Bandwidth and Aliasing in the Microwave SQUID Multiplexer

TL;DR

This paper investigates the bandwidth limitations and aliasing effects in microwave SQUID multiplexers, crucial for designing large-scale cryogenic detector systems in physics and astronomy.

Contribution

It provides a detailed analysis of bandwidth factors, including device intrinsic properties and electronics interactions, with simulations and measurements for improved system design.

Findings

Bandwidth is limited by device and electronics interactions.

Aliasing significantly affects system performance.

Simulations align with experimental measurements.

Abstract

The microwave SQUID multiplexer (umux) has enabled higher bandwidth or higher channel counts across a wide range of experiments in particle physics, astronomy, and spectroscopy. The large multiplexing factor coupled with recent commercial availability of microwave components and warm electronics readout systems make it an attractive candidate for systems requiring large cryogenic detector counts. Since the multiplexer is considered for both bolometric and calorimetric applications across several orders of magnitude of signal frequencies, understanding the bandwidth of the device and its interaction with readout electronics is key to appropriately designing and engineering systems. Here we discuss several important factors contributing to the bandwidth properties of umux systems, including the intrinsic device bandwidth, interactions with warm electronics readout systems, and aliasing. We present simulations and measurements of umux devices coupled with SLAC Microresonator RF (SMuRF) tone-tracking electronics and discuss several implications for future experimental design.