Adjacent channel interference detection & suppression circuit

Details Adjacent channel interference detection & suppression circuit Adjacent channel interference detection & suppression circuit

1994-05-31

1996-02-20

Eisenzopf, Reinhard J.

Telecommunications

Receiver or analog modulated signal frequency converter

Noise or interference elimination

455307, 455295, 455296, 455266, H04B 110, H04B 106

Patent

active

054937175

ABSTRACT:
FM radio receivers, particularly in moving vehicles, are subject to intermittent adjacent-channel interference. It is known to detect such interference and suppress it by narrowing bandwidth in the Intermediate Frequency (IF) signal path. However, it is desirable to again broaden the bandwidth once the interference has subsided. An improved system, which automatically and dynamically adjusts the bandwidth, employs first and second signal level evaluation circuits (11, 12), a comparison stage (13) which compares their outputs, and a variable-bandwidth filter stage (6, 14) controlled by the comparison stage. The comparison stage is programmed with a set of signal difference threshold values and corresponding filter bandwidth values, and controls the filter stage (6, 14) to adjust the bandwidth to the appropriate value, indicated by which signal difference threshold value has been exceeded. In a preferred embodiment, a second IF filter (15) does "double duty" as part of the variable-bandwidth filter stage.

REFERENCES:
patent: 3889108 (1975-06-01), Cantrell et al.
patent: 3953802 (1976-04-01), Morris et al.
patent: 4598426 (1986-07-01), Shiojima
patent: 4907293 (1990-03-01), Ueno
patent: 5095534 (1992-03-01), Hiyama
patent: 5220687 (1993-06-01), Ichikawa et al.
patent: 5303413 (1994-04-01), Braegas et al.
patent: 5339455 (1994-08-01), Vogt et al.

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