A segmented matched filter for CDMA code phase acquisition

This paper presents a segmented transversal matched filter (SMF) capable of performing code phase acquisition for a direct sequence spread spectrum (DS-SS) system in the presence of Doppler frequency shift and high co-user noise. Traditional acquisition methods such as serial search, sequential estimation, and I-Q matched filters are either too slow, incapable of overcoming high co-user noise, or unable to handle phase rotations due to Doppler shifts. The SMF has a high acquisition speed because it retains the signal history. A new code phase candidate can be tested as each new code chip is received. The segmentation of the SMF´s correlation function allows it to handle several cycles of phase rotation caused by carrier frequency offset (Doppler). Presented here is a 512 bit, 16 segment (32 bits per segment) SMF implemented as a mixed analog/digital integrated circuit (IC). Several ICs may be cascaded to extend the effective filter length