GB1050537A - - Google Patents

Abstract

1,050,537. Phase detectors. HUGHES AIRCRAFT CO. June 4, 1964 [June 28, 1963], No. 23238/64. Heading H3A. A phase detector comprises a bridge circuit, each arm of which includes a transistor switching circuit, means for applying a phase modulated signal across one diagonal of the bridge, means for switching the two sets of opposite transistor circuits alternately at a frequency equal to the carrier frequency of the phase modulated signal and a low pass filter connected across the other diagonal from which a signal is extracted having an amplitude proportional to the variation of phase of the input signal with respect to the carrier signal. The carrier signal e reference is applied to a keying circuit 16 which develops on lines 17, 18 oppositely phased square wave signals at the carrier frequency. Each arm of the bridge, e.g. arm 30, includes a pair of transistors 32, 34 and a pulse transformer connected such that on receipt of a negative half-cycle of carrier signal the transistors conduct and connect points 20 and 83 via a low impedance. Line 17 is connected to transistor switches 30, 60 and line 18 to switches 40, 50 hence during the halfcycle in which line 17 is negative terminals 10, 11 at which the phase modulated signal is applied are respectively connected to points 83, 86 of the low pass filter and during the halfcycle line 18 is negative the terminals are connected respectively to points 86, 83, i.e. the input signal is inverted. The low pass filter output signal at point 104 is connected via a fifth switching circuit 70 each time line 17 is negative to a capacitor 110 across which the output voltage is developed.