Dual speed squelch circuit and method

A method for squelch control in a radio receiver, the method comprising:

• filtering an audio signal with a bandpass sufficiently high relative to frequency components of the audio signal;
• generating an output signal having a positive polarity regardless of the polarity of the signal obtained through the audio filtering action;
• providing an integrating filter coupled to receive the positive polarity signal and supply an integrated signal, the integrating filter having at least one selectable filter coefficient indicative of the response time of the integrating filter;
• selecting a first value for the selectable filter coefficient so that during a first mode of operation the response time of the integrating filter is sufficiently fast to determine the power level of the integrated signal over a predefined time interval relative to respective squelch thresholds;
• and
• selecting a second value for the selectable filter coefficient so that during a second mode of operation subsequent to the first mode of operation, the response time of the integrating filter is sufficiently slow to smooth out power level variations, if any, due to fading of the audio signal.

A computer-readable medium including instructions causing a computer to control squelch in a radio receiver by:

• filtering an audio signal with a bandpass sufficiently high relative to frequency components of the audio signal;
• generating an output signal having a positive polarity regardless of the polarity of the signal obtained through the audio filtering action;
• configuring an integrating filter to receive the positive polarity signal and supply an integrated signal, the integrating filter having at least one selectable filter coefficient indicative of the response time of the integrating filter;
• selecting a first value for the selectable filter coefficient so that during a first mode of operation the response time of the integrating filter is sufficiently fast to determine the power level of the integrated signal over a predefined time interval relative to respective squelch thresholds;
• and
• selecting a second value for the selectable filter coefficient so that during a second mode of operation subsequent to the first mode of operation, the response time of the integrating filter is sufficiently slow to smooth out power level variations, if any, due to fading of the audio signal.