Abstract: A technique for reducing multipath distortion in a mobile FM receiver with a plurality of antennas is accomplished through a number of steps. Initially, a first antenna signal and a second antenna signal are received. The first antenna signal is weighted with a variable first weight and the second antenna signal is weighted with a variable second weight. The weighted first antenna signal and the weighted second antenna signal are then combined to provide a combined received signal having a combined signal level. The variable first and second weights are determined by an adaptation strategy that is substantially controlled by a first algorithm, when the combined signal level is greater than a predetermined signal level. When the combined signal level is less than the predetermined signal level, the variable first and second weights are determined by an adaptation strategy substantially controlled by a second algorithm.

Abstract: A technique for reducing multipath distortion in an FM receiver, with a plurality of switchable antennas, provides a fast distortion detector that monitors a received signal for significant distortion events of less than about 15 microseconds in duration. In response to a multipath event, the output of the fast distortion detector initiates a search for a lower distortion (better quality) antenna. To prevent frequent antenna searches from causing an audible disturbance, a threshold is introduced to desensitize the fast distortion detector. Threshold decay is a function of an overall received RF signal level. A slow distortion detector is also provided that measures distortions of the received signal relating to signal quality.