A broadband dual‐polarized end‐fire millimeter‐wave antenna array without ground clearance is proposed in this paper for 5G communication terminals. Horizontally polarized (HP) and vertically polarized (VP) radiation are realized using a quasi‐Yagi antenna and a substrate‐integrated waveguide cavity antenna, respectively. A multilayer dielectric plate for which the relative dielectric constant increases from top to bottom is used to achieve the HP antenna's end‐fire radiation without ground clearance. The VP antenna is implemented using the HP antenna, GND, and three rows of metallic vias. The HP and VP antennas are located in the same area, making the integrated design very compact. An inverted L‐shaped feeding structure was used to broaden the VP antenna's bandwidth with a low profile (0.12λL). Finally, a 4 × 1 array was processed to verify the proposed antenna. The measured results show that the overlapping bandwidth is 24 to 29.5 GHz (20.6%) for two polarization modes. The maximum gain varies between 7.6 to 9.1 and 6.5 to 9.1 dBi for the HP and VP modes, respectively.

In this paper, a novel miniaturized circularly polarized (CP) antenna is proposed for the use in B3 band of Compass Navigation Satellite System (CNSS). The primary radiator is a hexagon patch with four bending strips. A shorting pin is loaded with each strip to miniaturize the dimension of the proposed antenna, which achieves a small electrical size of 0.11λ × 0.11λ × 0.068λ (λ being the wavelength in free space at 1.268 GHz). In order to improve the bandwidth, Y-shaped coupled patches and bending-strips, which act as reactive loading, are coupled to an octagon patch. Four coupled bending-stubs with same turning directions of bending-strips are sequentially placed at the edge of the octagon patch to enhance CP performance. Finally, a prototype of the antenna is implemented and measured. The experimental results reveal that the proposed antenna achieves impedance bandwidth (IBW) of 19.6% (1.175-1.430 GHz) for |S 11 | ≤ −10 dB and 3-dB axial-ratio bandwidths (ARBW) of 27.5% (1.000-1.320 GHz). The radiation efficiency is more than 75%, and the gain keeps above 1.98 dBic over the B3 band. Thus, the proposed antenna can be a good candidate for the applications of CNSS.

A novel design of horizontally polarized end-fire antenna array with a complete ground (GND) for the fifthgeneration (5G) millimeter wave (mmWave) applications is proposed in this article. The antenna employs four dielectric layers with the relative permittivity successively increasing from top to bottom. Utilizing the refraction of the radiated waves between different dielectric layers, the uptilting of the beam in the end-fire direction caused by the complete GND has been solved. A pair of butterfly dipole is fed by a balun to produce horizontal polarization. The simulated result shows that the proposed antenna unit achieves a fractional impedance bandwidth of 19.6% (24.25-29.5 GHz) with the gain varying from 4.3 to 6.51 dBi. Based on the antenna element, a 1 × 4 antenna array is proposed. The isolation of the array is 17.6 dB. Besides, the end-fire gain is 7.51 to 10.2 dBi over the frequency band of 24.25 to 29.5 GHz. And the beam scanning range of the array covers from −54 to +54. A prototype is fabricated and measured, which validates the simulated results. Both the simulation and experiment results prove that the proposed antenna is promising for 5G mmWave applications.