Telecommunications – Receiver or analog modulated signal frequency converter – Local control of receiver operation
Patent
1979-02-26
1981-05-12
Ng, Jin F.
Telecommunications
Receiver or analog modulated signal frequency converter
Local control of receiver operation
455296, 455315, H04B 126, H04B 110
Patent
active
042676053
ABSTRACT:
In a communication receiver, a first mixing circuit, a first band-pass filter responsive to the output of the first mixing circuit, a second mixing circuit responsive to the output of the first band-pass filter, a second band-pass filter with a different center frequency from that of the first band-pass filter responsive to the output of the second mixing circuit, a first local oscillator, the output of which is applied to the first mixing circuit and a second local oscillator, the output of which is applied to the second mixing circuit. Various kinds of interference signals are eliminated by changing the output frequencies of the first and second local oscillators to thereby vary the effective bandwidth and center frequency of the signals which can pass through the receiver and thus eliminate interference. In addition, a third mixing circuit is responsive to the output of the second band-pass filter. The output of the third mixing circuit is applied to a notch filter, the notch frequency of which is effectively made variable by changing the frequency injected into the third mixing circuit and a demodulation circuit. Hence, by varying the effective notch frequency, further interference can be eliminated.
REFERENCES:
patent: 2735001 (1956-02-01), Witters
patent: 2747084 (1956-05-01), Doelz
patent: 2998517 (1961-08-01), Beckerich
Matsuzawa Mitsuo
Yashita Hajime
Baker Joseph J.
Ferguson Jr. Gerald J.
Ng Jin F.
Trio Kabushiki Kaisha
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