Doppler Effect Compensation Method Based on Multi-Symbol Multi-Pilot Joint Sequence Frequency Offset Estimation and FPGA Implementation

In the face of low-orbit broadband satellite OFDM systems, the traditional frequency offset estimation algorithm has limited performance in frequency offset estimation for signal frames composed of multiple OFDM symbols, and does not consider the problem of inconsistent frequency offsets of each subcarrier. Based on the structure of Starlink inserting eight pilots on both sides of the signal, this paper proposes a Doppler effect compensation algorithm based on multi-symbol multi-pilot joint sequence frequency offset estimation. The algorithm extracts the timing sequence composed of all pilots of all OFDM symbols of the signal frame composed of multiple OFDM symbols and uses its FFT to perform frequency offset estimation and Doppler factor calculation, and then compensates for the inter-symbol interference caused by frequency offset and Doppler effect. For time domain compensation, this paper proposes a smaller multiple linear resampling FPGA implementation scheme based on index position judgment and pointer, and designs a resampling index position judgment structure. This structure is used to generate the index of the resampled data and judge the position of the new index in the original data index. According to this position, the corresponding sampling value is obtained by pointer addressing. Then, based on this sampling value, linear interpolation is used to calculate the resampled sampling value to achieve pipeline output and reach a sampling multiple of 0.99995-1.00005 times. At the same time, this paper proposes a four-way parallel FPGA implementation of the algorithm, which enables the algorithm to function at a lower clock while ensuring performance.