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Applied Physics Letters

Low-noise Josephson mixers at 115 GHz using recyclable point contacts

Y. Taur, Anthony R. Kerr

Published Jun 1, 1978• 32 citations
Publisher

Abstract

Thermally recyclable Nb point-contact Josephson junctions are investigated as low-noise mixers with an external local oscillator at 115 GHz. The best single sideband mixer noise temperature achieved is 140 (±20) K with a (SSB) conversion loss of 2.4 (±0.5) dB. Such rugged junctions are suitable for use in practical receivers and should give unprecedented sensitivity at the shorter millimeter wavelengths.

DOI
10.1063/1.89891

Related papers

Progress on millimeter wave Josephson junction mixers

Y. Taur, Anthony R. Kerr

Preset, recyclable Nb point contacts are tested as low‐noise Josephson mixers at a signal frequency of 115 GHz. The best result achieved is a mixer noise temperature (single sideband) of 120 K with unity conversion efficiency (SSB) for a junction at 6 K. Variation of mixer properties with temperature and other parameters is presented.

AIP conference proceedings•Jan 1, 1978•1 citation

Point-contact Josephson mixers at 130 GHz

J. H. Claassen, P. L. Richards

The properties of point-contact Josephson junctions operated as mixers with an external local oscillator at 130 GHz have been studied, and the results compared with predictions of the resistively shunted junction model. It was found that the junction’s output noise could be within a factor of 1.5 of the model prediction based on the thermal-driving noise. When the coupling to the rf source was optimized, a factor of 2 discrepancy was typical. The measured conversion efficiency agreed with the model, within the experimental uncertainty in the equivalent microwave circuit. The best coupling was achieved in full-height waveguide. The best overall performance, measured using the hot/cold source technique, was a single sideband conversion efficiency of 0.30 and a mixer-noise temperature of 180 K (both ±20%). The best junctions were made of Nb, with carefully prepared points. Nonideal behavior in other junctions is ascribed to heating effects. There is some evidence that junctions whose resistance exceeds a threshold value of ∼60 Ω are no longer well described by the RSJ model. A discussion is given of possible improvements in performance with better junctions or improved rf matching.

Journal of Applied Physics•Jul 1, 1978•28 citations

A Low-Noise 47-GHz Mixer Using a Permanent Josephson Junction

JOCHEN EDRICH

A new method to produce permanent Josephson junctions for millimeter-wave mixers is reported. In contrast to conventional point contacts which are mechanically unstable and require adjustments after each cooldown, these point contact junctions are set at room temperature, stay mechanically stable, and can be temperature cycled without readjustments. Using these junctions in a modified Sharpless wafer mixer mount, a single-sideband noise temperature of 71 K was measured at 47 GHz. Based on these results, system noise temperatures of less than 100 K are predicted for practical broad-band radiometers, RADAR, and communications receivers up to at least 100 GHz

IEEE Transactions on Microwave Theory and Techniques•Nov 1, 1976•7 citations

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Tim Poorter

Point-contact Josephson junctions with a submicron contact diameter have been used as high-frequency mixers (170–220 GHz) under high thermal background conditions. The junction is formed across a full height (0.56×1.06 mm2) waveguide between a 3–5-μm thick Nb whisker and a 0.2-mm diam Nb center conductor of a coaxial line. The best single-side band mixer-noise temperature that was measured is 165 K (± 25%) with a corresponding single-side band conversion efficiency of 0.36±0.03 (a loss of 4.5 ±0.4 dB) at a signal frequency of 185 GHz, including losses in the coupling horn and the waveguide. The performance was measured with the hot-cold source technique. The effects of nonheterodyne response in that situation were investigated in detail. The junctions have been operated in a coherent receiver that can be used on a telescope with only small adaptations. The instantaneous bandwidth of the receiver is about 20 GHz.

Journal of Applied Physics•Jan 1, 1982•27 citations

Experiments on a Point-Contact Josephson Mixer at 469 µm

Masayoshi Kobayashi, Shinji Ohara, Akira Katsuno +2 more

An Nb point-contact Josephson mixer with a corner reflector behind the Nb 4-wavelength wire antenna was constructed, and experiments were carried out at 469 µm (693 GHz). A 10 dB improvement in coupling efficiency was obtained by using the reflector. An SSB (single-side-band) mixer noise temperature of 1660 K was obtained, and the conversion efficiency of the mixer was -35.7 dB in the 9th harmonic mixing between 71 GHz LO and 693 GHz signal.

Japanese Journal of Applied Physics•Nov 1, 1985•1 citation

Josephson frequency conversion in the range 145–1600 GHz with Nb–Nb superconducting point contacts used as oscillator-mixer

G. Vernet, Robert Adde

The Josephson frequency conversion in the millimeter and submillimeter wave region is studied with superconducting Nb–Nb point-contact junctions at 4.2 °K, using the contact both as the local oscillator and the mixer with intermediate frequencies of 0.1, 0.3, and 9.2 GHz. The point contact is in a nonresonant structure and fed by a constant current source: neither a strong rf coupling of the contact with a cavity nor a stabilizing shunt resistance was proved necessary. The direct observation of frequency conversion was performed with a microwave receiver at 9.2 GHz in a range of Josephson frequencies between 145 and 1600 GHz. The experiments with intermediate frequencies fi of 0.1 and 0.3 GHz indicate that conventional frequency conversion does not occur but that the observed signals are related to noise effects. An analysis of the frequency conversion mechanism in a Josephson junction operated as an oscillator-mixer is proposed which includes the noise effects and also the feedback effects induced in a junction driven by a constant current source. The results show that low-frequency current components are induced in the junction, which can give large spurious signals when small i.f. are used.

Journal of Applied Physics•Jun 1, 1974•13 citations
Thermally recyclable Nb point-contact Josephson junctions are investigated as low-noise mixers with an external local oscillator at 115 GHz. The best single sideband mixer noise temperature achieved is 140 (±20) K with a (SSB) conversion loss of 2.4 (±0.5) dB. Such rugged junctions are suitable for use in practical receivers and should give unprecedented sensitivity at the shorter millimeter wavelengths.
The properties of point-contact Josephson junctions operated as mixers with an external local oscillator at 130 GHz have been studied, and the results compared with predictions of the resistively shunted junction model. It was found that the junction’s output noise could be within a factor of 1.5 of the model prediction based on the thermal-driving noise. When the coupling to the rf source was optimized, a factor of 2 discrepancy was typical. The measured conversion efficiency agreed with the model, within the experimental uncertainty in the equivalent microwave circuit. The best coupling was achieved in full-height waveguide. The best overall performance, measured using the hot/cold source technique, was a single sideband conversion efficiency of 0.30 and a mixer-noise temperature of 180 K (both ±20%). The best junctions were made of Nb, with carefully prepared points. Nonideal behavior in other junctions is ascribed to heating effects. There is some evidence that junctions whose resistance exceeds a threshold value of ∼60 Ω are no longer well described by the RSJ model. A discussion is given of possible improvements in performance with better junctions or improved rf matching.
A new method to produce permanent Josephson junctions for millimeter-wave mixers is reported. In contrast to conventional point contacts which are mechanically unstable and require adjustments after each cooldown, these point contact junctions are set at room temperature, stay mechanically stable, and can be temperature cycled without readjustments. Using these junctions in a modified Sharpless wafer mixer mount, a single-sideband noise temperature of 71 K was measured at 47 GHz. Based on these results, system noise temperatures of less than 100 K are predicted for practical broad-band radiometers, RADAR, and communications receivers up to at least 100 GHz
Point-contact Josephson junctions with a submicron contact diameter have been used as high-frequency mixers (170–220 GHz) under high thermal background conditions. The junction is formed across a full height (0.56×1.06 mm2) waveguide between a 3–5-μm thick Nb whisker and a 0.2-mm diam Nb center conductor of a coaxial line. The best single-side band mixer-noise temperature that was measured is 165 K (± 25%) with a corresponding single-side band conversion efficiency of 0.36±0.03 (a loss of 4.5 ±0.4 dB) at a signal frequency of 185 GHz, including losses in the coupling horn and the waveguide. The performance was measured with the hot-cold source technique. The effects of nonheterodyne response in that situation were investigated in detail. The junctions have been operated in a coherent receiver that can be used on a telescope with only small adaptations. The instantaneous bandwidth of the receiver is about 20 GHz.
The Josephson frequency conversion in the millimeter and submillimeter wave region is studied with superconducting Nb–Nb point-contact junctions at 4.2 °K, using the contact both as the local oscillator and the mixer with intermediate frequencies of 0.1, 0.3, and 9.2 GHz. The point contact is in a nonresonant structure and fed by a constant current source: neither a strong rf coupling of the contact with a cavity nor a stabilizing shunt resistance was proved necessary. The direct observation of frequency conversion was performed with a microwave receiver at 9.2 GHz in a range of Josephson frequencies between 145 and 1600 GHz. The experiments with intermediate frequencies fi of 0.1 and 0.3 GHz indicate that conventional frequency conversion does not occur but that the observed signals are related to noise effects. An analysis of the frequency conversion mechanism in a Josephson junction operated as an oscillator-mixer is proposed which includes the noise effects and also the feedback effects induced in a junction driven by a constant current source. The results show that low-frequency current components are induced in the junction, which can give large spurious signals when small i.f. are used.