Periodic PN sequence delay estimation using phase spectrum data

An algorithm for estimating the delay of a periodic pseudonoise (PN) sequence is presented. It is a rapid, block-based estimator that can be used for both linear and nonlinear codes. The algorithm exploits the periodicity of the difference between the phase spectra of the received sequence and a local reference. The estimator takes the Fourier transform of the phase spectrum difference data, and searches for the fundamental frequency. Unlike previously described methods, phase unwrapping is not required. The performance in the presence of additive white Gaussian noise (AWGN) and a continuous wave (CW) jammer is investigated using computer simulation. Comparisons are made against the delay maximum likelihood estimator (MLE) and other published results. While the proposed estimator has a complexity similar to that of the MLE, it has a relative performance loss of 7 dB under AWGN. However, the proposed estimator can outperform the MLE by 14.5 dB when a CW jammer is present