The shared aperture antenna is regarded as one of the promising approaches to support new frequencies with very efficient space utilization. To the best of the authors’ knowledge, there are few shared aperture antennas that include both the sub-6 GHz antenna and the millimeter-wave (mm-wave) beam-steering array for broadside applications. In this article, a broadside sharing aperture technique is developed so that a 2 $\times4\,\,26$ GHz beam-steering substrate-integrated DRA (SIDRA) array can be integrated into a 3.5 GHz bandwidth enhanced perforated patch antenna in a coplanar and aperture-shared way. The proposed solution benefits from several aspects. First, the 3.5 GHz antenna features a compact size as this part is built on the substrate (where the mm-wave SIDRA is constructed) with a high permittivity. Second, the mm-wave SIDRA is a 3-D-type device, and in the case of coplanar integration, its height can be freely adapted to the thickness of 3.5 GHz antenna without concerning the impact from surface waves as many 2-D-type antennas have to do. Third, the antenna can be implemented with the multi-layer printed circuit board (PCB) process, yielding a high integrity level. The dual-frequency antenna was designed, fabricated, and measured. The performances of the antenna are reported with reasonable agreement between the measured and simulated results observed.

A kind of circular polarized (CP) stacked dielectric resonator (DR) antenna with wide bandwidth and high gain is presented in this communication. For this design, a two-layer DR with improved performance in bandwidth and gain is used as the basic resonator. By further applying it into a stacked design, two similar modes with adjacent resonant frequencies can be merged together, providing a wide axial ratio bandwidth of more than 20%. The single-feed CP operation is achieved by adopting a coupling cross-slot, which is beneficial for fine-tuning and array forming, as compared to multifeed structures. Two design examples working at different frequency bands and for different senses of CP have been presented to demonstrate the effectiveness of the design concept.

A circularly polarized (CP) dielectric resonator antenna (DRA) with wide bandwidth and low axial ratio (AR) values is presented in this communication. The antenna consists of a stacked DRA, and it is fed by a substrate integrated waveguide (SIW) coupling slot from the bottom. The stacked DRA structure, with high permittivity dielectric strips layered on low permittivity substrate, is adopted for bandwidth and gain benefits. Here, a pair of dielectric strips rather than a single one is placed above the coupling slot with 45° inclination for generating good CP radiation, and it is elaborately designed to provide three closely coupled CP modes, constituting a wide operating bandwidth. To facilitate the application in antenna array, a cavity-backed antenna design along with a 2×2 sub-array are further presented. To verify the design, a sub-array prototype is developed and tested at Ku-band for satellite applications, showing an impedance bandwidth of 25.1%, a wide 1-dB AR bandwidth of 15.6%, and a peak gain of 15.1dBi.

A dielectric patch (DP) resonator (DPR) with silver-coated slots is investigated for designing wideband low-profile antenna in this communication. The low-profile DPR can be treated as an anisotropic dielectric resonator (DR) for analysis. A new equation for calculating the effective dielectric constant of the DPR operating at the TM modes is proposed. Based on this, the anisotropic property is investigated to enhance the gain of DP antenna (DPA). It is found from the theoretical analysis that the resultant antenna is a good compromise between the traditional microstrip patch antenna (MPA) and dielectric resonator antenna (DRA) in terms of profile, gain, efficiency and design freedom. By making full use of the multi-mode characteristic of the DPR, the silver-coated slots are introduced on the DP to shift high-order TM121 mode close to TM101 mode. As a result, the bandwidth of the antenna can be expanded significantly. For demonstration, the DPA element and 1×4 array prototype operating in the microwave band (5GHz) are implemented and measured.

In this communication, a new kind of dual-band hybrid dielectric resonator antenna (DRA) with its array design and extended dual-polarized version is presented for 5G millimeter-wave (mm-Wave) applications. The hybrid antenna which integrates three types of resonators of strip, slot, and DRA can generate four resonances in 28 GHz and 39 GHz frequency bands. In this design, the strip and slot modes are used to cover the lower frequency band of 26.41 - 30.42 GHz, while the TE111 and TE131 modes of the DRA are employed to cover the upper frequency band of 36.05 - 40.88 GHz. It shows that the 5G mm-Wave bands of n257 and n260 can be covered simultaneously. It should be mentioned that our proposed hybrid antenna has a compact size of 0.34 λ ₀₁ ×0.36 λ ₀₁ ×0.1 λ ₀₁ (λ ₀₁ means the free-space wavelength at 28 GHz). Based on the compact size of the antenna element, a 1×5 antenna array with the capability of beam steering is designed and simulated. Wide steering angles of ±50° and ±40° can be obtained at 28 GHz and 39 GHz frequency bands, respectively. Further, an extended dual-polarized antenna configuration is also described and measured that provides similar two port impedance and radiation performance with the single port counterpart.

The shared-aperture integration of microwave (MW) and millimeter-wave (MMW) band antennas has attracted lots of attention and interests recently. However, few designs, to date, can simultaneously satisfy the requirements of compact size for MW antenna, beam steerable array for MMW antenna, appreciable bandwidths for both bands, and high isolation between the two bands. In this communication, a dual-band 3.5/28 GHz shared-aperture antenna is proposed to solve this issue. By embedding two MMW 1×2 subarrays to the MW perforated patch antenna, the two antenna types can be accommodated in a shared volume and integrated into the same structure. The shared-aperture antenna, which has a very compact size of 0.4×0.26×0.04λ ³ ₀₁ (λ ₀₁ is the wavelength in the vacuum at 3.5 GHz), can be used as an array element to form the MW MIMO system and MMW beam-steering array. A validation array model with two cells is fabricated and measured. Measured results show that the antenna can cover a dual-band of 3.38-3.64 GHz (7.4%) and 26.4-29.8 GHz (12.1%). The peak gains of 6.9 and 14.6 dBi are obtained by the single MW element and 4×2 MMW array, respectively. The MMW array can support ±30° beam scanning in the H-plane. The channel isolation between the two bands can be more than 45 dB at 3.5 GHz and 40 dB at 28 GHz.