Television sound detection system using a frequency translation phase-locked loop
US4470071A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 30, 1982 |
| Grant date | Sep 4, 1984 |
| Priority date | — |
| Expiry date | Aug 30, 2002 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/60
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A frequency translation phase-locked loop (PLL) is provided for detecting the audio information from a television signal. A voltage controllable oscillator having a nominal oscillation frequency equal to the frequency difference between the intermediate frequency (IF) picture and sound carriers provides one input to a mixer and a substantially unmodulated picture carrier is supplied as the other input to the mixer. A phase detector has as its first input the output signal from the mixer and as its second input the sound carrier. A lowpass filter coupled between the output of the phase detector and a control input to the VCO completes the PLL. The detected audio information is provided at the output of the lowpass filter.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.