Multipath noise reducer, audio output circuit, and FM receiver
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsMasayuki Tsuji, Eiji 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 minimal distortion of the audio output signal. The multipath noise spikes are detected by comparing a rectified signal with a threshold signal derived from the rectified signal. When the multipath noise reducer is used in an FM stereo radio receiver, stereo separation may also be controlled according to the detection of multipath noise.
Claims13
A multipath noise reducer for reducing multipath noise present in an input signal, comprising:
- rectifying means for receiving the input signal and generating a rectified signal corresponding to an absolute value of the input signal;
- threshold-calculating means for receiving the rectified signal from the rectifying means and generating a threshold signal having a value related to the rectified signal;
- comparator means for receiving the rectified signal from the rectifying means and comparing the rectified signal with the threshold signal, thereby detecting said multipath noise in the input signal, and generating a detection signal indicating presence of said multipath noise in the input signal;
- and
- modification means for receiving the detection signal from the comparator means and modifying the input signal according to the detection signal, thereby reducing the multipath noise present in the input signal.
An audio output circuit for generating an audio signal from an input signal, comprising:
- rectifying means for receiving the input signal and generating a rectified signal corresponding to an absolute value of the input signal;
- threshold-calculating means for receiving the rectified signal from the rectifying means and generating a threshold signal having a value related to the rectified signal;
- comparator means for receiving the rectified signal from the rectifying means and comparing the rectified signal with the threshold signal, thereby detecting said multipath noise in the input signal, and generating a detection signal indicating presence of said multipath noise in the input signal;
- and
- modification means for receiving the detection signal from the comparator means and modifying the input signal according to the detection signal, thereby reducing the multipath noise present in the input signal.
An FM radio receiver comprising:
- rectifying means for receiving the input signal and generating a rectified signal corresponding to an absolute value of the input signal;
- threshold-calculating means for receiving the rectified signal from the rectifying means and generating a threshold signal having a value related to the rectified signal;
- comparator means for receiving the rectified signal from the rectifying means and comparing the rectified signal with the threshold signal, thereby detecting said multipath noise in the input signal, and generating a detection signal indicating presence of said multipath noise in the input signal;
- and
- modification means for receiving the detection signal from the comparator means and modifying the input signal according to the detection signal, thereby reducing the multipath noise present in the input signal.
A method of reducing multipath noise within an input signal, comprising the steps of:
- receiving an input signal from a receiver and passing the input signal through a high pass filter and absolute value calculator, which rectify the input signal;
- generating a threshold signal based on the rectified signal;
- generating a detection signal by comparing, in a comparator, the rectified signal and the threshold signal, the detection signal indicating the multipath noise within the input signal;
- and
- modifying the input signal according to the detection signal generated in the comparator thereby reducing the multipath noise in the input signal.
A multipath noise reducer for reducing multipath noise within an input signal, comprising:
- a rectifier which receives the input signal and generates a rectified signal corresponding to an absolute value of the input signal;
- a threshold generator operatively connected to said rectifier, said threshold generator generating a threshold signal based on the received rectified signal from said rectifier;
- a comparator operatively connected to said rectifier and said threshold generator, said comparator comparing the rectified signal with the threshold signal to create a detection signal indicating the presence of a multipath noise in the input signal;
- and
- an impulse noise reducer operatively connected to said comparator, said impulse noise reducer modifying the input signal according to the detection signal received from said comparator, thereby reducing the multipath noise present in the input signal.
Dependencies are inferred from the claim text.