Radio receiver having a multi-state variable threshold automatic gain control (AGC) for fast channel scanning acquisition and mehtod for using same

A radio receiver having an automatic gain control (AGC) system for use in a fast channel scanning acquisition mode comprising:

• at least one receiver amplifier having a variable gain control for controlling the power level of a received RF signal;
• an digital to analog converter (DAC) whose output voltage sets the gain of the receiver amplifier;
• an analog-to-digital converter (ADC) that samples the received signal at a first sample rate and converts the received signal to a digital signal;
• a digital section after the ADC that processes the ADC digital signal to a second sample rate therein generating a sampled digital signal after a finite delay proportional to the second sample rate;
• a digital signal processor (DSP) for final processing the sampled digital signal;
• a host processor for receiving the processed signal;
• a signal magnitude estimator whose output signal is proportional to the received signal level;
• at least one comparator that compares the output of the signal magnitude estimator to a reference threshold and changes state when the signal magnitude estimator output signal exceeds the reference threshold;
• an AGC controller for scaling a reference level of the at least one comparator for substantially low received signal levels;
• a digital signal path between the AGC controller and the host processor whereby the AGC controller may initiate an Interrupt Service Request (ISR) to the host processor when the at least one comparator changes state;
• and
• wherein the host processor uses the ISR to enable DSP processing of the processed signal to the host processor if a received signal is detected during the fast channel scanning acquisition mode.

A method for minimizing interruptions in the audio stream during channel scanning in a radio receiver comprising the steps of:

• controlling the gain of an analog signal in at least one receiver amplifier having an automatic gain control (AGC) performing a closed loop function;
• converting the analog signal to a digital signal using an analog-to-digital converter (ADC);
• processing the digital signal using a digital signal processor (DSP);
• receiving the signal from the DSP using a host processor;
• controlling operation of the AGC using a digital received signal magnitude estimate;
• and
• providing an interrupt service request (ISR) to the DSP and the host processor if an radio frequency (RF) signal is detected during a fast channel scanning acquisition mode while minimizing interruptions in the digital signal at the output of the ADC by configuring the AGC controller to detect priority channel activity while the DSP is processing legacy samples on the non-priority channel.