Power consumption of parallel spread spectrum correlator architectures

Parallel correlation in direct-sequence spread spectrum system allows faster and more reliable coarse acquisition. However, the power consumed becomes significant especially for receivers that employ a large number of parallel correlators. In this paper, the power efficiency of various parallel correlator architectures is explored assuming baseband sampled signals of two samples per chip. Active correlators placed in parallel that use both two's complement and sign-magnitude accumulators are first presented. A functionally equivalent M-parallel passive correlators are then studied. In this approach, the baseband sampled signals are passed through a tapped delay-line. Each tap is then multiplied by a stationary reference pseudonoise code and summed using a binary tree network. The passive correlators are generally more power efficient compared to both types of active correlators, especially for large M values. Further reduction in power consumption is possible by splitting the tapped delay-line into even and odd delays and summing using two smaller binary tree adders. This proposed architecture consumes significantly less power compared to all other architectures. The power dissipation of M-parallel correlator architectures are evaluated for M = 8, 16, 32 using TSMC 0.35-μm CMOS technology at 3.3 V supply voltage.