New Integrated Circuits for Electronically-Tuned Automotive Radios

The increasing availability of digital tuning systems using phase-locked loops to control the radio local oscillator (LO) frequency and RF tuning, and the anticipated introduction of an AM stereo broadcast service, has motivated the development of a new set of integrated circuits (I/Cs) specifically designed to handle the broadcast signal processing functions of the radio. Features such as a valid station stop detector are provided for interfacing with the tuning system and improved FM performance is achieved, together with the use of dual-threshold AGC circuits and a novel, low-distortion quadrature detector. Special attention has been paid to the AM circuit design in order to accommodate the proposed AM stereo broadcast formats and a new decoder circuit has been developed to complement the improved performance obtainable with this I/C set.