Frequency demodulator having circuit cancelling undesired signal components
US4908581A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 21, 1988 |
| Grant date | Mar 13, 1990 |
| Priority date | — |
| Expiry date | Jul 21, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/21
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An FM signal obtained by modulating a carrier f.sub.c with a signal f.sub.s is demodulated by a frequency demodulator to obtain a demodulated signal which contains a lower sideband component as an undesired moire component. A moire component generator generates an mf.sub.c -nf.sub.s component (m and n: natural numbers) from the demodulated signal or generates an nf.sub.1 -(n-m)f.sub.c component (f.sub.1 : first lower sideband component of the FM signal) from the FM signal. A subtractor subtracts an output of the moire component generator from the demodulated signal so as to thereby eliminate the undesired moire component. Furthermore, to eliminate a cross-modulation moire due to crosstalk of a low-frequency signal f.sub.L, the moire component generator generates a 2f.sub.L component from the FM signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.