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

Abstract Ultra-light dark matter candidates, such as axions and dark photons, particularly within the mass range of $\mu 10^{\rm V}$ to ${\rm meV}$, have garnered significant research interest. Detection approaches such as the dish-antenna method benefit from broadband spectrometers, allowing for efficient scanning across a broad dark matter mass range. This study presents a novel spectrometer solution based on an RFSoC. The spectrometer’s programmable logic implements an optimized fast Fourier transform (FFT) that minimizes memory usage, enabling an instantaneous bandwidth of $4 \,{\rm GHz}$ with a frequency resolution of $16 \,{\rm kHz}$. 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.