This article presents a unique and compact coplanar waveguide (CPW) antenna that exhibits triband operation with circular polarization. The single antenna was designed to operate simultaneously in the following bands: WiMAX (3.3-3.6 GHz),

A broadband multilayer beam‐steering antenna array with a modified mushroom‐like radiating element is introduced. The two‐layer aperture‐coupled array consists of four equal sets of mushroom‐like elements, each of which is made of 16 unit cells in a 4 × 4 configuration. The feeding network is a modified quasi‐Butler matrix, which benefits from improved double‐box branch line couplers. The network has an isolation bandwidth between 4 and 7.9 GHz (65%) and a transmission bandwidth from 4.8 to 7.1 GHz (39%), which operates acceptably in most of the C‐band, especially at wireless local area network and Intelligent Transport Systems (ITS). A broadband Butler matrix uses broadband 3 dB couplers and a middle network. The geometry of the element and feeding network is utilized in array form to enhance the impedance bandwidth and radiation efficiency of the antenna. The results show that the antenna impedance bandwidth covers 3.82 to 8.2 GHz (port 1) and 3.8 to 8.28 GHz (port 2) for Snn ≤ −10 dB, which covers the C‐band fully (4–8 GHz). Moreover, it has a 3 dB gain‐bandwidth of 2.25 GHz that extends from 4.65 to 6.9 GHz with a peak value of 13.65 dBi. The antenna array has a 3 dB axial ratio bandwidth of 1.65 GHz that extends from 4.9 to 6.55 GHz and involves wireless local area network (5.15–5.825 GHz) and ITS (5.795–6.400 GHz). The radiation efficiency of the array for both port excitations is in excess of 75% when circular polarization is achieved. Two firing beams at elevation angles of 20° and −35° are obtained for ports 1 and 2 upon excitation, respectively.

A novel Fabry–Perot resonator (FPR) antenna array in a C‐band, which produces broader gain bandwidth, flatter radiation efficiency and wider circular polarisation in comparison with conventional antenna arrays, is introduced. These improved characteristics are obtained using a superstrate constituting two complementary frequency selective surfaces placed above a 2 × 2 antenna array and fed by a 4 × 4 modified Butler matrix. The performance of the FPR antenna was verified by simulated and experimental outcomes. The experimental results indicated that the FPR antenna array possesses an impedance bandwidth between 3.7 and 8.55GHz for S11 ≤ −10dB, which covers the C‐band fully (4–8GHz). Moreover, the impedance bandwidth is approximately covered by the 3dB gain bandwidth between 4.4 and 7.5GHz with a peak value of 18.1 dBi. Finally, the FPR antenna array has a 3dB axial‐ratio bandwidth of 3.5GHz between 4.35 and 7.85GHz that includes major wireless standards.

An 8 × 8 butler Vivaldi beam-steering antenna array is introduced for X-band application. Circularly polarized array is made of eight Vivaldi elements with 1×8 platform and an 8×8 beam feeding network. Vivaldi radiating element is used in array form to enhance impedance bandwidth and overall efficiency such as gain. Using microwave passive components, for instance, 3 dB branch line couplers and crossover help to have orthogonal modes for feeding each of the elements, hence circular polarization property is achieved. Extracted results show that the array has an impedance bandwidth over 7–12.7 GHz (~58%) for VSWR≤2 and an axial-ratio bandwidth of 3.15 GHz that is between 8.15 and 11.3 GHz (~33%). The peak gain of antenna array is 18 dBi at 10 GHz. The proposed beam-steering antenna with compact size and good operation is capable to cover an angle range from −42 to 55 degree in whole operation frequency.

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