A new method for complex spectral measurement in millimeter and submillimeter wave range

New method for measuring complex transmission or reflection coefficients has been proposed and demonstrated using a simple setup. High measurement quality was achieved: phase sensitivity 0.005 rad., amplitude reproduceability 1%, dynamic range to 10⁷ ÷ 10⁸ (previously 10⁴), phase shift range to be measured 10⁵. It is effective for BWT-Spectroscopy due to the absence of any mechanical adjustments during electronic frequency scan.     

Quasi-optical ferrite devices for millimeter and submillimeter wave bands

Main features of the development of quasi-optical ferrite devices, using Faraday effect, are considered. Properties of a polarizing divider and a ferrite rotator of a polarization plane are analysed with standpoint of minimum losses. A matching method, based on an utilization of the rotator element in a form of the multilayers ferrite structure, which can be adjusted independently for right-handed and left-handed cyrcularly polarized waves, is suggested. It is shown, that this method allows to obtain a total matching in a quasi-optical transmission line. Results of an investigation of quasi-optical ferrite devices for the oversized round waveguide withH ₁₁ mode are presented.     

Surface wave fields and power in millimeter wave integrated dipole antennas

In this paper simple closed form expressions of surface wave fields for microstrip dipoles on grounded substrates are presented. The surface power, radiated power and radiation efficiency are calculated. It is shown that the radiation efficiency decreases with the increase of substrate electrical thickness. Hence new type antennas are needed to radiate millimeter wave because of the effect of the surface waves in substrate.     

Method for radar cross section measurements in millimeter and submillimeter wave regions

We present a new method for electromagnetic modeling radar scattering processes. In this method we use a quasi-optical waveguide of the type of "hollow dielectric waveguide" as a fundamental component of radar cross section (RCS) instrumentation systems. Such waveguide structure produces required target-illuminating quasiplane wave and suppresses unwanted waves as well as transmits the legitimate signal from test object, mounted inside this waveguide, to the reception zone. Presented method is especially effective one in millimeter and submillimeter wave regions, in particular, for investigation RCS of targets with small reflectivity.     

Method of polarization reflection matrix measurement in the submillimeter wave range

Homodyne method of measurement of polarization reflection matrix, providing the possibility of simultaneous measurement of all four complex coefficients of polarization reflection matrix in submillimeter quasi-optical (QO) circuits is presented. Technical realizability of the method for QO waveguides of the class of "hollow dielectric wavequide" is shown.     

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.     

Hail embryons detection in clouds using passive and active radars in millimeter and submillimeter wave bands

Two detection methods of hail embryons in a cloud are discussed in the paper: combined passive/active and purely active sensing of a convective cloud from board of air or space carrier. The first method makes it possible to determine the spectral dependence of absorption coefficient by oversized drops in convective cloud in the millimeter (MM) and submillimeter (SbMM) wavebands. With this purpose a highly sensitive 16-channel Dicke radiometer is used. In the second method a multiwave (12 wavelength) active radar is used to determine the spectral dependence of backscatter coefficient in the same wavebands. Variation of these spectral characteristics in time makes possible the detection of physical processes taking place in a cloud, such as drops drowth and evaporation, as well as transition of oversized drops into the overcooled state. The instant of water/ice phase transition in oversized drops is determined in both methods by means of active radar in SbMM waveband (in the transparency window of ice and atmosphere, 0.64 mm). Corresponding hardware, antennas, and wavelengths are considered for active/passive and purely active sensind of clouds. The effect of antenna beamwidth in SbMM on anomalous backscatter is discussed.Finally the authors would like to acknowledge the helpful discussions and assistance of Dr. K.E.Karapetyan in calculation of the antenna E characteristics.     

Electromagnetic wave diffraction by axisymmetric diaphragms in the millimeter wavelength range

An automated radiophysical complex operating in the millimeter wavelength range is presented. We have measured the spatial amplitude and phase distributions of the electromagnetic field in its two orthogonal components for the case of diffraction of electromagnetic waves incident upon an object at near-grazing angles. Thw wave diffraction at the aperture and circular slot in the metal shield is investigated. The directivity patterns and transmission coefficient as functions of the relative aperture diameter and circular slot are given. The extremum in the dependence of the maximum angle on the width of the circular slot is found.Institute of Radiophysics and Electronics, Ukrainian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 7, pp. 719–729, July, 1995.     

Monolithic semiconductor antennas for millimeter wave Si and GaAs integrated circuit technologies

It has been reported that the radiation characteristics of semiconductor antennas can be controlled by modulating their conductivity during fabrication and/or operation. This paper describes novel physical layouts integrating these versatile antennas with other components used in the realization of millimeter wave systems. The monolithic integration is discussed for GaAs as well as Si IC technologies.     

Pulsed wideband orotrons of millimeter and submillimeter waves

We have developed a series of low-voltage orotrons operated in the short-wave part of the millimeter and long-wave section of the submillimeter wavelength range. The use of an open resonator as the electrodynamic system of the orotron ensures high stability of the radiation frequency and a wide band of frequency tuning. The output orotron power achieved experimentally amounts to hundreds of milliwatts, which is sufficient for many promising spectroscopy methods. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 11, pp. 958–963, November 2006.     

Interference filters for the millimeter and submillimeter spectral region

The properties of a Fabry-Perot interferometer (FPI) with mirrors in the form of metal gratings are discussed. For obtaining filters for the submillimeter and millimeter spectral region we suggest the use of an interferometer with crossed gratings, each grating being enclosed between dielectric plates. Our studies have shown that the half-width of the transmission band of such a filter amounts to 0.6 mm at =8.4 mm, the transmissivity being 77%.In conclusion, the authors wish to express their gratitude to M. A. Leontovich for valuable discussions and to V. D. Rusanov and V. M. Plekhov for their collaboration in the work.     

Resonance phenomena in the magnetized semiconductor plasma and their application for the design of the millimeter and submillimeter wave components

A review of physical principles of design as well as some ways of technical realization of controlled resonance semiconductor devices at millimeter and submillimeter wavelengths is presented. The operation of such devices is based on cyclotron and magnetoplasma resonances as well as on Fabry-Perot resonance. Such choice has been made due to the fact that these resonance phenomena are the most typical ones for the magnetized semiconductor plasma.     

Spectral measurements of dielectric characteristics of petroleum and petroleum oils in the millimeter wave range

We obtain experimental data on the complex refractive index N = n+ik of petroleum, five petroleum oils, and water-petroleum emulsion in the frequency range f = 75–120 GHz. Measurements were performed in a quasioptical equipment with a backward-wave oscillator generating the radiation and an OAP-7 optical-acoustic receivers for a temperature of 27°C of studied liquids. The refractive indices n of petroleum and oil have a weak negative dispersion (dn/df < 0) and close values. At a frequency of 100 GHz, they lie in the range n = 1.477–1.495. The absorption indices k have different frequency dependences such that k increases for four oils, while it decreases for petroleum and SM-4.5 oil with increasing f. At the frequency f = 100 GHz, the values of k vary in a wide range from 2.4 · 10⁻⁴ to 1.7 · 10⁻³. The measurement results for petroleum and oils are compared with experimental results obtained by other authors. The frequency dependences of n and k of water-petroleum emulsion for water concentrations 0.11% and 0.58% are compared with the data calculated using various analytical models of dielectric mixtures. The dependences n(f) and k(f) calculated by the Kubo-Nakamura formula are the closest to the experimental data. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 6, pp. 485–495, June 2007.     

The millimeter and submillimeter rotational spectrum of 1,3-dihydroxyacetone

Recent detection of the 2C sugar glycolaldehyde in the Sgr B2(N-LMH) hot core source as well as the presence of several sugars and other polyhydroxylated species in the Murchison meteorite have led to interest in observational searches for higher order sugars in the interstellar medium. 1,3-Dihydroxyacetone, the simplest 3C sugar, is one of the species detected in Murchison and is of considerable importance for observational searches as the next step in complexity for interstellar sugars. However, little spectroscopic information is available for this molecule. We present here the Doppler-limited rotational spectrum of 1,3-dihyroxyacetone to 450 GHz. Assignments include the ground state up to J=104 and four additional vibrational states. Standard rotational and quartic centrifugal distortion constants have been determined for each of these states.