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IEEE Transactions on Applied Superconductivity

A 4 : 1 Transmission-Line Impedance Transformer for Broadband Superconducting Circuits

Leonardo Ranzani, Lafe Spietz, Zoya B. Popovic, José Aumentado

Published Sep 1, 2012• 9 citations
Publisher

Abstract

We present a 4 : 1 superconducting transmission-line impedance transformer for cryogenic applications. The device transforms 25 Ω in the coplanar waveguide to 6.25 Ω in the microstrip and is designed to operate at 20 mK. Calibrated measurements in a dilution refrigerator demonstrate a -3 dB bandwidth from 1.6 to 13 GHz. In a modified Ruthroff design, a small capacitor is integrated at the input as a direct-current block, making it suitable for biasing and matching to low-impedance active circuits, such as superconducting quantum interference device (SQUID) amplifiers.

DOI
10.1109/tasc.2012.2202116

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We present a 4 : 1 superconducting transmission-line impedance transformer for cryogenic applications. The device transforms 25 Ω in the coplanar waveguide to 6.25 Ω in the microstrip and is designed to operate at 20 mK. Calibrated measurements in a dilution refrigerator demonstrate a -3 dB bandwidth from 1.6 to 13 GHz. In a modified Ruthroff design, a small capacitor is integrated at the input as a direct-current block, making it suitable for biasing and matching to low-impedance active circuits, such as superconducting quantum interference device (SQUID) amplifiers.
In this work, we characterize the 2-port scattering parameters of a superconducting quantum interference device amplifier at ∼20 mK over several gigahertz of bandwidth. The measurement reference plane is positioned on a 6.25 Ω microstrip line situated directly at the input and output of the device by means of a thru-reflect-line cryogenic calibration procedure. From the scattering parameters, we derive the device available power gain, isolation, and input impedance over the 2–8 GHz range. This measurement methodology provides a path towards designing wide-band matching circuits for low impedance superconducting amplifiers operating at dilution refrigerator temperatures.
A planar superconducting circuit designed for use in low-noise cryogenic applications is presented. The circuit is a bias-T combined with a 4–8 GHz impedance matching circuitry, which employs entirely planar design with a novel layout. The proposed and tested circuitry is intended to be used with a SIS mixer and incorporates a double section transformer based on microstrip line technology with a total impedance transformation of 5:1 within the frequency band. One of the transformer sections employs a three-line coupled line, which also serves as a DC block capacitor. The microstrip lines were manufactured using superconducting Nb metallization, which provides a conduction loss-free solution at the operation temperature of 4 K. S-parameter measurements at 4 K temperature were performed and found to be in a good agreement with the simulations. The device measured return loss is better than −10 dB within the frequency band. Furthermore, the circuit was tested as a part of 385 – 500 GHz double sideband heterodyne SIS receiver demonstrating a flat noise temperature response of 80 – 90 K over the entire IF band of 4 – 8 GHz.
We describe a wide-band Josephson Parametric Amplifier (JPA) that is impedance-matched using an integrated compact superconducting transmission line transformer. The impedance transformer consists of two broadside coupled transmission lines configured in a Ruthroff topology which enables a wide matching bandwidth from 2 to 18GHz, reducing the input line impedance and the device resonance quality factor by a factor of 4. This enables gain flatness and flexibility in the choice of the amplifier’s tuning range. The amplifier has up to 20dB gain, with less than 1dB of ripple, 2-3GHz gain-bandwidth product and -126dBm input 1-dB compression point. Moreover, the device active area fits into a 1mm×1mm space, thus easing integration into large quantum systems.
Quantum-limited Josephson parametric amplifiers play a pivotal role in advancing the field of circuit quantum electrodynamics by enabling the fast and high-fidelity measurement of weak microwave signals. Therefore, it is necessary to develop robust parametric amplifiers with low noise, broad bandwidth, and reduced design complexity for microwave detection. However, current broadband parametric amplifiers either have degraded noise performance or rely on complex designs. Here, we present a device based on the broadband impedance-transformed Josephson parametric amplifier that integrates a hornlike coplanar waveguide transmission line, which significantly decreases the design and fabrication complexity while keeping comparable performance. The device shows an instantaneous bandwidth of 700 (200) MHz for 15 (20) dB gain with an average input saturation power of −110 dBm and near quantum-limited added noise. The operating frequency can be tuned over 1.4 GHz using an external flux bias. We further demonstrate the negligible backaction from our device on a transmon qubit. The amplification performance and simplicity of our device promise its wide adaptation in quantum metrology, quantum communication, and quantum information processing. Published by the American Physical Society 2024
Abstract High-performance cryogenic amplifiers are essential components for quantum information technology and astronomical observation. In this work, we report the design and characterization of a microwave amplifier based on a superconducting quantum interference device (SQUID). The design incorporates input and output impedance transformers to center the operating frequency at approximately 5.5 GHz for specific applications. Preliminary characterization at a bath temperature of 4.2 K demonstrates a peak gain of 10.79 dB at 5.39 GHz and a saturation power of approximately −115 dBm.
We present a fishbone-like lumped-element artificial transmission line to overcome impedance mismatch in a reflection-type Josephson parametric amplifier between a nonlinear resonator and an external transmission line. Using this easily prepared architecture, we design and fabricate a broadband Josephson parametric amplifier, which has gain in an excess of 20 dB with a bandwidth of hundreds of MHz. Furthermore, by varying the working point of the device, the operating frequency of amplification can be tuned in a wide frequency range of 1 GHz while the amplifier operates in the mode of either three-wave mixing or four-wave mixing. Such a parametric amplifier is suitable for engineering applications of superconducting circuit quantum electrodynamics.