A compact circularly-polarized patch antenna with wide axial-ratio beamwidth (ARBW) operating at dual bands compatible for GPS satellite navigation application is proposed in this paper. The antenna consists of two stacked patches, which account for GPS L1 band (1575 ± 2 MHz) and L2 band (1228 ± 2 MHz). To realize significant size miniaturization, four pillars are introduced and strongly coupled to the lower patch. To adjust the beamwidth response of the far-field components, the antenna is backed by a modified metallic cavity, which in turn widen the 3-dB axial ratio beamwidth (ARBW) at two operating bands effectively Finally, the proposed design with excellent performance is realized in a size of 0.368 λ0 (diameter) and 0.105 λ0 (height). Simulated and measured results show that the ARBWs at L1 and L2 bands are as wide as 173° and 133°, respectively. For practical application, its satisfactory GPS signal receiving capability is also verified by outdoor positioning test.

A transmitting lens antenna with focused beams by employing four-layer phase-gradient metasurface (PGMS) is proposed. A wideband slot-coupled antenna is mounted close to the focal position of the PGMS acting as a feed. The electromagnetic wave radiated through the feed source is transformed to plane wave within a wide frequency covering from 9.4 GHz to 10.6 GHz. The in-band measured gain is from 16.7 dBi to 19.4 dBi and a 3-dB gain bandwidth of around 10% is achieved, which demonstrates that the proposed four-layer PGMS still has the ability to focus electromagnetic wave within a wide frequency band efficiently though its transmission phase range at some specific frequency bands does not meet 360°.

In this paper, we demonstrate that the solid cylinder dielectric resonator antenna (CDRA) is a high radiation efficient device to generate orbital angular momentum (OAM) waves with different OAM modes at different frequencies. Theoretical formulations of its radiation fields are deduced in the cylindrical coordinate system, which shows that all components of the electric and magnetic fields have the azimuth dependence of e ^jmφ . A full-wave simulation on a practical size CDRA is then implemented to validate the theoretical derivations. The simulation results show that different separated OAM modes can be obtained at different frequencies. Specifically, the higher order OAM modes are generated at higher electron magnetic modes, which makes CDRA a promising method to overcome the narrow band and multiband issues existing in the design of current OAM devices. Furthermore, a maximum radiation efficiency of 97.1% at 13.3 GHz, and a minimum radiation efficiency of 72.4% at 19.45 GHz are obtained in our simulation, which is a high radiation efficiency feature at the OAM resonant frequencies.

A novel azimuth-pattern reconfigurable antenna based on a water grating reflector is proposed in this paper. A planar circular monopole antenna operating at 5.7-GHz band is designed with three sets of water grating reflectors mounted along the edge of the antenna with an angle-interval of 120°. By choosing the states of loading and unloading water, each set of water grating is switched as a reflector. Radiation patterns of the antenna can be pointed to three specified directions with different angle intervals in the azimuth plane. Key structures of the water grating reflector that affect the radiation performance of the antenna have been investigated in this paper. Simulated and measured results show that the proposed approach is a potential candidate for beam-steering applications.

A fully dielectric packaged liquid patch antenna based on liquid metal alloy is presented. In this work, there are two hollow cavities embedded in a dielectric box, including a rectangular cavity placed at the upper portion acting as the radiating element, and a non-planar cavity with a central groove under the radiating element serving as the ground plane. The antenna is realized by 3D printing technique, alleviating assembly tolerance and uncertainties from printed-circuit-board approach which would degrade antenna performance. The radiating element and the ground plane are fully metallized by filling liquid metal alloy. Unlike traditional liquid antennas, the liquid packaging antenna is completely metallized by conductive liquids which does not contain any solid metals. The proposed antenna is designed to operate at 5.2 GHz. Results show that the proposed liquid patch antenna produces a satisfactory impedance matching, and a good agreement between simulation and measurement in terms of radiation characteristics is achieved at the desired frequency.

In this article, a wideband and low-profile multi-polarization reconfigurable filtering antenna based on metasurface (MS) is investigated. The proposed antenna consists of two layers, which are the feeding layer and the MS layer. The filtering function is achieved by utilizing a non-uniform MS and inserting a short via between the feedline and ground plane. Besides, by rotating the MS to change its surface current distribution, the antenna can switch among linear polarization (LP), left-hand circular polarization (LHCP), and right-hand circular polarization (RHCP). To demonstrate the simulated design, the proposed antenna is manufactured and measured. As the measured results show, when the antenna works in LP modes, it obtains an -10-dB overlapped impedance bandwidth of 22.4% and an in-band peak gain of 8.8 dBi. Furthermore, the antenna achieves 14-dB and 19-dB out-of-band radiation suppression levels for LP1 and LP2 modes, respectively. Whereas it operates in CP modes, the measured -10-dB overlapped impedance bandwidth and 3-dB axial ratio (AR) bandwidth of the antenna reach 26.5% and 22%, respectively. Meanwhile, its out-of-band radiation suppression level is more than 17.5 dB, with an in-band peak gain of 7.3 dBic. Hence, there illustrates a pretty good agreement between the simulated and measured results.