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.     

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 NbTiN-Based 850 GHz SIS Receiver for the Caltech Submillimeter Observatory

We have developed a niobium titanium nitride (NbTiN) based superconductor-insulator-superconductor (SIS) receiver to cover the 350 micron atmospheric window. This frequency band lies entirely above the energy gap of niobium (700 GHz), a commonly used SIS superconductor. The instrument uses an open structure twin-slot SIS mixer that consists of two Nb/AlN/NbTiN tunnel junctions, NbTiN thin-film microstrip tuning elements, and a NbTiN ground plane. The optical configuration is very similar to the 850 GHz waveguide receiver that was installed at the Caltech Submillimeter Observatory (CSO) in 1997. To minimize front-end loss, we employed reflecting optics and a cooled beamsplitter at 4 K. The instrument has an uncorrected receiver noise temperature of 205K DSB at 800 GHz and 410K DSB at 900 GHz. The degradation in receiver sensitivity with frequency is primarily due to an increase in the mixer conversion loss, which is attributed to the mismatch between the SIS junction and the twin-slot antenna impedance. The overall system performance has been confirmed through its use at the telescope to detect a wealth of new spectroscopic lines.     

Investigation of a heterodyne receiver with open structure mixer at 324 GHz and 693 GHz

The performance of a submillimeter heterodyne receiver using an HCOOH laser local oscillator and an open structure mixer with a Schottky barrier diode has been optimized for 693 GHz. Working at room temperature a single sideband (SSB) system noise temperature of 7,300 K, a mixer noise temperature of 6,100 K and a conversion loss of 12 dB has been achieved. The same receiver system has been investigated at 324 GHz using an HCOOD laser local oscillator yielding a noise temperature of 3,100 K (SSB), a mixer noise temperature of 2,400 K (SSB) and a conversion loss of 10 dB (SSB). An acousto-optical spectrometer has also been constructed, with 1024 channels and a channel-bandwidth of 250 kHz. The system NEP per channel was 2.5×10^–17 W/Hz^1/2 at 324 GHz and 5.0×10^–17 W/Hz^1/2 at 693 GHz.     

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.     

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.     

A 345GHz SIS receiver for radio astronomy

A 345GHz superconductor insulator superconductor (SIS) tunnel junction receiver utilizing a full height rectangular waveguide mixer with two tuning elements, i.e. an E-plane and backshort tuner, has been constructed and installed on the Caltech Submillimeter Observatory 10m antenna on Mauna Kea, Hawaii. The receiver exhibits a best double side-band noise temperature response of 150K±20K (averaged over a 500 MHz IF bandwidth centered at 1.5GHz) at a design center frequency of 345GHz and at an ambient temperature of approximately 3.8K. Additional measurements show that the receiver has an excellent response at selected points within an RF input range of 280 to 363GHz.     

Submillimeter-wave receiver with a balanced monolithic mixer

We describe the design of a superheterodyne receiver with a balanced monolithic integrated mixer and describe the technique and results of parameter measurements of the receiver and mixer over the frequency range 287–365 GHz. In the middle of this range, the double-band noise temperature of the receiver is 1500±50 K, while the double-band noise temperature and conversion loss of the mixer are 1250±50 K and 10±0.5 dB, respectively. Comparison with mixers and receivers of other types is performed. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 6, pp. 573–580, February 1999.     

High Doping Density Schottky Diodes in the 3MM Wavelength Cryogenic Heterodyne Receiver

The paper describes a 3mm cryogenic mixer receiver using high doping density (“room-temperature”) Schottky diodes. The measured equivalent noise temperature T_eq of the diodes is 109 K at 20 K, which is much higher than the T_eq of the low doping density (“cryogenic”) diodes. In spite of this, the double-sideband (DSB) noise temperature of the cryogenic receiver developed is 55 K at 110 GHz, owing to the low conversion loss of the mixer and ultra-low noise of the PHEMT IF amplifier. This is the lowest noise temperature ever reported for a Schottky diode mixer receiver. The results obtained are useful for the development of submm receivers in which high doping density Schottky diodes are used.     

Low noise completely quasioptical SIS receiver for radioastronomy at 115 GHZ

Completely quasioptical heterodyne SIS receiver for radioastronomical applications at 115 GHz was designed and tested. Gaussian beam two lens input guide system and open structure SIS mixer with immersion lens were used. Integrated quasioptical structure consists of planar equiangular spiral antenna and superconductor—insulator—superconductor (SIS) tunnel junction as a mixing element connected to the antenna via microstrip impedance transformer. The best SIS mixer noise temperature at hot input and for heterodyne frequency 109.8 GHz with IF central frequency 1.4 GHz (DSB) was 28±7 K at the first quasiparticle step and 8±6 K at the second step.     

A 275–370 GHz Receiver Employing Novel Probe Structure

We present the results of the development of a 275–370 GHz, fixed-tuned double sideband (DSB) receiver based on superconductor-insulator-superconductor (SIS) junction mixer. The mixer block uses a full height rectangular waveguide and employs a novel radial-like probe structure with integrated bias-T. The measured uncorrected receiver noise temperature is 30–50 K corresponding to about 2–3 quantum noise across the full frequency band with an IF from 3.8 to 7.6 GHz. The mixer is to be used on the Atacama Pathfinder EXperiment (APEX) submillimeter telescope in Chile.     

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.     

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.     

A 650-GHz Band SIS Receiver for Balloon-Borne Limb-Emission Sounder

A superconducting low-noise receiver has been developed for atmospheric observations in the 650-GHz band. A waveguide-type tunerless mixer mount was designed based on one for the 200-GHz band. Two niobium SIS (superconductor-insulator-superconductor) junctions were connected by a tuning inductance to cancel the junction capacitance. We designed the R_nC_j product to be 8 and the current density to be 5.5 kA/cm². The measured receiver noise temperature in DSB was 126-259 K in the frequency range of 618-660 GHz at an IF of 5.2 GHz, and that in the IF band (5-7 GHz) was 126-167 K at 621 GHz. Direct detection measurements using a Fourier transform spectrometer (FTS) showed the frequency response of the SIS mixer to be in the range of about 500-700 GHz. The fractional bandwidth was about 14%. The SIS receiver will be installed in a balloon-borne limb-emission sounder that will be launched from Sanriku Balloon Center in Japan.     

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.     

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).     

1-THz low-noise SIS mixer with a double-dipole antenna

A quasi-optical mixer containing two Nb/Al/AlO_x/Nb superconducting tunnel junctions integrated into a NbTiN/SiO₂/Al microstrip line is studied experimentally in the 800–1000 GHz frequency range. The mixer is developed as an optional front end of the heterodyne receiver operating in frequency band 3 or 4 and incorporated into the HIFI module of the Herschel space-borne telescope. The double-dipole antenna of the mixer is made of NbTiN and Al films; the quarter-wavelength reflector, of a Nb film. The mixer is optimized for the IF band of 4–8 GHz. The double-sideband noise temperature T _RX measured at 935 GHz is 250 K at a mixer temperature of 2 K and an IF of 1.5 GHz. Within 850–1000 GHz, T _RX remains below 350 K. The antenna pattern is symmetrical with a sidelobe level below −16 dB.