FM demodulators with local oscillator frequency control circuits
US4580101A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 4, 1984 |
| Grant date | Apr 1, 1986 |
| Priority date | — |
| Expiry date | Apr 4, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/1525
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
An FM demodulator includes frequency conversion means (20) to derive from an FM input signal (10) a pair of like signals that are mutually phase-displaced by 90.degree.. Such signals are filtered (26,28), squared (30,32) and sampled (38). The output signal (40) of the sampling means (38) is used to control (62) the local oscillator (16) of the frequency conversion means (20). In one arrangement, the magnitude of the control applied to the oscillator (16) is dependent on the frequency of one of the squared (30) signals, whereas the direction is dependent on the logic state of the output signal (40). A similar control method can be applied to a superheterodyne receiver.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.