A fast method for the acquisition of weak long-code signal

The growing demand for positioning, navigation and timing services is boosting the development of new signal systems that are gradually being adopted by Global Navigation Satellite System (GNSS), such as the BDS, the Galileo and the modernized GPS. A common feature of these new signal systems is that they have longer pseudorandom noise (PRN) code lengths than the old ones, which greatly improves the ranging accuracy and anti-interference ability of signals. However, the longer PRN code length leads to increased computational complexity and reduced acquisition speed, especially in low-carrier-to-noise-ratio (CNR) conditions. A rapid scheme for the acquisition of weak long-code signal is proposed. The reduced Doppler shift and code-phase space are pre-estimated with inertial navigation system (INS) aiding and ephemeris, and an FFT-based parallel time–frequency domain search method is used to realize rapid two-dimensional search. To further reduce the computational complexity of weak long-code signals, a parallel code-phase search (PCS) method with reduced code-phase space based on matrix partition and reconfiguration is proposed inside the correlator, which can realize the rapid coherent operation of signals. The proposed algorithm can greatly reduce the theoretical operands of FFT operation in the acquisition without loss to the relevant peak, to meet the requirements of receiver sensitivity and acquisition speed in the low-CNR conditions. Finally, computer simulations verify the effectiveness of this acquisition scheme.