Phase locked loop with pre-set and squelch
US4061979A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 20, 1975 |
| Grant date | Dec 6, 1977 |
| Priority date | — |
| Expiry date | Oct 20, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03L7/14
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A phase locked loop with pre-set and squelch capability particularly adapted for burst type signals. In addition to the conventional phase detector, loop filter (LF) and voltage controlled oscillator (VCO) the loop includes a squelch switch connected between the phase detector and LF. A track and hold circuit is connected in series with another switch between output and input of the LF. Both switches and the track and hold circuit itself are controlled by the output of a level detector which indicates presence of an intermittent (i.e., bursty) carrier. The squelch switch is closed, connecting the phase detector to the LF, when the output of the level detector indicates the presence of a carrier burst. At the same time, the second switch is opened so that the LF is not affected by the output of the track and hold circuit. In addition, the track and hold circuit is enabled to track the error voltage output of the LF. At the conclusion of a burst the squelch switch is opened so that the noisy output of the phase detector will not affect the LF. In addition, the second switch is closed to allow the output of the track and hold circuit to reach the LF and finally, the track and hold cir…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.