CCAT: a two-octave 1.024 GHz KID readout featuring an overlap-channel polyphase synthesis filter bank on RFSoC - arXiv:2608.13852v1

Oct 3, 2026

Next-generation submillimeter instrumentation needs gigahertz-scale readout bandwidths to scale microwave kinetic inductance detector (KID) array counts. To meet CCAT Prime-Cam 850GHz and 410GHz module requirements, a second-generation (Gen2) KID readout system was built on a Xilinx ZCU111 RFSoC. The two-octave parallelized overlap-channel polyphase synthesis filter bank and wideband channelizer read four independent RF networks with 1.024GHz instantaneous bandwidth and up to 2048 detectors each. DSP simulation and RF loopback plus KID test-chip measurements validate performance, including noise comparisons to Gen1, preliminary noise-limited behavior off resonance, measured digital crosstalk, FPGA resource/power assessment, and scalability toward large-format instruments.

LanguageEnglish

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Abstract

1. Introduction

arXiv :2608 . 13852v1 [ astro-ph .IM] 14 Aug 2026 CCAT: a two-octave 1.024 GHz KID readout featuring an overlap-channel polyphase synthesis filter bank on RFSoC Ruixuan (Matt) Xiea,* , Adrian K. Sinclairb , James Burgoynea , Maxwell Chapmand , Scott Chapmanc,a , Steve K. Choie , Anthony I. Hubera , Ben Kellerf, and Michael D. Niemackf,g aDept. of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada b The William H. Miller III Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, United States c Dept. of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada d Dept. of Mechanical Engineering, McGill University, Montreal, QC, Canada e Center for Experimental Cosmology and Instrumentation, Dept. of Physics and Astronomy, University of California, Riverside, CA 92521, USA fDept. of Physics, Cornell University, Ithaca, NY, 14853, USA g Dept. of Astronomy, Cornell University, Ithaca, NY, 14853, USA ABSTRACT Next-generation submillimeter instruments require gigahertz-scale readout bandwidths to support the growing detector counts of large microwave kinetic inductance detector (KID) arrays. Designed to meet the readout bandwidth and tone-capacity requirements of the CCAT Prime-Cam 850GHz and 410GHz instrument modules, we developed our second-generation (Gen2) KID readout system on a Xilinx ZCU111 radio frequency system-onchip (RFSoC), based on a parallelized overlap-channel polyphase synthesis filter bank and a companion wideband receiving channelizer. This two-octave architecture reads out four independent RF networks, each with 1.024GHz instantaneous bandwidth and up to 2048 detectors. The polyphase synthesis doubles the baseline channel count and bandwidth, and enables on-the-fly control of individual tone frequency, amplitude and phase, facilitating optimized KID biasing and providing a gateway to tone tracking. These capabilities may also be useful more broadly across Prime-Cam and in similar frequency-division multiplexed (FDM) readout systems. We present the design in DSP simulation, and measurements in RF loopback as well as with two KID test chips, one spanning the full two-octave band. Loopback measurements demonstrate comparable noise performance between the firstgeneration (Gen1) baseline and Gen2; preliminary on/off-resonance measurements indicate detector-noise-limited operation for the majority of channels; and the digital channel crosstalk is measured and discussed. We report FPGA resource and power utilization and assess scalability toward future large-format KID instruments. Keywords: MKID, KID, RFSoC, polyphase filter bank, DSP, frequency-division multiplexing, tone tracking, submillimeter astronomy, CCAT, Prime-Cam *Correspondence should be addressed [to R.X.:](to R.X.: MattXie956@gmail.com)[ MattXie956@gmail.com](to R.X.: MattXie956@gmail.com) 1. INTRODUCTION Observations at submillimeter and far-infrared wavelengths probe some of the most anticipated and informative processes in the Universe, including galaxy assembly through the epoch of reionization, large-scale structure through the Sunyaev–Zeldovich effect, cosmic star formation, and dust-polarized foregrounds for CMB B-mode measurements.1 The scientific return from these observations scales strongly with mapping speed, which in turn scales with detector count. Microwave kinetic inductance detectors (KIDs) have emerged as a technology of choice for large-format sub-mm focal planes, because of their high multiplexing factor, photon-noise-limited sensitivity, 2 fabrication simplicity, and natural compatibility with frequency-division multiplexing (FDM) readout.3 In FDM, thousands of KIDs, each a superconducting LC resonator with a unique resonant frequency, are capacitively coupled to a single coaxial transmission line and simultaneously read out via a wideband frequency comb of probe tones (also called bias tones) .4 , 5 As detector counts grow, the readout bottlene

FAQs

What problem does the Gen2 CCAT Prime-Cam KID readout address?

It targets the readout bottleneck by providing gigahertz-scale bandwidth and tone capacity as KID detector counts grow in submillimeter instruments.

What hardware platform and key digital architecture are used in the Gen2 system?

A Xilinx ZCU111 RFSoC implements a parallelized overlap-channel polyphase synthesis filter bank together with a companion wideband receiving channelizer.

How is performance validated in the paper?

Results include DSP simulations and RF loopback measurements, along with measurements using two KID test chips, including one spanning the full two-octave band.

Oct 3, 2026

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