Harmonic Mixing Using a HTS Step-Edge Josephson Junction at 0.6 THz Frequency

© 2002-2011 IEEE. A high-temperature superconducting (HTS) terahertz (THz) heterodyne mixer based on a thin-film antenna-coupled YBa 2Cu3O7-x step-edge Josephson junction is presented. The frequency down-conversion from 0.6 THz to an intermediate frequency (IF) of 2 GHz was achieved using high-order harmonic mixing of a local oscillator (LO), thus removing the need to use a second THz source as the LO pumping source. The DC and RF characteristics of the harmonic mixer as well as the relationship of the IF output power versus the harmonic number were experimentally studied and compared with simulated results. Most of our measurements were made at 40 K, but we also observed stable harmonic mixing at 77 K which we believe has not been reported previously in HTS junction mixers

Growth mechanism, microstructure, EPMA and Raman studies of pulsed laser deposited Nd1-xBa2+xCu3O7-delta thin films

Superconducting thin films of Nd1-xBa2+xCu3O7-delta have been grown on single crystal SrTiO3 substrates by pulsed laser deposition (PLD) using an off-stoichiometric Nd0.97Ba2.03Cu3O6 (Ba-rich NBCO) target. The statistical methods of Experimental design and regression analysis were used to understand and optimise the growth mechanism. The structural properties of both the target and the films were investigated by X-ray diffraction (XRD). The surface morphology of the films was examined by atomic force microscopy (AFM) and scanning tunnelling microscopy (STM). Electron probe microanalysis (EPMA) using a scanning electron microscope equipped with wavelength-dispersive X-ray (WDX) spectrometers was used to carry out qualitative and quantitative analysis of both the target and films. Micro-Raman spectroscopy was used to study the oxygen sublattice vibrations of both the target and the films. (c) 2005 Elsevier B.V. All rights reserved

A self-pumped high-temperature superconducting Josephson mixer: Modelling and measurement

We have recently developed a high-temperature superconducting (HTS) Josephson self-pumped mixer with an on-chip heterodyne local oscillator. The device is based on HTS step-edge junction technology and a resistive- superconducting quantum interference device (RSQUID) configuration. The heterodyne local oscillator and mixer output are frequency-tunable from below 10 MHz to 5 GHz by a control current. The performance of the autonomous Josephson mixer-local oscillator has been experimentally evaluated in terms of the current-voltage characteristics, intermediate frequency (IF)-tunable bandwidth, operation range, linearity, bias current, and temperature dependence of the IF output (or mixer conversion efficiency). We find the results are in good overall agreement with numerical simulation. © 2012 American Institute of Physics

Studies of growth, microstructure, IMP Raman spectroscopy and annealing effect of pulsed laser deposited Ca-doped NBCO thin films

Superconducting thin films of Ndl-xCaxBa2Cu3O7-delta (x = 0.03 and 0.08) have been grown on single crystal SrTiO3 substrates by pulsed laser deposition. The statistical methods of Experimental Design and regression analysis were used to optimize the film properties and to understand the correlation between the growth parameters and film properties. The orientation of the films was investigated by x-ray diffraction. The surface morphology of the films was examined by atomic force microscopy and scanning tunnelling microscopy. Qualitative and quantitative elemental analyses of the films were carried out using electron probe microanalysis. Micro-Raman spectroscopy was used to study the oxygen sublattice vibrations of the films. The effect of annealing oil the superconducting transition temperature of the patterned films was also studied

Optimised conversion efficiency of a HTS MMIC Josephson down-converter

© 2014 IOP Publishing Ltd. A high-Tc superconducting (HTS) monolithic microwave integrated circuit (MMIC) Josephson down-converter that approaches zero conversion loss is reported. The all-HTS YBa2Cu3O7-x thin-film circuit consists of a step-edge Josephson junction mixer, a 10-12 GHz bandpass filter for the RF input, a lowpass filter for the IF output and a resonant strip line for local oscillator isolation; all are integrated on a single 10 mm × 20 mm MgO substrate. The DC characteristics of the junction and its mixing properties have been experimentally studied and compared to the results of (a) a single Josephson mixer without the on-chip HTS filters, and (b) our previously reported MMIC down-converter which had very different junction characteristics. The Josephson junction parameters are analysed to give insight into their effect on the mixer performance