Radio receiver
US4628518A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 15, 1983 |
| Grant date | Dec 9, 1986 |
| Priority date | — |
| Expiry date | Sep 15, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/152
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A mixer receives a frequency shift keyed (FSK) radio signal having two transmission frequencies and mixes the radio signal with a first or a second local oscillator signal from a local oscillator to provide a mixed signal. The mixed signal lies within a high or low band of frequencies depending upon the frequency of the FSK signal and upon the local oscillator signal received by the mixer. A detector receives the mixed signal and detects in which band of frequencies the mixed signal lies, and generates a switching signal in dependence upon the band of frequencies in which the mixed signal lies. If the FSK signal changes to a different transmission frequency and this causes the mixed signal to lie in the low band of frequencies, then a switching signal is generated which switches the local oscillator such that the oscillator generates a different local oscillator signal which causes the mixed signal to shift to the high band of frequencies. In this way, the mixed signal is shifted back to the high band of frequencies whenever the detector detects that it has shifted to the low band of frequencies due to a change in the transmission frequency of the FSK signal. The switching signal t…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.