Circuit and method of suppressing inter-station radio tuning noise

Claim 1

A radio receiver, particularly FM receiver having an audio stage providing an audio signal and an audio transmission path, said audio stage having a muting stage which includes a gate circuit (3) which mutes output signals in the transmission path during tuning of the receiver; and inhibiting means (7, 4, 9, u 1 ) coupled to and controlling the gate circuit for inhibiting transmission of audio signals to an audio signal terminal (6) for a muting interval (T M ), and permitting passage of audio signals after the muting interval, said radio receiver further comprising a switchable high-pass filter (2) connected in the transmission path to the muting stage and having a first low-frequency cut-off frequency level (f g1 ) and a second low-frequency cut-off frequency level (f g2 ) which is at a higher frequency than said first frequency level; and muting control circuit means (7, 4, 8, u 2 ) connected to and controlling the high-pass filter (2) to the second and higher low-frequency cut-off level (f g2 ) for a predetermined limited time period (T E ) after said muting interval, and while the gate circuit (3) transmits the audio signals in said transmission path, wherein the second higher frequency cut-off level (f g2 ) is just above the frequency of noise interference due to the tuning of the receiver.

Claim 8

A method of suppressing inter-station radio tuning noise in a radio receiver, particularly a frequency modulation (FM) receiver providing an audio signal, said noise occurring upon tuning the radio receiver from a first station to a second station said method comprising the steps of (a) muting a reproduction of the entire audio signal for the duration of a muting interval (T M ) when the audio signal has a characteristic representative of interstation noise; and (b) additionally suppressing a portion only of the audio signal during a limited time period (T E ), subsequent to the muting interval (T M ), which portion consists of a first portion comprising the low audio spectrum and, or lowest frequency range of the frequency spectrum of the audio signal, so that a remaining portion of the audio signal comprising the higher frequency spectrum and above said low audio spectrum end, or lowest frequency range of the frequency spectrum of the audio signal, is reproduced by the radio receiver during said limited time period (T E ) and subsequent to the muting interval (T M ).

Claim 9

A method of suppressing inter-station radio tuning noise in a radio receiver, particularly a frequency modulation (FM) receiver providing an audio signal, said noise occurring upon tuning the radio receiver from a first station to a second station said method comprising the steps of (a) muting a reproduction of the entire audio signal for the duration of a muting interval (T M ) when the audio signal has a characteristic representative of interstation noise; and (b) additionally suppressing a portion only of the audio signal during a limited time period (T E ), subsequent to the muting interval (T M ), which portion consists of a first portion comprising the low audio spectrum and, or lowest frequency range of the frequency spectrum of the audio signal, so that a remaining portion of the audio signal comprising the higher frequency spectrum and above said low audio spectrum end, or lowest frequency range of the frequency spectrum of the audio signal, is reproduced by the radio receiver during said limited time period (T E ) and subsequent to the muting interval (T M ).