A chip set for 7 KHz handfree telephony

This paper presents three VLSI circuits developed for an enhanced quality handfree telephone terminal (bandwidth up to 7 KHz). A first circuit performs the intensive computation task required by an adaptive filter of up to 1020 taps at 16 kHz sampling frequency for acoustic echo cancellation (AEC). A microprogrammed DSP with a specific architecture implements the bit rate compression/expansion (IUT G722 recommendation) and controls the gain of the AEC. The third circuit performs AD and DA conversion with corresponding filtering at 16 Ksamples/s with 15 bits resolution. The three circuits have been designed in 1 /spl mu/ CMOS (AEC and analog front end) and 0,8 /spl mu/ CMOS technology (DSP). Measure results are also presented.>