Multipath noise reducer, audio output circuit, and FM receiver
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsMasayuki Tsuji, Eizi Asano, Masahiro Tsujishita, Kenichi Taura, Masayuki Ishida
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Abstract
A multipath noise reducer detects and removes the individual noise spikes occurring in an interval of multipath noise, thereby reducing the multipath noise with relatively little distortion of the output signal. The threshold signal used to detect multipath noise is varied depending on reception conditions. The gate pulses indicating the presence of multipath noise spikes are preferably expanded by variable amounts, depending on both reception conditions and the signal level. Multipath noise spikes are preferably replaced by a smoothed signal. These provisions further reduce perceived distortion of the audio output signal.
Claims22
A multipath noise reducer for reducing multipath noise in an input signal, comprising:
- a signal state determiner determining a state of said input signal, thereby generating state information;
- a threshold generator coupled to said signal state determiner, generating a threshold value responsive to said state information;
- a high-frequency signal extractor detecting high-frequency components of said input signal, thereby obtaining a high-frequency signal;
- a comparator unit coupled to said threshold generator and said high-frequency signal extractor, comparing said high-frequency signal with said threshold value, thereby generating a multipath noise detection signal;
- and
- a correction unit coupled to said comparator unit, modifying said input signal responsive to said multipath noise detection signal and said state information, thereby generating a corrected output signal.
A method of reducing multipath noise in an input signal, comprising the steps of:
- (a) determining a state of said input signal, thereby generating state information;
- (b) generating a threshold value responsive to said state information;
- (c) detecting high-frequency components of said input signal, thereby obtaining a high-frequency signal;
- (d) comparing said high-frequency signal with said threshold value, thereby generating a multipath noise detection signal;
- and
- (e) modifying said input signal responsive to said multipath noise detection signal and said state information, thereby generating a corrected output signal.
A machine-readable medium having stored thereon a plurality of executable instructions, the plurality of instructions comprising instructions to:
- determine a state of an input signal to generate state information;
- generate a threshold value responsive to said state information;
- detect high-frequency components of said input signal to generate a high-frequency signal;
- compare said high-frequency signal with said threshold value to generate a multipath noise detection signal;
- and
- modify said input signal responsive to said multipath noise detection signal and said state information to generate a corrected output signal.
Dependencies are inferred from the claim text.