Implementation of a Space-borne Dual-frequency GPS RO FPGA Receiver with High-dynamic Bit Assist Acquisition

Radio occultation (RO) is a powerful satellite telemetry technique for providing vertical profiles of temperature and electron density of the ionosphere, which assures higher-value meteorological applications. In RO applications, receivers must collect dual-frequency Global Navigation Satellite System (GNSS) signals which pass through the atmosphere with different signal bending angles and modulate with their spreading code. Receiving secondary L2 signal by the satellite receiver is subject to the high mobility, fast channel parameter drift, longer L2 spreading code, and weak RO signals, therefore we implemented a GPS RO receiver with an adaptive channel link on the FPGA to perform high-dynamic aid acquisition to rapidly acquire the secondary GPS RO signal, achieving high-dynamic and weak signal detection, initializing its following tracking loop with a small loop initial error. To verify the scheme, a high-performance GNSS simulator was applied to generate the high-dynamic signal. Experiments at the seaside were performed to clarify the performance of receiving low-elevation RO signals from sea level.