Dual pilot phase lock loop for radio frequency transmission
US4618996A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 24, 1984 |
| Grant date | Oct 21, 1986 |
| Priority date | — |
| Expiry date | Apr 24, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/0803
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A radio frequency transmission system contains at least one coherently modulated information signal, for example, a T.V. signal. At a transmission, the information signal is combined with two pilot tones, F1 and F2, related by the equation F1=N/M F2, where N and M are integers. The combined signal is suppressed-carrier modulated at microwave frequencies and transmitted to a receiver. At the receiver, the signals are demodulated by a local oscillator. The two pilot tones are then separated from the information signal and are compared to each other. The local oscillator frequency is controlled in response to this comparison such that the pilot tones at the receiver bear the same relationship to each other that they had at the transmitter. When this is achieved, the local oscillator frequency is the same as the suppressed-carrier frequency and co-channel interference is prevented.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.