Research On High Dynamic Weak GNSS Baseband Signal Acquisition Algorithms Based On CPM

Continuous phase modulation(CPM) signal has several good characteristics of constant envelope, high power, high frequency spectrum utilization and strong anti-interference ability and so on. So in this paper, high dynamic weak GNSS signal acquisition algorithms is studied in detail based on CPM transmission system.The relevant technology of the GNSS receiver, baseband signal acquisition and tracking are the core technology; the correct acquisition is the precondition of system for subsequent work. The sensitivity and speed of signal acquisition can directly determine the performance of GNSS receiver. At present, GNSS system has got wide application in the world. However, it is used in the environments where GNSS signals are good. Receiver carriers are high speed movement and the signal will be affected by all kinds of negative effects in the actual environment that are the main areas where humans live in. So require GNSS receiver sensitivity in such an environment, the higher the better. But the weak signal and high dynamic complicated environment are key problems for GNSS signal acquisition. In this paper, factors affecting the acquisition performance are analyzed under high dynamic condition and weak signal. Firstly, dynamic fast coherent technique is obtained by comparing the acquisition scheme of basic signal acquisition. Secondly, four accumulation algorithms combining the high-dynamic weak GPS signal acquisition factors are discussed. Their applicable occasions are given through the experimental analysis, and by comparation we choose the combination of coherent accumulation and simple differential coherent accumulation acquisition algorithm as high dynamic weak GPS signal acquisition scheme, which efficiently captures the GPS signal under the environment of the extremely low-SNR, the carrier has a large movement speed and acceleration.Generally speaking, acquisition must be fast enough under high dynamic condition, so the integral time is the shorter the better, but enough integration time should be needed when the GPS signal is weak, we can see these two conditions are contradiction. For this problem, the best acquisition scheme is 1ms coherent accumulation and 10 ms simple differential coherent accumulation, which can guarantee the processing gain of 8d B and satisfy the weak signal acquisition conditions. In order to reduce the computational complexity of the algorithm, the data preprocessing technology and FFT parallel technology are studied in detail, which can effectively improve the performance of the algorithm.