Design of Chip Set for CDMA Mobile Station

Abstract

In this paper, we present a design of modem and vocoder digital signal processor (DSP) chips for CDMA mobile station. The modem chip integrates CDMA reverse link modulator, CDMA forward link demodulator and Viterbi decoder. This chip contains 89,000 gates and 29 kbit RAMS, and the chip size is 10 mm x 10.1 mm which is fabricated using a 0.8 μm 2 metal CMOS technology. To carry out the system-level simulation, models of the base station modulator, the fading channel, the automatic gain control loop, and the microcontroller were developed and interfaced with a gate-level description of the modem application specific integrated circuit (ASIC). The Modem chip is now successfully working in the real CDMA mobile station on its first fab-out. A new DSP architecture was designed to implement the Qualcomm code exited linear prediction (QCELP) vocoder algorithm in an efficient way. The 16 bit vocoder DSP chip has an architecture which supports direct and immediate addressing modes in one instruction cycle, combined with a RISC-type instruction set. This turns out to be effective for the implementation of vocoder algorithm in terms of performance and power consumption. The implementation of QCELP algorithm in our DSP requires only 28 million instruction per second (MIPS) of computation and 290 mW of power consumption. The DSP chip contains 32,000 gates, 32k (2k x 16 bit) RAM, and 240k (10kx24 bit) ROM. The die size is 8.7 mmx8.3 mm and the chip is fabricated using 0.8 μm CMOS technology.