Off-air phase lock technique
US6433830B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 14, 1999 |
| Grant date | Aug 13, 2002 |
| Priority date | — |
| Expiry date | Jun 14, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/102
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The proposed phase lock technique uses various feedback loops to lock the frequency and phase of a CATV modulator output signal to that of an off-air signal without directly measuring the output frequency. One embodiment includes a tuner for receiving the off-air signal and generating an intermediate frequency signal and a phase-frequency detector for comparing the frequency and phase of the intermediate frequency signal generated by the tuner with the frequency and phase of an intermediate frequency signal generated by the modulator based on a reference input signal. The output of the phase-frequency detector is used to control the reference input signal into the modulator and the reference input signal to the tuner such that the frequency and phase of the modulator output signal is locked to the frequency and phase of the received off-air signal. A second embodiment uses two tuners with a common reference frequency and a third embodiment eliminates the need for a tuner, using direct counting of the broadcast signal to derive the modulator reference signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.