Digital processing radio receiver with adaptive bandwidth control

摘要

An adaptive intermediate frequency bandwidth control system detects IF signal levels both before and after channel filtering. The two levels are compared to provide a measure of the presence of interfering adjacent channels. This measure is compared to a programmable threshold and the IF bandwidth is narrowed if any interferers are detected. Digital FIR or IIR filtering is used. The invention allows bandwidth switching to be done very quickly with minimal transient effects. A difference threshold is selected depending upon the IF channel bandwidth being used at any given time.