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IEEE Transactions on Magnetics

The antenna-coupled SIS quasiparticle array mixer

S. Rudner, M. J. Feldman, E. Kollberg, T. Claeson

Published Jan 1, 1981• 27 citations
Publisher

Abstract

We report SIS mixing with Pb(In) junction arrays at 73.5 GHz. The array geometry and antenna coupling can be scaled to 300 GHz with existing technology. The measured SSB conversion loss is as good as 2.0±0.9 dB. This is marginally the best conversion result for a resistive mixer without image rejection yet published and agrees well with the quantum theory of mixing. We examine Josephson effect noise and thereby give a rough upper frequency limit for single-junction SIS mixers.

DOI
10.1109/tmag.1981.1061162

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Quasiparticle mixers have shown strong quantum effects, conversion gain, and noise levels approaching the quantum limit, but only in tunnel junctions with very low sub-gap "leakage" conductance. It has been suggested that SIS' tunnel junctions, made from two different conductors with unequal gaps, will function as high gain mixers since the dynamic conductance below the gap is negative. We report results of the first SIS' mixing and direct detection experiments. At 36 GHz, a conversion efficiency of -4 dB with a noise temperature of 33 K (SSB) has been obtained. A novel gain mechanism for SIS' direct detectors is predicted. A direct detector responsivity of 250 A/W was measured. We compare our results to quantum theory models. In addition, we demonstrate quasiparticle harmonic mixing of a 36 GHz signal with an 18 GHz local oscillator in tin SIS junctions. Harmonic mixers can have important advantages at high microwave frequencies where insufficient local oscillator power is available.

IEEE Transactions on Magnetics•May 1, 1983•15 citations
We report SIS mixing with Pb(In) junction arrays at 73.5 GHz. The array geometry and antenna coupling can be scaled to 300 GHz with existing technology. The measured SSB conversion loss is as good as 2.0±0.9 dB. This is marginally the best conversion result for a resistive mixer without image rejection yet published and agrees well with the quantum theory of mixing. We examine Josephson effect noise and thereby give a rough upper frequency limit for single-junction SIS mixers.
We report high-frequency mixing at 75 GHz using superconductor-insulator-superconductor (SIS) tunnel junction arrays of various length and composition. Short (6-junction) arrays, both of Pb (In) and of Pb, and long (36-junction) arrays of Pb are used. The array geometry and antenna coupling can be scaled to 300 GHz with existing technology. Comparing the experiments to each other and to theory provides criteria for SIS mixer design. The measured single side band (SSB) conversion loss is as good as 2.0±0.9 dB. This is marginally the best published conversion result for any resistive mixer without image rejection, and quantitatively agrees with the quantum theory of mixing. We examine Josephson effect noise in this device and give a rough upper frequency limit for single-junction SIS mixers. Conversion maxima are also noted close to the half-gap singularity present in Pb (In) junctions.
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.
A Superconducting quasiparticle mixer receiver for 35-50 GHz is described. An array of six Pb In-oxide-Pb0.7Bi0.3tunnel junctions with 40 Ω array normal resistance and a shunt capacitance of 0.2 pF is used. The mixer is immersed into liquid helium and operated at 2 K. A 3.7-4.2 GHz parametric amplifier, also at 2 K is used as the if amplifier. The high if frequency allows single sideband operation with a system noise temperature of 140 K at 47 GHz. A lens guide is used for guiding the signal from the Cassegrain telescope focus to the liquid helium cooled lens corrugated horn and the mixer. The SSB system noise temperature varies rather smoothly from ≈ 220 K at 35 GHz to ≈ 140 K at 50 GHz suggesting that quantum gain effects are becoming more important at the high frequency end. The receiver is operational in the 20 m mm-wave telescope at the Onsala Space Observatory.
Quasiparticle mixers have shown strong quantum effects, conversion gain, and noise levels approaching the quantum limit, but only in tunnel junctions with very low sub-gap "leakage" conductance. It has been suggested that SIS' tunnel junctions, made from two different conductors with unequal gaps, will function as high gain mixers since the dynamic conductance below the gap is negative. We report results of the first SIS' mixing and direct detection experiments. At 36 GHz, a conversion efficiency of -4 dB with a noise temperature of 33 K (SSB) has been obtained. A novel gain mechanism for SIS' direct detectors is predicted. A direct detector responsivity of 250 A/W was measured. We compare our results to quantum theory models. In addition, we demonstrate quasiparticle harmonic mixing of a 36 GHz signal with an 18 GHz local oscillator in tin SIS junctions. Harmonic mixers can have important advantages at high microwave frequencies where insufficient local oscillator power is available.