IEEE Transactions on Applied Superconductivity

Development of a waveguide NbN-based SIS mixer in the 900-GHz band

Mahoto Takeda, Yoshinori Uzawa, Zhen Wang, Atsushi SAITO, Akira Kawakami

Published Jun 1, 2003• 6 citations

Abstract

We have designed and fabricated waveguide superconductor-insulator-superconductor (SIS) receivers at 870 GHz with NbN/AlN/NbN tunnel junctions on an MgO substrate. A waveguide probe was incorporated into the mixer chip for a waveguide-to-microstrip transition. As the tuning circuit for the SIS mixer, we designed a resonant distributed junction whose length is one wavelength and critical current density is 20 kA/cm/sup 2/. The mixing properties were calculated based on the quantum theory of mixing. The SSB mixer noise temperature should be less than 100 K and conversion gain larger than -8.0 dB in the frequency range from 840 to 920 GHz. We also observed the resonance steps of the fabricated SIS mixer. The tuning frequency was slightly higher than the designed frequency.

DOI: 10.1109/tasc.2003.814003

Related papers

Waveguide-Type SIS Receiver Using All-NbN Technique

M. TAKEDA

This paper describes the first experimental results for a waveguide-type all-NbN superconductor-insulator-superconductor (SIS) heterodyne mixer on an MgO substrate designed to operate over the gap frequency of Nb. The mixer consists of an NbN/MgO/NbN junction, which has a length of one wavelength at 880GHz as a tuning circuit, an NbN/MgO/NbN microstrip as a λ/4 impedance transformer, and an RF choke filter. The mixer chip was designed using a high-frequency-structure simulator. Its return-loss and embedding-impedance characteristics were examined using a 180-times-scaled mixer model. By optimizing the cutting and polishing processes for the MgO substrate, we were able to fabricate the mixer chip with an accuracy of less than 5 μm. We succeeded in mounting the chip on a mixer block and in estimating the receiver noise temperature. The uncorrected minimum double-sideband receiver noise temperature was 740 K at 824 GHz. A comparison of the receiver noise temperature in a quasi-optical SIS mixer fabricated on the same wafer as the waveguide mixer showed that input noise was the major contributor to receiver noise in the waveguide mixer.

IEICE Transactions on ElectronicsFeb 1, 20065 citations

Low-noise waveguide SIS mixer with NbN/AlN/NbN tunnel junctions tuned by an NbN/MgO/NbTiN microstrip circuit

Masanori Takeda, Wenlei Shan, Takafumi Kojima +4 more

The low-noise performance of a waveguide SIS mixer with NbN/AlN/NbN tunnel junctions and an NbN/MgO/NbTiN tuning circuit on an MgO substrate was demonstrated at frequencies above the gap frequency of Nb. To design the mixer, the complex refractive index of the MgO substrate was measured by using a THz time-domain spectrometer. The superconductive properties of NbTiN films on MgO were examined in detail. An uncorrected receiver noise temperature of 262 K (DSB) at 820 GHz was achieved in an IF bandwidth of 4-12 GHz at a bath temperature of 4.2 K. By comparing the measured and calculated conversion gains, the loss in the NbN/MgO/NbTiN tuning circuit was estimated to be 0.98 dB at 810 GHz.

Superconductor Science and TechnologyJun 10, 200910 citations

High-Gap Nb-AlN-NbN SIS Junctions for Frequency Band 790–950 GHz

Andrey V. Khudchenko, Andrey M. Baryshev, Kirill I. Rudakov +4 more

We have designed, fabricated, and tested superconductor-insulator-superconductor (SIS) mixers based on Nb/AlN/NbN twin tunnel junctions for waveguide receivers operating in a frequency range of 790-950 GHz. Electromagnetic simulations and measurement results of the mixer performance are presented. The junctions have a high gap voltage of 3.15 mV and a high current density of about 30 kA/cm2, providing a wide receiver band, which was confirmed by Fourier transform spectrometer (FTS) and noise temperature measurements. The corrected receiver noise temperature varies from 240 K at low frequencies to 550 K at the high end of the band. The influence of the SIS junction heating on its characteristics has been studied and compared to another similar high current density technologies. The heating does not have a critical impact on the mixer performance.

IEEE Transactions on Terahertz Science and TechnologyDec 24, 201549 citations

Waveguide-type all-NbN SIS mixers on MgO substrates

Masanori Takeda, Yoshinori Uzawa, Akira Kawakami +2 more

We present the first experimental results on waveguide-type all-NbN SIS receivers fabricated on MgO substrates designed in a frequency range from 780 to 960 GHz. The receiver has a resonant distributed SIS junction one wavelength long at 870 GHz as the tuning circuit and a diagonal feed horn. The mixer chip was fabricated with accuracies of less than 10 im in width and +/5 jam in thickness by optimizing the cutting and polishing conditions for MgO substrates and was successfully mounted in a waveguide-mixer block. Using a conventional Y-factor method for receiver noise measurement, a minimum DSB receiver noise temperature of 700 K was obtained at an LO frequency of 770 GHz. The contribution to noise made by the input system was dominant in receiver noise and the input noise temperature was more than 300 K over the measured band.

Softwaretechnik-TrendsJan 1, 20041 citation

Mixing Properties of NbN-Based SIS Mixers With NbTiN Wirings

Mahoto Takeda, Wenlei Shan, Takafumi Kojima +5 more

We report on the mixing properties of waveguide SIS mixers with epitaxial NbN/AlN/NbN junctions and NbN/SiO2/NbTiN microstrips on MgO substrates. The superconducting transition temperature and 20-K resistivity of NbTiN film on the SiO2dielectric were 14.7 K and 175 muOmega cm, respectively. The junction tuning circuit was composed of an NbN/SiO2/NbTiN microstrip and two parallel-connected NbN/AlN/NbN junctions 0.9 mum in diameter. The critical current density and normal-state resistance of the fabricated NbN junction were 13 kA/cm2and 22 Omega, respectively. The heterodyne response was measured using 295- and 77-K blackbody sources, a local oscillator (LO) source, and a 25-mum-thick Kapton film as a beam splitter. An intermediate frequency (IF) amplifier with a bandwidth of 4-12 GHz was used in the measurements. The receiver noise temperature corrected for losses in the beam splitter and in the vacuum window of the cryocooler was 370 K at 860 GHz and was comparable to that of all-NbN mixes with NbN/MgO/NbN microstrips.

IEEE Transactions on Applied SuperconductivityMay 27, 200910 citations

Performance of all-NbN quasi-optical SIS mixers for the terahertz band

Yoshinori Uzawa, Akira Kawakami, Shigehito Miki +1 more

We have designed, fabricated, and tested terahertz superconductor-insulator-superconductor (SIS) mixers having a self-compensated NbN/AlN/NbN tunnel junction and an epitaxially grown NbN/MgO/NbN microstripline. The junction as a distributed element was 0.8-/spl mu/m wide and 2.4-/spl mu/m long, and its current density was 50 kA/cm/sup 2/. The microstripline consisted of a 200-nm-thick NbN ground plane, a 180-nm-thick MgO insulator, and a 350-nm-thick NbN wiring layer. An investigation of the mixer in our receiver configuration showed flat noise characteristics from 870 to 960 GHz. The lowest receiver noise temperature of about 550 K was obtained at 909 GHz, including a 9-/spl mu/m-thick Mylar beam splitter loss and other optical losses. These characteristics suggest that SIS mixers with self-compensated NbN/AlN/NbN junctions and NbN/MgO/NbN microstriplines are appropriate for used in wideband and low-noise operations at terahertz frequencies.

IEEE Transactions on Applied SuperconductivityMar 1, 200121 citations