GB552483A - Improvements in carrier-signal detectors - Google Patents

Abstract

552,483. Valve circuits for wireless reception. HAZELTINE CORPORATION Dec. 29, 1941, No. 16745. Convention date, Feb. 25. [Class 40 (v)] A modulated carrier signal detector comprises a frequency selectivity network including a transformer and forming two network sections, provided with a single piezo-electric crystal coupled effectively in shunt to at least portions of the two sections and adapted to attenuate the sidebands relatively to the carrier frequency, and a pair of rectifiers individually coupled in the sections and each having a load across which a unidirectional voltage is produced and from which at least one output voltage is utilized. The Figure shows a supersonic heterodyne receiver for amplitude modulated signals employing both automatic frequency control and automatic volume control. The error detector is of the split-phase type comprising transformer 9, diodes 29, 30 and loads 31, 32 with the addition of a piezo-electric crystal 21 and associated coils 27, 28 thus providing a circuit which attenuates the sidebands relatively to the carrier, the condenser 26 being materially smaller than conventionally used so that the portion of primary voltage injected by it is one-tenth of the voltage developed across either of the sections of the secondary winding. The output signal is taken across resistance 32 and the frequency control voltage across both resistances 31, 32. In a receiver for frequency modulated waves the amplifier may include a limiter and the output is taken across resistances 31, 32. Automatic volume control voltage is obtained across resistance 38 by rectification of the primary voltage by rectifier 37. In this way the control voltage is dependent on the sideband energy with the carrier energy at amplitude reduced by the effect of the crystal 21. The Specification gives response curves and vector diagrams to show the response of the circuits and the control voltages produced and data for a specific embodiment.