We present the development of a second generation digital readout system for photon counting microwave kinetic inductance detector (MKID) arrays operating in the optical and near-IR wavelength bands. Our system retains much of the core signal processing architecture from the first generation system, but with a significantly higher bandwidth, enabling readout of kilopixel MKID arrays. Each set of readout boards is capable of reading out 1024 MKID pixels multiplexed over 2 GHz of bandwidth; two such units can be placed in parallel to read out a full 2048 pixel microwave feedline over a 4 -- 8 GHz band. As in the first generation readout, our system is capable of identifying, analyzing, and recording photon detection events in real time with a time resolution of order a few microseconds. Here, we describe the hardware and firmware, and present an analysis of the noise properties of the system. We also present a novel algorithm for efficiently suppressing IQ mixer sidebands to below -30 dBc.
@article{arxiv.2011.06685,
title = {Second Generation Readout For Large Format Photon Counting Microwave Kinetic Inductance Detectors},
author = {Neelay Fruitwala and Paschal Strader and Gustavo Cancelo and Ted Zmuda and Ken Treptow and Neal Wilcer and Chris Stoughton and Alex B. Walter and Nicholas Zobrist and Giulia Collura and Isabel Lipartito and John I. Bailey and Benjamin A. Mazin},
journal= {arXiv preprint arXiv:2011.06685},
year = {2021}
}