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.     

Heterodyne mixing at 70 GHz with superconductor-insulator-superconductor tunnel junctions

A laboratory heterodyne receiver working at 70 GHz was built up using superconductor-insulator-superconductor tunnel junction as mixing element. Single sideband conversion loss L_C as low as 1.92±0.23 and mixer noise temperature T_M of less than 100 K have been achieved while local oscillator pump power is 4·10^–8W.     

A 119 GHz planar Schottky diode mixer for a space application

A planar single-ended GaAs Schottky diode mixer has been designed, built, and tested at 119 GHz. The mixer front end includes also a waveguide filter for image rejection, and a temperature compensated ring filter. Measurements at room temperature showed a conversion loss of 7 dB and a noise temperature of 900 K (SSB). At 100 K the measured noise temperature of the mixer was 500 K (SSB).     

180–425 GHz low noise SIS waveguide receivers employing tuned Nb/AIOx/Nb tunnel junctions

We report recent results on a 20% reduced height 270–425 GHz SIS waveguide receiver employing a 0.49 µm² Nb/AlO _x /Nb tunnel junction. A 50% operating bandwidth is achieved by using a RF compensated junction mounted in a two-tuner reduced height waveguide mixer block. The junction uses an end-loaded tuning stub with two quarter-wave transformer sections. We demonstrate that the receiver can be tuned to give 0–2 dB of conversion gain and 50–80% quantum efficiency over parts of it's operating range. The measured instantaneous bandwidth of the receiver is 25 GHz which ensures virtually perfect double sideband mixer response. Best noise temperatures are typically obtained with a mixer conversion loss of 0.5 to 1.5 dB giving uncorrected receiver and mixer noise temperatures of 50K and 42K respectively at 300 and 400 GHz. The measured double sideband receiver noise temperature is less than 100K from 270 GHz to 425 GHz with a best value of 48K at 376 GHz, within a factor of five of the quantum limit. The 270–425 GHz receiver has a full 1 GHz IF passband and has been successfully installed at the Caltech Submillimeter Observatory in Hawaii. Preliminary tests of a similar junction design in a full height 230 GHz mixer block indicate large conversion gain and receiver noise temperatures below 50K DSB from 200–300 GHz. Best operation is again achieved with the mixer tuned for 0.5–1.5 dB conversion loss which at 258 GHz resulted in receiver and mixer noise temperature of 34K and 27K respectively.     

Wide-band low noise MM-wave SIS mixers with a single tuning element

Several SIS quasiparticle mixers have been designed and tested for the frequency range from 80 to 115 GHz. The sliding backshort is the only adjustable RF tuning element. The RF filter reactance is used as a fixed RF matching element. A mixer which uses a single 2×2 m² Pb-alloy junction in a quarter-height waveguide mount has a coupled conversion gain of G_M(DSB)=2.6±0.5 dB with an associated noise temperature of T_M(DSB)=16.4±1.8 K at the best DSB operation point. The receiver noise temperature T_R(DSB) is 27.5±0.8 K for the mixer test apparatus. This mixer provides a SSB receiver noise temperature below 50 K over the frequency range from 91 to 96 GHz, the minimum being T_R(SSB)=44±4 K. Another mixer with an array of five 5×5 m² junctions in series in a full-height wave-guide mount has much lower noise temperature T_M(DSB)=6.6±1.6 K, but less gain G_M(DSB)=–5.1±0.5 dB.Contribution of the U.S. Government, not subject to copyright     

A 385–500 GHz SIDEBAND-SEPARATING (2SB) SIS MIXER BASED ON A WAVEGUIDE SPLIT-BLOCK COUPLER

We have developed a 385–500 GHz sideband-separating (2SB) mixer, which is based on a waveguide split-block coupler at the edge of the H-plane of the 508 μm × 254 μm (WR 2.0) waveguide, for the Atacama Large Millimeter/submillimeter Array (ALMA). An RF/LO coupler, which contains an RF quadrature hybrid, two LO couplers, and an in-phase power divider, was designed with the issue of mechanical tolerance taken into account. The RF/LO coupler was measured optically with a microscope and electrically with a submillimeter vector network analyzer. The image rejection ratio (IRR) and the single-sideband (SSB) noise temperature of the receiver using the RF/LO coupler have also been measured. The IRR was found to be larger than 8 dB and typically ∼ 12 dB in the 385–500 GHz band. The SSB noise temperature of this receiver is 80 K at the band center, which corresponds to 4 times the quantum noise limit (hf/k) in SSB, and 250 K at the band edges. An erratum to this article can be found at     

Measured mixer noise temperature and conversion loss of a cryogenic Schottky diode mixer near 800 GHz

We accurately measured the noise temperature and conversion loss of a cryogenically cooled Schottky diode operating near 800 GHz, using the UCB/MPE Submillimeter Receiver at the James Clerk Maxwell Telescope. The receiver temperature was in the range of the best we now routinely measure, 3150 K (DSB). Without correcting for optical loss or IF mismatch, the raw measurements set upper limits ofT _M=2850 K andL _M=9.1 dB (DSB), constant over at least a 1 GHz IF band centered at 6.4 GHz with an LO frequency of 803 GHz. Correction for estimated optical coupling and mismatch effects yieldsT _M=1600 K andL _M=5.5 dB (DSB) for the mixer diode itself. These values indicate that our receiver noise temperature is dominated by the corner cube antenna's optical efficiency and by mixer noise, but not by conversion loss or IF mismatch. The small fractional IF bandwidth, measured mixer IF band flatness from 2 to 8 GHz, and similarly good receiver temperatures at other IF frequencies imply that these values are representative over a range of frequencies near 800 GHz.     

A low-noise SIS receiver measured from 480 GHz to 650 GHz using Nb junctions with integrated RF tuning circuits

A heterodyne receiver using an SIS waveguide mixer with two mechanical tuners has been characterized from 480 GHz to 650 GHz. The mixer uses either a single 0.5 × 0.5 µm² Nb/AlO_x/Nb SIS tunnel junction or a series array of two 1 µm² Nb tunnel junctions. These junctions have a high current density, in the range 8 – 13 kA/cm². Superconductive RF circuits are employed to tune the junction capacitance. DSB receiver noise temperatures as low as 200 ± 17 K at 540 GHz, 271 K ± 22 K at 572 GHz and 362 ± 33 K at 626 GHz have been obtained with the single SIS junctions. The series arrays gave DSB receiver noise temperatures as low as 328 ± 26 K at 490 GHz and 336 ± 25 K at 545 GHz. A comparison of the performances of series arrays and single junctions is presented. In addition, negative differential resistance has been observed in the DC I–V curve near 490, 545 and 570 GHz. Correlations between the frequencies for minimum noise temperature, negative differential resistance, and tuning circuit resonances are found. A detailed model to calculate the properties of the tuning circuits is discussed, and the junction capacitance as well as the London penetration depth of niobium are determined by fitting the model to the measured circuit resonances.     

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.     

A Low-Noise 230 GHz SIS Receiver for Radio Astronomy Employing Untuned Nb/AlOx/Nb Tunnel Junctions

A heterodyne receiver based on a 1/3 reduced height rectangular waveguide SIS mixer with two mechanical tuners has been built for astronomical observations of molecular transitions in the 230 GHz frequency band. The mixer used an untuned array (R_nC_j3, R_n70 ) of four Nb/AIOx/Nb tunnel junctions in series as a nonlinear mixing element. A reasonable balance between the input and output coupling efficiencies has been obtained by choosing the junction number N=4. The receiver exhibits DSB (Double Side Band) noise temperature around 50 K over a frequency range of more than 10 GHz centered at 230 GHz. The lowest system noise temperature of 38 K has been recorded at 232.5 GHz. Mainly by adjusting the subwaveguide backshort, the SSB (Single Side Band) operation with image rejection of 15 dB is obtained with the noise temperature as low as 50 K. In addition, the noise contribution from each receiver component has been studied further. The minimum SIS mixer noise temperature is estimated as 15 K, pretty close to the quantum limit v/k11 K at 230 GHz. It is believed that the receiver noise temperatures presented are the lowest yet reported for a 230 GHz receiver using untuned junctions.     

A lownoise 665 GHz SIS quasi-particle waveguide receiver

We report recent results on a 565–690 GHz SIS heterodyne receiver employing a 0.36µm² Nb/AlO _x /Nb SIS tunnel junction with high quality circular non-contacting backshort and E-plane tuners in a full height waveguide mount. No resonant tuning structures have been incorporated in the junction design at this time, even though such structures are expected to help the performance of the receiver. The receiver operates to at least the gap frequency of Niobium, 680 GHz. Typical receiver noise temperatures from 565–690 GHz range from 160K to 230K with a best value of 185K DSB at 648 GHz. With the mixer cooled from 4.3K to 2K the measured receiver noise temperatures decreased by approximately 15%, giving roughly 180K DSB from 660 to 680 GHz. The receiver has a full 1 GHz IF passband and has been successfully installed at the Caltech Submillimeter Observatory in Hawaii.     

A Very Low-Noise Integrated 3MM-Wave Schottky Diode Mixer and PHEMT IF Amplifier

An integrated 3mm-wave Schottky diode mixer and pseudomorphic high-electron-mobility transistor (PHEMT) IF amplifier with record noise performance at room temperature is described. The design has shown the room-temperature double-sideband (DSB) receiver noise temperature T_R^DSB of 190 K at 100 GHz due to a very low conversion loss in the full-height waveguide mixer and an ultra-low noise of the PHEMT IF amplifier. The receiver noise temperature has been reduced by a factor of 1.5 in comparison with the best previously reported 3mm-wave Schottky diode mixer receiver.     

230 and 492 GHz low noise sis waveguide receivers employing tuned Nb/AlOx/Nb tunnel junctions

We report results on two full height waveguide receivers that cover the 200–290 GHz and 380–510 GHz atmospheric windows. The receivers are part of the facility instrumentation at the Caltech Submillimeter Observatory on Mauna Kea in Hawaii. We have measured receiver noise temperatures in the range of 20K–35K DSB in the 200–290 GHz band, and 65–90K DSB in the 390–510 GHz atmospheric band. In both instances low mixer noise temperatures and very high quantum efficiency have been achieved. Conversion gain (3 dB) is possible with the 230 GHz receiver, however lowest noise and most stable operation is achieved with unity conversion gain.A 40% operating bandwidth is achieved by using a RF compensated junction mounted in a two-tuner full height waveguide mixer block. The tuned Nb/AlO _x /Nb tunnel junctions incorporate an end-loaded tuning stub with two quarter-wave transformer sections to tune out the large junction capacitance. Both 230 and 492 GHz SIS junctions are 0.49µm² in size and have current densities of 8 and 10 kA/cm² respectively.Fourier Transform Spectrometer (FTS) measurements of the 230 and 492 GHz tuned junctions show good agreement with the measured heterodyne waveguide response.     

Millimeter wave monolithic schottky diode imaging arrays

Planar Schottky diodes are integrated with bow-tie antennas to form a one-dimensional array. The energy is focused onto the antennas through a silicon lens placed on the back of the gallium-arsenide substrate. A polystyrene cap on the silicon lens reduces the reflection loss. A self-aligning process with proton isolation has been developed to make the planar Schottky diodes with a 1.1-THz zero-bias cutoff frequency. The antenna coupling efficiency and imaging properties of the system are studied by video detection measurements at 94 GHz. As a heterodyne receiver, a double-sideband mixer conversion loss of 11.2 dB and noise temperature of 3770°K have been achieved at a local oscillator frequency of 91 GHz. Of this loss, 6.2 dB is attributed to the optical system and the antenna.     

Hot electron bolometric mixers: new terahertz technology

This paper presents an overview of recent results for NbN phonon-cooled hot electron bolometric (HEB) mixers. The noise temperature of the receivers based on both quasioptical and waveguide versions of HEB mixers has crossed the level of 1 K GHz⁻¹ at 430 GHz (410 K), 600–650 GHz (480 K), 750 GHz (600 K), 810 GHz (780 K) and is close to that level at 1.1 THz (1250 K) and 2.5 THz (4500 K). The gain bandwidth measured for quasioptical HEB mixer at 620 GHz reached 4 GHz and the noise temperature bandwidth was almost 8 GHz. Local oscillator power requirements are about 1 μW for mixers made by photolithography and about 100 nW for mixers made by e-beam lithography. A waveguide version of 800 GHz receiver was installed at the Submillimeter Telescope Observatory on Mt. Graham, AZ, to conduct astronomical observations of known submillimeter lines (CO, J=7→6, CI, J=2→1). It was proved that the receiver works as a practical instrument.     

A Fixed-Tuned W-Band Waveguide SIS Mixer with 4.0-7.5 GHz IF

The design and performance of a fixed-tuned W-band SIS mixer with a wide band IF of 4.0-7.5 GHz is presented. Waveguide-to-stripline transition of the SIS mixer is designed using the lumped-gap-source port provided by HFSS^TM. Measured receiver noise temperature is less than 25 K in the frequency range of 95-120 GHz, with a minimum value of around 19 K achieved. Mixer noise temperature is determined to be about 8.5 K, which is around twice the quantum limit (i.e., 2hw/k). In spite of the high IF frequencies (f ₀ = 6 GHz), the performance of the SIS receiver is comparable or even superior to those of the best mechanically-tunable waveguide SIS receivers at low IF frequencies (f ₀ = 1.5 GHz). This result suggests that it is easy to design waveguide-to-stripline transitions without scale-model measurements.     

基于二极管精确电路模型的183GHz分谐波混频器设计

针对亚毫米波混频二极管管对电路模型不够精确的问题,采用场路结合协同分析,将进出二极管的频率信号分类处理,建立了一种应用于亚毫米波分谐波混频器电路的反向并联二极管对精确电路模型。基于获取的管对精确电路模型,建立了全局性的分谐波混频器电路的集总元件等效电路模型,设计并实现了一款183GHz分谐波混频器。测试结果表明混频器在本振频率为92GHz、功率为2mW,射频频率176~192GHz范围内,双边带变频损耗小于6.8dB,等效噪声温度小于800K,在182GHz测得最小双边带变频损耗为4.9dB,与仿真数据吻合较好。     

AN UNCOOLED VERY LOW NOISE SCHOTTKY DIODE RECEIVER FRONT-END FOR MIDDLE ATMOSPHERIC OZONE AND CARBON MONOXIDE MEASUREMENTS

The paper describes an uncooled front-end of the Schottky diode receiver system, which may be applied for observations of middle atmospheric ozone and carbon monoxide thermal emission lines at frequencies 110.8 GHz and 115.3 GHz, respectively. The mixer of the front-end has utilized high-quality Schottky diodes that allowed us to reduce the mixer conversion loss. The combination of the mixer and an ultra-low-noise IF amplifier in the one integrated unit has resulted in double-sideband (DSB) receiver noise temperature of 260 K at a local oscillator (LO) frequency of 113.05 GHz in the instantaneous IF band from 1.7 to 2.7 GHz. This is the lowest noise temperature ever reported for an uncooled ozone receiver system with Schottky diode mixers.