In this paper, a compact ultra wideband (UWB) monopole antenna with a band-notched characteristic is presented. The bandnotched characteristic is achieved by inserting a U-shaped slot in the half elliptical ring radiating patch. The measured bandwidth of the designed antenna for |S 11 | −10 dB spans 3.1 GHz to 9.3 GHz with a notched band (|S 11 | > −10 dB) spanning 5.12 GHz to 5.99 GHz. A quasi-omnidirectional radiation pattern in the x-z plane and quasisymmetrical radiation patterns in the x-y and y-z planes are obtained throughout the operating band. The antenna is suitable for UWB communication applications and also reduces the interference with wireless local area network (WLAN) systems. The parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated in this paper.

A microstrip antenna array (MAA) loading with metasurface is designed and fabricated for ultra-wideband radar cross-section (RCS) reduction while preserving its radiation characteristics. A new physical mechanism based on size adjustment of the multiple basic unit cells is proposed for ultra-wideband manipulation of electromagnetic waves. To obtain the excellent RCS performance, the selection of the basic unit cells is optimised by the hybrid optimisation algorithm. Both simulated and measured results indicate that the proposed MAA can reduce the RCS significantly in an ultra-wide frequency band from 6.2 to 27.3 GHz under x-and y-polarised normal incidence. The radiation characteristics of the MAA are well preserved simultaneously.

The characteristics of a novel antipodal Vivaldi antenna array mounted on a dielectric cone are presented. By employing antipodal Vivaldi antenna element, the antenna array shows ultrawide bandwidth and end-fire radiation characteristics. Our simulations show that the cone curvature has an obvious influence on the performance of the conformal antenna, in terms of both the bandwidth and the radiation patterns. The thickness and permittivity of the dielectric cone have an effect on the bandwidth of the conformal antenna. Measurement results of both single antenna and conformal antenna array show a good agreement with the simulated results. The measured conformal antenna can achieve a −10 dBS11with bandwidth of 2.2–12 GHz and demonstrate a typical end-fire radiation beam. These findings provide useful guidelines and insights for the design of wideband end-fire antennas mounted on a dielectric cone.

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