TV Interface RF modulation circuitry
US4386377A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 10, 1981 |
| Grant date | May 31, 1983 |
| Priority date | — |
| Expiry date | Apr 10, 2001 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/7755
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An interface circuit for selectively generating TV RF signals on one of two adjacent TV channels is designed with two independent RF oscillator-modulator circuits. The respective double sideband modulated signals generated by the RF modulators are respectively passed through separate frequency rejection filters designed to attenuate the lower sound sideband of each of the modulated signals. The resultant signals are applied to a common bandpass filter via an isolation network. The pass band of the bandpass filter encompasses substantially the combination of the pass bands of the broadcast TV channels corresponding to the RF signals generated. Consequently the lower frequency RF modulated signal is similar to a conventional vestigal sideband TV signal and the higher frequency RF modulated signal is a double sideband signal minus the lower sound sideband. The isolation network provides electrical connection between the rejection filters and the bandpass filter but establishes a relatively constant impedance at the respective filter output and input terminals irrespective of changes in the filter impedances so that the filters may be tuned to the desired resonances without interaction…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.