CMOS analog front-end for conversational video phone modem

Abstract

A description is given of an analog front-end chip relating to a video phone for transmission of audio signals and freeze-frame video images over voice-grade telephone lines. The device is implemented in a 3-μm CMOS process, utilizes switched-capacitor circuit technology and contains major functional blocks, such as a synchronous demodulator, transmit/receive filters, baseband and interpolating filters, an 8-bit digital-to-analog converter, a programmable gain amplifier, and clock and carrier recovery circuits. The chip occupies 27000 mil ² and dissipates 100 mW. System and circuit aspects of the design are discussed