GB592271A - Superregenerative receiver - Google Patents

Abstract

592,271. Valve receiving circuits; automatic gain control. HAZELTINE CORPORATION. Jan. 16, 1945, No. 1350. Convention date, Feb. 11, 1944. [Class 40 (v)] In a super-regenerative receiver, a control potential is developed dependent on an operating condition of the receiver to vary the characteristic of the quench voltage. Both amplitude and frequency of the quench voltage may be varied by the control potential to cause variations in the band width or sensitivity of the receiver. The control potential may be derived, from a separate aerial or a preceding radio frequency amplifier. The valve 10<1>, Fig. 3, connected to the tuned circuit comprising an inductance 11 and stray capacity C<1> is fed with a quench voltage over transformer 141 from the heptode 17<1>, the inner grid and anode of which are connected in an oscillatory circuit consisting of an inductance 19<1> and condenser 20<1> with feedback coil 22<1>. In the absence of an incoming signal, the receiver noise causes valve 10<1> to oscillate-during each positive cycle of the quench voltage, the oscillations being rectified.by diode 30<1> to produce a voltage across the load resistance 33<1>. The quench frequency component, fed through amplifier 411 and rectifier 42<1> develops a control potential across potentiometers 43, 44 having their centre taps earthed. The potential on the slider of potentiometer, 44 varies the bias on the outer control grid of heptode 17<1> to vary the gain and hence the amplitude of the quench voltage. The potential of the slider of potentiometer 43 is applied to the grid of reactance valve 25, the anode of which is back coupled to the grid over condenser 26, to .cause variations in the frequency generated by the inner electrodes of the heptode 17<1>. By suitable adjustment of the sliders on potentiometers 43, 44, the band width or sensitivity of the receiver, may be maintained constant or varied according to any desired law. The demodulated signal appearing across load resistances 33<1> is fed to a normal amplifier, pulse modulated signals due to their low modulation frequency being ineffective in varying the control voltage developed across potentiometers 43, 44. When receiving C.W. signals,. the control voltage varies with the incoming signal to give an A.V.C. action. For the response of pulse modulated signals the amplifier 41<1> may be arranged to have the maximum response at some frequency less than the quench component and minimum response at that frequency, the control voltage being developed from the noise component. In a transponder for use as a beacon for an interrogating aircraft, Fig. 4, the grid of the receiving valve 60 is normally biassed off, the quench frequency oscillator 69, through the intermediate amplifier 71, removing the paralysing bias, periodically. The received signal is fed to the tuned circuit comprising inductance 61 and stray capacity C<11> over coupling condenser 86 and inductance 87, the amplified oscillations being rectified by diode 75. The quench frequency component appearing across the load 78 is passed through amplifier 81 to diode 82, the control voltage developed across load resistance 84 being used to vary the gain of the intermediate amplifier 71. The signal from load 78 also feeds a pulse generator 97 which is only operated by signals above a predetermined amplitude, the output pulsing the transmitter valve 90 which utilises the common tuned circuit 61, C<11> feeding the aerial 88. Due to the now of cathode current during the oscillations, condenser 94 charges up to terminate the pulse after a predetermined time, the condenser 94 discharging over resistance 95 between pulses. Specification 592,269 is referred to.