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Absract Optimization design of wideband concentric-ring arrays for three-dimensional beam scanning with a minimum peak side-lobe level is addressed in this article. To obtain three-dimensional beam scanning with the lowest peak side-lobe level over a wide bandwidth, concentric-ring array geometries, i.e., radius and inter-element spacing of each ring, are optimized. Optimal array geometries are solved via the differential evolution algorithm, and the results are presented for wideband concentric-ring arrays with different scan angles. The peak side-lobe level of the optimal wideband concentric-ring arrays dropped significantly compared to the periodic arrays after geometry optimization was performed. In addition, the comparison with the periodic wideband array shows that not only does the optimal wideband concentric-ring array have a comparable directivity, but the number of elements is also saved.

A new method to improve the gain of patch antenna with metamaterial composed of ring aperture lattice spaced periodically along two arbitrary vectors is presented. The properties of the metamaterial are discussed, and the effective index of refraction and effective permittivity can be retrieved at all frequencies. Then a patch antenna with metamaterial is fabricated and measured. The experimental results show that this method is effective and this structure can realize congregating the radiation energy, thus the gains of the patch antenna with metamaterial can be greatly increased compared with the conventional one.

In this paper, a broadband CPW-fed slot antenna with a gradual-changed ground plane for bandwidth enhancement is proposed and experimentally studied. The effect of various shapes of the slot on broadband operation is investigated. From the experimental results, the measured impedance bandwidth, defined by 10 dB return loss, could be as large as 3.75 GHz or about 105% centered at about 3.56 GHz. The antenna radiation patterns within the operation band were also measured and studied.

This paper presents a novel technique to change the impedance characteristics of patch antenna to achieve multi-band. The proposed structure is based on the metamaterial concept. By replacing the conventional substrate of patch antenna with metamaterial, the impedance characteristics can be effectively changed to produce multi-band property. The design is based on the dispersive characteristic of the substrate by using metamaterial structure. To validate the proposed approach, numerical and experimental results are presented; the results show the validity of our approach.