GB593361A - Improvements in or relating to super-generative receivers - Google Patents

Abstract

593,361. Valve super regenerative circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Sept. 13, 1944, No. 17544. Convention date, June 25, 1942. [Class 40 (v)] In a super-regenerative receiver for frequency or amplitude modulated signals, the variations in quench frequency caused by variations in the amplitude of the applied signal are converted by a frequency detector into amplitude variations corresponding to the modulation of the carrier. A frequency modulated signal is converted into an amplitude modulated signal by the discriminating action of detuning the input circuit of the super-regenerative detector. In Fig. 1, self-quenching oscillator 3 has loop input circuit 1, 2 tuned, as shown in response curve of Fig. 2, for receiving an amplitude modulated carrier, but detuned for receiving a frequency modulated carrier in order to produce amplitude modulation in the usual manner. The secondary 12 of transformer 10 is tuned by condenser 13 to the quench frequency generated when no signal is received by valve 3. The increase in quench frequency produced by the carrier signal moves the operating point to the sloping sides of the response curve of tuned circuit 12, 13 as shown in Fig. 3, to produce magnified amplitude variations from the variations in quench frequency produced by the original amplitude modulation. In a modification, not shown, tuned circuit 12, 13 is replaced by a band-pass circuit so that small changes in quench frequency due to noise keep the operating point on the flat top of the characteristic in the absence of input signals so minimizing the inter-station noise level. Specification 489,094 and U.S.A. Specification 2,280,530 are referred to.