GB441591A - Improvements in or relating to modulated carrier wave receivers and demodulators - Google Patents

Abstract

441,591. Wireless receiving systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Elektra House, Victoria Embankment, London.-(Assignees of Conklin, J. W. ; Rocky Point, Long Island, New York, U.S.A.) March 23, 1935, No. 9152. Convention date, March 23, 1934. [Class 40 (v)] Frequency-modulated carrier waves are converted into amplitude modulated waves by passing them through a circuit comprising a resistance and a resonant circuit connected in series, and combining the voltages so produced. The frequency-modulated waves after frequency reduction by heterodyning or after amplification at A are applied across the resistance Z1 and the resonant circuit Z2 connected in series. A resultant voltage is taken from a variable tapping 4 on the resistance, and by a variable magnetic coupling L2 to the circuit Z2, and is applied to the grid circuit of a detector valve V. The circuit Z2 is preferably tuned to one of the extreme values of the carrier frequency, and the frequency variations cause the voltage picked up by the coil L2 to vary in phase. When this voltage is combined vectorially with the voltage across Z1, an amplitude-modulated wave results which is detected by any ordinary detector V. In a modification, the lower end of the resistance Z1 is connected to an intermediate point on the coil Z2 and the resultant voltage is taken off across the tapping 4 and one end of the coil Z2 (Fig. 2, not shown).