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A wideband and compact Fabry–Perot resonator antenna (FPRA) employing two layers of partially reflective surfaces (PRSs) is presented in this letter. The proposed PRSs with regular hexagonal units are used in wideband FPRA for the first time. Based on the compact arrangement of regular hexagon units and the addition of tripod branches, the size of FPRA is greatly reduced. Furthermore, the regular hexagonal units are arranged periodically along three directions on the 2-D plane, which means that one regular hexagon unit has six identical units around it. Therefore, there is a strong coupling between the PRS units, and units obtain a positive phase gradient in a wide range of 9.1–13.5 GHz, which is the basis for the formation of the wideband FPRA. The FPRA with dimensions of (2.2×2.2×0.6) λ03 (λ0 is the wavelength of the center frequency) has a 3 dB gain bandwidth over 9.2–13 GHz, relatively 34.2%, with a peak gain of 14.2 dBi. The prototype has been fabricated and tested, and validate the simulated results.

In this letter, a broadband 1 bit reconfigurable transmitarray antenna (RTA) based on polarization rotation element is proposed. The transmitarray element is composed of two split circular rings connected by two narrow strips and sandwiched by two orthogonal polarizers. As phase shift and polarization conversion structure, the two patches are separated by the air layer, and the p-i-n diodes are soldered in the center of the narrow strips. The polarizer grids are used as dc bias lines to conduct p-i-n diodes. By controlling the p-i-n diodes in the on and off states, the polarization orientation of the wave emitted by the RTA element is changed. Then, the outgoing waves in the two states physically form a broadband 180° phase difference, which broadens the operating bandwidth of the RTA effectively. By utilizing the novel unit cell, a 16 × 16 elements RTA is designed, fabricated, and measured. The measured results show that the 3 dB and 1 dB gain bandwidths are 45% and 17%, respectively. The peak gain is 16.8 dBi with aperture efficiency of 18.4%. Furthermore, the proposed RTA has good beam scanning performance with 2-D scanning range of ±40°.

An octagonal prism conformal antenna array for x-band with vertically polarized omnidirectional radiation pattern is presented in this letter. The proposed antenna consists of a feeding network, radiation patches, parasitic patches, and dielectric layer. The 16 patches are placed on the outer surface of the octagonal cylinder and fed by a feeding network with uniform magnitude and phase. The patches are divided into upper and lower layers, each of which has eight units. Thus, the proposed antenna can obtain an omnidirectional radiation. To enhance the isolation between the elements, slots are introduced to decrease electromagnetic coupling between elements through the medium. By utilizing 16 conformal patches, the gain in the horizontal plane can be improved, especially for the range of $\boldsymbol{\theta}=80^{0}$ to $\boldsymbol{\theta}=100^{0}$ . The proposed antenna is designed and simulated. Simulation results reveal that the proposed antenna can provide an impedance bandwidth of 20% (7.16–8.76 GHz). Additionally, the minimum gain of the range which from $\boldsymbol{\theta}=80^{0}$ to $\boldsymbol{\theta}=100^{0}$ is greater than 2.8 dBi over the frequency band.

A wideband omnidirectional vertically polarized antenna is proposed which mounted on an unmanned aerial vehicle (UAV). The antenna adopts the structure of the printed dipole array back to back microstrip patches which fed by coaxial cable. The antenna is loaded by two shorted pin and realized characteristics of low profile and vertical polarization. The patch radiators and feed lines on one side of the ground plane are reversed in positions compared to the other side, and hence with radiators on both sides an azimuthal omnidirectional pattern is formed. The antenna realizes omnidirectional radiation in the horizontal plane. The antenna has a measured $\vert \mathbf{S}_{11}\vert bandwidth of 3.9-5.0 GHz (24.7%). The prototype antenna can be widely used in the field of communication antenna on unmanned aerial vehicle for its advantages of simple structure, small wind resistance, omnidirectional patterns, and low profile.