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Frequency Domain Multiplexing for Microwave Kinetic Inductance Detectors: Comparing the Xilinx ZCU111 RFSoC with the New 2x2 RFSoC Board


The Xilinx ZCU111 Radio Frequency System on Chip (RFSoC) is a promising solution for reading out large arrays of microwave kinetic inductance detectors (MKIDs). The board boasts eight on-chip 12-bit / 4.096 giga samples-per-second (GSPS) analogue-to-digital converters (ADCs) and eight 14-bit / 6.554 GSPS digital-to-analogue converters (DACs), as well as field programmable gate array (FPGA) resources of 930,000 logic cells and 4,272 digital signal processing (DSP) slices. While this is sufficient data converter bandwidth for the readout of 8,000 MKIDs, with a 2 MHz channel-spacing and a 1 MHz sampling rate (per channel), additional FPGA resources are required to perform the DSP needed to process this large number of MKIDs, due to a mismatch between the data converter bandwidth relative to the FPGA resources of the ZCU111. A solution to this problem is the new Xilinx RFSoC 2x2 board. This board costs only one fifth of the ZCU111 while still providing the same logic resources, albeit with only a quarter of the data converter resources. Thus, using multiple RFSoC 2x2 boards would provide a better balance between FPGA resources and data converters, allowing the full utilization of the RF bandwidth provided by the data converters, while also lowering the cost per pixel value of the readout system; from approximately €2.50 per pixel with the ZCU111 to €1 per pixel with the 2x2.

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Data Availability

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.


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This material is based upon works supported by the Science Foundation Ireland under Grant No. grant 15/IA/2880. The authors would also like to thank Dr Deli Geng from Durham University for providing the mixer board which was used to help generate the data for Figs. 3 and  4. Furthermore, the authors would like to thank Cathal McCabe of Xilinx for providing the Vivado licenses used in the project.

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Baldwin, E., De Lucia, M., Bracken, C. et al. Frequency Domain Multiplexing for Microwave Kinetic Inductance Detectors: Comparing the Xilinx ZCU111 RFSoC with the New 2x2 RFSoC Board. J Low Temp Phys 209, 640–648 (2022).

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  • Microwave kinetic inductance detectors
  • Kinetic inductance detectors
  • MKIDs
  • KIDs