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International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)

Quasi-optical 0.5 THz SIS receiver with twin junction tuning circuit

Stellan Jacobsson

Published Aug 30, 1993• 3 citations
Publisher

Abstract

A quasi optical SIS mixer for the frequency band 400-550 GHz has been designed and successfully testedin a laboratory receiver setup. The intrinsic SIS junction capacitance was tuned out by a novel pair (twin) SISjunction compensation circuit. The 4µm2 area Nb-A10x-Nb junctions, with (oRnC product as high as 7.4 at500 GHz, were patterned by optical lithography and integrated with a equiangular spiral antenna to give broad- band SIS mixer operation. The receiver demonstrated flat response within the tuning range of the available LOsource (440 - 520 GHz) with DSB noise temperatures below 300 K over the entire band and with the best re- ceiver noise temperature below 250 K DSB at 453 GHz (measured at 3.5 K physical temperature). No mechani- cal tuning was employed in the SIS mixer. These noise temperatures include all losses and was measured atan IF center frequency of 1.5 GHz.

DOI
10.1117/12.2298570

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IEEE Transactions on Microwave Theory and Techniques•Jul 1, 1996•51 citations
A quasi optical SIS mixer for the frequency band 400-550 GHz has been designed and successfully testedin a laboratory receiver setup. The intrinsic SIS junction capacitance was tuned out by a novel pair (twin) SISjunction compensation circuit. The 4µm2 area Nb-A10x-Nb junctions, with (oRnC product as high as 7.4 at500 GHz, were patterned by optical lithography and integrated with a equiangular spiral antenna to give broad- band SIS mixer operation. The receiver demonstrated flat response within the tuning range of the available LOsource (440 - 520 GHz) with DSB noise temperatures below 300 K over the entire band and with the best re- ceiver noise temperature below 250 K DSB at 453 GHz (measured at 3.5 K physical temperature). No mechani- cal tuning was employed in the SIS mixer. These noise temperatures include all losses and was measured atan IF center frequency of 1.5 GHz.
We report on the continuing development of submillimeter quasi-optical slot antenna SIS mixers which use two-junction tuning circuits [1]. The mixers use 10 kA/cm2 Nb/Al-Oxide/Nb junctions and Nb wiring, and have generated DSB receiver noise temperatures around 5hv/kB to 700 GHz, and 16hv/kB (620 K) at 798 GHz. We present Fourier-transform spectrometer (FTS) measurements and heterodyne measurements on several such devices. In general, the measured response at frequencies below the gap of Nb is in good agreement with the predicted performance. Introduction SIS mixers with Nb-trilayer tunnel junctions offer excellent performance at frequencies below 800 GHz, and should perform competitively at frequencies as high as 1.4 THz [2-5]. Our goal is to develop a suite of ultra-low-noise SIS mixers which cover frequencies from = 400 GHz to more than I THz. At frequencies below the Nb gap (< 700 GHz), existing devices perform quite well [6], but further improvements in noise temperatures remain important. In addition, it is quite useful to be able to predict device performance given the design parameters. One can then optimize the device design for a particular frequency band, and confirm that we indeed understand the physics of the device. Progress in the design and operation of devices in this frequency range is presented below. At frequencies above the Nb gap, RF photons can break Cooper pairs, resulting in greater signal loss and higher receiver noise temperatures. The loss is particularly important in the slender microstrip lines used to resonate the junction capacitance and to transform the antenna impedance down to the RF junction impedance. However, the actual coupling of radiation into Nb junctions above the gap should still be reasonably efficient -more than 30% at 800 GHz [7]. In addition to RF loss, one is also affected by increased dispersion at frequencies near the gap. The Nb microstriplines have therefore been carefully designed to ensure the desired bandpass is achieved. We demonstrate for the first time that all-Nb SIS receivers can have substantially better performance than GaAs Schottky receivers for the astronomically important CI ( P2 — P 1 ) and CO (7-6) transitions near 810 GHz. Receiver Configuration Since waveguide mixers become difficult to construct at short submillimeter wavelengths, we have adopted a quasi-optical approach. Here, lenses take the place of waveguide horns, and the incoming radiation is collected by a planar antenna on the SIS mixer substrate [8]. This offers several other advantages, such as on-chip broad-band silt a SS 114 SSE WA Wa Sta MX Dewar 120 Mylar Window SIS Mixer 295 IQ 77 K Mylar Load Bearnsplitter ICI 1= NZ IC =1 HEN1T Amplifier Polyethylene Lens
We recently reported (1996) a quasi-optical SIS mixer which used Nb/Al-oxide/Nb tunnel junctions and a normal-metal (Al) tuning circuit to achieve an uncorrected receiver noise temperature of 840 K (DSB) at 1042 GHz. Here we present results on several different device designs, which together cover the 300-1200 GHz frequency range. The mixers utilize an antireflection-coated silicon hyper-hemispherical lens, a twin-slot antenna, and a two-junction tuning circuit. The broad-band frequency response was measured using Fourier transform spectrometry (FTS), and is in good agreement with model calculations. Heterodyne tests were carried out from 400 GHz up to 1040 GHz, and these measurements agree well with the FTS results and with calculations based on Tucker's theory (1985).
Abstract A 400–550‐GHz fixed tuned quasioptical Nb/AlOx/Nb SIS heterodyne receiver has been built, and its performance has been evaluated. The receiver, operated at 3.5 K, showed noise temperatures ≤ 300‐K DSB within the tuning range of the available LO source (440–520 GHz). The SIS junction capacitance was tuned out by a novel twin‐junction circuit, which offered 130‐GHz fixed tuned bandwidth at 480 GHz. Large‐area SIS junctions (3.5 μm2, ωRnC ≈︁ 7.5 at 500 GHz), patterned by optical lithography, were used. © 1995 John Wiley & Sons, Inc.
91101. Abstract—We report on the design and characterization of broadband quasi-optical SIS receirvers for the 1 THz frequency band. The mixer design utilizes a twin-slot antenna, an antirefiection-coated silicon hyperhemispherical lens, Nb/Al-oxide/Nb tunnel junctions, and an aluminum normal-metal tuning circuit in a two-junction configuration. The fre- quency response of the device was measured using a Fourier transform spectrometer and agrees reasonably well with the theoretical prediction. Heterodyne tests were carried out from 822-1042 GHz and low receiver noise temperatures of about 770 K were obtained after correcting the losses from the LO/signal beamsplitter.
We report on low-noise heterodyne mixing with NbN/A1N/NbN tunnel junctions in the submillimeter-wave region for the first time. The receiver consists of the quasi-optical NbN SIS mixer with an integrated tuning circuit in which a radial short stub tuner is incorporated to resonate out the junction capacitance for RF matching and a balanced IF circuit for broadband IF matching. The prepared NbN SIS junction has a current density of 20 kA/cm 2 and is about 1 I1111 in diameter, supplying a small coC JRN product (o)CJRN = 3 at 300 GHz). The junctions showed good dc I-V characteristics, excellent submillimeter-wave responses and sensitive heterodyne mixing responses. From 254 to 350 GHz the average receiver noise temperature measured using by the standard Y-factor method was about 250 K (DSB) at 5 K. The lowest receiver noise temperature, 200 K (DSB), was obtained at around 303 GHz. Comparing NbN/A1N/NbN and Nb/A10x/Nb tunnel junction performance with the same tuning circuit showed that the frequency dependence of the receiver noise temperature agreed well in the two receivers. These results suggest that our well-controlled NbN SIS junctions can be used for terahertz mixer elements instead of Nb SIS junctions.
We report on the development of low-noise quasi-optical SIS mixers for the frequency range 400-850 GHz. The mixers utilize twin-slot antennas, two-junction tuning circuits, and Nb-trilayer junctions. Fourier-transform spectrometry has been used to verify that the frequency response of the devices is well predicted by computer simulations. The 400-850 GHz frequency band can be covered with four separate fixed-tuned mixers. We measure uncorrected double-sideband receiver noise temperatures around 5h/spl nu//k/sub B/ to 700 GHz, and better than 540 K at 808 GHz. These results are among the best reported to date for broadband heterodyne receivers.