# Performance of a low-parasitic frequency-domain multiplexing readout

## TL;DR

This paper presents a low-parasitic frequency-domain multiplexing readout for CMB experiments, improving crosstalk and noise performance, enabling higher multiplexing factors and better bolometer optimization.

## Contribution

It introduces a design that reduces parasitic impedance, doubling parasitic resistance reduction and enhancing readout performance for CMB detector arrays.

## Key findings

- Achieved a twofold reduction in parasitic resistance.
- Demonstrated noise performance comparable to existing hardware.
- Enabled operation of lower-resistance bolometers for improved noise performance.

## Abstract

Frequency-domain multiplexing is a readout technique for transition edge sensor bolometer arrays used on modern CMB experiments, including the SPT-3G receiver. Here, we present design details and performance measurements for a low-parasitic frequency-domain multiplexing readout. Reducing the parasitic impedance of the connections between cryogenic components provides a path to improving both the crosstalk and noise performance of the readout. Reduced crosstalk will in turn allow higher multiplexing factors. We have demonstrated a factor of two improvement in parasitic resistance compared to SPT-3G hardware. Reduced parasitics also permits operation of lower-resistance bolometers, which enables better optimization of R$_{\rm{bolo}}$ for improved readout noise performance. The prototype system exhibits noise performance comparable to SPT-3G readout hardware when operating SPT-3G detectors.