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Applied Physics Letters

Noise and conversion performance of a high-Tc superconducting Josephson junction mixer at 0.6 THz

Xiang Gao, Jia Du, Ting Zhang, Yingjie Jay Guo

Published Nov 6, 2017• 25 citations
Publisher

Abstract

This letter presents both theoretical and experimental investigations on the noise and conversion performance of a high-Tc superconducting (HTS) step-edge Josephson-junction mixer at the frequency of 0.6 THz and operating temperatures of 20–40 K. Based on the Y-factor and U-factor methods, a double-sideband noise temperature of around 1000 K and a conversion gain of −3.5 dB were experimentally obtained at 20 K. At the temperature of 40 K, the measured mixer noise and conversion efficiency are around 2100 K and −10 dB, respectively. The experimental data are in good agreement with the numerical analysis results using the three-port model. A detailed performance comparison with other reported HTS terahertz mixers has confirmed the superior performance of our presented mixer device.

DOI
10.1063/1.5004733

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This letter presents both theoretical and experimental investigations on the noise and conversion performance of a high-Tc superconducting (HTS) step-edge Josephson-junction mixer at the frequency of 0.6 THz and operating temperatures of 20–40 K. Based on the Y-factor and U-factor methods, a double-sideband noise temperature of around 1000 K and a conversion gain of −3.5 dB were experimentally obtained at 20 K. At the temperature of 40 K, the measured mixer noise and conversion efficiency are around 2100 K and −10 dB, respectively. The experimental data are in good agreement with the numerical analysis results using the three-port model. A detailed performance comparison with other reported HTS terahertz mixers has confirmed the superior performance of our presented mixer device.
Abstract This paper presents a wideband terahertz (THz) mixer based on a thin-film antenna-coupled high-temperature superconducting (HTS) YBa 2 Cu 3 O 7−x (YBCO) step-edge Josephson junction. The HTS mixer enables the flexible harmonic mixing operation at multiple THz bands with the same microwave local oscillator (LO) source, and features very wide intermediate-frequency or instantaneous bandwidth. In order to optimize the frequency down-conversion performance of the mixer, systematic electromagnetic design and analysis have been carried out to improve the power coupling of THz radiation as well as wideband transmission of microwave signals. Experimental characterization of a fabricated device prototype has demonstrated that the mixer exhibits good performance at both the 200 GHz and 600 GHz bands. Detailed measurement results including the DC characteristics, LO pumping requirement, frequency response, mixing linearity and conversion gain are presented in this paper.
High-Tc superconducting (HTS) receivers are promising candidates for terahertz (THz) communication applications due to their superior sensitivity and the cooling attainability with a miniature cryogenic system. Nevertheless, currently reported HTS mixers are mostly single-junction devices, and a more complicated architecture like the balanced configuration has not been investigated. This paper presents the design of a 600-GHz single-balanced HTS mixer, where detailed electromagnetic simulations are carried out to optimize the coupling efficiency and port isolation, as well as desired amplitude and phase relationship. To predict the noise and conversion performance, we present an innovative multiport network interleaving-based modeling method that enables powerful simulation verifications for single-balanced HTS Josephson mixers. Simulation results show that the presented device exhibits very good HTS mixer performance at the 600-GHz band, which validates the effectiveness of the design and the potential of the mixer for THz communication applications.
High-Tcsuperconducting (HTS) harmonic mixers are attractive frontends for terahertz wireless communication and sensing applications. However, the investigation of HTS harmonic mixers has long been hindered by the lack of effective theoretical method in device modeling. This article presents a modeling approach for analyzing the noise and conversion properties of HTS harmonic mixers. By quantitively analyzing the contribution of the parasitic components to frequency conversion, a parasitics-selection based equivalent circuit model is built with the architecture complexity reduced to a six-port network. Besides, a fast hybrid-solution method that combines the single-tone current excitation and perturbation-derivation processing techniques, is developed for efficiently calculating the conversion impedance matrix for harmonic mixing. Detailed derivations are then carried out to acquire the semianalytic expressions of noise temperature and conversion gain after solving the noise correlation matrix for harmonic mixing. The presented modeling method has been verified by the fourth harmonic mixing experiments for a dual-band antenna-coupled HTS Josephson-junction mixer module. The measured and simulated results are in good agreement in terms of the noise temperature and conversion gain as well as their dependance on dc biasing, local oscillator pumping, and operating temperatures. The results have validated the effectiveness of the presented modeling method for analyzing the properties of HTS Josephson junction mixers.
We report the experimental evaluation of a high-temperature superconducting (HTS) Josephson mixer. The mixer is fabricated from a HTS step-edge junction on MgO substrate. The mixer device operates as a lower side-band down-converter from a radio frequency between 6 and 10 GHz to a 1-2 GHz intermediate frequency under the action of a local oscillator. The experimental results of the current-voltage characteristics, optimal bias conditions, dynamic range, linearity, conversion gain, and the temperature dependence of the mixer are presented.
A high-temperature superconducting (HTS) terahertz (THz) frequency down-converter or mixer based on a thin-film ring-slot antenna coupled YBa 2 Cu 3 O 7– x (YBCO)/MgO step-edge Josephson junction is reported. The frequency down-conversion was achieved using higher order harmonics of an applied lower frequency (19–40 GHz) local oscillator signal in the Josephson junction mixing with a THz signal of over 600 GHz, producing a 1–3 GHz intermediate frequency signal. Up to 31st order of harmonic mixing was obtained and the mixer operated stably at temperatures up to 77 K. The design details of the antenna, HTS Josephson junction mixer, the matching and isolation circuits, and the DC and RF performance evaluation are described in this paper.
We have measured the noise performance and conversion efficiency of Y–Ba–Cu–O bicrystal Josephson mixers at operating temperatures between 20 and 60 K and at operating frequencies around 90 GHz. A double-sideband mixer noise temperature of about 1600 K and a conversion efficiency of −10 dB at 20 K operating temperature has been measured using the Y-factor method. The absorbed local oscillator power was in the range of 10 nW. The dependence of the mixer performance on the normalized frequency Ω and the fluctuation parameter Γ has been studied. In accordance with the resistively shunted junction model, the experimental data show the presence of excess noise. The temperature dependence of the mixer noise temperature can be explained by the variation of the linewidth of the Josephson oscillations with the operating temperature.