  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.
