Title:
HIGH-SENSITIVITY FM DEMODULATING SYSTEM
Document Type and Number:
WIPO Patent Application WO/1983/000974
Kind Code:
A1
Abstract:
A demodulating system for improving in the noise characteristics of a wide band television (FM) signal. In the system, a band-pass filter (7) is followed by an adaptor for an improvement in the C/N ratio and the output of the adaptor is demodulated at a discriminator (14) through a limiter (13). The adaptor includes a variable band-pass filter (8) having controllable center frequency and band width and inserted into a signal path. The band width of the variable band-pass filter (8) is controlled so as to be wide when an input signal is strong and to be narrow when the signal is weak. The center frequency of the variable band-pass filter (8) is controlled in response to the color sub-carrier component (3.58 MHz) in an input television signal and, for extracting the color sub-carrier component, a phase detecting circuit (10) is arranged between the input and output terminals and the output of the circuit controls the variable band-pass filter (8) through a narrow band-pass filter.
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Inventors:
OHTA TOMOZO (JP)
Application Number:
PCT/JP1981/000207
Publication Date:
March 17, 1983
Filing Date:
August 31, 1981
Export Citation:
Assignee:
OKI ELECTRIC IND CO LTD (JP)
International Classes:
H03D3/00; H03G5/16; H04N7/045; H04N9/64; H04N11/00; H04N11/24; (IPC1-7): H04N9/50
Foreign References:
| JPS5684005A | 1981-07-09 |
Other References:
NHK Giken Geppo Vol. 20, No. 5 (1977-5) Nippon Hoso Shuppan Kyokai, Konishi Yoshihiro "SHF Jushinki" p. 176-181 especially page 1798 left column, line 7 from the bottom to right column, line 198 fig. 2(b).
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