| Summary: | Spaceborne synthetic aperture radar (SAR) plays an important role in many fields of national defense and the national economy, and the Fast Fourier Transform (FFT) processor is an important part of the spaceborne real-time SAR imaging system. How to meet the increasing demand for ultra-large-scale data processing and to reduce the scale of the hardware platform while ensuring real-time processing is a major problem for real-time processing of on-orbit SAR. To solve this problem, in this study, we propose a 128k-point fixed-point FFT processor based on Field-Programmable Gate Array (FPGA) with a four-channel Single-path Delay Feedback (SDF) structure. First, we combine the radix-2<sup>3</sup> and mixed-radix algorithms to propose a four-channel processor structure, to achieve high efficiency hardware resources and high real-time performance. Secondly, we adopt the SDF structure combined with the radix-2<sup>3</sup> algorithm to achieve efficient use of storage resources. Third, we propose a word length adjustment strategy to ensure the accuracy of calculations. The experimental results show that the relative error between the processor and the MATLAB calculation result is maintained at about 10<sup>−4</sup>, which has good calculation accuracy.
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