Automobile radio receivers must perform well under varying reception conditions, and increasingly sophisticated mobile audio gear requires better sound quality for AM and FM reception. Fujitsu Ten have developed a mobile AM tuner IC to meet these requirements. The IC features an RF-AGC circuit which enables the receiver to tune in remote signals while rejecting strong local signals, a variable IF bandwidth control circuit to demodulate broader bandwidths, and a new tracking circuit for the RF tuning circuits and local oscillator. These features enable the received frequency range to be expanded (to 1710 kHz) and to improve the quality of AM stereo reception.
The techniques developed for the new mobile AM tuner IC are described below.