Single-sideband Noise Temperature Research Articles

A 345-GHz Sideband-Separating Receiver Prototype With Ultra-Wide Instantaneous Bandwidth

In this paper, we present a sideband-separating (2SB) receiver prototype for operation between 300 and 360 GHz with ultra-wide instantaneous bandwidth. This was achieved using wide bandwidth superconductor–insulator–superconductor (SIS) mixer designs and intermediate frequency (IF) components, including a multi-octave IF hybrid placed outside the cryostat. We tested the prototype with a 3-junction SIS device from the wideband Submillimeter Array (wSMA) high-band receiver, as well as a newly designed 1-junction device. Our measurements demonstrated that the prototype receiver had a usable IF range of 4–13 GHz with the 1-junction device and 4–17 GHz with the 3-junction device. The measured single-sideband noise temperatures were 96±8 K from 312 to 363 GHz with the 1-junction device and 109±14 K from 314 to 367 GHz with the 3-junction device. Over the same frequency range, the image rejection ratio was above 12.3 dB and 11.0 dB for 90% of the data points with the 1-junction and 3-junction devices, respectively. We have identified methods to further enhance the performance of this prototype and we believe that an upgraded receiver can provide a usable IF bandwidth up to 4–20 GHz.

Modular 2SB SIS Receiver for 600–720 GHz: Performance and Characterization Methods

A modular sideband-separating (2SB) receiver for 600–720 GHz has been built and tested. The used modular design allows to characterize all the parts separately, including testing of the superconductor–insulator–superconductor (SIS) junctions individually in a double-sideband mode before building them in to the 2SB assembly. The developed 2SB mixer has a single sideband noise temperature below 380 K in the entire operating band and reaches a level of 200 K in the best point. At the same time, the image rejection ratio (IRR) was demonstrated to be better than 11.5 dB over the entire band. However, we have found a discrepancy between the observed and expected performance. To investigate this problem, we have developed and applied methods to characterize RF and intermediate frequency imbalances of a fully assembled 2SB mixer using the SIS junction properties. As result, the IRR of our mixer was found to be limited by the RF imbalance, which is caused by complex standing waves created by reflections from the SIS junctions, the RF hybrid and the RF absorption load.

Performance and Uniformity of Mass-Produced SIS Mixers for ALMA Band 8 Receiver Cartridges

We developed SIS mixers for Atacama large millimeter/submillimeter array (ALMA) Band 8 (385-500 GHz) receiver cartridges and evaluated their performance. DC IV curves of the SIS mixers showed small leakage current at the high current density. The current density and quality factor (R-{sg}/R-{n}) of the Band 8 SIS junction were 13 \hbox{kA/cm}{2} and approximately 20, respectively. Double-sideband noise temperature of the 266 SIS mixers was 92.8 K at 4.0 K bath temperature on the average from 385 to 500 GHz with a standard deviation of 7.0%. A couple of sideband-separating (2SB) mixers for dual polarizations were used in the Band 8 receiver cartridge. The 73 receivers have met ALMA specifications of the noise temperature. Single-sideband noise temperature and image rejection ratio of the receivers were 139.5 K and 20.5 dB on the average from 385 to 500 GHz, respectively. These test results of the receivers indicate high quality and uniformity of the 2SB mixers.

Performance of the Production Band 3 receivers (84-116 GHz) for the Atacama Large Millimeter Array (ALMA)

This paper presents the performance of production Band 3 receivers (84-116 GHz) for the Atacama Large Millimeter Array (ALMA) that operate in Chile at 5000 m altitude. The fabrication, and testing of a total of 73 receivers necessitated stringent quality control during assembly and custom designed automated test set for accurate and reproducible measurement results. Interfaces to the ALMA receiver system are described in details. The average single side band noise temperature of band 3 production receivers is 33.2 K, with a minimum of 24.4 K and a maximum of 45.5 K. As for image rejection, the average is 18 dB, with a minimum at 12 dB and a maximum of 21 dB. Other performances with test methodology are described such as gain variation within the IF band, the gain and phase stability, gain compression, and beam patterns. This paper also describes the interfaces to the ALMA front end system, the testing methodology used, and the test results.

Development of a 385–500 GHz Sideband-Separating Balanced SIS Mixer

A submillimeter (385-500 GHz) low-noise sideband-separating balanced SIS (Superconductor Insulator Superconductor) mixer (Balanced 2SB mixer) with high IRR (Image Rejection Ratio) has been successfully developed, whose SSB (Single SideBand) noise temperature is similar to 200 K (10hf/k) with an image rejection ratio of a parts per thousand yenaEuro parts per thousand a1/410 dB. Balanced mixers have become a promising technology which would break through the limitation especially in terahertz receivers and heterodyne arrays. However, though there are examples in microwave with relatively worse noise performance, submillimeter and terahertz balanced mixers have rarely been developed in spite of their astronomical importance. The developed balanced 2SB mixer is not only the first one demonstrated at submillimeter frequency range, but also has very low noise, high IRR, wide detectable frequencies (385-500 GHz), and a flat IF output spectrum. The balanced 2SB mixer is composed of three RF hybrids, four DSB (Double SideBand) mixers, two 180A degrees IF hybrids, and an IF quadrature hybrid. Several important performance indicators such as noise temperature, IRR, required LO (Local Oscillator) power, and IF spectra were measured. The measured LO power required for the balanced 2SB mixer was typically similar to 14 dB less than that of the single-ended mixers.

Design and Performance of a 600–720-GHz Sideband-Separating Receiver Using ${\hbox{AlO}}_{x}$ and AlN SIS Junctions

We present the design, modeling, construction, and characterization of a sideband separating heterodyne receiver that covers the frequency range from 600 to 720 GHz. The receiver has been constructed using waveguide technology in the split-block technique. The core of the mixer consists of a quadrature hybrid, two directional couplers to inject the local oscillator signal, two superconductor-insulator-superconductor (SIS) junctions, three signal-termination loads, and two planar IF/bandpass-filter/dc-bias circuits. The instrument that we have constructed presents excellent performance as demonstrated by two important figures of merit: receiver noise temperature and sideband ratio. Across the entire band, the uncorrected single-sideband noise temperature is below 500 K and reaches 190 K at the best operating point. The sideband ratio is greater than 10 dB over most of the frequency operating range. Superconducting junctions containing AlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> - and AlN-tunnel barriers were tested.

Design and Characterization of a 211–275 GHz Sideband Separating Mixer for the APEX Telescope

We present the final results of the development and characterization of the sideband separating superconductor-insulator-superconductor (SIS) mixer for the APEX telescope band 1 (211-275 GHz). The sideband separation is achieved by using a quadrature scheme where the radio frequency (RF) and a local oscillator (LO) power are applied to two identical double sideband SIS mixers. All mixer components, including the LO and RF distribution circuitry, are integrated into a single mixer block. To achieve a compact design we developed a superconducting Lange coupler, based on Nb thin film, which is used as an intermediate frequency hybrid. Typical single sideband noise temperature of 100 K and sideband rejection ratio of about 12 dB and are measured.

Improving the Efficiency of Single-Sideband Millimeter-Wave Reception by Returning the Signal Converted into Image

We describe the technique, apparatus, and the results of studies of the possibility of millimeter-wave single-sideband reception with minimum loss, associated with conversion into image. The single-sideband noise temperature of the receivers is improved by a factor of 1.4-1.9 in the N and Y bands.

A 200-300 GHz single sideband SIS mixer for radio astronomy

We present an ultra broadband low noise single sideband (SSB) SIS mixer developed for 200-300 GHz radio astronomy receivers. The mixer uses two Nb/AlO/sub x//Nb junctions. Image band rejection by 20 dB is provided in the entire 200-300 GHz band using a mechanical tuning of the single noncontacting backshort in the mixer. The SIS receiver SSB noise temperature is close to 50 K in the main part of the band. A speed-up of the observations at radio telescopes by a factor 2-3 is expected with the new receiver.

Subharmonic waveguide mixer at 215 GHz utilizing quasivertical Schottky diodes

The design of a 215 GHz subharmonic waveguide mixer utilizing an antiparallel pair of quasivertical Schottky diodes is presented. The impedance matching is provided by series and parallel waveguide tuners. A single sideband noise temperature of 3500 K and conversion loss of 9.2 dB have been measured (antenna loss included). © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 93–97, 2000.

A new generation of SIS receivers for millimeter-wave radio astronomy

A new generation of low-noise, dual-polarization heterodyne receivers covering all atmospheric windows between 68 and 300 GHz has been developed for the 12-m telescope on Kitt Peak, AZ, operated by the National Radio Astronomy Observatory (NRAO). A modular approach to the receiver construction has been used. Each receiver channel is constructed as a self-contained insert which is mounted in a dewar equipped with a closed-cycle 4 K refrigerator capable of cooling up to eight inserts, thereby enabling several frequency bands to be contained within one dewar. The telescope and receiver optics are so arranged that switching between frequency bands may be accomplished rapidly by rotating the optical elements placed in the signal path. Single-sideband noise temperatures ranging from 50 to 400 K are obtained across the frequency range.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Millimeter-Wave, Shot-Noise Limited, Fixed-Tuned Mixer

In a companion paper, two computer-controlled measurement systems for testing millimeter-wave Schottky-barrier diode mixers between 90 and 350 GHz have been presented. In this paper, a typical application of the measurement system to the testing and evacuation of a practical W-band, cryogenic, fixed-tuned Schottky diode mixer is used to demonstrate the performance of the instruments. The mixer is shown to have a single-sideband noise temperature of less than 140 K between 98 and 118 GHz and, at 110 GHz, achieves shot-noise limited performance, with a SSB noise temperature of only 81 K and corresponding conversion loss of 5.7 dB.

CO survey of the Southern Milky Way

When the Columbia Southern Millimeter-Wave Telescope on Cerro Tololo, Chile, began operation in January 1983, one of the main goals was to make the first extensive out-of-plane survey of 2.6-mm CO emission in the Southern Milky Way. Because this telescope, a 1.2-meter Cassegrain, is a close copy of the Columbia telescope in New York – with nearly identical antenna, feed, and calibration – it will be very easy to join our northern and southern surveys to make the first homogeneous radio survey of the entire Galaxy. The Chile telescope does have one important improvement over the New York system: a liquid-nitrogen-cooled receiver with a single-sideband noise temperature of 385 K. Details of the telescope are given in Cohen (1983).

Low-noise 115-GHz receiver using superconducting tunnel junctions

A 110–118-GHz receiver based on a superconducting quasiparticle tunnel junction mixer is described. The single-sideband noise temperature is as low as 68±3 K. This is nearly twice the sensitivity of any other receiver at this frequency. The receiver was designed using a low-frequency scale model in conjunction with the quantum mixer theory. A scaled version of the receiver for operation at 46 GHz has a single-sideband noise temperature of 55 K. The factors leading to the success of this design are discussed.

CO (J=2-1) Observations of the Carina Nebula and G 333.6-0.2 and a Search for CO in LMC and SMC

We used the ESO 3.6 m telescope at La Silla (Chile) in conjunction with the Estec heterodyne receiver to observe CO (J=2-1) emission from southern sources. The telescope HPBW was 2.2 arcmin, the beam efficiency 43 per cent. The receiver used backward-wave oscillators and Schottky barrier diode mixers. It had a single-sideband noise temperature of 4000 K at 230 GHz. The backend was a 256 channel filterbank of 1 MHz (1.3 km s−1) bandwidth per channel. Calibration was done in the usual way.

A Low-Noise 47-GHz Mixer Using a Permanent Josephson Junction

A new method to produce permanent Josephson junctions for millimeter-wave mixers is reported. In contrast to conventional point contacts which are mechanically unstable and require adjustments after each cooldown, these point contact junctions are set at room temperature, stay mechanically stable, and can be temperature cycled without readjustments. Using these junctions in a modified Sharpless wafer mixer mount, a single-sideband noise temperature of 71 K was measured at 47 GHz. Based on these results, system noise temperatures of less than 100 K are predicted for practical broad-band radiometers, RADAR, and communications receivers up to at least 100 GHz

Unidentified Interstellar Microwave Line

DURING a search for H12C14N (hydrogen cyanide) and its molecular isotope H13C14N, we have detected a new molecular line. The discovery was made in June 1970 using the 36-foot telescope of the National Radio Astronomy Observatory in Tucson, Arizona. The receiver was a 3-mm mixer radiometer developed by NRAO in conjunction with Jefferts, Wilson and Penzias of the Bell Telephone Laboratories. The single sideband noise temperature of the radiometer was 3000 K and it covered frequencies from 85 to 90 GHz. At these frequencies the telescope has a beamwidth of 1′ of arc and a beam efficiency of 50 per cent under optimum conditions. The filter bank receiver used consisted of forty filters spaced 1 MHz apart covering a velocity range of 130 km s−1.