A ±45° dual polarized broadband magneto-electric dipole antenna with gain improvement at low elevation angle is proposed in this paper for base station. The proposed antenna covers 2.45GHz to 2.8GHz, indicating a 13.3% impedance band. In order to improve the gain at ±60° angle, a notched metal wall is employed and the gain of proposed antenna at ±60°angle is improved 2dB over the entire band compared with the original antenna. Moreover, the proposed antenna has good performances with stable radiation patterns, a front to back ratio over 20dB and a cross-polarization discrimination over 15dB. An antenna prototype is fabricated and measured for verification. A good agreement is met between the simulation and measurement and good performances make it a candidate for 5G base station.

A shared aperture metasurface (SA‐MS) is proposed to achieve the wideband radar cross‐section (RCS) reduction and gain enhancement of a circularly polarised (CP) microstrip antenna simultaneously. The SA‐MS is composed of a wideband polarisation conversion surface and a partially reflecting surface (PRS). A 180° phase difference can be obtained by the polarisation conversion surface, which results in a wideband RCS reduction in normal incident direction. The Fabry–Perot resonator cavity is constructed by the PRS and the metallic ground of the CP microstrip antenna to enhance the gain. Experimental results show that the gain enhancement reaches 1.15 dB around the operating band and a wideband RCS reduction is obtained in the frequency range of 9–17 GHz, in which the average RCS reduction is 10.9 and 10.68 dB for dual polarisation in the normal incident direction.

A wide-angle scanning circularly polarized (CP) shared-aperture array is presented in this paper. The proposed dual-band shared-aperture element consists of a dual CP stacked patch antenna and a single CP $\bar{u}$ -slot patch antenna. To alleviate the scanning gain drop when beam steering in a wide range, a beam-shaped method is proposed. By employing the metal cavity and bent metal pins, a vertical current can be induced and the radiation pattern can be reshaped. As a result, a dip is introduced to the boresight of the element pattern and the gain at large angles can be improved, which is beneficial to achieve a lower scan loss in a wider scanning range. Based on this shaped-beam element, an eight-element linear array is fabricated and measured. The proposed array can steer the main beam from -65° to +65° and -60° to +60° at dual band with a small average scan loss of 2.2dB and 2.5dB, respectively. The measured results are consistent with the simulated ones.

A sextuple band circularly polarized (CP) shared- aperture antenna (SAA) with a small frequency ratio (FR) is presented in this paper. The SAA consists of a wideband scanning array and five narrow-band antennas. For a high integration, the stacked, interlaced and structure-reused schemes are employed comprehensively. To solve the problem of the insufficient area of the lower antenna to support the upper antenna in a stacked scheme, the metal column is introduced and it can also shield out the effects of feeding coaxial lines on the performance of the lower antenna. By loading the cavity, the degraded performance at the low elevation angle can be compensated. The SAA has a high ratio of aperture reduction compared with tradition multiple separate antennas, while keeping a lower profile. It can achieve 2D beam steering in a scanning range of ±45°.The prototype was fabricated and the measured results are consistent with the simulated ones. This SAA is well suited for navigation and wireless communication.

In this paper, a new method for radar cross section (RCS) reduction of circularly polarized (CP) microstrip antenna array with small element spacing is proposed. By employing the element rotation technique and loading EBG structures, the in-band and out-of-band RCSs are reduced simultaneously despite the extreme small space between array elements. The simulated results show that the proposed antenna has an average RCS reduction over 10 dB in the X-band for x-polarized and y-polarized incident waves impinging from normal direction compared to the original CP microstrip antenna array, indicating a fractional bandwidth of 40%. The maximum RCS reduction is over 25 dB. Meanwhile, the radiation performance of the proposed antenna array is kept.

A wide-angle scanning phased array with dual circular polarization in the Ka-band is presented in this paper. To improve the scanning capability of the phased array, the microstrip element is modified by loading many metal posts at its center and periphery. In addition, a stripline coupler is designed to achieve dual circularly polarized (CP) radiation, and the inner conductor of the subminiature micro-push-on (SSMP) connectors for feeding the coupler is extended to the top layer of the multilayer element by introducing an open stub, which simplifies the assembly process between the SSMP connector and multilayer printed circuit board (PCB) due to through-hole soldering instead of blind-hole soldering. The proposed element can cover a frequency range from 28 GHz to 30.5 GHz with a relative bandwidth of 8.5% in the Ka-band. An 8 × 8 phased array is constructed based on this proposed element, and a wide-angle scanning range from −65° to +65° is obtained for the dual circular polarization. The proposed array has a gain fluctuation of 5.1 dB and an axial ratio (AR) of less than 3.3 dB during beam-steering. The prototype is fabricated and measured, with a good agreement between the measured and simulated results. The proposed phased array can be applied in a Ka-band millimeter-wave (MMW) communication system.