| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that it is difficult to set a passband width W<SB>F</SB>of a band-pass filter (IBPF) in an FM receiver so that noise voice distortion, and adjacent-channel interference are sufficiently suppressed in various states of receiving electric field intensity, a modulation degree, and the intensity of adjacent-channel interference. SOLUTION: The IFBPF 80 can variably set the passband width W<SB>F</SB>and an attenuation slope K<SB>F</SB>. A bandwidth control circuit 102, which is constituted in hardware, controls the W<SB>F</SB>in accordance with a receiving state, which is composed of a combination of receiving electric field intensity, a modulation degree, and the intensity of adjacent-channel interference. A microcomputer 54 controls the K<SB>F</SB>on the basis of a program stored in a nonvolatile memory 60 and finely adjusts the effective passband width. Control of the W<SB>F</SB>contradictory for prevention of audio distortion and control of adjacent-channel interference is required when high modulation and adjacent-channel interference exist in a weak electric field state, and the setting becomes difficult. In this particular case, a configuration in which the K<SB>F</SB>can be modified by a program allows an advantageous receiving state to be readily obtained. COPYRIGHT: (C)2009,JPO&INPIT
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