Receiver noise reduction with expanding gated pulses
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsMasahiro Tsujishita, Kenichi Taura, Masayuki Tsuji, Masayuki Ishida
Life of this patent
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Abstract
A noise reducer generates a gate signal by detecting noise in a demodulated signal, and changes the lengths the gate pulses indicating the presence of noise according to the electric-field strength of a radio signal from which the demodulated signal has been obtained. The demodulated signal is modified during intervals indicated by the gate pulses, to reduce the noise. The amount of change of the gate-pulse lengths is preferably increased as the electric-field strength decreases. Noise can then be removed satisfactorily under even weak electric-field conditions.
Claims12
A noise reducer for reducing noise included in a demodulated signal obtained by demodulation of a received radio signal, comprising:
- an electric-field-level decision unit comparing an electric-field strength of the radio signal with at least one predetermined reference value, thereby generating an indicator signal indicating said electric-field strength;
- a noise-detection unit receiving said demodulated signal and detecting said noise;
- a noise-width generation unit coupled to the electric-field-level decision unit and the noise-detection unit, generating gate pulses responsive to said indicator signal and to detection of said noise, the gate pulses generated when the indicator signal indicates a comparatively weak electric-field strength being lengthened in a relation to the gate pulses generated when the indicator signal indicates a comparatively strong electric-filed strength;
- and
- a correction unit coupled to the noise-width generation unit, modifying said demodulated signal during intervals indicated by the gate pulses, thereby reducing said noise.
A method of reducing noise in a demodulated signal obtained by demodulation of a radio signal, comprising:
- (a) determining an electric-field strength of said radio signal;
- (b) comparing said electric-field strength with at least one predetermined reference value, thereby generating an indicator signal indicating said electric-field strength;
- (c) detecting the noise in said demodulated signal;
- (d) generating gate pulses responsive to said indicator signal and to detection of said noise, the gate pulses generated when the indicator signal indicates a comparatively weak electric-field strength being lengthened in relation to the gate pulses generated when the indicator signal indicates a comparatively strong electric-field strength;
- and
- (e) modifying said demodulated signal during intervals indicated by the gate pulses, thereby generating a modified demodulated signal from which noise has been removed.
Dependencies are inferred from the claim text.