Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1989-10-02
1991-06-11
Eisenzopf, Reinhard J.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
455266, 455340, H04B 116
Patent
active
050239392
ABSTRACT:
An FM tuner including a PLLFM demodulation circuit is provided, which selectively employs one of two BPFs having different extraction bandwidths as an IFBPF. This FM tuner is configured such that by employing a relationship between a lock range and an input signal level of the PLLFM demodulation circuit, an optimum value of the lock range of the demodulation circuit is set for a bandwidth of an input signal, even if any of the BPFs is selected. When the BPF having a narrower bandwidth is selected as the IFBPF, a signal to be inputted to the PLLFM demodulation circuit is attenuated to decrease the level of the input signal of the demodulation circuit to be lower that the level when the other BPF with a larger bandwidth is selected as the IFBPF. As a result, a lock range width of the PLLFM demodulation circuit is reduced.
REFERENCES:
patent: 3909735 (1975-09-01), Anderson et al.
patent: 4479091 (1984-10-01), Yoshisato
patent: 4792993 (1988-12-01), Ma
patent: 4816770 (1989-03-01), Naumann
Charouel Lisa
Eisenzopf Reinhard J.
Sharp Kabushiki Kaisha
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