IF-to-digital converter for FM/AM/IBOC radio

Abstract

An IF-to-digital converter that can handle AM, FM, and IBOC (In Band On Channel) signals is presented. The highest radio quality is obtained by a front-end with a single tuner and two IF-to-digital converters for seamless blending between the AM/FM and the IBOC (digital radio) mode. The IF-to-digital converters incorporate mixers that are highly insensitive to parasitic double sampling. Besides the converters the chip includes digital IF post-processing circuitry, three radio DSPs (digital signal processors) and the audio part to fulfill the rest of the car radio functions. Radio functions like signal quality improvement, signal demodulation, weak signal handling, multipath, phase antenna diversity and customer specific features are implemented in software for high system flexibility. The IF-to-digital converter is processed in a 0.18 /spl mu/m CMOS process and achieves 99dB in a 3kHz Am bandwidth, 79dB in the 200kHz FM band and 74dB in 575kHz for IBOC.