Study of inhomogeneities of extended media by the method of passive-active radiometry in the millimeter wavelength range

We present the results of studies of backscattering characteristics of extended inhomogeneous media using a passive-active complex of near-field radio-wave imaging. The complex includes an 8-mm wavelength radiometer, a focusing antenna system, and a system of illumination of studied objects by a wideband noise signal. This radiometric complex is intended for the formation of a high-resolution radio image of the internal structure of spatially inhomogeneous media explored at distances commensurable with the size of the antenna aperture. The system of radio-wave imaging can be used for medical and biological studies of a human body and detection of extended objects hidden under the surface of a medium not transparent for visual observation, but partially transparent in the operating wavelength range.     

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.     

The optical constants of indium antimonide at 1.5K in the near millimeter wavelength region

The results of a determination of the optical constants of n-type indium antimonide at 1.5K in the spectral region between 4 and 40 cm^–1 are presented. The absorption spectrum was determined by the two thickness method, while the refraction spectrum was determined both by an extension of the two thickness method and by an analysis of a channel spectrum. The errors involved in the application of these approximate methods are discussed. The material measured was of detector quality and, therefore, the results are relevant to the design of near millimetre wavelength detectors with optimised performance.Gong Ya-Qian is on leave of absence from Shanghai Institute of Applied Physics     

Investigation of coherent Vavilov-Cherenkov radiation in the millimeter wavelength range generated in PTFE and paraffin target

In this paper, we present an experimental observation of coherent Cherenkov radiation in the millimeter wavelength range. Coherent Cherenkov radiation is generated by a 6.1-MeV bunched electron beam passing by dielectric targets (PTFE and paraffin). The characteristics of Cherenkov and diffraction radiation measured under the same conditions are compared. The experiment is carried out with the electron beam of the microtron at Tomsk Polytechnic University.     

近程高速水声毫米波通信仿真与试验验证*

水声信道的严重双扩特性极大地限制了水声高速通信的稳健性。针对近程高速水声通信技术的需求,该文基于水声毫米波频段,提出了一种基于超奈奎斯特发射技术及高阶调制技术的单载波的水声毫米波通信技术。而超奈奎斯特发射技术以及高阶调制给接收机带来了极大的挑战:一是超奈奎斯特发射技术引入了严重的符号间干扰,二是高阶调制系统的符号检测对信道估计的精度要求很高。针对以上问题,该文提出了一种基于迭代信道估计技术的迭代软反馈DFE接收机技术。仿真实验表明:采用128QAM高阶调制时,在较为严重的多途衰落信道条件下,采用所提出的接收机可以在15 dB时实现无误码传输。信道水池试验证明:当通信带宽为300 kHz,通信符号率为300k符号/秒且采用64QAM调制时,在发射平台慢速运动的条件下可以实现900 kbps的净数据率,其相应的频谱利用率高达6 Bits/s/Hz。     

Measurements of near millimeter wave atmospheric attenuation in the temperature range 259K to 282K

Field measurements of absorption of near millimetre waves by the atmosphere at temperatures below 280°K have confirmed that there is an additional absorption component characterised by a much larger temperature exponent than can be attributed to water dimers in equilibrium.     

On frequency multiplication in the millimeter range inn-InSb

An experimental investigation was made of the generation of the third harmonic in n-InSb at a temperature 77K in the millimeter range of wavelengths. The results are compared with a theoretical calculation on the assumption that the nonlinear susceptibility is caused by the nonparabolicity of the conduction bands.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 15, No. 2, pp. 300–304, February, 1972.In conclusion the authors sincerely thank A. M. Belantsev and V. N. Genkin for discussing the results of the work and for a number of valuable comments.     

The millimeter wavelength spectrum of diatomic sulfur

The gas phase spectrum of diatomic sulfur has been detected in the millimeter wave-length region. Six lines have been measured. The rotational and fine structure parameters obtained are B₀ = 8831.8676 ± 0.006 MHz, D₀ = 5.9 ± 0.7 kHz, λ₀ = 353040 ± 27 MHz, and γ₀ = ? 200.9 ± 0.7 MHz. In addition, reanalysis of EPR data has yielded g_z + 1.18g_n = 2.0021 + 0.0014 and g_z - g_⊥ = ?0.0089 ± 0.0017. On the basis of the frequencies obtained in this work, it was also possible to exclude the assignment of several interstellar emissions to the sulfur dimer.     

Experimental studies of magnetostatic waves in the millimeter range

The paper discusses various aspects of the magnetoelectronics in the millimeter range. The principal data published in Soviet and foreign literature over the past five to seven years are presented. The difficulties and the specific features of the millimeter range are discussed. The results of experimental studies on the excitation and propagation of magnetostatic waves in different electrodynamic systems in the frequency range above 20 GHz are given and are compared with data from theoretical calculations and estimates.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 86–105, November, 1988.     

Pulse surface wave generator of millimeter band wavelength

Theoretical and experimental studies of high-power, relativistic surface-wave microwave Cherenkov generators are briefly considered. Some simulation and experiment results included, the experimentation being made in mm-wave region.     

Untuned resonators for near millimeter waves

A brief account is given of the reasons for revitalizing an old technique for near millimeter wave measurements. The principles of the method are outlined and the scope of its application indicated. The potential importance of the technique for liquid phase and biological material studies is illustrated.     

Methods for investigating thin dielectric films in the millimeter range

An original method based on determining the characteristics of open Fabry-Perot resonator modes with different polarizations is proposed for measuring parameters of dielectric plates and films with a thickness smaller than λ/2 in the millimeter and submillimeter wavelength ranges. This method is used for determining the refractive index and tanδ, as well as the thickness of films made of isotropic materials. For anisotropic films of known thickness, the method makes it possible to measure the permittivity tensor components. Popular film materials such as Teflon (polytetrafluoroethylene, PTFE), lavsan (Mylar, polyethyleneterephthalate, PETP), and polyamide with a minimal thickness of ∼5 μm are investigated. Appreciable anisotropy of roll film materials and the dependence of the dielectric properties on the thickness, which is associated with manufacturing technology, are revealed. The dependence of the refractive index and tanδ on the air humidity is investigated     

A millimeter wavelength radiation source using a dual gratingresonator

A novel means of producing coherent radiation by passing an electron through a dual-grating resonator is presented, The observed radiation is in accordance with the Smith-Purcell dispersion relation for a single grating. Feedback is provided by a second grating. Experiments carried out at beam energies from 30-55 keV produced radiation at wavelengths from 6 to 0.75 mm. Power measurement were used to clarify the grating beam interaction, Indications are that operation could be easily extended to shorter wavelengths to provide an inexpensive and compact radiation source in the far-infrared