Lowest Receiver Noise Temperature Research Articles

L-band cryogenic radio astronomy receiver front-end of the Square Kilometre Array

This paper describes the design and measured performance of the band 2 (L-band, 950 MHz–1760 MHz) cryogenic receiver front-end of the Square Kilometre Array (SKA) radio telescope dish array. The system comprises a wide flare-angle axially corrugated conical horn, a dual linearly polarized orthogonal mode transduce, a noise injection directional coupler, and two amplification stages. Its compact design and cryogenic cooling allow for a very low receiver noise temperature, and it presents another step in the continuous improvement of the noise temperature performance. A Gifford–McMahon cooler physically cools the OMT with its integrated directional coupler to around 70 K, and the first stage low-noise amplifier to about 15 K. A bespoke measurement setup was designed to measure the system’s performance. The measured receiver noise is about 6 K across the frequency band.

Noise temperature distribution of superconducting hot electron bolometer mixers**Project supported by the Chinese Academy of Sciences (Grant Nos. GJJSTD20180003 and QYZDJ-SSW-SLH043), the National Key Basic Research and Development Program of China (Grant Nos. 2017YFA0304003 and 2018YFA0404701), the National Natural Science Foundation of China (Grant Nos. 11603081, 11673073, U1831202, and 11873099), and PICS projects between the CAS and the CNRS.

We report on the investigation of optimal bias region of a wide-band superconducting hot electron bolometer (HEB) mixer in terms of noise temperature performance for multi-pixel heterodyne receiver application in the 5-meter Dome A Terahertz Explorer (DATE5) telescope. By evaluating the double sideband (DSB) receiver noise temperature (Trec) across a wide frequency range from 0.2 THz to 1.34 THz and with a large number of bias points, a broad optimal bias region has been observed, illustrating a good bias applicability for multipixel application since the performance of the HEB mixer is uniquely determined by each bias point. The noise temperature of the HEB mixer has been analyzed by calibrating the noise contribution of all RF components, whose transmissions have been measured by a time-domain spectroscopy. The corrected noise temperature distribution shows a frequency independence relation. The dependence of the optimal bias region on the bath temperature of the HEB mixer has also been investigated, the bath temperature has limited effect on the lowest receiver noise temperature until 7 K, however the optimal bias region deteriorates obviously with increasing bath temperature.

A High-Order L-Band HTS Filter for Sensitive Detecting

In this paper, a new high-temperature superconducting (HTS)-based microwave radiometer with an improved sensitivity is presented. The cryogenic receiver front end consists of an HTS filter and a cryogenic low noise amplifier (LNA). The cryogenic receiver front end shows an ultra-low noise figure and can suppress radio frequency interference (RFI) effectively. The proposed HTS filter works at a center frequency of 1.4135 GHz with a bandwidth of 25 MHz. The measured mid-band insertion loss, side band steepness, and out-of-band attenuation of the HTS filter are 0.14 dB, 35 dB/MHz, and 80 dB, respectively. The noise figure of the cryogenic LNA is about 0.27 dB at a temperature of 77 K. Compared with other total power radiometers, the proposed radiometer has a lower receiver noise temperature, which can improve the sensitivity with a short integration time of the satellite-based salinity meter. In addition, since the bandwidth of the salinity meter is fixed and the integration time of satellite-based equipment is limited, such a low receiver noise temperature can increase the flexibility of future satellite payload configuration program.

Intrinsic mixing behavior of superconducting NbTiN hot electron bolometer mixers based on in situ technique

In this paper, we present the comparison of measured and simulated results for 0.8 and 1.5THz waveguide NbTiN HEB mixers fabricated by in situ technique, with a relatively thick NbTiN film (10.8nm). The dimension of NbTiN HEB mixers are 1–1.5μm in width and 0.15–0.2μm in length respectively. The lowest receiver noise temperature is measured to be as low as 410K and reduced to 210K after the correction of the losses of quasi-optical path and IF amplifier chain at both 0.8 and 1.5THz. We adopt an optimized hot spot model to simulate the DC and RF behaviors of the NbTiN HEB mixer by combining phonon-cooling and diffusion-cooling mechanisms together. The measured and calculated current–voltage curves are in good agreement. The modeled lowest intrinsic mixer noise temperature are 85 and 100K at 0.8 and 1.5THz respectively, which are smaller than the measured results by factor of about 2times. The IF gain bandwidth are observed to be quite sensitive to the microbridge length, with 2.5GHz for 0.15-μm long device down to 1.9GHz for 0.2-μm length. The calculated and measured results show the two cooling mechanism work together to improve the performance of the waveguide NbTiN HEB mixers.

ARIS-Campaign: intercomparison of three ground based 22 GHz radiometers for middle atmospheric water vapor at the Zugspitze in winter 2009

Abstract. This paper presents the Alpine Radiometer Intercomparison at the Schneefernerhaus (ARIS), which took place in winter 2009 at the high altitude station at the Zugspitze, Germany (47.42° N, 10.98° E, 2650 m). This campaign was the first direct intercomparison between three new ground based 22 GHz water vapor radiometers for middle atmospheric profiling with the following instruments participating: MIRA 5 (Karlsruhe Institute of Technology), cWASPAM3 (Max Planck Institute for Solar System Research, Katlenburg-Lindau) and MIAWARA-C (Institute of Applied Physics, University of Bern). Even though the three radiometers all measure middle atmospheric water vapor using the same rotational transition line and similar fundamental set-ups, there are major differences between the front ends, the back ends, the calibration concepts and the profile retrieval. The spectrum comparison shows that all three radiometers measure spectra without severe baseline artifacts and that the measurements are in good general agreement. The measurement noise shows good agreement to the values theoretically expected from the radiometer noise formula. At the same time the comparison of the noise levels shows that there is room for instrumental and calibration improvement, emphasizing the importance of low elevation angles for the observation, a low receiver noise temperature and an efficient calibration scheme. The comparisons of the retrieved profiles show that the agreement between the profiles of MIAWARA-C and cWASPAM3 with the ones of MLS is better than 0.3 ppmv (6%) at all altitudes. MIRA 5 has a dry bias of approximately 0.5 ppm (8%) below 0.1 hPa with respect to all other instruments. The profiles of cWASPAM3 and MIAWARA-C could not be directly compared because the vertical region of overlap was too small. The comparison of the time series at different altitude levels show a similar evolution of the H2O volume mixing ratio (VMR) for the ground based instruments as well as the space borne sensor MLS.

Characterization of the Performance of a Quasi-Optical NbN Superconducting HEB Mixer

In this paper we focus mainly on the investigation of the performance of a quasi-optical (planar log-spiral antenna) phonon-cooled NbN superconducting hot electron bolometer (HEB) mixer, which is cryogenically cooled by a close-cycled 4-K cryocooler, at 500 and 850 GHz frequency bands. The mixer's noise performance, stability of IF output power, and local oscillator (LO) power requirement are characterized for three NbN superconducting HEB devices of different sizes. The transmission characteristics of Mylar and Zitex films with incidence waves of an elliptical polarization are also examined by measuring the mixer's noise temperature. The lowest receiver noise temperatures (with no corrections) of 750 and 1100 K are measured at 500 and 850 GHz, respectively. Experimental results also demonstrate that the bigger the HEB device is, the higher the stability of IF output power becomes.

Characterization of a quasi-optical NbN superconducting HEB mixer

In this paper, the performance of a quasi-optical NbN superconducting hot-electron bolometer (HEB) mixer, cryogenically cooled by a close-cycled 4-K refrigerator, is thoroughly investigated at 300, 500, and 850 GHz. The lowest receiver noise temperatures measured at the respective three frequencies are 1400, 900, and 1350 K, which can go down to 659, 413, and 529 K, respectively, after correcting the loss and associated noise contribution of the quasi-optical system before the measured superconducting HEB mixer. The stability of the quasi-optical superconducting HEB mixer is also investigated here. The Allan variance time measured with a local oscillator pumping at 500 GHz and an IF bandwidth of 110 MHz is 1.5 s at the dc-bias voltage exhibiting the lowest noise temperature and increases to 2.5 s at a dc bias twice that voltage.

Characterization of a Quasi-optical NbN Superconducting Hot-electron Bolometer Mixer

In this paper, we report the performance of a quasi-optical NbN superconducting HEB (hot electron bolometer) mixer measured at 500 GHz. The quasi-optical NbN superconducting HEB mixer is cryogenically cooled by a 4-K close-cycled refrigerator. Its receiver noise temperature and conversion gain are thoroughly investigated for different LO pumping levels and dc biases. The lowest receiver noise temperature is found to be approximately 1200 K, and reduced to about 445 K after correcting the loss of the measurement system. The stability of the mixer’s IF output power is also demonstrated.

A new 22-GHz radiometer for middle atmospheric water vapor profile measurements

We report on the Middle Atmospheric Water Vapor Radiometer (MIAWARA) instrument, a new ground-based 22-GHz-radiometer that provides water vapor profiles with an altitude coverage of 22-80 km. This paper focuses on the instrumentation and calibration of the new instrument. It is a noncooled instrument with a very low receiver noise temperature, even lower than receiver noise temperatures of existing cooled instruments. The calibration of MIAWARA is achieved with so-called tipping-curve and balanced calibration schemes. The combination of these two calibration techniques allows us to set up a different calibration scheme than most of the other, rarely existing, water vapor profile radiometers at 22 GHz without the commonly used liquid nitrogen calibration. With the use of tipping-curve calibrations, the instrument operates as a standalone instrument. This independence of liquid-nitrogen-cooled calibration targets and of other instruments makes MIAWARA a suitable instrument for campaign use. In addition to the instrumental and calibrational description, a validation technique for the tipping-curve calibration is presented. Finally, first results obtained by measurements carried out in the Swiss plateau are reported.

Low-noise heterodyne mixing with NbN microbolometers at 800 GHz

Mixer performance of NbN transition edge microbolometers was investigated in a frequency range from 795 to 813 GHz. The devices consist of a parallel array of 3 NbN lines with submicron length patterned by e-beam lithography in a self-aligned process. The heterodyne mixer response was proven by means of two superposed oscillator signals at the receiver input and the observation of a discrete line in the output spectrum. Receiver noise temperatures, Trec, were determined by the hot/cold load Y-factor method in a quasioptical receiver at 4.2 K. The accessible intermediate frequency (IF) band was 1000 to 1750 MHz. We have compared devices with a NbN film thickness of 100 and 50 Å. Lowest receiver noise temperatures were obtained at 800 GHz. Uncorrected Trec values around 900 K were measured for both devices at a 1000 MHz IF frequency. For higher IF frequencies, Trec increased much less in the 50 Å device than in the 100 Å device. At 800 GHz and 1750 MHz IF frequency, Trec was only 1180 K. This result indicates that in an optimized NbN bolometric mixer the IF frequency band can extend to reasonable high values for radioastronomical applications.

NbN-MgO-NbN junctions prepared on room-temperature quartz substrates for quasiparticle mixers

NbN tunnel junctions are of great interest for THz heterodyne receivers because their large gap voltage of 5 mV yields an upper frequency limit of 4/spl Delta//h=2.4 THz for quasiparticle mixing. AC losses in NbN films, however, imply that a NbN matching circuit can be used at most to the NbN gap frequency, 2/spl Delta//h=1.2 THz. Another issue is the poor thermal conductivity of NbN films which complicates heat extraction from the junction. One solution to these problems are hybride mixer chips in which NbN junctions are integrated into appropriate superconducting or normal metal matching circuits. Both for waveguide mixers and quasioptical mixers quartz substrates are the first choice. We report on a room-temperature process for NbN-MgO-NbN junction fabrication which permits the realization of hybride mixer chips on quartz substrates. Appropriate plasma conditions for NbN film deposition are created by employing a second Nb target as a selective nitrogen pump. NbN films on quartz substrates without and with intermediate layers of Nb, Al, Al/SiO/sub 2/, and Nb/SiO/sub 2/ have critical temperatures above 15 K and normal state resistivities from 100 to 130 /spl mu//spl Omega/cm. In the first step, NbN junctions with nominal areas of 0.36 /spl mu/m/sup 2/ and current densities of 10 kA/cm/sup 2/ at 5.5 mV were integrated into Nb films forming the tuning circuit and a dipole antenna. The lowest receiver noise temperature in the 350 GHz range was 245 K double side band.

Quasi-optical NbN/AlN/NbN mixers in submillimeter wave band

We have designed, fabricated and evaluated a quasi-optical SIS receiver with NbN/AlN/NbN tunnel junctions in the submillimeter-wave region. The receiver consists of a planar self-complementary log-periodic antenna and MgO hyperhemispherical lens with an anti-reflection cap for RF optics, NbN SIS junctions and a radial short stub tuner to resonate out its capacitance for RF matching. The prepared NbN SIS junction has a current density of 20 kA/cm/sup 2/ and is about 1 /spl mu/m in diameter, supplying a small /spl omega/C/sub J/R/sub N/ product (/spl omega/C/sub J/R/sub N/=3 at 300 GHz). From 297 to 356 GHz the average double sideband (DSB) receiver noise temperature measured by using the standard Y-factor method was about 200 K. The lowest receiver noise temperature, 167 K (DSB), was obtained at around 303 GHz. These results suggest that our NbN SIS junctions can be used for terahertz mixer elements instead of Nb SIS junctions.

Quasi-optical submillimeter-wave mixers with NbN/AlN/NbN tunnel junctions

We demonstrate low-noise heterodyne mixing with NbN/AlN/NbN tunnel junctions in the submillimeter-wave region. The prepared junction size was 1 μm in diameter and the current density was about 20 kA/cm2, supplying a small ωCJRN product (ωCJRN=3 at 300 GHz). The mixer used a lens-coupled log-period antenna and an integrated tuning circuit which incorporated a radial short stub tuner for resonating out the junction capacitance. 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 the standard Y-factor method was about 250 K double sideband (DSB). The lowest receiver noise temperature, 200 K (DSB), was obtained around 303 GHz.

Heterodyne mixing with Nb tunnel junctions above the gap frequency

The noise and gain of a heterodyne waveguide mixer employing Nb/Al2O3/Nb superconducting tunnel junctions with an on-chip integrated tuning element are measured and analyzed at 680–750 GHz and at 840 GHz. The lowest receiver noise temperatures are 400 K (double side band) at 720 GHz and 1500 K (3000 K including the beam splitter loss) at 840 GHz. We compare data of the pumped I–V curves with the quantum theory of mixing and demonstrate good agreement at frequencies well above the gap frequency.

Pb/Bi/In and Nb/Al junctions for a 345 GHz open structure astronomical receiver

The authors report on the preparation and properties of Pb/Bi/In-oxide-Pb/Bi and Nb-Al oxide-Nb junctions prepared for a 345-GHz open-structure heterodyne receiver. The lowest receiver noise temperature with the Pb/Bi/In junctions is 215 K DSB. In this case, no matching network is integrated to tune out the junction capacitance. For the Nb/Al junctions, a microwave transmission line compensates the capacitance around 345 GHz. With the Nb-Al oxide-Nb two-junction array at 4.2 K, the lowest receiver noise temperature is 80 K at 330 GHz. The receiver is in use at the IRAM (Institut de Radio Astronomie Millimetrique) 30-m radio telescope in Spain.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A low noise 230 GHz heterodyne receiver employing 0.25- mu m/sup 2/ area Nb-AlO/sub x/-Nb tunnel junctions

The authors report recent results for a full-height rectangular waveguide mixer with an integrated IF matching network. Two 0.25 mu m/sup 2/ Nb-AlO/sub x/-Nb superconducting-insulating-superconducting (SIS) tunnel junctions with a current density of approximately=8500 A/cm/sup 2/ and omega RC of approximately=2.5 at 230 GHz have been tested. One of these quasiparticle tunnel junctions is currently being used at the Caltech Submillimeter Observatory in Hawaii. Detailed measurement of the receiver noise have been made from 200-290 GHz for both junctions at 4.2 K. The lowest receiver noise temperatures were recorded at 239 GHz, measuring 48 K DSB at 4.2 K and 40 K DSB at 2.1 K. The 230-GHz receiver incorporates a one-octave-wide integrated low-pass filter and matching network which transforms the pumped IF junction impedance to 50 Omega over a wide range of impedances. >

Fabrication of micron size Nb/Al-Al/sub 2/O/sub 3//Nb junctions with a trilevel resist liftoff process

A trilevel resist, consisting of polyimide planarization, SiO/sub 2/ barrier, and photoresist, was used to pattern junction areas in Nb/Al-Al/sub 2/O/sub 3//Nb trilayer films. After reactive ion etching to define the junction areas, the perimeter of the junction was revealed, and excellent liftoff structures were defined with an oxygen plasma shrink of the exposed polyimide sidewalls. A subsequently deposited insulation layer seals the sides and the top surface along the perimeter of the Nb counter electrode button. High-quality superconductor-insulator-superconductor (SIS) junctions with diameters as small as 1.2 mu m and V/sub m/ as large as 1500 mV at 2.0 K have been fabricated. An SIS receiver using these junctions with integrated tuning elements has a DSB noise temperature of 58 K at 230 GHz. This is believed to be the lowest receiver noise temperature ever reported at this frequency.

Dual‐frequency (40/100 GHz) SIS receiver for nobeyama millimeter‐wave array

AbstractThe authors developed a dual‐frequency (40/100 GHz) SIS receiver with SIS quasi‐particle tunneling junction element as the mixer, for use in the millimeter‐wave array at Nobeyama Radio Observatory, National Astronomical Observatory. The SIS element used is an array composed of four series‐connected Nb/Al‐AlOx/Nb junctions. The receiver is refrigerated to 4.3 K by a closed‐cycle He refrigerator. The receiver realized a very low receiver noise temperature for a wideband, such as 50 to 80 K for 43 to 49 GHz, and 60 to 100 K for 86 to 115 GHz. A wide dynamic range is also realized. At 40 Ghz, the saturation noise temperature is 2000 to 3000 K, compared with the wideband noise. These results indicate that the SIS array element can effectively improve the mixer saturation level without degrading the receiver performance.