Converter for digital radio receiver system - uses phase locked loop controlled by DC voltage to provide reference mixer signal

摘要

The converter for a digital radio receiver comorises a digital receiver (1) for 118 MHz operation; with a SAQ filter (2), and an amplifier (3) with anti-phase outputs. It also has synchronous demodulators (4,4'), an oscillator (5), 90 deg. phase shifter (6), amplifiers (7,7'), decoder (8), audio output channels (9,9'), anti-phase modulators (10,10'), phase locked loop circuit (12) and an input circuit (13,14,16,17) with mixing stage (15). The reference frequency is controlled from a reference oscillator circuit (19) connected to a variable capacitance diode (21). Pref., the voltage on the potentiometer (24) controls the reference frequency. Additionally, voltage may be taken automatically from an AFC circuit (11). USE/ADVANTAGE - Satallite radio receivers. Increased resolution.