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Design and Characterization of Two-Junction Tuning Circuits for Submillimeter SIS Mixers

Michael C. Gaidis, M. Bin, David A. B. Miller, Jonas Stasys Zmuidzinas, Henry George LeDuc, Jeff A. Stern

Published Mar 1, 1995• 2 citations
OpenAlex

Abstract

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

Related papers

Two-junction tuning circuits for submillimeter SIS mixers

Jonas Stasys Zmuidzinas, Henry George LeDuc, J. A. Stern +1 more

The capacitance of superconducting tunnel junctions can seriously degrade the performance of quasiparticle (SIS) mixers operating in the submillimeter band, so it is essential to provide a circuit for tuning out this capacitance at the operating frequency. In this article, we present two new tuning circuits for SIS mixers which use a pair of SIS junctions connected by an inductance. Compared to previously proposed tuning circuits, ours have a broader bandwidth, are easier to scale to higher frequencies, and may be easier to fabricate. We have constructed quasi-optical mixers which employ these tuning circuits, using Nb/Al-Oxide/Nb SIS junctions defined by optical lithography. The performance of these devices is excellent, giving receiver noise temperatures of 113 K (DSB) at 490 GHz and 230 K DSB at 612 GHz. In addition to demonstrating the effectiveness of our tuning circuit, these results show that quasi-optical mixers can be competitive with or superior to waveguide mixers at submillimeter wavelengths. The mixers continue to perform well at frequencies up to 672 GHz, which is about 95% of the Nb gap frequency.>

IEEE Transactions on Microwave Theory and Techniques•Apr 1, 1994•128 citations

Low-noise THz Niobium SIS Mixers

Mei Bin

This thesis describes the development of low-noise heterodyne receivers at THz frequencies for submillimeter astronomy using Nb-based superconductor-insulator-superconductor (SIS) tunneling junctions. The mixers utilize a quasi-optical configuration which consists of a planar twin-slot antenna and antisymmetrically-fed two-junctions on an antireflection-coated silicon hyperhemispherical lens. On-chip integrated tuning circuits, in the form of microstrip lines, are used to obtain maximum coupling efficiency in the designed frequency band. To reduce the rf losses in the integrated tuning circuits above the superconducting Nb gap frequency (~ 700 GHz), normal-metal Al is used to replace Nb as the tuning circuits. To account the rf losses in the micros trip lines, we calculated the surface impedance of the AI films using the nonlocal anomalous skin effect for finite thickness films. Nb films were calculated using the Mattis-Bardeen theory in the extreme anomalous limit. Our calculations show that the losses of the Al and Nb microstrip lines are about equal at 830 GHz. For Al-wiring and Nb-wiring mixers both optimized at 1050 GHz, the RF coupling efficiency of Al-wiring mixer is higher than that of Nb-wiring one by almost 50%. We have designed both Nb-wiring and Al-wiring mixers below and above the gap frequency. A Fourier transform spectrometer (FTS) has been constructed especially for the study of the frequency response of SIS receivers. This FTS features large aperture size (10 inch) and high frequency resolution (114 MHz). The FTS spectra, obtained using the SIS receivers as direct detectors on the FTS, agree quite well with our theoretical simulations. We have also, for the first time, measured the FTS heterodyne response of an SIS mixer at sufficiently high resolution to resolve the LO and the sidebands. Heterodyne measurements of our SIS receivers with Nb-wiring or Al-wiring have yielded results which arc among the best reported to date for broadband heterodyne receivers. The Nb-wiring mixers, covering 400 - 850 GHz band with four separate fixed-tuned mixers, have uncorrected DSB receiver noise temperature around 5hv/kb to 700 GHz, and better than 540 K at 808 GHz. An Al-wiring mixer designed for 1050 GHz band has an uncorrected DSB receiver noise temperature 840 K at 1042 GHz and 2.5 K bath temperature. Mixer performance analysis shows that Nb junctions can work well up to twice the gap frequency and the major cause of loss above the gap frequency is the rf losses in the microstrip tuning structures. Further advances in THz SIS mixers may be possible using circuits fabricated with higher-gap superconductors such as NbN. However, this will require high-quality films with low RF surface resistance at THz frequencies.

•Sep 1, 1997•8 citations

Characterization of low-noise quasi-optical SIS mixers for the submillimeter band

Michael C. Gaidis, Henry George LeDuc, Mei Bin +3 more

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.

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Characterization of submillimetre quasi-optical twin-slot double-junction SIS mixers

Michael C. Gaidis, M. Bin, D Miller +3 more

We report on the continuing development of submillimetre quasi-optical slot antenna SIS mixers, which use two-junction tuning circuits. Direct and heterodyne Fourier transform spectrometer measurements have been performed to compare device performance with predictions. Demonstrated double-sideband receiver noise temperatures of better than 540 K at 808 GHz make these SIS mixers substantially better than GaAs Schottky receivers for the astronomically important CI and CO transitions near 810 GHz.

Superconductor Science and Technology•Apr 1, 1996•0 citations

Quasi-optical SIS mixers with normal metal tuning structures

Mei Bin, Michael C. Gaidis, Jonas Stasys Zmuidzinas +2 more

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).

IEEE Transactions on Applied Superconductivity•Jun 1, 1997•24 citations

Theoretical and Experimental Studies of Nb-Based Tuning Circuits for THz SIS Mixers

Victor Y. Belitsky, S. W. Jacobson, Lyudmila V. Filippenko +1 more

Three Nb-A10x-Nb SIS mixers tuned to operate in the 400-550, 550-700 and 600-750 GHz frequency bands have been investigated by modeling and experimentally by employing Fourier Transform Spectrometer (FTS) technique and mixer measurements. The mixers were of quasioptical type with spiral antennas and twin junction tuning circuits integrated onto the apex area of the antenna arms. Modeling was employed for optimizing the tuning circuits and evaluating its performance. The comprehensive model for the SIS mixer bases on Tucker-Feldman theory of quasiparticle SIS mixer and Mattis-Bardeen theory of anomalous skin-effect. Very good agreement between modeling, FTS measurements and mixer experiment results was achieved. Accuracy in prediction of the tuning band and the coupling efficiency for the tuning circuits is better or about 15% within 400-1000 GHz band. Introduction The SIS mixer optimum performance can be reached when the intrinsic capacitance of the SIS junction is tuned out. Different integrated on chip tuning circuits have been developed for waveguide and open structure (quasioptical) Nb-A10x-Nb SIS mixers for 100-820 GHz band [16] providing broadband low-noise operation of the receivers [7-11]. These tuning circuits mainly utilize different microstrip lines, made from Nb with SiO or Si02 insulator, to resonate out SIS junction capacitance. The focus of this work is theoretical (by modeling) and experimental investigation of twin junction tuning circuit [4-6] for frequency band about 400-1000 GHz. Mattis-Bardeen theory was employed for the tuning circuit modeling. Fourier Transformer Spectrometer technique as well as mixer measurements of developed SIS mixers were used to determine tuning circuits performance, to compare experimental data and results of modeling. At the first step of the tuning circuit development simplified free-of-loss model has been employed for evaluating of the tuning circuit behavior and its optimization [11,191 The coupling efficiency of the spiral antenna output and the tuning circuit input was used as a quality parameter for loss-free circuitry (Fig. 1). However Fourier Transform Spectrometer (FTS) measurements of the tuning circuits [19] have shown noticeable discrepancy between tuning circuit coupling efficiency at above the gap frequency and model predicted performance. This associated with loss in Nb microstrip tuning circuitry. Near the gap frequency of Nb material (-690 GHz for film) the Nb based microstrip lines become dispersing [12, 13] and above this frequency having increasing losses [14, 15]. Mattis– Bardeen theory [16] of skin anomalous effect describes behavior of a superconductor at these frequencies in teillis of complex conductivity a: cr= G–ja2 , (1) where real a l and imaginary 32 components translate directly into the normal-electron and cooperpare currents in a superconductor. Following fundamental paper of R.L. Kautz [14] these components above can be presented in integral form: zo (7) Page 88 Sixth International Symposium on Space Terahertz Technology 2 E2±2 + E j = de[f (s)— f (e + hco)} O 7: ha) 2 2 1/2 2 2 A h + 1 ' er dep. 2f(hco hw i, 21 — A2 — A2} 112 (s2 _2 ) / (11(0 _ e) ha)

•Mar 1, 1995•3 citations
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
The capacitance of superconducting tunnel junctions can seriously degrade the performance of quasiparticle (SIS) mixers operating in the submillimeter band, so it is essential to provide a circuit for tuning out this capacitance at the operating frequency. In this article, we present two new tuning circuits for SIS mixers which use a pair of SIS junctions connected by an inductance. Compared to previously proposed tuning circuits, ours have a broader bandwidth, are easier to scale to higher frequencies, and may be easier to fabricate. We have constructed quasi-optical mixers which employ these tuning circuits, using Nb/Al-Oxide/Nb SIS junctions defined by optical lithography. The performance of these devices is excellent, giving receiver noise temperatures of 113 K (DSB) at 490 GHz and 230 K DSB at 612 GHz. In addition to demonstrating the effectiveness of our tuning circuit, these results show that quasi-optical mixers can be competitive with or superior to waveguide mixers at submillimeter wavelengths. The mixers continue to perform well at frequencies up to 672 GHz, which is about 95% of the Nb gap frequency.>
This thesis describes the development of low-noise heterodyne receivers at THz frequencies for submillimeter astronomy using Nb-based superconductor-insulator-superconductor (SIS) tunneling junctions. The mixers utilize a quasi-optical configuration which consists of a planar twin-slot antenna and antisymmetrically-fed two-junctions on an antireflection-coated silicon hyperhemispherical lens. On-chip integrated tuning circuits, in the form of microstrip lines, are used to obtain maximum coupling efficiency in the designed frequency band. To reduce the rf losses in the integrated tuning circuits above the superconducting Nb gap frequency (~ 700 GHz), normal-metal Al is used to replace Nb as the tuning circuits. To account the rf losses in the micros trip lines, we calculated the surface impedance of the AI films using the nonlocal anomalous skin effect for finite thickness films. Nb films were calculated using the Mattis-Bardeen theory in the extreme anomalous limit. Our calculations show that the losses of the Al and Nb microstrip lines are about equal at 830 GHz. For Al-wiring and Nb-wiring mixers both optimized at 1050 GHz, the RF coupling efficiency of Al-wiring mixer is higher than that of Nb-wiring one by almost 50%. We have designed both Nb-wiring and Al-wiring mixers below and above the gap frequency. A Fourier transform spectrometer (FTS) has been constructed especially for the study of the frequency response of SIS receivers. This FTS features large aperture size (10 inch) and high frequency resolution (114 MHz). The FTS spectra, obtained using the SIS receivers as direct detectors on the FTS, agree quite well with our theoretical simulations. We have also, for the first time, measured the FTS heterodyne response of an SIS mixer at sufficiently high resolution to resolve the LO and the sidebands. Heterodyne measurements of our SIS receivers with Nb-wiring or Al-wiring have yielded results which arc among the best reported to date for broadband heterodyne receivers. The Nb-wiring mixers, covering 400 - 850 GHz band with four separate fixed-tuned mixers, have uncorrected DSB receiver noise temperature around 5hv/kb to 700 GHz, and better than 540 K at 808 GHz. An Al-wiring mixer designed for 1050 GHz band has an uncorrected DSB receiver noise temperature 840 K at 1042 GHz and 2.5 K bath temperature. Mixer performance analysis shows that Nb junctions can work well up to twice the gap frequency and the major cause of loss above the gap frequency is the rf losses in the microstrip tuning structures. Further advances in THz SIS mixers may be possible using circuits fabricated with higher-gap superconductors such as NbN. However, this will require high-quality films with low RF surface resistance at THz frequencies.
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.
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).
Three Nb-A10x-Nb SIS mixers tuned to operate in the 400-550, 550-700 and 600-750 GHz frequency bands have been investigated by modeling and experimentally by employing Fourier Transform Spectrometer (FTS) technique and mixer measurements. The mixers were of quasioptical type with spiral antennas and twin junction tuning circuits integrated onto the apex area of the antenna arms. Modeling was employed for optimizing the tuning circuits and evaluating its performance. The comprehensive model for the SIS mixer bases on Tucker-Feldman theory of quasiparticle SIS mixer and Mattis-Bardeen theory of anomalous skin-effect. Very good agreement between modeling, FTS measurements and mixer experiment results was achieved. Accuracy in prediction of the tuning band and the coupling efficiency for the tuning circuits is better or about 15% within 400-1000 GHz band. Introduction The SIS mixer optimum performance can be reached when the intrinsic capacitance of the SIS junction is tuned out. Different integrated on chip tuning circuits have been developed for waveguide and open structure (quasioptical) Nb-A10x-Nb SIS mixers for 100-820 GHz band [16] providing broadband low-noise operation of the receivers [7-11]. These tuning circuits mainly utilize different microstrip lines, made from Nb with SiO or Si02 insulator, to resonate out SIS junction capacitance. The focus of this work is theoretical (by modeling) and experimental investigation of twin junction tuning circuit [4-6] for frequency band about 400-1000 GHz. Mattis-Bardeen theory was employed for the tuning circuit modeling. Fourier Transformer Spectrometer technique as well as mixer measurements of developed SIS mixers were used to determine tuning circuits performance, to compare experimental data and results of modeling. At the first step of the tuning circuit development simplified free-of-loss model has been employed for evaluating of the tuning circuit behavior and its optimization [11,191 The coupling efficiency of the spiral antenna output and the tuning circuit input was used as a quality parameter for loss-free circuitry (Fig. 1). However Fourier Transform Spectrometer (FTS) measurements of the tuning circuits [19] have shown noticeable discrepancy between tuning circuit coupling efficiency at above the gap frequency and model predicted performance. This associated with loss in Nb microstrip tuning circuitry. Near the gap frequency of Nb material (-690 GHz for film) the Nb based microstrip lines become dispersing [12, 13] and above this frequency having increasing losses [14, 15]. Mattis– Bardeen theory [16] of skin anomalous effect describes behavior of a superconductor at these frequencies in teillis of complex conductivity a: cr= G–ja2 , (1) where real a l and imaginary 32 components translate directly into the normal-electron and cooperpare currents in a superconductor. Following fundamental paper of R.L. Kautz [14] these components above can be presented in integral form: zo (7) Page 88 Sixth International Symposium on Space Terahertz Technology 2 E2±2 + E j = de[f (s)— f (e + hco)} O 7: ha) 2 2 1/2 2 2 A h + 1 ' er dep. 2f(hco hw i, 21 — A2 — A2} 112 (s2 _2 ) / (11(0 _ e) ha)