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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Modelling and performance of Nb SIS mixers in the 1.3 mm and 0.8 mm bands

We describe the modeling and subsequent improvements of SIS waveguide mixers for the 200-270 and 330-370 GHz bands (Blundell, Carter, and Gundlach 1988, Carter et al 1991). These mixers are constructed for use in receivers on IRAM radiotelescopes on Pico Veleta (Spain, Sierra Nevada) and Plateau de Bure (French Alps), and must meet specific requirements. The standard reduced height waveguide structure with suspended stripline is first analyzed and a model is validated through comparison with scale model and working scale measurements. In the first step, the intrinsic limitations of the standard mixer structure are identified, and the parameters are optimized bearing in mind the radioastronomical applications. In the second step, inductive tuning of the junctions is introduced and optimized for minimum noise and maximum bandwidth. In the 1.3 mm band, a DSB receiver temperature of less than 110 K (minimum 80 K) is measured from 180 through 260 GHz. In the 0.8 mm band, a DSB receiver temperature of less than 250 K (minimum 175 K) is obtained between 325 and 355 GHz. All these results are obtained with room-temperature optics and a 4 GHz IF chain having a 500 MHz bandwidth and a noise temperature of 14 K.

Karpov, A.↗
NASA NTRS1992

A low-noise 492 GHz SIS waveguide receiver

We discuss the design and performance of an SIS waveguide receiver which provides low noise performance from 375 to 510 GHz. At its design frequency of 492 GHz, the receiver has a double sideband noise temperature of approx. 172 K. By using embedded magnetic field concentrators, we are able to effectively suppress Josephson pair tunneling. Techniques for improving receiver performance are discussed.

Walker, C. K.↗
NASA NTRS1992

Evaluation of integrated tuning elements with SIS devices

The resonance of integrated tuning stubs in combination with SIS detectors is measured and modeled. The predicted resonances are compared with measurements of stubs integrated with Nb/Al2O3/Nb junctions in a log-periodic antenna using a Michelson interferometer. Different stub lengths were made on different substrates (on 200 micron thick quartz and on a 7 micron thick silicon membrane) and the results show a fairly good agreement with the model calculations. Quartz substrates showed resonances up to 580 GHz, silicon membrane stub resonances reach as high as 480 GHz. An observed resonance at 560 GHz is probably a substrate effect from the membrane. The gap frequency for all the samples is 650 GHz and no resonances are detected above this frequency. Up to the maximum detected frequency dispersion is found to be negligible.

Dierichs, M. M. T. M.↗
NASA NTRS1993

Experimental verification of the photodiode theory of SIS mixers

The authors describe the characterization and interpretation of the performance of SIS receivers within the framework of the photodiode theory of mixing. The quantum efficiency plays a dominant role in the theory, and a simple method of accurately measuring this parameter is presented. It is demonstrated that the quantum efficiency measurements can be conveniently made on a standard radio astronomy receiver and combined with the usual hot and cold load characterization to improve the understanding of the receiver's performance. The measurements verify that the photodiode theory of mixing accurately describes the receiver noise even at local-oscillator power levels well above the linear response range. The results for receivers operating at 100 and 240 GHz verify the utility of this approach. These methods should also prove useful in evaluating submillimeter receivers.

Woody, David P.↗
NASA NTRS1996

Submillimeter-Wave Receiver Containing An SIS Mixer

Submillimeter-wave heterodyne receiver designed to operate at input frequencies in range of 480 to 650 GHz. Intended for use in radio astronomy at frequency of 547 or 626 GHz. Heart of receiver is waveguide mixer that includes adjustable backshort and electric-field-plane tuner. Mixing element high-current-density superconductor/insulator/superconductor (SIS) tunnel junction integrated with superconductive microstrip radio-frequency circuit that tunes out capacitance of junction; matching complex impedance of junction to available tuning range of waveguide mount.

Febvre, Pascal↗
NASA NTRS1997

Quasi-Optical SIS Mixer Development

This grant supported our ongoing development of sensitive quasi-optical SIS mixers for the submillimeter band. The technology developed under this grant is now being applied to NASA missions, including the NASA/USRA SOFIA airborne observatory and and the ESA/NASA FIRST/Herschel space astronomy mission.

Zmuidzinas, J.↗
NASA NTRS2004

Broadband Heterodyne SIS Spectrometer Prototype: First Results

The broadband heterodyne SIS receiver system described elsewhere (reference 1) has been assembled and tested both in the laboratory and during two observing runs on the Cassegrain focus of the 10 meter telescope at the Caltech Submillimeter Observatory on Mauna Kea, Hawaii. Here we present a brief summary of the initial results.

Rice, F.↗
NASA NTRS1993

A Submillimeter Wave SIS Receiver for 547 GHz

The most sensitive heterodyne receivers used for millimeter wave and submillimeter wave radioastronomy employ superconductor-insulator-superconductor tunnel junctions as the nonlinear mixing element.

heterodyne receivers submillimeter wave SIS tunnel↗