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IEEE Transactions on Electron Devices

Josephson-junction mixer analysis using frequency-conversion and noise-correlation matrices

Yuan Taur

Published Oct 1, 1980• 42 citations
Publisher

Abstract

A complete characterization and optimization have been carried out for an externally pumped Josephson-junction mixer. A noise-driven nonlinear pump equation is first solved in the time domain on a computer in order to obtain a conversion matrix and noise-correlation matrix for the small-signal current and voltage. A set of linear circuit equations formed by the matrices is then solved in the frequency domain for the mixer noise temperature and conversion efficiency. Finally, optimization is made with respect to circuit, bias, and junction parameters to find the ultimate theoretical performance.

DOI
10.1109/t-ed.1980.20129

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The results of extensive analog computer simulations of a Josephson junction used as a mixer with an external local oscillator are presented. The Resistively Shunted Junction model was used throughout, and the effects of intrinsic junction noise were included. When the source impedance is much greater than the junction resistance R our simulations permit predictions of conversion efficiency, noise temperature, and saturation level to be made for a wide range of experimental parameters. The possibility of harmonic mixing has also been considered. With a source resistance comparable to R (i.e., conventional matching) the behavior of the system is too complicated to permit such general predictions of performance. From the results of simulations for a particular set of parameters it appears that the best noise temperature will usually be achieved for a source impedance somewhat greater than R. An upper limit for the mixer noise temperature is approximately 40 T over a broad range of junction parameters, where T is the effective temperature of the junction. The Conversion efficiency under these circumstances should be comparable to what is potentially available from Schottky diode mixers. Our simulations show that with stronger microwave coupling it is possible to obtain conversion gain - i.e., a conversion efficiency exceeding unity. This, however, will probably be at the expense of a higher mixer noise temperature.

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Journal of Applied Physics•Jul 1, 1978•42 citations
A complete characterization and optimization have been carried out for an externally pumped Josephson-junction mixer. A noise-driven nonlinear pump equation is first solved in the time domain on a computer in order to obtain a conversion matrix and noise-correlation matrix for the small-signal current and voltage. A set of linear circuit equations formed by the matrices is then solved in the frequency domain for the mixer noise temperature and conversion efficiency. Finally, optimization is made with respect to circuit, bias, and junction parameters to find the ultimate theoretical performance.
The behavior of the voltage−biased Josephosn junction coupled to a general external circuit is studied in the small−signal limit. The Josephson relations are formulated in the frequency domain in the form of an infinite set of difference equations relating the current and voltage amplitudes of different frequency components. The results are subsequently utilized to develop a general theory of the self−oscillating Josephson mixer, including noise. The noise temperature and conversion gain of the mixer are derived taking into consideration the image frequency response. A comparison is made between the operation of the negative−resistance converter in the SC regime and its operation in the OC regime.
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.
This paper presents theoretical analysis and modeling of YBaCuO superconducting Josephson mixer for terahertz frequency band. The study was carried out both for the mixing at the first harmonic and for the case of high harmonic mixing. The numerical solution based on resistively shunted junction model was obtained for the YBaCuO junction with typical experimental parameters. Optimizing mixer performance included choosing the proper operating point and the local oscillator power. A study on the effect of RF input power, frequency and the harmonic number on conversion efficiency was carried out. The theoretical predictions presented in the work provide a simple method for optimal control of the Josephson mixer and demonstrate good qualitative agreement with direct modeling. For the first time, the optimum of the conversion efficiency versus signal frequency was analytically obtained.
The results of extensive analog computer simulations of a Josephson junction used as a mixer with an external local oscillator are presented. The Resistively Shunted Junction model was used throughout, and the effects of intrinsic junction noise were included. When the source impedance is much greater than the junction resistance R our simulations permit predictions of conversion efficiency, noise temperature, and saturation level to be made for a wide range of experimental parameters. The possibility of harmonic mixing has also been considered. With a source resistance comparable to R (i.e., conventional matching) the behavior of the system is too complicated to permit such general predictions of performance. From the results of simulations for a particular set of parameters it appears that the best noise temperature will usually be achieved for a source impedance somewhat greater than R. An upper limit for the mixer noise temperature is approximately 40 T over a broad range of junction parameters, where T is the effective temperature of the junction. The Conversion efficiency under these circumstances should be comparable to what is potentially available from Schottky diode mixers. Our simulations show that with stronger microwave coupling it is possible to obtain conversion gain - i.e., a conversion efficiency exceeding unity. This, however, will probably be at the expense of a higher mixer noise temperature.
We present the results of extensive analog-computer simulations of a Josephson junction used as a mixer with an external local oscillator. The resistively shunted junction model was used throughout, and the effects of intrinsic junction noise were included. When the source impedance is much greater than the junction resistance R, our simulations permit predictions of conversion efficiency, noise temperature, and saturation level to be made for a wide range of experimental parameters. The possibility of harmonic mixing has also been considered. With a source resistance comparable to R (i.e., conventional ’’matching’’) the behavior of the system is too complicated to permit such general predictions of performance. From the results of simulations for a particular set of parameters, it appears that the best noise temperature will usually be achieved for a source impedance somewhat greater than R. An upper limit for the mixer-noise temperature is ∼40T over a broad range of junction parameters, where T is the effective temperature of the junction. The conversion efficiency under these circumstances should be comparable to what is potentially available from Schottky-diode mixers. Our simulations show that with stronger microwave coupling it is possible to obtain conversion gain—i.e., a conversion efficiency exceeding unity. This, however, will probably be at the expense of a higher mixer-noise temperature. Saturation can be important even for source temperatures ∼300 K. To avoid saturation it is necessary either to restrict the coupling bandwith or use an array of junctions.