Long‐term integration based on two‐stage differential acquisition for weak direct sequence spread spectrum signal

Fast acquisition in space telemetry and telecontrol communication system is challenged significantly by the high dynamic and low signal-to-noise ratio. Increasing the dwell time to obtain better acquisition sensitivity, based on two-dimensional time-frequency search, is impossible because of resource limitation in receiver. To tackle these problems, this study proposes a two-stage differential acquisition (TSDA) algorithm. The differential coherent integration is employed by the first stage of TDSA to extend integration time, during which keystone transform and fast Fourier transform are used to compensate the linear code phase drift and obtain high accumulation gain. The carrier-frequency offset is estimated in terms of the code phase difference between the two parts of received signal divided by the second stage of TSDA in which the two-dimensional searching process is avoided. The proposed TSDA algorithm and the traditional acquisition methods are compared under the same acquisition time and typical parameters of S-band space telemetry and telecontrol communication system. Simulation results demonstrate that the proposed TSDA algorithm attains a higher acquisition probability and better acquisition sensitivity than the traditional acquisition methods.