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IEEE Transactions on Magnetics

Progress in the development of SIS quasiparticle mixers

P. L. Richards

Published Mar 1, 1987• 9 citations
Publisher

Abstract

A summary is presented of recent SIS quasiparticle heterodyne mixer work done at Berkeley. Developments related to millimeter wavelength waveguide mixers include techniques for accurate measurements of noise and gain, integrated RF matching elements for large instantaneous bandwidths, large scaled modeling experiments, new W-band mixers with wide tuning bandwidth and only one mechanical adjustment, observation of very large coupled gain, systematic studies of the properties of array mixers, analysis of the effect of saturation on mixer measurements, very low noise in mixers with high quality junctions, and computer modeling to test the quantum theory of mixing. Developments related to planar lithographed mixers with quasi-optical antennas include construction of test apparatus, large scale modeling, and the design and evaluation of mixers which use RF matching structures integrated with bow tie antennas.

DOI
10.1109/tmag.1987.1065033

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European Microwave Conference (EuMC)•Sep 1, 1986•2 citations
A summary is presented of recent SIS quasiparticle heterodyne mixer work done at Berkeley. Developments related to millimeter wavelength waveguide mixers include techniques for accurate measurements of noise and gain, integrated RF matching elements for large instantaneous bandwidths, large scaled modeling experiments, new W-band mixers with wide tuning bandwidth and only one mechanical adjustment, observation of very large coupled gain, systematic studies of the properties of array mixers, analysis of the effect of saturation on mixer measurements, very low noise in mixers with high quality junctions, and computer modeling to test the quantum theory of mixing. Developments related to planar lithographed mixers with quasi-optical antennas include construction of test apparatus, large scale modeling, and the design and evaluation of mixers which use RF matching structures integrated with bow tie antennas.
A description is given of recent work at Berkeley on superconducting mixers and detectors for infrared and millimeter wavelengths. The first report is a review article which summarizes the status of development of superconducting components for infrared and millimeter wave receivers. The next report describes accurate measurements and also theoretical modeling of an SIS quasiparticle waveguide mixer for W-band which uses very high quality Ta junctions. The best mixer noise is only 1.3 times the quantum limit. Both the mixer gain and the noise are in quantitative agreement with the quantum theory. Next, a report is given on measurements and theoretical modeling of the absorptivity (surface resistance) of high quality epitaxial films of the high {Tc} superconductor YBCO from 750 GHz to 21 THz. Finally, there are reports on the design and experimental performance of two different types of high {Tc} bolometric detectors. One is a conventional bolometer with a gold-black absorber. The other is an antenna coupled microbolometer.
The SIS quasiparticle tunnel junction has been demonstrated to be the most sensitive mixing element for millimeter wave receivers [1,2]. Conversion gain greater than 1 and noise temperature approaching the quantum limit [3,4] has been observed. The required local oscillator power, which can be as small as 10−8W, leads to a low saturation threshold for these mixers [5,6]. The practical benefits, including higher saturation power, of using series arrays are sufficiently important that a substantial number of experiments using arrays have been reported [2,6,7,8,9]. It has not been clear, however, whether there has been any sacrifice in mixer conversion efficiency (gain) or noise. We present a systematic experimental investigation of mixing performance in series arrays of N junctions, where N = 1, 5, 10, 25 and 50.
Recent work done at Berkeley on the development of millimeter-wave heterodyne mixers using superconductor-insulator-superconductor (SIS) junctions is reviewed. Two types of mixers have been developed; a conventional waveguide system using a resonant cavity and an open-structure quasioptical system using planar antennas and lenses. Using the waveguide system, the lowest mixer noise level yet obtained (within 25% of the quantum limit) at 95 GHz has been achieved. The quasioptical system has achieved a good mixer performance up to 200 GHz, and it has shown promise for use at submillimeter wavelengths.>
A novel superconductor-insulator-superconductor (SIS) mixer coupling scheme with an integrated millimeter-wave transformer has been designed and tested. The impedance transformation allows larger junction sizes and easier fabrication than is possible with single junction or array mixers. Experiments with the front-end transformer mixers demonstrated mixer gains up to 10 dB and instantaneous bandwidths of 700 MHz at W-band. In addition to heterodyne mixing, direct detection measurements were made to measure instantaneous signal bandwidth. Current responsivities of 1000 A/W were measured with a 3-dB bandwidth of 8 GHz. The direct detection performance falls to within experimental uncertainty at the quantum limit of one-electron-per-photon.
The authors have tested the performance of planar SIS (superconductor-insulator-superconductor) mixers with log-periodic antennas at near millimeter and submillimeter wave frequencies from 90 to 360 GHz. The large omega R/sub N/C product ( approximately 10 at 90 GHz) of the Nb/NbO/sub x//Pb-In-Au junctions requires an integrated inductive tuning element to resonate the junction capacitance at the operating frequencies. Two types of integrated tuning element were used which were designed with the aid of measurements using a Fourier transform spectrometer. Preliminary results indicate that the tuning elements can give very good mixer performance up to at least 200 GHz. An inductive wire in parallel with a 5-junction array gives a minimum mixer noise temperature of 115 K (DSB) at 90 GHz with a FWHM (full width at half maximum) bandwidth of 8 GHz. An open-ended microstrip stub in parallel with a single junction gives minimum mixer noise temperatures at 150 and 200 K (DSB) near 90 and 180 GHz with FWHM bandwidths of 4 and 3 GHz, respectively. The relatively high mixer noise temperatures compared to those of waveguide SIS mixers in a similar frequency range are attributed mainly to the losses in the optical system.>
Several SIS quasiparticle mixers have been designed and tested for the frequency range from 80 to 115 GHz. The sliding back short is the only adjustable RF-tuning element. The RF-filter reactance is used a s a fixed RF-matching element. A mixer which uses a single 2 × 2 μm2Pb-alloy junction in a 1/4-height waveguide mount has a coupled conversion gain of GM(DSB) = 2.6 ± 0.5 dB with an associated noise temperature of TM(DSB) = 16.4 ± 1.8 K at the best DSB operation point. The receiver noise temperature TR(DSB) is 27.5 ± 0.8 K for the test apparatus. This mixer provides a SSB receiver noise temperature below 50 K over the frequency range from 91 to 96 GHz, the minimum being TR(SSB) = 44 ± 4 K. Another mixer with an array of five 5 × 5 μm2junctions in series has much lower noise TM(DSB) = 6.6 ± 1.6 K, but less gain GM(DSB) = -5.1 ± 0.5 dB.