Interaction of thin metal wires with microwave radiation in а waveguide (longitudinal geometry)

Abstract

Subject and Purpose. In laser measurements technique, the absorption and scattering of microwave radiation in a wire, which diameter is much smaller than the wavelength, can be very large. The absorption and scattering efficiency factors can reach values of several hundreds. This effect has been investigated under the conditions when a plane wave falls on a wire in free space and the electric vector of the wave is parallel to the wire axis. The effect also appears if the wire is located along the axis of the radiation beam, but in this case the absorption in thin wires is appeared to be less. In thicker wires, it may be large. This paper shows that such an effect exists when a thin wire is located along the axis of the beam propagating in a hollow metallic waveguide. Methods and methodology. An experimental study of the effect of strong interaction of microwave radiation with very thin (d << l) metal wires located along the axis of a hollow metal waveguide was carried out. The transmittance and reflection coefficients of the waveguide section with a wire in the frequency range from 12 to 18 GHz were measured. The absorption and scattering coefficients of the wires are evaluated. The diameters of the wires ranged from 50 to 1000 microns, while their length ranged from 100 to 200 mm. The waveguide cross-section is 8 ´ 16 mm, the wave type is H10. Results. Our experiments have shown that the transmittance values of the section with the fiber are in the range of 80…90 %; the reflectance values are in the range 1…5 %, depending on the fiber length and its diameter. At some frequencies, where resonances are observed, the transmittance reduces down to 10…20 %, and the reflectance increases up to 10…40 %. Conclusions. The results of our study have showed the existence of the effect of strong interaction of microwave radiation with very thin conductive fibers in the waveguide with a longitudinal fiber arrangement. The effect can be used in the development of waveguide elements for measuring equipment: attenuators, absorbing loads, etc.

Keywords

• absorption
• measurement
• microwave radiation
• scattering
• thin wire
• waveguide