Injection-locked video frequency oscillator
US4613828A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 25, 1985 |
| Grant date | Sep 23, 1986 |
| Priority date | — |
| Expiry date | Jun 25, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N9/88
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A pair of crystal-controlled oscillators generate respective signals at specific frequencies that are useful in processing a video signal, such as in providing clock-driven signal delay or producing a subcarrier signal. The frequencies are used in such a way that they feed through into the frequency spectrum of the processed video signal. Though the frequencies are nominal multiples of each other they cannot be maintained invariant because of normal circuit conditions, such as ambient temperature variations and circuit aging. The frequencies therefore mix and a difference frequency develops in the processed video signal. By injecting a suitable harmonic of the lower frequency signal into the crystal oscillator generating the higher frequency signal, the higher frequency will lock to variations in the lower frequency. The difference frequency consequently disappears.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.