Propagation Of Microwave Radiation Research Articles

Propagation of microwave radiation through an inhomogeneous plasma layer in a magnetic field

The problem of reliable microwave communication through a plasma sheath has its origin from the beginning of space flights. During reentry of spacecraft, the plasma layer can interrupt the communication. At sufficiently high plasma density, the plasma layer either reflects or attenuates radio wave communications to and from the vehicle. In this work, we present a simple analytical one-dimensional algorithm to study the propagation of electromagnetic (EM) waves through a nonuniform plasma layer in a static nonuniform magnetic field. The experimental study of the EM wave transmission and reflection through plasma layer was carried out on the (i) microwave set and (ii) on the unit using a high-voltage pulsed discharge.

Absorption and Reflectance Spectra of Microwave Radiation by an Epoxy Resin Composite with Multi-Walled Carbon Nanotubes

A procedure for dispersing multi-walled carbon nanotubes in the two-component polymer SpeciFix-20 (epoxy resin + hardener) using combined hydromechanical and ultrasonic mixing was developed. New composites with carbon nanotubes were produced. Their structures and optical and electrophysical characteristics were studied. The propagation of microwave radiation (26–38 GHz) in experimental composite samples was investigated. It was shown that the strong absorption of the composites appeared only with significant additions of multi-walled carbon nanotubes and was caused by the resulting electrical conductivity of the composites. A size effect of the additive on the optical characteristics of the produced composites was established. Equal absorption coefficients for microwave radiation could be achieved by using a smaller amount of carbon nanotubes with smaller diameters and greater specific surface areas in the composite.

Propagation and amplification of microwave radiation in a plasma channel created in gas by a high-power femtosecond UV laser pulse

The time evolution of a nonequilibrium plasma channel created in a noble gas by a high-power femtosecond KrF laser pulse is investigated. It is shown that such a channel possesses specific electrodynamic properties and can be used as a waveguide for efficient transportation and amplification of microwave pulses. The propagation of microwave radiation in a plasma waveguide is analyzed by self-consistently solving (i) the Boltzmann kinetic equation for the electron energy distribution function at different spatial points and (ii) the wave equation in the parabolic approximation for a microwave pulse transported along the plasma channel.

Resonance modes in coplanar lines with integrated Josephson circuits

The propagation of microwave radiation in co-planar superconducting lines with Josephson circuits (microresonators) of various configurations is investigated. It is shown that dips in the frequency dependence of the transmission power of the waveguide line modes are associated with local modes of the circuit. The dependencies of shape and position of the dips on an external magnetic field and applied power are found. The calculation results can be used for developing modern cryoelectronic microwave superconducting devices.

Amplification of microwave radiation in ice upon pressure-induced phase transition

Measurement results of propagation of microwave radiation with frequencies of 13.7 and 34 GHz through a microexplosion region in freshwater ice are reported. An increase in the power of the passing signal at 13.7 GHz by approximately 1 dB/m for about 1 ms was observed. This effect is presumably connected with formation of quasi-liquid films and their consequent freezing.

Channeling of microwave radiation in a double line containing a plasma filament produced by intense femtosecond laser pulses in air

The channeling of microwave radiation is demonstrated experimentally in a double line in which a plasma filament produced in air by intense femtosecond laser pulses serves as one of the conductors. It is shown that during the propagation of microwave radiation in this line, ultrashort pulses are formed, their duration monotonically decreasing with increasing the propagation length (down to the value comparable with the microwave field period). These effects can be used for diagnostics of plasma in a filament.

Anisotropy in the transparency of HTS films at millimeter and submillimeter microwave radiation

The propagation of microwave radiation through YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// and Tl/sub 2/Ba/sub 2/Cu/sub 1/O/sub 6/ films deposited on Al/sub 2/O/sub 3/, MgO, LaAlO/sub 3/ and LaSrAlTaO single crystal substrates, as well as through the bare substrates, has been studied in the 60-600 GHz frequency range. The angular dependence of the transmitted radiation was found to have a rather complicated structure. The dependence is affected by anisotropy of the substrate due to birefringence, resonance in substrate modes, non-homogeneity and the granular structure of the HTS film. To reduce reflections from the surface of the substrate, quarter-wave matching layers were used at selected frequencies. After correction for stray effects, the common feature is the presence of four maxima with a period of /spl pi//2 with four minima in between that can be due to the energy gap anisotropy in d-wave superconductors.

Interaction of Microwave Radiation with a Polar Gas under Conditions of Power Saturation

The propagation of microwave radiation through a gas-phase dielectric under conditions of power saturation is considered. It is shown that the nonuniform polarization gives rise to additional modes of electromagnetic oscillation. The amplitudes of the induced electric field are estimated and shown to be small. The results of the calculation substantiate that Harrington's method of averaging the power distribution in determining the power density distinction function φwg is correct for application to microwave spectroscopy.