Progress of the ECHo SDR Readout Hardware for Multiplexed MMCs

Abstract The electron capture in $$^{163}$$ 163 Holmium (ECHo) experiment seeks to achieve sub-eV sensitivity of the neutrino mass through calorimetric decay spectroscopy Ho large arrays cryogenic magnetic microcalorimeters (MMCs). Microwave SQUID multiplexing serves efficiently increase number readout channels, thus calorimeters per array and ultimately cryostat. A corresponding frequency room temperature software-defined radio (SDR) system is development enable this increased MMCs cable. SDR consists a custom FPGA platform that provides signal generation analysis capabilities, as well tailored conversion analog conditioning front end electronics room-temperature-to-cryogenic interface. Ultimately, will read out 400 multiplexer channels with double pixel detectors bandwidth 4 GHz (IEEE C band). As high-resolution data converters are limited sample rate, C-band split into five sub-bands using two-stage mixing method. In contribution, prototype heterodyne RF design presented. It comprises one 800 MHz for target range between 8 GHz. Furthermore, second version A/D converter stage presented, capable generating digitizing up complex basebands 1 GSs $$^{-1}$$ - 1 converters, reference clocks flux-ramp signal. We show first results their single combined characterization lab. current state hardware enables preliminary measurements, only slightly higher noise. Potential improvements could be derived implemented full bandwidth, 5-sub-band PCB design.