We report here the performance improvement of frequency doublers using substrate transfer technique, the method by
which the diodes/MMIC circuits made on GaAs substrate have been subsequently transferred on to a host substrate like
Quartz and Aluminium Nitride. These host substrates have low loss and high thermal conductivity at mm-wave and sub
millimeter wave frequencies. The substrate transfer technique on RAL doubler circuits designed at 160 GHz gives a
conversion efficiency ~ 30% and 3 dB BW >15%, which is a significant performance improvement compared to the
same diodes on GaAs substrate. The efficiency and bandwidth at a constant input power has been studied using doubler
diodes of different anode areas and the results are presented in this paper. The measured data is compared to simulations,
and the test results agree closely to predictions.
A compact, solid state, zenith looking 94 GHz meteorological radar is described. Samples of the reflectivity data obtained from representative samples of hydrometeors, including cirrus cloud and fog, are presented. This bistatic FMCW radar delivers continuous information on the distribution and thickness of cloud layers, permitting accurate determination of the cloud base altitude and upper limit. The maximum range is 16 km, with a corresponding resolution of 30 m: both range and averaging time are user selectable in ranges 2-16 km and 5-60 s respectively. A radiated millimetre wave power of below 200 mW yields a dynamic range of over 60 dB in the received signal.
Most parts of the electromagnetic spectrum are well understood and exploited, but the terahertz region between the microwave and infrared is still relatively under developed. Potential receiver applications are wide-ranging and cross-disciplinary, spanning the physical, biological, and medical sciences. In this spectral region, Schottky diode technology is uniquely important. InP MMIC amplifiers are generally limited to frequencies less than ~200 GHz, above which their noise performance rapidly deteriorates. Superconducting circuits, which require cooling, may not always be practical. Either as varistor diodes (heterodyne mixing), or varactor diodes (sub-millimetre power generation), Schottky technology underpins terahertz receiver development.
We report upon the development of a 190 GHz MMIC frequency doubler and 380 GHz sub-harmonic mixer using
foundry planar Schottky diodes. The devices have been fabricated by the company UMS using their BES process, and
post-processed afterwards to transfer the GaAs circuit membranes onto a quartz substrate. This novel substrate transfer
technique is presented. Preliminary measurements give a doubler output power over 3 mW in the frequency range 170-205 GHz.
MARSCHALS is the airborne simulator of a proposed future satellite instrument to measure millimetre-wave limb emission from O3, H2O, CO and other trace gases in the upper troposphere and lower stratosphere.
To achieve comparatively high vertical resolution and pointing stability, MARSCHALS scans the atmospheric limb in 1km vertical steps using a 235mm diameter antenna controlled by a dedicated inertial measurement unit. A quasi-optical network directs radiation from the antenna or an ambient (~300K) or cold (~90K) calibration target into three front-end receivers and suppresses each unwanted side-band by >30dB using multi-layer frequency selective surfaces. Each receiver comprises a waveguide mixer pumped subharmonically by a phase-locked LO and a wideband IF preamplifier. The IF outputs are directed to channeliser spectrometers of 200MHz resolution which instantaneously and contiguously cover 12GHz wide (RF) frequency bands centred near 300, 325 and 345GHz. To identify clouds, images of near-IR sunlight scattered into the limb direction are recorded concurrently by an 850nm wavelength camera.
MARSCHALS has been built under ESA contract by a consortium led by Rutherford Appleton Laboratory in the UK, and had its first flights on the Russian Geophysica (M55) aircraft during 2005, culminating in a deployment during the SCOUT-O3 campaign based in Darwin, Australia. This paper describes the MARSCHALS instrument and an initial assessment of its performance, determined on ground and during flight.
A compact sub-millimetre wavelength Nb superconducting tunnel junction receiver (TIRGO) has been installed on the UKIRT facility, Hawaii. The receiver, used in combination with an acousto-optic spectrometer, exhibited excellent noise performance, achieving a best noise equivalent temperature of 280K (DSB) at 808GHz. Despite unfavourable observing conditions, spectral observations of a variety of astronomical sources were made that effectively verified the sensitivity and usefulness of the instrument for astronomical research. The design, construction and performance of the receiver system are described and some of the astronomical data acquired during the observation period briefly presented.
We present a design concept for a new state-of-the-art balloon borne atmospheric monitor that will allow enhanced limb sounding of the Earth's atmosphere within the submillimeter and far-infrared wavelength spectral range: TELIS, TErahertz and submm LImb Sounder. The instrument is being developed by a consortium of major European institutes that includes the Space Research Organization of the Netherlands (SRON), the Rutherford Appleton Laboratory (RAL) will utilize state-of-the-art superconducting heterodyne technology and is designed to be a compact, lightweight instrument cpaable of providing broad spectral coverage, high spectral resolution and long flight duration (~24 hours duration during a single flight campaign). The combination of high sensitivity and extensive flight duration will allow evaluation of the diurnal variation of key atmospheric constitutenets sucyh as OH, HO2, ClO, BrO togehter will onger lived constituents such as O3, HCL and N2O. Furthermore, TELIS will share a common balloon platform to that of the MIPAS-B Fourier Transform Spectrometer, developed by the Institute of Meteorology and Climate research of the over an extended spectral range. The combination of the TELIS and MIPAS instruments will provide atmospheric scientists with a very powerful observational tool. TELIS will serve as a testbed for new cryogenic heterodyne detection techniques, and as such it will act as a prelude to future spaceborne instruments planned by the European Space Agency (ESA).
MARSCHALS (Millimeter-wave Airborne Receivers for Spectroscopic CHaracterization in Atmospheric Limb Sounding) is being developed with funding from the European Space Agency as a simulator of MASTER (Millimeter-wave Acquisitions for Stratosphere Troposphere Exchange Research), a limb sounding instrument in a proposed future ESA Earth Explorer Core Mission. The principal and most innovative objective of MARSCHALS is to simulate MASTER's capability for sounding O3, H2O and CO at high vertical resolution in the upper troposphere (UT) using millimeter wave receivers at 300, 325, and 345 GHz. Spectra are recorded in these bands with 200 MHz resolution. As such, MARSCHALs is the first limb-sounder to be explicitly designed and built for the purpose of sounding the composition of the UT, in addition to the Lower Stratosphere (LS) where HNO3, N2O and additional trace gases will also be measured. A particular attribute of millimeter-wave measurements is their comparative insensitivity to ice clouds. However, to assess the impact on the measurements of cirrus in the UT, MARSCHALs has a near-IR digital video camera aligned in azimuth with the 235 mm limb-scanning antenna. In addition to UT and LS aircraft measurements, MARSCHALs is capable of making mid-stratospheric measurements from a balloon platform when fitted with a 400 mm antenna. Provision has been made to add further receiver channels and a high resolution spectrometer.
Doris Maier, Niklaus Kaempfer, W. Amacher, M. Wuethrich, J. de la Noe, P. Ricaud, P. Baron, Gerard Beaudin, C. Viguerie, J.-R. Pardo, Juan Gallego-Puyol, Alberto Barcia, J. Cernicharo, Brian Ellison, Richard Siddans, David Matheson, Klaus Kuenzi, U. Klein, B. Franke, J. Louhi, J. Mallat, M. Gustafsson, A. Raeisaenen, Alexandre Karpov
The objective of the European project EMCOR was the development of a heterodyne receiver for the frequency range of 201 to 210 GHz for the measurement of the amounts of various minor constituents of the stratosphere involved in ozone chemistry. In order to be able to measure even very faint spectral lines a superconducting tunnel junction has been chosen as mixer element. Additionally, special care has been taken in developing the calibration unit of the system. Besides the classical hot-cold calibration three different balancing methods can be employed: a beam-switch technique with an atmospheric reference signal, a beam switch technique with a reference signal from a variable reference load or a frequency switch technique. The system has been integrated and is currently under testing. It will be installed at the International Scientific Station Jungfraujoch in he Swiss Alps and operated within the framework of the European Alpine stations of the Network for the Detection of Stratospheric Change.
Receiver B3 is a common-user facility instrument for the JCMT and was commissioned in December 1996. It includes the following features: (1) Frequency coverage of 315 to 372 GHz with optimum performance at 345 GHz. (2) Two spatially- coincident channels with orthogonal linear polarizations. (3) An IF of 4 GHz with an instantaneous bandwidth of 1.7 GHz in each channel. (4) Single side-band capability with the rejected side-band terminated on a cold load. (5) High- efficiency, frequency-independent optics. (6) Independent adjustment of the local oscillator power to the two mixers. (7) Internal ambient and cold loads for accurate receiver calibration. (8) Fully automated operation.
Recent astronomical observations of neutral carbon at 492 GHz have shown that its distribution is widespread in interstellar molecular coulds. Studies of the distribution and excitation of neutral carbon are of key importance in understanding the chemistry of such regions. Observations of CI at 809 GHz to complement those at 492 GHz would be of great importance in such studies. We are currently building as SIS receiver for the frequency band 800-900 GHz for use in observing submillimeter spectral lines, including CI. The receiver will be operated on the TIRGO infrared telescope, situated on the summit of the Gornergrat, Switzerland (altitude 10,390 ft). It is anticipated that this receiver will be mounted on the TIRGO telescope towards the end of 1996, or the beginning of 1997.
A low Tc Pb alloy Superconductor-Insulator-Superconductor (SIS) tunnel junction heterodyne receiver has been constructed for astronomical use and tested over the frequency range of 400 to 540 GHz. Various alloy structures have been investigated in order to allow the production of small area SIS junctions with stable electrical characteristics and resistance to stress on cooling from 300 K to 4.2 K. Improvements in photolithography and thin film deposition techniques have been made that allow the fabrication of reliable sub-micron area junctions using suspended photoresist stencil and E-beam evaporation techniques. A single sub-micron area junction is mounted in a reduced height two tuner waveguide structure, which provides an optimum impedance match between the junction and the received signal. Performance measurements made with the receiver installed on the James Clerk Maxwell Telescope, Hawaii, show a total system double sideband noise equivalent temperature of 160 K at 460 GHz and 220 K at 490 GHz, measured in a 1 GHz instantaneous IF bandwidth centered at 4 GHz. The receiver demonstrates that Pb alloy tunnel junctions provide excellent sensitivity at submillimetre wavelengths and are sufficiently stable and reliable to allow use at a remote observing site.
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