A millimeter-wave high-gain dual-polarized antenna array with an enhanced bandwidth is presented. An innovative air-filled differential feeding cavity loaded with a short-ended cross-shaped waveguide is investigated to serve as the feed network and the mode splitter simultaneously of the $2\,\,\times2$ dual-polarized subarrays. Wideband characteristics and a compact planar size that are desirable for the wideband array design are achieved. Moreover, a wideband dual-polarized waveguide-fed magnetoelectric (ME) dipole antenna with a lightweight self-support geometry and wideband H-plane parallel feed networks with modified dual-layered configurations are proposed, which are convenient to connect with the differential feeding cavity directly. With the use of a commercial metallic 3-D printing facility, the proposed radiating elements, feeding cavities, and feed networks can be combined successfully in a whole piece with a lightweight geometry. The printed $8 \times 8$ array prototype operating in the Ka-band confirms a wide bandwidth of about 30%, a gain of up to 28.5 dBi, and stable unidirectional radiation patterns for the two polarizations. Benefitted from the advantages of the promising wideband dual-polarized radiations and convenience of fabrication, the proposed antenna array would be attractive for millimeter-wave polarization diversity applications.

In this article, a novel planar annular leaky-wave antenna (LWA) based on substrate integrated waveguide (SIW) for generating conical beam is proposed, which exhibits properties of beam angle designable in the elevation plane, low profile, and small size. It contains two layers, i.e., radiating layer and feeding layer. Propagation properties of wave in the radiating layer are analyzed, which provide theoretical basis for design procedure. In the feeding layer, a coupled feeding network is utilized for improving impedance bandwidth. Three types of the proposed LWA with different sizes are fabricated and measured to validate the design. The measurement results agree well with the simulation results. This kind of antenna can be a suitable candidate for mobile communication.

A novel fixed-frequency leaky-wave antenna array (LWAA) in millimeter-wave band that achieves wide-angle scanning in both elevation and azimuth is presented in this paper. The LWAA consists of an electronically controlled holographic surface (ECHS), a gap-waveguide array (GWA), and two 16-ways power dividers. The ECHS consists of 32 rows of 1-bit amplitude modulation elements (1-bit AMEs). By loading PIN diodes, the power amplitude of each element can be independently switched between two states, hence the varying aperture field distribution can be obtained. The GWA consists of 16 parallel-arranged and separated rows of GWs, each row transmits TE ₁₀ mode waves and excites two rows of 1-bit AMEs in the form of traveling waves. A slow wave ridges are introduced in the GWs, and the appropriate phase constants are obtained by optimizing the height of the ridge. A binarized holographic method (BHM) is developed to quickly obtain antenna parameters for wide-angle scanning. An FPGA control module is designed to electrically control the antenna. Measured results verify that the proposed LWAA can achieve a scanning range of -30°~30° in elevation and -60°~60° in azimuth, and a peak gain of 25.8dBi. The developed antenna has potentials to be used in millimeter-wave communication systems.

This paper presents a fixed-frequency beam-scanning leaky-wave antenna (LWA) based on phase control in millimeter-wave (mm-wave) band. The antenna is composed of a groove gap waveguide (GGW) with TE ₀₁ single-mode transmission and 56 perturbation elements with 2-bit phase modulation capability. The radiation of each patch unit is controlled by four diodes which are welded on the bottom pads. By controlling the states of diodes, the unit can realize four phase states of 0°, 90°, 180° and 270°. By changing the phase states of all the perturbation elements located on the LWA aperture, the beam-scanning property at a fixed-frequency can be realized. Then a method to suppress the side-lobe levels caused by high-order harmonics is proposed. The overall transmission structure of the antenna is based on an air-filled GGW, which is utilized to reduce the dielectric loss in the mm-wave band. The antenna is simulated and manufactured. The measured results show that the antenna has a high realized gain of 16.4dBi, and a wide beam-scanning range of more than 110° over the operating frequency band, demonstrating the feasibility and potential application values of the antenna.

In this paper, a theoretical model based on the electric field integration method is proposed to analyse radiation properties of the slotted annular Leaky-Wave Antenna (LWA), which can generate a Circularly Polarized (CP) conical beam or broadside beam. The annular LWA contains radiating elements arranged along a circular travelling-wave structure with equal intervals. By combining the proposed model and LWA theory, the design procedure for the annular SIW LWA is presented. To verify the model, three examples of LWAs with different beam angles have been designed and fabricated. Calculation results from the proposed model are consistent with the simulation and measurement results. The model can significantly reduce the design period and is an instructive tool for antenna design.