Design and implementation of a real-time L2C IF signal simulator

Commercial GNSS RF signal simulators are expensive and few of them provide modernized GPS L2C signal simulation capability so far. Based on the SDR architecture of a GNSS RF signal simulator developed by Beihang University, China, this paper focuses on the design and implementation of the L2C IF signal generator. The calculation and updating of waveform control parameters, the modulation of baseband signals, the combination of multiple satellite channel signals, and the generation of analog IF signal are implemented using DSP + FPGA + DAC. A method of fast alignment of the initial phase of L2C CL code is proposed, and the power control of the combined signal is also explored. The accuracy and quality of the simulated signals are validated by the acquisition, tracking and positioning results using a software receiver. The L2C signal simulator can serve as a signal source for the development of high-performance receivers.