Broadband, Dead-Time-Free Spectrometer Using RFSoC for WISP Dark Matter Searches

Ultra-light dark matter candidates, such as axions and dark photons, particularly within the mass range of $\mu$eV to meV, have garnered significant research interest. However, the effectiveness of existing experiments is often hindered by the narrow bandwidths of conventional spectrometers. This study presents a novel spectrometer solution based on a RFSoC, which integrates a high-speed data converter, field programmable gate array (FPGA), and a CPU within a single chip. The spectrometer's programmable logic implements an optimized fast Fourier transform (FFT) that minimizes memory usage, enabling an instantaneous bandwidth of 4 GHz with a frequency resolution of 16 kHz. This configuration achieves more than 99.6% time efficiency, effectively doubling search efficiency, compared with traditional approaches. This paper provides a comprehensive description of the hardware architecture, FPGA firmware, and software implementation, with a focus on the resource-efficient pipelined FFT algorithm. Performance validation results are also presented, demonstrating the accuracy and time efficiency of the developed spectrometer, highlighting its potential for advancing dark matter search.