Phase-shifting multiplication type FM signal demodulation circuit
US4122394A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 14, 1977 |
| Grant date | Oct 24, 1978 |
| Priority date | — |
| Expiry date | Jan 14, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D3/18
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A phase-shifting multiplication type FM demodulation circuits comprises a gate circuit including a first and a second switching circuit adapted to be switched for an FM intermediate frequency signal, a resonance circuit and a phase-shifting element. The FM intermediate frequency signal is phase-shifted for about .pi./2 (or 90.degree.) and the phase-shifted signal (frequency) is fed to the second switching circuit of the gate circuit after the phase-conversion of the phase-shifted FM signal by means of a phase-shifter device. The demodulation circuit further includes a bias resistor for the second switching circuit which resistor serves also as a resonance resistor of the resonance circuit, a substraction circuit for detecting output signal from the gate circuit, an output resistor for determining magnitude of the output signal from the subtraction circuit, and a lowpass filter for eliminating higher harmonics from the output signal appearing across the output resistor thereby producing a demodulated output.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.