A 75-mW 128-MHz DS-CDMA Baseband Demodulator for High-Speed Wireless Applications

A DS-CDMA demodulator uses analog sampled-data signal processing to achieve a 75-mW power dissipation and a 128-MS/s processing rate in a 1.2m double-metal double-poly CMOS process. To demodulate the signal, a low-power passive correlation technique is introduced that eliminates the integrating opamp with its associated power and settling time overhead. In a prototype demodulator, six 64-chip correlators recover the 2Mb/s data stream from the doubly modulated [pseudorandom noise (PN) and Walsh] quadrature input signal. An on-chip 10-b pipelined ADC sampling at 8 MS/s follows the analog correlation to permit digital implementation of the acquisition and tracking algorithms.