A Multibeam SIS Mixer Module for a Focal Plane Array Receiver

The integration of many receiver units into a receiver array is a common method of improvement of imaging systems. This approach, well known in the mm band for Schottky mixer arrays, has not so far been developed for Superconductor - Insulator - Superconductor (SIS) junction mixers, which give the best sensitivity in the short mm wave range and in the submm range.We demonstrate for the first time a practical low noise multibeam receiver module using SIS mixer technology. The basis for the integration of several SIS mixers with a common local oscillator source is given by the saturation of the SIS receiver noise dependence upon local oscillator power. The module comprises three identical SIS mixers integrated with a common local oscillator, coupled through a three branch waveguide directional coupler. The multibeam module has been developed for a focal plane array receiver of the 30 meter radio telescope of the Institut de Radioastronomie Millimétrique (IRAM).     

Characterization of the IF Noise of a Submillimeter SIS Receiver

A fitting method is presented here for the accurate characterization of the IF noise contribution of a sub-millimeter SIS receiver. By fitting the mixer's IF output power response and junction's IV curve of an SIS mixer without LO pumping, we can obtain the IF noise contribution, the physical temperature of the isolator connected just behind the SIS mixer, the output mismatching of the mixer, and the total gain of the IF chain. Differing from a conventional method, which only uses the normal-state (linear) branch of the junction's IV curve, the method proposed here also includes the nonlinear portion around the gap voltage. The dynamic resistance in this portion is varied dramatically, providing us a good probe to characterize the output mismatching of the mixer, as well as other parameters.     

A 400–500 GHz Balanced SIS Mixer with a Waveguide Quadrature Hybrid Coupler

We have developed a 400–500 GHz low-noise balanced SIS (Superconductor Insulator Superconductor) mixer, which is based on a waveguide RF quadrature hybrid coupler. The RF quadrature hybrid was designed and fabricated as a broadband hybrid with good performance at 4 K. The fabricated RF quadrature hybrid was measured at room temperature with a submillimeter vector network analyzer to check amplitude and phase imbalance between two output ports. Then the balanced mixer was assembled with the RF hybrid, two DSB mixers, and a 180° IF hybrid. Several important parameters such as noise temperature, LO power reduction, and IF spectra were measured. The LO power reduction is defined as how much LO power the balanced mixer saves compared with a typical single-ended mixer. The measured noise temperature of the balanced mixer was ~ 55 K at the band center which corresponds to ~ 3 times the quantum noise limit (hf/k) in DSB, and ~ 120 K at the band edges. The noise performance over LO frequency was almost the same as that of the worse DSB mixer used in the balanced mixer. In addition the LO power required for the balanced mixer is ~ 11 dB less than that of the single-ended mixers.     

Simulation of Sub-harmonic SIS Mixers with a Full Five-Port Model

The performance of superconductor-insulator-superconductor (SIS) sub-harmonic mixers is thoroughly investigated in this paper. On account of the importance of the harmonic effect, a full five-port model combined with an enhanced Newton solution is applied to calculate the local oscillator (LO) waveform. The mixer performance is studied as functions of principal parameters including the embedding admittances, LO power and bias voltage. The results are compared with those from the quasi five-port model.     

100 GHz mixer vertically integrated (stacked) SIS junction array

A Vertically Integrated Array (stacked array) of single windowSIS junctions (VIA SIS), based on a stacked five layer structure of Nb-AlO_x-Nb-AlO_x-Nb, has been fabricated and tested in a quasi optical mixer configuration at 106 GHz. This particular VIA SIS design has two stacked junctions fabricated by standard tri-layer process employing photolithography, reactive ion and wet etching processes. A simple expression for calculating the specific capacitance of single and arrayed SIS junctions is suggested. Due to the absence of interconnection leads between the individual junctions and reduced overall capacitance, compared to a single SIS junction, has the VIA SIS good future prospects for use in submillimeter wave SIS mixers The VIA SIS may be regarded as a lumped rather than a distributed structure at least up to the gap frequency at 730 GHz for Nb. DC-IV measurements show high quality of the Individual SIS junctions and good reproducibility of the array parameters over the substrate area. The first VIA SIS mixer experiments yielded a receiver noise temperature of 95 K (DSB) at a LO frequency of 106 GHz.     

An SIS waveguide heterodyne receiver for 600 HGz-635 GHz

A waveguide SIS heterodyne receiver using a Nb/AlO_X/Nb junction has been built for astronomical observations of molecular transitions in the frequency range 600 GHz - 635 GHz, and has been successfully used at the Caltech Submillimeter Observatory (CSO). We report double sideband (DSB) receiver noise temperatures as low as 245 K at 600 GHz -610 GHz, and near 300 K over the rest of the bandwidth. These results confirm that SIS quasiparticle mixers work well at submillimeter-wave frequencies corresponding to photon energies of at least 90% of the superconductor energy gap. In addition, we have systematically investigated the effect on the receiver performance of the overlap between first-order and second-order photon steps of opposite sign at these frequencies. The receiver noise increases by as much as 40% in the region of overlap. We infer potential limitations for operating submillimeter-wave Nb/AlO_x/Nb mixers.     

Noise and thermal properties of a submillimeter mixer with the SINS tunnel junction

In this work we present for the first time a low-noise submillimeter receiver with a mixer using Superconductor-Insulator-Normal metal-Superconductor (SINS) junctions. Junctions containing a normal metal layer may be free of the Josephson current and of the related perturbations of mixer operation specific for the standard SIS mixers. This SINS mixer quality is important for the application in the multibeam submillimeter receiver. The SINS mixer stability of operation and independence on the magnetic field have been confirmed in our experiment. Minimum SINS receiver noise in the 290 – 330 GHz band is about 135 K when the junction R_NC is about 30. Noise, conversion gain and thermal properties of the SINS mixer have been studied and compared with the SIS mixers. The limit of SINS mixer operation improvement is discussed at the end of the work.     

Compact 1.9 THz BWO local-oscillator for the GREAT heterodyne receiver

The 1.9 THz local-oscillator (LO) of the GREAT heterodyne receiver is presented. The LO is based on a frequency tripled backward-wave oscillator source. The frequency stabilization system is described and an astigmatic imaging system, developed for improved beam coupling, is presented. Allan variances and temperature dependent power drifts are analyzed. The LO is designed as a stand-alone system and fits into GREAT’s local-oscillator compartments. It produces more than 1.5 μW of stable output power to pump the hot electron bolometer mixers of the GREAT instrument.     

300GHz超导SIS接收机系统的设计与构建

超导SIS(Superconductor-Insulator-Superconductor)混频技术是新兴的低噪声检测技术.其卓越的低噪声性能已使其成为毫米波和亚毫米波频段灵敏度最高的谱线接收设备,接收机的自动控制和稳定性有更高的要求,研制能够长期稳定工作的接收机有很重要的意义.本文主要讨论了我们自行研究设计工作在4K温度,准光学系统的毫米波超导SIS接收机的组成部件,根据我们制备的超导SIS隧道结器件的特性指标,计算设计了300GHz波段的超导接收机天线和结的集成芯片.     

An Integrated Sideband-Separating SIS Mixer Based on Waveguide Split Block for 100 GHz Band with 4.0–8.0 GHz IF

We have developed an integrated sideband-separating SIS mixer for the 100 GHz band based on the waveguide split block. The measured receiver noise temperatures with 4.0–8.0 GHz IF are less than 60 K in the LO frequency range of 90–110 GHz, and a minimum value of around 45 K is achieved at 100 GHz. The image rejection ratios are more than 10 dB in the frequency range of 90–110 GHz. We have installed the sideband-separating SIS mixer into an atmospheric ozone-measuring system at Osaka Prefecture University and successfully observed an ozone spectrum at 110 GHz in SSB mode. This experimental result indicates that the sideband-separating SIS mixer is very useful for astronomical observation as well as atmospheric observation.     

Spurious Signal Response of Broadband Solid–State Frequency Multipliers at Millimeter and Submillimeter Wavelengths

Heterodyne instruments at millimeter and submillimeter wavelengths often use wideband fixed-tuned frequency multipliers, in conjunction with broadband power amplifiers driven by frequency synthesizers, as the local oscillator (LO) source. At these frequencies the multipliers use Gallium Arsenide (GaAs) based Schottky varactor diodes as the nonlinear element, and like most other harmonic generators are susceptible to spurious signal interference. The state-of-the-art LO sources at these wavelengths use high power MMIC amplifiers at the initial stages, and are used to drive the subsequent multiplier stages to have enough LO power to pump the mixers. Because of the high input power environment and the presence of noise in the system, the multipliers become vulnerable to spurious signal interference. As the spurious signals propagate through the receiver system, they generate inter-modulation products which might fall in the passband of the heterodyne instrument and seriously degrade its performance. In this paper spurious signal response of solid-state frequency multipliers at millimeter and submillimeter wavelengths is investigated. Results of numerical harmonic balance simulations and laboratory experiments, which were found to show good agreement, are presented here.     

A Waveguide Band-Stop Filter as an Image Rejection Filter for Measurement of Stratospheric Ozone

In this report we present the performance and test observation results of a waveguide band-stop filter (BSF) as an image rejection filter for the measurement of stratospheric ozone. By using the waveguide BSF, we are able to adopt a very simple optical system and achieve a good image rejection ratio. Additionally, we are able to observe in both single sideband (SSB) mode and double sideband (DSB) mode by only changing the local oscillator (LO) frequency. We have installed the waveguide BSF into an atmospheric ozone-measuring system using a superconductive (SIS) receiver and have successfully observed an ozone spectrum at 110 GHz in SSB and DSB mode. The receiver noise temperature (SSB) and the image rejection ratio at 110 GHz are about 60 K and more than 30 dB, respectively.Because of the IF power ripple, the waveguide BSF cannot be used with a wide-band spectrometer. However, it is quite practical for narrow-band observation.     

The Development of a Dual Channel SIS Receiver of Trao Telescope

We developed a low noise dual channel receiver with 100GHz and 150GHz band, which is used to make the simultaneous observation with two bands. The SIS mixers are used in both bands. The constructed dewar for the receiver has a performance with a vacuum of 10^–8torr and a temperature of 4.2K. The receiver noise temperature is 50K(DSB) for 100GHz band and 80K(DSB) for 150GHz band, respectively. In order to achieve the simultaneous observations, the quasioptical system is precisely designed, and also evaluated by measurements in the laboratory. The relative pointing offset between two bands is 3. We have observed the various sources using the receiver since October 1998.     

A Novel Circuit Architecture for High Performance of High-order Subharmonic Mixers

A novel circuit architecture for high performance of high-order subharmonic (SH) mixers is proposed in this paper. According to the specified harmonic mixing order, one or more mixer diodes sub-arrays and corresponding power divider as well as phase shift network for RF and LO signals are arranged in the circuit. This proposed SH mixer circuit has improved conversion loss, wide dynamic range and high port isolation for high-order SH mixers. By phase cancellation of idle frequencies, the proposed SH mixer circuit can eliminate complicated design procedure of idle frequency circuits; by phase cancellation of leakage LO power to RF and IF port, and leakage RF power to LO port, the mixer circuit can get high port isolation in LO-IF/RF and RF-LO. The increased antiparallel diode pairs in each sub-array will also lead to well performance by lowering effective series resistance. The proposed SH mixer circuit can be easily realized with power divider and phase shift network for RF and LO signals. Supported in part by National Natural Science Foundation of China (NSFC) under Grants 60621002 and in part by NSFC under Grants 60471017.     

Recent developments in millimeter and submillimeter waves

Millimeter and submillimeter-wave observations provide important information for the studies of atmospheric chemistry and astrochemistry (molecular clouds, stars formation, galactic study, comets and cosmology). But, these observations depend strongly on instrumentation techniques and on the site quality. New techniques or higher detector performances result in unprecedented observations and, sometimes, the observational needs drive developments of new detector technologies, for example, superconducting junctions (SIS mixers) because of their high sensitivity in heterodyne detection in the millimeter and submillimeter wave range (100–700 GHz), HEB (Hot Electron Bolometer) mixers which are being developed by several groups for application in THz observations. For the sub-millimetre wavelengths heterodyne receivers, the local oscillator (LO) is still a critical element. So far, solid state fundamental sources are often not powerful enough for most of the applications at millimetre or submillimetre wavelengths: large efforts using new planar components (HBV) and integrated circuits, or new technics (laser mixing) are now in progress, in a few groups.The new large projects as SOFIA, FIRST, ALMA, … for astronomy; SMILES, EOS-MLS, … for aeronomy and other projects for the planetary science (ROSETTA, Mars Explorer, …), will benefit of the new developments.     

An Accurate Method for Determining the IF Noise in SIS Heterodyne Receivers

We present a new method to determine the contribution of the IF-amplifier chain to the overall noise performance of an SE-based receiver. Using simulated I-V and IF power characteristics, we show that the standard method used to date to evaluate the IF noise can underestimate the contribution because of non-negligible curvature in the post-gap SIS I-V characteristic. We demonstrate that the new method is not susceptible to the post-gap curvature, and discuss its benefits and limitations to the accurate and precise evaluation of IF noise contributions.     

ALMA Band 10 tertiary optics

The ALMA Band 10 (787–950 GHz) receiver is a dual-polarization heterodyne system based on NbTiN superconducting technology. The coupling of energy from the secondary mirror of the ALMA Cassegrain antenna to the Superconductor–Insulator–Superconductor (SIS) mixers used for down-conversion is achieved by a frequency-independent optical system composed of two elliptical mirrors to focus and redirect the incoming radiation, a wire-grid to separate orthogonal linear polarizations and two corrugated horns, one for each polarization and SIS mixer. In this paper, we present the ALMA Band 10 tertiary optics design and evaluate its performance by quasi-optical techniques, Physical Optics simulations and measurements. Detailed results of secondary aperture efficiency and beam-squint are provided. The characterization procedure described in this paper can be used for any optical system at around 1 THz.     

Concept of a mixer based on a cold-electron bolometer

A phase-sensitive terahertz heterodyne mixer of a new type based on a cold-electron bolometer is proposed. In this mixer, a normal-metal thin-film absorber is connected to a planar antenna via superconductor-insulator-normal metal (SIN) tunnel junctions, thus forming a SINIS structure. The SINIS mixer combines the advantages of a hot-electron bolometer (HEB), such as a high signal frequency at a small local oscillator power, with the advantages of an SIS mixer, including low noise level, a high intermediate frequency, and wide working temperature range (up to a critical temperature of the superconductor). In contrast to the HEB and SIS mixers, the proposed device is less sensitive to external magnetic noise and exhibits no additional noise related to the superconducting transition and the Josephson effect.     

A 40 GHz band SIS receiver using Nb/Al?AlOx/Nb array junctions

A 40 GHz band SIS mixer receiver has been built using Nb/Al–AlOx/Nb array junctions and a 4.3 K closed cycle helium refrigerator. The minimum conversion loss of the mixer is 2±1 dB and the single sideband receiver noise temperature (T_RX (SSB)) is as low as 110±10 K at 36 GHz. T_RX (SSB) is almost constant in the IF bandwidth of 600 MHz. The mixer saturation level is as high as 15 nW, which is comparable to the injected LO power.Nobeyama Radio Observatory (NRO), a branch of the Tokyo Astronomical Observatory, University of Tokyo, is a cosmic radio observing facility open for outside users.     

High conversion gain cascode quadruple subharmonic mixer for millimeter-wave applications

In this paper, we have presented millimeter-wave high conversion gain quadruple subharmonic mixers adopting the cascode structure. The subharmonic mixers were successfully integrated by using 0.1 μm GaAs pseudomorphic HEMTs (PHEMT's) and the coplanar waveguide (CPW) structures. From the measurement at LO power of 13 dBm at 14.5 GHz, it shows that conversion gain is 3.4 dB which is one of the best conversion gains at 60.4 GHz. Isolations of LO-to-IF and LO-to-RF were −53.6 dB and −46.2 dB, at a frequency of 14.5 GHz, respectively.