| 摘要 |
An AM radio receiver comprises an RF amplifier, a first mixer that converts the RF signal to a first intermediate-frequency signal, a first bandpass filter that band-limits the first intermediate-frequency signal, a second mixer that converts the output from the first bandpass filter to a second intermediate-frequency signal, a second bandpass filter that band-limits the second intermediate-frequency signal, an intermediate-frequency amplifier that amplifies the output from the second bandpass filter, an AM detector that demodulates the output from the intermediate-frequency amplifier and provides output of an audio signal, and a noise detector for detecting and eliminating ambient noise. The noise detector comprises a first noise detector that detects noise from the RF signal and eliminates the noise contained in the first intermediate-frequency signal, and a second noise detector that detects noise from the second intermediate-frequency signal and eliminates that noise. The AM radio receiver further comprises a halting device that halts the second noise detector for a predetermined period of time when the first noise detector has detected noise. Thus, distortion of the audio signal caused by redundant noise elimination operations is avoided and noise contained in the second intermediate-frequency signal can be detected and eliminated appropriately.
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