H - Electricity – 03 – C
Patent
H - Electricity
03
C
332/71
H03C 1/52 (2006.01) G01S 1/50 (2006.01) H03C 1/58 (2006.01)
Patent
CA 1056468
ABSTRACT OF THE DISCLOSURE A modulator employs a pair of variable RF attenuators to produce a double sideband, suppressed carrier output. The attenuator devices are PIN diodes which are rendered alternately conductive in synchro- nism with the recurring half cycles of the audio fre- quency input signal which is to be impressed upon the radio frequency signal as modulation. As each diode conducts the RF signal, its attenuation is varied by a control signal in a manner to provide the conducted RF signal with a modulation envelope that follows the amplitude of the audio input. The modulated signals from both diodes are combined at the modulator output, after a phase reversal of the modulated signal from one of the diodes, in order to thereby provide a double sideband, suppressed carrier output signal. The control signal for each conducting diode is produced by a func- tion generator operating within a closed loop feedback system. The generator receives the audio input and a recreated modulating signal derived without carrier in- sertion from an envelope detector on the modulator out- put, and compares the recreated modulation with the original audio input to provide the control signal with the proper wave shape. An electronic goniometer for a VOR navigation system employs two of the double sideband modulators responsive to 30 Hz input signals that are 90° out of phase; thus a 90° modulation envelope phase differ- ence exists at the goniometer outputs as required for the variable phase antenna feeds of a VOR transmitting system.
236216
Mears William E.
Mueller Clifford E.
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