Application Of The Metamaterial In The Antenna Design

Antennas are the most important element of the wireless communication system.With the development of the modern communication technology, the betterperformance of the antenna is required. However it is finite to enhance the performanceof the antenna by traditional methods. New methods should be introduced to enhancethe performance of the antenna. In recent years, the appearance of the metamaterialprovide a new way to design new type antenna, and the metamaterial is often utilized inthe antenna configuration for improving the performance of the antenna, such asenhancing gain, realizing miniaturization, expanding operating band and so on, due totheir exotic electromagnetic properties.In this paper, the application of the metamaterial in the antenna design isinvestigated. Three antennas are designed with low radar cross section (RCS), low sidelobe lever (SLL), and beam steering, respectively.In the first part, we present a method for reducing radar cross section (RCS) of apatch antenna in two frequency bands. This method is based on the absorbingmetamaterial loaded around the patch exciting source. The metamaterial is composed ofdouble-square-loop structure inserted with resistors, which can absorb incident wave attwo frequency bands. Compared with the conventional patch antenna, RCS is obviouslyreduced in two bands. The RCS characteristic of the proposed antenna is investigated bynumerical simulation and measurement. In addition, it is found that the loadedmetamaterial almost have no negative influences on the antenna performance.In the second part, a method to realize tunable side lobe lever (SLL) of an antennaarray is reported. The frequency selective surface (FSS) composed of metallic cross andcross split is employed as a superstrate for a horn antenna array to modulate the SLL ofthe antenna. The PIN diodes are loaded at the split along the E-plane to modulate theamplitude of the transmitted electromagnetic wave while keeping the phase almost thesame value. Thus the SLL in the E-plane of the new antenna can be tuned purposely bychanging the bias current of the diode. Three different SLLs are simulated todemonstrate the ability of the tunable SLL. In the last part, the multilayer annular split structure is adopted to realize the beamsteering of the antenna, due to its ability of modulating the phase of the incidentelectromagnetic wave. A traditional horn antenna is used as excited source, and threecases are simulated and measured. The azimuth of the beam is10°,20°,30°,respectively, and there is a good agreement between measured and simulated results.