Abstract: The present invention provides a search window delay tracking procedure for use in a multipath search processor of a CDMA radio receiver. A channel impulse responses is estimated for a received signal containing plural paths, each path having a corresponding path delay. A search window defines a delay profile that contains the plural paths of the received signal. A mean or average delay is calculated for the estimated channel impulse response (CIR), and an error is determined between the mean CIR delay and a desired delay position corresponding to the center of the CIR search window. An adjustment is made to reduce that error so that the center of the search window and the mean CIR delay are aligned. The error may be processed either linearly (in one embodiment) or non-linearly (in another embodiment) to minimize the error and to reduce an influence of noise.

Abstract: Incoming signals in a receiver for Direct Sequence Code Division Multiple Access systems are despread using Offset-QPSK spreading as the transmitting spreading format combined with arbitrary data modulation formats, such as BPSK and QPSK. The receiver has a pseudonoise (PN) generator for generating a unique PN sequence signal. The PN sequence signal is divided into a real and an imaginary component. The complex input signal is divided into inphase and quadrature components. The inphase and the quadrature components of the input signal are downsampled to provide either two complex samples per chip period or one complex sample per chip period. In the latter case, the downsampling instants are delayed by a quarter of a chip period. Each downsampled complex signal is correlated with the corresponding segment of the complex PN sequence signal of the receiver.