Heterodyne Instruments Research Articles

Microwave amplification based on quasiparticle SIS up and down frequency converters

Heterodyne instruments have recently attained quantum-limited low-noise performance, particularly in radio astronomy, but it is difficult to develop large heterodyne arrays such as a modern radio camera using cryogenic sensitive detectors based on microwave kinetic inductance detectors, transition edge sensors, etc. In the realization of the heterodyne array, the reduction of power dissipation for semiconductor-based amplifiers remains a major challenge. Alternatively, superconducting parametric amplifiers still seem to have several barriers to application, especially in terms of operating temperature. Here, we show a novel concept of microwave amplification based on up and down frequency-conversion processes using quasiparticle superconductor-insulator-superconductor (SIS) tunnel junctions. We demonstrate positive gain using a proof-of-concept test module, which operates with a power dissipation of several μW at a bath temperature of 4 K. The performance of the module suggests great potential for application in large arrays.

Automated reduction of sub-millimetre single-dish heterodyne data from the James Clerk Maxwell Telescope using orac-dr

With the advent of modern multi-detector heterodyne instruments that can result in observations generating thousands of spectra per minute it is no longer feasible to reduce these data as individual spectra. We describe the automated data reduction procedure used to generate baselined data cubes from heterodyne data obtained at the James Clerk Maxwell Telescope. The system can automatically detect baseline regions in spectra and automatically determine regridding parameters, all without input from a user. Additionally it can detect and remove spectra suffering from transient interference effects or anomalous baselines. The pipeline is written as a set of recipes using the ORAC-DR pipeline environment with the algorithmic code using Starlink software packages and infrastructure. The algorithms presented here can be applied to other heterodyne array instruments and have been applied to data from historical JCMT heterodyne instrumentation.

Crucial problems in the design of a terahertz tripler

A frequency-multiplied source at the terahertz band using discrete planar Schottky diodes, which is a critical element in heterodyne instruments, has been studied by some domestic research institutions in recent years. Besides the design method, there are still many crucial problems that must be taken into consideration in the design. This article mainly discuss three aspects based on the measured data of a 225 GHz tripler that we designed. Firstly, the accuracy of the diode model concerns the reliability of the simulation results. According to the Spice parameters and the measured results, the physical size and the DC parameter of the Schottky diode can be corrected until there is a good consistency between the simulated and measured results. Secondly, the heat accumulation happens to the Schottky junction when the high input power is added. A steady-state thermal simulation is done and the results show that the hottest temperature is about 140 °C with 250 mW input power, which is safe to the diode. Lastly, some non-ideal factors are brought during the assembly process such as the uncertainty in the conductive adhesive shape and location deviation of the circuit. Furthermore, the effect on the performance of the frequency multiplier is calculated in this work.

АКУСТООПТИЧЕСКИЕ АНАЛИЗАТОРЫ СПЕКТРАЛЬНОГО СОСТАВА ИЗЛУЧЕНИЯ ОПТИЧЕСКОГО И РАДИОТЕХНИЧЕСКОГО ДИАПАЗОНОВ НА ОСНОВЕ БРЭГГОВСКИХ РЕЗОНАНСОВ ВЫСШИХ ПОРЯДКОВ

The results of studies of characteristics of acousto-optics spectrum analyzers of radiation in the optical and radio ranges based on the use of Bragg resonances of the first and second orders are showed. The characteristics of acoustooptics devices using the first and second diffraction orders are showed to depend differently on the parameters of acoustooptics interaction because the selection of optical and radio signals is based on different principles of acousto-optics interaction. Key words: acousto-optics , spectral analysis of optical and radio signals Manuscript submitted 10.02.2014 Radio phys. radio astron. 2014, 19(2): 186-192 REFERENCES 1. GOLOSOVSKY, O. A. and RAZDOBUDKO, V. V., 2011. Acoustooptic spectro-analyzers: current state and prospects. Progresses of modern radio electronics. no. 12, pp. 43–56 (in Russian). 2. SIEBERTZ, O., SCHIEDER, R., GAL, C., OLBRICH, M., and HARTOGH, P. Acousto-optical spectrometers for THz heterodyne instruments [online] Available from: http://researchgate.net/publication/237754888_Acoustooptical_spectrometer_for_THz_heterodyne_instruments 3. HILLMAN, J. J., CLENAR,D. A., KUEHN, D. M., CHANOVER, N. J.,and BLASS, W. E. Compact Imaging Spectrometers using Acousto-Optic Tunable Filters [online] Available from: http://www.stsci.edu/stsci/meetings/space_detectors/pdf/hillman.pdf 4. ZILBERMAN , G. Ye., SIDOROV, I. N., KUPCHENKO, L. F., 1982. To the theory of light diffraction by ultrasound. Radio engineering and electronics . vol. 27, no. 2, pp. 241–247 (in Russian). 5. KUPCHENKO, L. F., PLAKHOV, Y. M., EFIMOVA, O. V., LOBYREV, V. B., CHERKASHINA, E. L., SHEVCHENKO , A. V., 1999. Diffraction Efficiency of Second Order Bragg Diffraction at Interaction of Light with Ultrasound under Double Bragg's Angle. Radio Phys. Radio Astron . vol.4, no. 4, pp. 342-348 (in Russian).

Design and Characterization of a Room Temperature All-Solid-State Electronic Source Tunable From 2.48 to 2.75 THz

We report on the design, fabrication and test of an all-solid-state, frequency agile source that produces over across the 2.48-2.75 THz band at room temperature. This frequency-multiplied source is driven by a W-band synthesizer followed by a power amplifier that delivers 350-450 mW (25.5-26.5 dBm) and a cascade of three balanced frequency triplers. The first stage tripler is based on four power-combined six-anode GaAs Schottky diode devices, and the second stage tripler is based on two four-anode GaAs devices. The output tripler uses a single unbiased device featuring two anodes monolithically integrated onto a thin GaAs membrane. The source delivers a record at 2.58 THz at room temperature. This frequency multiplied source is analyzed with a Fourier transform spectrometer (FTS) and the unwanted harmonics are found to be at least 29 dB below the desired signal. This source, when used as the local oscillator for a hot-electron bolometer mixer, will enable heterodyne instruments for future space missions to map the cosmologically-important 2.675 THz HD molecular line.

Optimization of mapping modes for heterodyne instruments

<i>Context. <i/>Astronomic line mapping with single-pixel heterodyne instruments is usually performed in an on-the-fly (OTF) or a raster-mapping mode depending on the capabilities of the telescope and the instrument. The observing efficiency can be increased by combining several source-point integrations with a common reference measurement. This is implemented at many telescopes, but a thorough investigation of the optimum calibration of the modes and the best way of performing these observations is still lacking.<i>Aims. <i/>We derive optimum mapping strategies and the corresponding calibration schemes based on the known instrumental performance in terms of system stability and slew times.<i>Methods. <i/>We use knowledge of the instrumental stability obtained by an Allan variance measurement to derive a mathematical formalism for optimizing the setup of mapping observations. Special attention has to be paid to minimizing of the impact of correlated noise introduced by the common OFF integrations and to the correction of instrumental drifts. Both aspects can be covered using a calibration scheme that interpolates between two OFF measurements and an appropriate OFF integration time. <i>Results. <i/> The total uncertainty of the calibrated data consisting of radiometric noise and drift noise can be minimized by adjusting the source integration time and the number of data points observed between two OFF measurements. It turns out that OTF observations are very robust. They provide a low relative noise, even if their setup deviates considerably from the optimum. Fast data readouts are often essential to minimize the drift contributions. In particular, continuum measurements may be easily spoiled by instrumental drifts. The main drawback of the described mapping modes is the limited use of the measured data at different spatial or spectroscopic resolutions obtained by additional rebinning.

Upgrade of the X-mode reflectometry diagnostic for radial correlation measurements in the Joint European Torus

The recent upgrades and the potential of the X-mode reflectometry diagnostic on the Joint European Torus (JET), dedicated to measurement of the turbulence radial correlation length, are presented in this article. The reflectometer system now consists of four independent heterodyne instruments working at different probing frequencies, which in principle enables analysis of the density fluctuations at four distinct radial regions in the plasma. A VERSA Module Eurocard-based computer connected to the JET database computer system is used to control all of the diagnostic in particular the frequency of the tunable sources and frequency of the fast acquisition boards. The diagnostic is fully operated by remote control. A study of the effects of type-I edge localized modes observed at JET illustrates its potential. The main limitation comes from the low quality of the transmission lines, which leads to a strong attenuation of the signal and makes the measurements difficult especially in the plasma core. To reach higher performances, new low attenuation corrugated circular waveguides (with an expected gain of 20 dB) will be installed in the summer of 2004 during the JET shutdown.

Moliere (v5): a versatile forward- and inversion model for the millimeter and sub-millimeter wavelength range

Recent advancements in the development of passive millimeter and sub-millimeter wave heterodyne techniques for ground-based, air-borne, and space-borne observations of key parameters in Earth's middle atmosphere have triggered the development of adequate data analysis methods and models. This paper provides a detailed description of the versatile forward- and inversion-model for the millimeter- and sub-millimeter wavelength range, MOLIERE (v5) (Microwave Observation LIne Estimation and REtrieval, version 5). Present applications of the model include data analysis for ground-based and space-borne heterodyne instruments such as the sub-millimeter radiometer (SMR) on board the Odin satellite as well as definition studies for future limb sensors dedicated to Earth observation and Mars exploration. The physical and mathematical basics of the forward- and retrieval-model parts are presented. The main emphasis is then put on the description of the numerical implementation of the algorithms for radiative transfer and weighting function computations as well as on the employed method for modeling atmospheric refraction.

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.

Optimal sub-millimeter bands for passive limb observations of stratospheric HBr, BrO, HOCl, and HO 2 from space

Present and near future limb-sounding heterodyne instruments operating at millimeter or sub-millimeter wavelengths will be capable to gather profile information on a variety of stratospheric trace gases with relatively strong spectral features such as O 3, H 2O, O 2 (temperature), N 2O, HCl, ClO, HNO 3, CH 3Cl, and CO. Some species however, which are of particular interest for the understanding of stratospheric ozone chemistry, have only very weak spectral signatures, either due to their very small abundances and/or spectroscopic properties. These are amongst others the radical BrO, the potential bromine reservoir HBr, HOCl as a member of the chlorine family, and the hydroperoxyl radical HO 2. Often, these target species are very difficult to detect and profiles have not yet been measured by space-borne sensors at all, even considering other spectral ranges and observation techniques. A study was therefore dedicated to the investigation of the retrieval of species with spectral features close to the detection limit of a typical state-of-the-art space-borne heterodyne receiver. A survey of the millimeter- and sub-millimeter spectral range was performed in order to identify appropriate spectral bands, followed by retrieval simulations for a representative atmospheric and instrumental scenario in order to explore the relative merits of the pre-selected bands and to derive associated parameters as measurement precision, altitude range and resolution. The feasibility of retrieving profile information from limb observations at sub-millimeter wavelengths of the “weak line” species under investigation is demonstrated. Optimal dedicated bands are recommended for HBr (1999.8 GHz) , BrO (525.2 GHz) , and HOCl (613.6 GHz) . For HO 2 five more or less equivalent bands between 585 and 962 GHz are identified.

Assurance of Uniformity of Measurements of Superhigh Frequency Attenuation Based on Circular Comparisons of Heterodyne Instruments

The need for the development and application of standards documents for performing circular comparisons of equipment for the measurement of attenuation is considered. Requirements for the selection of a reference measure and data on the experimental investigation of a circular comparison circuit and control measure are presented.

FIRST — Far Infrared and Submillimetre Space Telescope

The present status of the ESA cornerstone mission FIRST is presented. A recent industrial study has generated a spacecraft concept employing a 4.5 m passively cooled telescope with focal plane instrument cooling provided by a superfluid helium cryostat. The model payload complement includes two direct detection instruments as well as two heterodyne instruments. After a shared launch by Ariane 5 into GTO, FIRST propels itself into the 24-hour highly eccentric operational orbit, where observations can be conducted up to 17 hours per day with an expected approximate mission duration of 3 years. An additional complementary study of a non-cryostat spacecraft option will also be performed.