Pekka Ikonen

In the present paper we discuss the effect of artificial magneto-dielectric substrates on the impedance bandwidth properties of microstrip antennas. The results found in the literature for antenna miniaturization using magnetic or magneto-dielectric substrates are revised, and discussion is addressed to the practically realizable artificial magnetic media operating in the microwave regime. Using a transmission-line model we, first, reproduce the known results for antenna miniaturization with non-dispersive material fillings. Next, a realistic dispersive behavior of a practically realizable artificial substrate is embedded into the model, and we show that frequency dispersion of the substrate plays a very important role in the impedance bandwidth characteristics of the loaded antenna. The impedance bandwidths of reduced size patch antennas loaded with dispersive magneto-dielectric substrates and high-permittivity substrates are compared. It is shown that unlike substrates with dispersion-free permeability, practically realizable artificial substrates with dispersive magnetic permeability are not advantageous in antenna miniaturization. This conclusion is experimentally validated.

In this paper we study the possibility of utilizing a loaded wire medium as an artificial material for beam shaping element in base station antenna applications. The wires in the lattice are loaded with a proper capacitive impedance to come up with a structure effectively operating as a dielectric lens at the UMTS (Universal Mobile Telecommunications System) frequency range. It is proven with full-wave simulations that the interpretation of a finite size wire lattice as a dielectric lens is physically sound even with a moderate number of lattice periods. A prototype having a mechanically reconfigurable beam width is constructed and measured. It is shown that very promising performance can be achieved with a rather simple structure and a cheap manufacturing process.