Carrier regeneration circuit for multiplex signals - uses simplified four-phase modulation with phase locked loop and has doubler circuit

摘要

The input signal (1) passes through a doubler circuit (25) and is converted to a double-phase-modulated signal and processed by the remodulation loop. The carrier is frequency -doubled in the process and a divider (26) halves it so that the correct carrier frequency is regenerated and appears at the output (27). The processing loop comprises a demodulator (2) with an input connected to a phase-shift network (3). A phase-locked loop is formed from a phase-detector (7), low-pass filter (8) and voltage-controlled oscillator (4) the output of which controls the phase networks. The demodulated signal passes through a limiter (5) which produces a control signal for the modulator (6) where the input signal is again modulated.