A fast direct acquisition algorithm of GPS L2C CL signal based on time-frequency dual folding technique

L2C is the second civilian signal broadcasted on the modernized block of GPS satellites. Compared with L1C/A, the length of L2C code is longer, and includes the civil moderate code (CM code, 20ms) and the civil long code (CL code, 1.5s), which are based on time division multiplexing. For the long CL code, rapid acquisition is difficult due to the large search space. To accelerate the search process and improve detection performance, a fast direct GPS L2C CL signal acquisition algorithm based on time-frequency dual folding technique is introduced in this paper. By folding both the incoming and local signals, the method can be used to significantly accelerate the acquisition speed, and the degraded code correlation properties are insignificant. The effectiveness of the method of fast direct acquisition algorithm based on the time-frequency folding technique is proven through both theoretical performance analysis and real GPS L2C signal experiments.