Digital FM demodulator with distortion correction
US4862099A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 17, 1988 |
| Grant date | Aug 29, 1989 |
| Priority date | — |
| Expiry date | Aug 17, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D2200/0082
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A frequency demodulator includes an analog-to-digital converter for converting an inputted FM signal into a digital signal. A 90.degree. phase shifter is used to phase shift the converted digital signal. The phase shifted signal and the converted signal are utilized to determine the results of tan.sup.-1 (X/Y). X represents the converted signal, and Y represents the phase shifted signal. The result from the calculation is delayed for a period of time equal to one sampling cycle. The frequency demodulator also includes a subtractor for subtracting the delayed signal from the calculation result. A discontinuity corrector corrects any discontinuity in an output from the subtractor, and a reversal phenomenon compensator compensates the output from the discontinuity corrector when the output from the discontinuity corrector exceeds a predetermined range of levels. These levels correspond to an appearance of discrete lines of black or white color on a reproduced picture.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.