V. S. Solosin

Minishields of electromagnetic radiation

Resonant minishields based on a pair of closely spaced capacitive gratings are proposed. The resonance frequency of such screens is calculated and measured. The possibility of realization of minishields at frequencies of 1.8 and 2.5 GHz is shown.

Implementation of electromagnetic minishields at frequencies of 0.9, 1.8, and 2.4 GHz

Resonance minishields for frequencies of 2.4, 1.8, and 0.9 GHz are implemented. Estimation formulas for resonance frequencies are presented. Scattering cross sections and shielding characteristics of experimental samples are measured.

Reflectometer for small reflection coefficient measurements in millimeter and centimeter wave bands

The new technique for measurements of complex reflection coefficients, especially small ones (up to ¿85dB), in millimeter and centimeter wave bands is developed on base of hollow metal-dielectric waveguides.

METHODS AND EQUIPMENT FOR MEASURING REFLECTION COEFFICIENTS FOR FLAT SPECIMENS AT MILLIMETER WAVELENGTHS

Reflection coefficients need to be measured directly in open space in many applications. Regular panoramic VSWR meters do not give correct measurements without modification. A basic condition for correct measurement is exact matching of the measurement system to free space. Special horns have been developed for the purpose, whose reflection coefficients characterize the matching, which are dependent on the taper angle and exit aperture. To provide a low reflection level, the taper angle in radians should be small relative to the wavelength. The horn reflection coefficient R 0 in decibels is given by an asymptotic formula for small taper angles and large exit apertures [i]: b ~ )2]-I Ro=-20!g [3 [4~ ~ ] / / 1 (~-d -}-

Radar cross section and the surface impedance of a resonator with properties of an artificial magnetic conductor

A flat resonator having properties of an artificial magnetic conductor is analyzed. Frequency dependences of the radar cross sections (RCSs) of such resonators are calculated and measured at microwave frequencies. Surface impedances |Z| of resonators with different thicknesses are calculated numerically. It is demonstrated that the maxima of local RCSs and impedance averaged over the surface |Z|av are shifted towards lower frequencies as the resonator thickness increases. It is found that the maximum values of |Z|av reach 3000 Ω, which many times greater than the value of the free-space impedance 120π Ω. The frequency band in which |Z|av > 1000 Ω is wider than 200 MHz.

Measuring of the reflection coefficients close to 1 with the help of a quasi-optical reflectometer, based on hollow metal-dielectric waveguides

This paper considers the measurement technique features of large reflection coefficients at millimeter wavelengths and structure and design parameters of the measuring bench, containing a quasi-optical reflectometer, built on the basis of hollow rectangular metal-dielectric waveguides. Measurement results of the reflection coefficients of planar samples with reflection coefficient close to 1 (metallized films, fine-period metal grids) are presented. The results may be of interest in the development of foldable antennas and devices for controlling the backscattering of electromagnetic waves from the objects of complicated geometrical form.

Scattering of a Plane Wave by a Cascade of Two Frequency-Selective Structures

Propagation of a plane electromagnetic wave through a multilayer frequency-selective dielectric structure with biperiodic metallization of two interfaces is considered. A method is proposed for calculation of the reflection and transmission coefficients of the structure. Computation results are presented for a structure with gratings consisting of metal rings. The effects of longitudinal and transverse shifts of gratings on the electrodynamic characteristics of the frequency-selective structure are studied. The computation results are compared to experimental data obtained in the microwave band.

A new technique for permittivity and permeability measurements at millimeter waves

A new technique is proposed to determine the permittivity and permeability of planar samples at millimeter wavelengths. The values of /spl epsiv/ and /spl mu/ are determined from the measurement of power reflected from the system planar specimen + metallic reflector for various positions of the reflector. The technique is realized using the precise quasioptical reflectometer.

Method for measuring reflection coefficients in free space for decimetric waves

We give an analysis of the design of various materials, structures, and constructions using their electrodynamic parameters obtained by measuring the reflection characteristics. We describe a method for measuring the reflection coefficients under laboratory conditions in free space for decimetric waves.