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.     

On the anomalies and role of water clusters in atmospheric absorption of millimeter and submillimeter radio waves

Experimental data are presented which do not confirm the existence of anomalies observed by many investigators in the atmospheric absorption of millimeter and submillimeter radio waves and make questionable the hypothesis on the importance of large water clusters in absorption that is invoked to explain the anomalies.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 4, pp. 483–495, April, 1996.This work was supported in part by the Russian Foundation for Fundamental Research under Project No. 94-02-05407-a).     

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.     

Modern millimeter and submillimeter receiver systems for radio astronomy

In this review we consider the composition and placement of receiver complexes on millimeter and submillimeter wave radio telescopes as well as their components and circuitry. Examples of receiver complexes are given for both ground-based and space radio telescopes.     

Absorption of millimeter to submillimeter waves by atmospheric water molecules

Using the values of the rotational molecular parameters (including cencrifugal distortion terms) of the H₂ ¹⁶O molecule, which can explain 12 observed transitions below 800 GHz, all rotational energy levels with normalized Boltzmann factors larger than 5×10^–8 at 300°K are calculated. Probabilities of all possible electric dipole transitions among these states, 2277 lines, are calculated using the eigenfunctions thus obtained, and the permanent electric dipole moment of 1.8546 Debye. Assuming the single and full Lorentzian line forms, we calculated the absorption coefficient for millimeter to submillimeter region. Our result, using the single term Lorentzian line form, agrees quite well with experiment for 1 Torr of water vapor in 760 Torr air at 300°K.     

Metal mesh couplers using evanescent waves at millimeter and submillimeter wavelengths

In this paper we introduce a metal mesh evanescent wave coupler that makes use of evanescent wave coupling between a metal mesh and a dielectric plate, as a quasi-optical component for millimeter and submillimeter wavelengths. The transmission properties of this type of couplers have been investigated experimentally and theoretically for both capacitive and inductive metal meshes in the frequency range from 40 GHz to 60 GHz. The transmittance of a capacitive metal mesh evanescent wave coupler can be adjusted more than 70% by changing the spacing between the capacitive mesh and the silicon plate less than 0.15 mm at around 57 GHz.     

Using millimeter radio waves to probe the earth's atmosphere

Radio Engineering and Electronics Institute, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 1, pp. 3–10, January, 1989.     

Propagation of centimeter and millimeter radio waves at small grazing angles: The model of multiple screen diffraction

Specific features of the microwave propagation over a disturbed sea surface at small grazing angles are studied numerically in the approximation of multiple Fresnel diffraction by semiplanes. We consider two cases: 1) the case of very small grazing angles and low altitudes of the observation points over the sea surface and 2) the case of moderately small grazing angles where the asymptotic approximation of the Fresnel integral is applicable. It is shown that such a model permits one to explain, in particular, the high field-intensity levels and fluctuation characteristics observed at observation-point altitudes comparable with the sea-wave height. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 8, pp. 700–710, August 2008.     

Simulation of attenuation of millimeter radio waves in dry snowfalls

Attenuation of millimeter waves in dry snowfalls is numerically simulated with allowance for the actual shape of snowflakes. It is shown that for moderate-intensity snowfalls the values of attenuation cross-sections averaged over the snowflake orientations are well approximated by power-law function depending on the equivalent diameter of the snowflakes. This allows us to obtain an analytical expression for the attenuation coefficient of a plane electromagnetic wave by snowfall for size distributions of particles of the gamma-distribution type and its modifications. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 4, pp. 446–455, April, 1998.     

Physical aspects of the model of propagation of centimeter and millimeter radio waves along inclined paths in the earth’s atmosphere

We present the physical aspects of constructing a computer model of propagation of centimeter and millimeter radio waves along inclined paths in the earth’s atmosphere, which allows us to calculate the integral attenuation in the frequency spectrum from 3 to 100 GHz, the time of group delay of the signal, refraction of radio waves, and the brightness temperature of the atmosphere for certain regions on the basis of standard atmospheric models and optimal statistical extrapolation of surface meteorological elements. The results of this paper were presented in part at the XVIIIth All-Russia Conference on Propagation of Radio Waves (St. Petersburg, September 17–19, 1996 [1] Radiophysical Research institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 12, pp. 1463–1478, December, 1997.     

Propagation of millimeter waves in GaAs and Si double-layer dielectric waveguides

We study the propagation parameters (attenuation and phase shift) of electromagnetic waves in the frequency range 75–110 GHz in dielectric waveguides made of high-resistivity gallium arsenide and silicon, as well as in double-layer n-i and p-n structures based on them. The appearance of new modes is revealed in the case where the vector of the electric field is perpendicular to the interface between the layers, which is related to the presence of the potential barrier and the corresponding charge capacitance. The mode transformation can be used to generate high harmonics (due to the varactor effect) and to monitor the uniformity and the influence of external factors on the properties of dielectric waveguides in the integrated circuits of the millimeter-wavelength range.     

Rain induced attenuation of millimeter waves radio link in Indian continent

The performance and reliability of millimeter wave radio link is degraded mainly by rain. In the present paper the aspect of rain induced attenuation with respect to raindrop is described. How the microstructure details of rain are necessary for estimating the rain induced attenuation in millimeter wave region are explained on the basis of the rain data for different stations of India.