Stereo decoder without subcarrier restoration
Abstract
A stereo decoder is described which includes automatic phase-lock frequency control in the shaper of switching pulses and does not require restoring the spectrum of polarity-modulated oscillations. This eliminates the need for restoring the subcarrier-frequency signal to detection level and the need for compensating amplitude and phase distorations of the ultrasonic component in the spectrum of the complex stereo signal. The gist of this innovation is that the complex stereo signal proceeds from the FM detector to a proportionally differentiating filter and, after conversion in the latter, is demodulated by two synchronous detectors. The switching pulses necessary for synchronous detection are produced by a pulse shaper consisting of an oscillator with automatic phase-lock frequency control and a band-pass filter for the synchronizing voltage. Automatic control is provided by a paraphrase amplifier-limiter with one transistor and diode-diode logic shaping the signal which triggers a push-pull phase detector. The output signal from this detector proceeds through a low-pass filter to a voltage-controlled multivibrator oscillator built with diode-diode logic.
- Publication:
-
USSR Rept Electron Elec Eng JPRS UEE
- Pub Date:
- January 1985
- Bibcode:
- 1985RpEEE.......12P
- Keywords:
-
- Decoders;
- Frequency Control;
- Oscillations;
- Phase Locked Systems;
- Switching;
- Amplifiers;
- Electric Potential;
- Printed Circuits;
- Pulses;
- Communications and Radar