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SQUID readout scheme with high dynamic range and intrinsic MHz frequency-division multiplexing capability

Daniel Richter, A. Fleischmann, C. Enss, Sebastian Kempf

Published Jan 1, 2019• 0 citations
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Dc-SQUID readout with high dynamic range and intrinsic frequency-domain multiplexing capability

Sebastian Kempf, Daniel Richter, A. Fleischmann +1 more

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Dc-SQUID Readout with High Dynamic Range and Intrinsic MHz Frequency-Division Multiplexing Capability

Daniel Richter, A. Fleischmann, C. Enss +1 more

We present a novel dc-SQUID readout scheme that provides linearization of the relation between the input and output signal without using a conventional flux-locked loop circuit. It relies on applying a periodic, sawtooth-shaped magnetic flux signal to the modulation coil of the SQUID to continuously measure the flux-to-voltage SQUID characteristic within each period of the flux ramp. In case that the amplitude and repetition rate of the ramp are chosen such that multiple flux quanta are induced in the SQUID and that the input signal is quasistatic within one period of the flux ramp, the input signal adds a constant magnetic flux offset to the SQUID that leads to a phase shift of the SQUID characteristic being proportional to the input signal. We show that this scheme allows for significantly increasing the dynamic range and that it intrinsically allows for MHz frequency-division SQUID multiplexing.

IEEE International Superconductive Electronics Conference (ISEC)•Jul 1, 2019•1 citation

Maximizing multiplexing in 1–100 MHz frequency domain readout of transition edge sensor arrays via crosstalk suppression

Xin Gao, Qian Wang, Jing-Yi Zhang +1 more

Abstract The 1-100 MHz frequency band remains relatively unexplored for Frequency Division Multiplexing (FDM) readout of TransitionEdge Sensor (TES) arrays, despite its potential to increase channel counts beyond the traditionally used 1-5 MHz range. Thisgap, however, is becoming increasingly addressable with advancements in the fabrication of high-resonance-frequency LCresonators and wide-band Superconducting Quantum Interference Devices (SQUIDs). It still partly stems from understudiedcrosstalk challenges in this higher-frequency regime, where mutual inductance, SQUID input inductance, and carrier leakageeffects tend to be more pronounced, which may limit the feasibility of high-multiplexing systems.In this work, we aim to addressthis less explored area by modeling crosstalk between the 1-100 MHz range under a lumped-parameter framework, with afocus on static crosstalk (ECTstatic)—a metric that has received less attention in lower-frequency studies. To mitigate mutualinductance, we propose a chessboard pixel arrangement that maximizes frequency differences between adjacent channels.Leveraging the 1-100 MHz bandwidth with a 0.1 MHz channel spacing, this configuration can suppress crosstalk by up to 59.4dB.Our simulations show that with this layout and through dynamic carrier frequency design, reducing mutual inductance to 3nH enables 186 channels under a 1% ECTstatic constraint when the SQUID input inductance is 1 nH; this count increases to 299channels when the input inductance is reduced to 0.5 nH. Relaxing the threshold to 3.2% or 10% further expands the channelcounts—for instance, reaching 612 or 2067 channels with 1 nH input inductance, respectively.This study preliminarily exploresthe crosstalk characteristics of 1-100 MHz FDM for TES arrays, offering a framework for low-crosstalk, high-channel-countreadout systems and highlighting key trade-offs in this relatively unexplored frequency range.

Scientific Reports•Aug 3, 2026•0 citations

RF-SQUID CHARACTERISTICS IN A HIGH-FREQUENCY LIMIT

Oleg V. Snigirev

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Frequency division multiplexing readout of 60 low-noise transition-edge sensor bolometers

Qian Wang, P. Khosropanah, Jan van der Kuur +8 more

We demonstrate multiplexing readout of 60 transition edge sensor (TES) bolometers operating at 90 mK using a frequency division multiplexing readout chain with bias frequencies ranging from 1 to 3.5 MHz and with a typical frequency spacing of 32 kHz. The readout chain starts with a two-stage SQUID amplifier and has a noise level of 9.5 pA/Hz. We compare current–voltage curves and noise spectra of TESs measured in a single-pixel mode and in a multiplexing mode. We also map the noise equivalent power (NEP) and the saturation power of the bolometers in both modes, where there are 43 pixels that do not show more than 10% difference in NEP and 5% in saturation power when measured in single pixel and multiplex modes. We have read out a TES with an NEP of 0.45 aW/Hz in the multiplexing-mode, which demonstrates the capability of reading out ultra-low noise TES bolometer arrays for space applications.

Applied Physics Letters•Nov 1, 2021•4 citations
We present a novel dc-SQUID readout scheme that provides linearization of the relation between the input and output signal without using a conventional flux-locked loop circuit. It relies on applying a periodic, sawtooth-shaped magnetic flux signal to the modulation coil of the SQUID to continuously measure the flux-to-voltage SQUID characteristic within each period of the flux ramp. In case that the amplitude and repetition rate of the ramp are chosen such that multiple flux quanta are induced in the SQUID and that the input signal is quasistatic within one period of the flux ramp, the input signal adds a constant magnetic flux offset to the SQUID that leads to a phase shift of the SQUID characteristic being proportional to the input signal. We show that this scheme allows for significantly increasing the dynamic range and that it intrinsically allows for MHz frequency-division SQUID multiplexing.
Abstract The 1-100 MHz frequency band remains relatively unexplored for Frequency Division Multiplexing (FDM) readout of TransitionEdge Sensor (TES) arrays, despite its potential to increase channel counts beyond the traditionally used 1-5 MHz range. Thisgap, however, is becoming increasingly addressable with advancements in the fabrication of high-resonance-frequency LCresonators and wide-band Superconducting Quantum Interference Devices (SQUIDs). It still partly stems from understudiedcrosstalk challenges in this higher-frequency regime, where mutual inductance, SQUID input inductance, and carrier leakageeffects tend to be more pronounced, which may limit the feasibility of high-multiplexing systems.In this work, we aim to addressthis less explored area by modeling crosstalk between the 1-100 MHz range under a lumped-parameter framework, with afocus on static crosstalk (ECTstatic)—a metric that has received less attention in lower-frequency studies. To mitigate mutualinductance, we propose a chessboard pixel arrangement that maximizes frequency differences between adjacent channels.Leveraging the 1-100 MHz bandwidth with a 0.1 MHz channel spacing, this configuration can suppress crosstalk by up to 59.4dB.Our simulations show that with this layout and through dynamic carrier frequency design, reducing mutual inductance to 3nH enables 186 channels under a 1% ECTstatic constraint when the SQUID input inductance is 1 nH; this count increases to 299channels when the input inductance is reduced to 0.5 nH. Relaxing the threshold to 3.2% or 10% further expands the channelcounts—for instance, reaching 612 or 2067 channels with 1 nH input inductance, respectively.This study preliminarily exploresthe crosstalk characteristics of 1-100 MHz FDM for TES arrays, offering a framework for low-crosstalk, high-channel-countreadout systems and highlighting key trade-offs in this relatively unexplored frequency range.
We demonstrate multiplexing readout of 60 transition edge sensor (TES) bolometers operating at 90 mK using a frequency division multiplexing readout chain with bias frequencies ranging from 1 to 3.5 MHz and with a typical frequency spacing of 32 kHz. The readout chain starts with a two-stage SQUID amplifier and has a noise level of 9.5 pA/Hz. We compare current–voltage curves and noise spectra of TESs measured in a single-pixel mode and in a multiplexing mode. We also map the noise equivalent power (NEP) and the saturation power of the bolometers in both modes, where there are 43 pixels that do not show more than 10% difference in NEP and 5% in saturation power when measured in single pixel and multiplex modes. We have read out a TES with an NEP of 0.45 aW/Hz in the multiplexing-mode, which demonstrates the capability of reading out ultra-low noise TES bolometer arrays for space applications.