciently for full sensi- 60 megacycles and the quenching frequency is tivity. Accordingly, it is a further object of the 10W, for example, about 15,000 cycles. Under present invention t6 provide a quenching osci11a such conditions a quenching oscillator of the sinetor system which provides preferably a wave Wave type embedying inductance a pa ity formhaving a long positive portion and a relatuning means Will p e a relatively high detively short negative portion, thereby permitting glee 0f Sensitivitythe present system, howr quenching at rapid rates above the rate normally ever, a lower Signal frequency s c n emplated. and 0 considered practicable the quenching frequency is increased to accom- The invention will, however, be better undermodate higher modulation frequency p evalent stood from the following description when cont t present time. Under this condition the 40 sidered in connection with the accompanying DOSltiVe Portion of a normal S Wa cyc e Soon 40 drawing and its scope will be pointed out in the becomes too short for the radio u n y osappended ciaims cillations to reach optimum value and loss of In the drawing, Figure 1 is schematic sensitivity results. Therefore, a quenching wave cuit diagram of a super-regenerative receiver emform having a relatively g positive portion 4) bodying th invention, d and a relatively short negative portion is desired.

' Fig. 2 is a curve representing the wave form at Stated in th w rds n at v i puls s of hi h present preferred and as provided by the system amplitude and ShOIt duration occurring at relaof Fig. 1 for quenching the radio frequency ostively high frequency with respect to the highest cillations. signal modulation frequency are necessary.

50 According to Fig. 1, asuper-regenerative re- Under this condition, the positive half-waves are ceived comprising an oscillating detector 5 of relatively long and of minimum amplitude, formthe electric discharge type comprising a cathode ing intervals between the impulses.

l, a control grid 9 and an anode II is connected A wave form which is at present preferred is with the tuned signal circuit indicated at [3. that shown in Fig. 2 at 49 having a square wave The latter comprises the inductance l5 and shunt form and negative impulses or half-waves SI of a o relatively short duration and high amplitude thereby providing a relatively, low amplitude, long positive half-waves between impulses.

Any impulse generator which will produce a negative impulse or half-wave of short duration with respect to the positive half-wave may be used but it has been found that an oscillator of the type known as a relaxation oscillator is preferable as its frequency is determined by the series combination of a resistor and a capacitor rather than an inductor and a capacitor. For example, a multivibrator type of resistance-capacity oscillator may be used. The frequency of impulses may be increased up to a limit determ ned by the tube capacity.

Such an oscillator is shown in 45 in connection with the super-regenerative receiver circuit and comprises a suitable electric discharge amplifier device 53 having a cathode 55, an anode 51, a control grid 59, a screen grid BI and a suppressor grid 63. The oscillator circuit comprises a variable capacitor 65 and a variable resistor 61 connected in series between the screen grid 6| as an oscillator grid and the cathode 55, the cathode connection including a grounded lead 69 and a bias resistor M in, series with the oscillator circuit elements 65 and 61. Positive potential is applied to the oscillator or screen grid 6| from a positive supply lead 13 through a coupling resistor 15. The control grid is connected to cathode through a lead 11. The suppressor grid 63 as an oscillator anode is connected to the junction between the capacitor 65 and resistor 61 as indicated at 19. A positive operating potential is applied from a supply lead 8| through a coupling resistor 83 to the anode 51 and connection is made at 85 through a coupling capacitor 86, a variable resistor 81 and a radio frequency choke coil 89 with the terminal 41 for applying the quenching oscillations to the super-regenerative circuit. The capacitor 86 serves to isolate the anode potential from the grid of the detector and the resistor is variable to control the amplitude of the oscillations applied to the detector. Radio frequency current is prevented from leaving the detector by the choke coil 89.

The impulse frequency of the relaxation oscillator or impulse generator 45 is largely determined by the time constant of the circuit 65, 51 and the duration of the negative impulse is determined by the value of the capacitor. Therefore, for any quenching frequency, the quenching cycle can be proportioned to best suit the oscillating detector. The negative impulses appear at the anode, which is not included in the oscillator circuit per se, and are applied to the detector at an electrode which serves to suppress the oscillations, such as the grid, in the present example.

Maximum quenching frequencies up to 100,000 times per second, and with maximum sensitivity, may be obtained with a pentode type of tube shown. It is not feasible to reduce the negative impulse indicated at 5| of Fig. 2 sufficiently to maintain sensitivity because of the internal tube capacitance which may remain when the capacity of the device 65 is reduced to zero. Complete quenching may, however, be obtained as high as 200,000 turns per second but with lowered sensitivity. p

I This system .is therefore of benefit when the quenching frequency or quenching impulses must be relatively rapid and when the signal frequency is relatively low whereby long positive portions are obtained with relatively short high amplitude negative impulses as shown in Fig. 2. The system has the further advantage that the circuit elements are relatively few in number and comprise only variable resistors and capacitors and a degree of control limited only by the tube capacitance.

I claim as my invention:-

1. In a super-regenerative receiver, an oscil- -lating detector, means for applying thereto a quenching signal comprising a series of high frequency impulses, and means for limiting said impulses to negative half-waves of relatively high amplitude and of short duration with respect to the positive half-wave intervals therebetween.

2. In a super-regenerative receiver, the combination with an oscillating detector, of an oscillator, means for applying a quenching signal from the oscillator to the detector, means for operating said oscillator to provide a quenching signal having a relatively high frequency with respect to the signal modulation frequency, and means for controlling said oscillator to limit said quenching signal to negative half-wave impulses of relatively high amplitude and of relatively short duration with respect to positive half-wave intervals between impulses.

3. In a super-regenerative receiving system, a

square wave form quenching oscillator, means for limiting the output of said oscillator to high frequency negative half-wave impulses of relatively short duration with respect to the positive half-wave intervals between impulses, and means for controlling the duration and frequency of said impulses. I

4. In a super-regenerative receiving system, the combination with an oscillating detector, of an oscillator comprising an electric discharge device including oscillator electrodes and an out-- put anode, a substantially non-inductive frequency determining circuit coupling said oscillator electrodes and including resistance and capacity elements only, one of said elements being variable, means for deriving from the anode a quenching signal comprising a series of high frequency negative half-wave impulses of relatively short duration with respect to positive half-wave intervals therebetween and means for variably applying said impulses to said detector.

5. The combination with a super-regenerative oscillating detector for receiving modulated high frequency signals, of means for applying thereto a substantially square wave form quenching signal comprising successive negative half-wave impulses of relatively high amplitude and of relatively short duration with respect to the time between impulses occupied by the positive halfwaves and at a rate higher than the highest signal modulation frequency.

6. The combination with a super-regenerative oscillating detector for receiving modulated high frequency signals, of means for applying thereto a quenching oscillatory signal comprising successive negative electrical half-wave impulses of relatively high amplitude and. of relatively short duration with respect to the time between impulses occupied by the positive half-waves and at a rate higher than the highest signal modulation frequency, said last named means comprising an oscillation generator including an electric discharge tube having an anode, a cathode, and oscillator electrodes therebetween independent of the anode, an oscillator circuit coupling said oscillator electrodes and the cathode and including non-inductive tuning elements, means for operating said oscillator whereby said negative impulses appear on the anode and means for coupling said anode to said detector.

7. In a super-regenerative receiving system, an oscillation generator providing a quenching signal oscillation generator, said generator including an oscillator tube and a relaxation oscillator circuit having capacity and resistance connected between two of the electrodes thereof and with the capacity of such low value as to approach the value of the internal capacity of the tube between said electrodes thereby to produce at the anode a quenching signal comprising negative half-wave impulses of minimum time dura .tion and positive half-Wave extended intervals of minimum amplitude in each cycle.

8. In a super-regenerative receiving system, an oscillation generator providing a quenching signal oscillation generator, said generator including an oscillator tube and an oscillator circuit having capacity and resistance connected between two of the electrodes thereof and with the capacity of such low value as to approach the value of the internal capacity of the tube between said electrodes thereby to produce at the anode a square wave form quenching signal comprising negative half-wave impulses of minimum time duration with respect to the positive half-waves of said signal, an oscillating detector comprising an electric discharge device having an electrode for suppressing oscillations, means for coupling said electrode with the anode of the oscillation'generator and means for varying said coupling.

9. In a super-regenerative receiving system, the combination as defined in claim 4, further characterized by the fact that one of the oscillator electrodes is more negative than the cathode of said device whereby said device is operative to produce strong oscillations.

10. In a super-regenerative receiver, an oscillating detector for received modulated carrier waves, means for applying to the detector a quenching voltage wave comprising a series of half-wave voltage impulses at a frequency higher than the modulation frequency, and means "for limiting the form of the voltage wave to negative impulses of relatively high amplitude and of short duration with respect to the positive half-wave intervals therebetween.

ALFRED H. TURNER.

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