Sound signal and impulse noise detector for television receivers
US4514763A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 29, 1982 |
| Grant date | Apr 30, 1985 |
| Priority date | — |
| Expiry date | Oct 29, 2002 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/607
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
In a television signal processing apparatus, a phase-locked loop (PLL) is provided for detecting the audio information from the television signal and for providing a defect control signal which, when applied to compensation circuitry, reduces impulse noise effects in the video information. The PLL includes a phase detector, a lowpass filter (LPF) and a voltage controlled oscillator (VCO). The phase detector has a first input coupled to be responsive to the frequency modulated sound signal produced by the tuner, a second input coupled to be responsive to the output of the VCO and an output coupled to the LPF. The LPF provides a phase control signal to the VCO and provides the detected audio information. A signal mixer serving as a synchronous detector has first and second inputs coupled to the first and second inputs, respectively, of the phase detector and has an output for providing the defect control signal indicative of the amplitude variations of the frequency modulated sound carrier.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.