engleski

Rectangular Waveguide filled with Artificial Backward Material

Some of recently introduced artificial materials have unusual magnetic and electric properties such as negative effective permittivity and negative effective permeability within a finite frequency band. Combining these two properties into one structure recently led to the development of the left-handed material, (or alternatively backward materials). In such a material, direction of phase velocity (wave vector k) is opposite to the direction of energy flow (Poynting vector P). This is accompanied with reversal of some basic electromagnetic phenomena such as Snell law and Doppler effect. This unusual behaviour opens a completely new way of thinking and may lead to the new engineering applications, such as high resolution electromagnetic lenses and sub-wavelength resonators. So far, the backward materials have been studied experimentally in free-space (or in scattering chamber which simulate free-space propagation [3]). The properties of rectangular waveguide filled with backward material are studied in this paper. Since the electromagnetic field in dominant (TE01) mode of the rectangular waveguide can be thought of two planar electromagnetic waves, the previously reported artificial materials tested with a plane wave can be used for filling. Thus, the negative permittivity was achieved using an array of parallel thin copper wires stretched between the lower und upper walls of the X band (8.2-12.4 GHz) waveguide. The wires are connected to the walls by soldering. The measurement results showed shift of the cut-off to the higher frequency (comparing with an empty waveguide), due to plasma-like behaviour of negative permittivity achieved by thin wires. A separated waveguide was filled with capacitively loaded loops laid on a foam. In order to achieve equivalent two-dimesional homogenous material, each unit cell comprised two orthogonal loops. The measurements showed the stop-band associated with resonance behaviour of negative permeability. Finally, both thin wires and loaded loops were mounted within the waveguide in order to achieve a backward material. As expected, the measurements revealed appearance of the pass-band with backward properties.

rectangular waveguide ; backward material

nije evidentirano