A tri-polarized antenna with diverse radiation characteristics is proposed in this paper. This design mainly consists of two pairs of loop radiating dipoles and an omnidirectional monopole antenna element, which are used for the fifth generation (5G) and vehicle to everything (V2X) communications, respectively. By adding eight pairs of inverted L-shaped patches with unequal sizes around the proposed dipoles, wide beamwidths in both E- and H-planes can be obtained across the desired lower and upper frequency bands. Furthermore, by employing eight fork-shaped microstrip stubs to combine the circular monopole antenna element and the L-shaped patches, the flare angle of the conical beam can be increased to 180 $^{\circ }$ , which results in gain enhancement in the azimuth plane. Finally, the proposed loop radiating dipoles are excited by a pair of symmetrical differentially-fed feeding lines. Consequently, high port isolation for the proposed loop radiating dipoles as well as low gain variations for the monopole antenna element can be achieved. Measured results show that the impedance bandwidths of 32.84 $\%$ (2.8–3.9 GHz) and 18.18 $\%$ (4.5–5.4 GHz) can be achieved for the 5G communications. Wide half power beamwidths (HPBW) of larger than 103 $^{\circ }$ in E-plane and 91 $^{\circ }$ in H-plane can be achieved across the operating bands. In addition, a bandwidth of 5.5 $\%$ (5.82–6.15 GHz) with gain of 2.47 $\pm$ 0.69 dBi in the azimuth plane can also be obtained for V2X communications.

A Tri-Polarized Antenna With Diverse Radiation Characteristics for 5G and V2X Communications

A millimeter wave (mm-wave) wideband dual-linearly polarized antenna array with the end-fire radiation is presented as a promising candidate for device-to-device (D2D) communications in the 5G wireless systems. To realize the property of dual polarizations, two types of orthogonally-polarized radiators are arranged alternately, forming a linear array. By using the crossover, the whole array architecture, including radiators and feed networks, is built into a same layer. A 2 × 4-element array prototype is architected based on the substrate integrated waveguide (SIW) technology. Both radiators and feed networks are carefully designed and analyzed for a wideband operation. Experimentally, the proposed array obtains an impedance bandwidth of 28.6% (24∼32 GHz) for both polarizations. The port isolation is larger than 18.85 dB. Peak gains are 10.5 dBi and 11.6 dBi for the horizontal and vertical polarizations, respectively.

Single-Layer Wideband End-Fire Dual-Polarized Antenna Array for Device-to-Device Communication in 5G Wireless Systems

A dual-band shared-aperture phased array antenna with wide-angle scanning capability (WASC) is presented in this paper for mobile communications. Each shared-aperture antenna element consists of two wideband microstrip antenna units with air-cavity for the C -band and one wide beam magnetic-electro dipole antenna unit for the S -band. To achieve the wide-angle scanning, a phased array should have low inter-element mutual coupling and wide array-element beam-width. A simple metallic strip (MS), comprising four metal stubs and one rectangle shaped metal pillar, is utilized to improve the inter-element isolation of the array in and between the C - and S -bands. Furthermore, the metal strip can also broaden the beam-width of the C -band antenna units without distorting the wide-beam property of the S -band units. The shared-aperture array with a simple metallic strip is designed based on the above elements, and WASC is realized in both the C - and S - bands with low mutual coupling. To verify the proposed method, the shared-aperture array is fabricated and characterized, yielding good performance within the overall operating bandwidth. The measured results align very well with the simulated. The proposed array realizes the scanning coverage of ±60° with realized gain reduction of less than 3 dB in both the C - and S -bands, which is a good candidate for the base station in the mobile environment.

A Dual-Band Shared-Aperture Antenna With Wide-Angle Scanning Capability for Mobile System Applications

A dual-band dual-circularly polarized (CP) all-metal antenna is proposed in this paper for vehicular communications to realize large signal coverage and high isolation over two bands. On the one hand, by combining two rings of three-dimensional (3-D) L-shaped stubs and a circular patch, opposite CP radiations, i.e., right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP), can be achieved in lower and higher working frequency bands respectively, thus ensuring the isolation between different channels. On the other hand, both radiation patterns of two bands are conical-beam, i.e., omnidirectional, so as to realize large signal coverage, which is beneficial for vehicular communication especially when the car is moving or located on nonplanar plane. Besides, the proposed antenna is all-metal and can be easily manufactured by computer numerical control (CNC) machining technology. As such, it is expected to have higher power capacity than the conventional printed circuit board (PCB) structure. A prototype operating at 2.6 and 2.98 GHz is fabricated and measured, indicating that small frequency ratio between two operating bands can be realized. The proposed antenna is promisingly useful for application on vehicle to ensure simultaneous communications between different links without crosstalk, such as vehicle-to-satellite and vehicle-to-basestation communications.

Dual-Band Dual-CP All-Metal Antenna With Large Signal Coverage and High Isolation Over Two Bands for Vehicular Communications

This paper presents a compact dual-port dual-frequency planar shared-aperture antenna with large frequency ratio. It consists of a microwave magneto-electric (ME) dipole antenna and a millimeter-wave parallel-plate resonator antenna (PPRA). It has two vertical conducting walls that form an upper-band parallel-plate resonator and meanwhile provide a magnetic source to the lower-band ME dipole. The design is a shared-aperture structure and is therefore very compact. For demonstration, a dual-frequency antenna simultaneously covering the 5.9-GHz vehicle-to-vehicle (V2V) band (5.855–5.925 GHz) and the 28-GHz 5G band (27.5–28.35 GHz) was designed, fabricated, and measured. Good agreement between the measured and simulated results was found. The lower and upper bands have the measured 10-dB impedance bandwidths of 41.6% (5.30–8.08 GHz) and 6.66% (27.15–29.02 GHz), and measured peak antenna gains of 5.80 dBi and 8.46 dBi, respectively. The antenna can be used on vehicular platforms for providing V2V communications and 5G millimeter-wave connections simultaneously.

Compact Dual Microwave/Millimeter-Wave Planar Shared-Aperture Antenna for Vehicle-to-Vehicle/5G Communications

In this paper, a low-profile dual-band stacked microstrip monopolar patch antenna is proposed. By utilizing a stacked-patch configuration, a dual-band property is achieved. A coupled annular ring and a set of conductive vias are loaded into the antenna structure to widen the impedance bandwidth. In order to verify the performance of the proposed antenna, a fully functional prototype was fabricated and measured. The measured results demonstrate that the antenna can achieve impedance bandwidths from 2.24 to 2.53 GHz in the low band and from 5.42 to 5.98 GHz in the high band, separately. Within the operating frequency, omnidirectional radiation patterns are also observed. Besides, the proposed antenna possesses a low-profile structure with a height of 4.175 mm or $0.057\lambda _{0}$ (where $\lambda _{0}$ is the free-space wavelength of 4.1 GHz), which can be easily hidden on the top of a vehicle. With these merits, the proposed design is very appropriate for wireless local area network (2.4–2.48 GHz and 5.75–5.825 GHz) and car-to-car (5.85–5.925 GHz) communications.

Low-Profile Dual-Band Stacked Microstrip Monopolar Patch Antenna for WLAN and Car-to-Car Communications

A low-profile dual-band antenna with different polarization and radiation properties over two bands for vehicular communications is presented in this correspondence paper. The dual-band property is realized by employing a stacked-patch structure. By utilizing TM01 and TM10 modes of the truncated upper square patch, a unidirectional radiation pattern with circular polarization is achieved in the low band. By using TM01 and TM02 modes of the lower circular patch, omnidirectional radiation with linear polarization can be obtained in the high band. In order to widen the antenna bandwidth, a U-shaped slot is etched in the truncated square patch, and 12 conductive vias are inserted to short the circular patch to the ground plane. A fully functional prototype was developed and tested. The measurements show that an axial-ratio (AR) bandwidth (AR ≤ 3 dB) from 2.49 to 2.54 GHz and an impedance bandwidth ( S 11 ≤ −10 dB) from 2.34 to 2.57 GHz are obtained in the low band and an impedance bandwidth ( S 11 ≤ −10 dB) from 3.54 to 4.40 GHz is achieved in the high band. Unidirectional circular polarization and omnidirectional linear polarization are observed over two bands. In addition, the proposed antenna exhibits other advantages, such as low profile and high gain. With these characteristics, the proposed design is very suitable to be applied on a vehicle to meet both satellite and mobile communications.

A Low-Profile Dual-Band Antenna With Different Polarization and Radiation Properties Over Two Bands for Vehicular Communications

In this letter, a novel low-profile magnetoelectric (ME) dipole antenna is proposed. By utilizing a pair of vertically oriented folded shorted patches, the antenna height is reduced from 0.25 λ 0 to 0.116 λ 0 compared with the original ME dipole antenna ( λ 0 is the center-frequency free-space wavelength). A fully functional prototype is constructed and tested. The measurement shows that a fractional impedance bandwidth ( S 11 ≤ –10 dB) of 43.6% from 1.81 to 2.82 GHz is achieved. Within the operating frequency, the antenna gain is stable located at 9 dBi. Besides, stable unidirectional radiation patterns in both E- and H-planes with high front-to-back ratio are obtained. Due to the dc grounded property, the antenna can be applied outdoors.

Magnetoelectric Dipole Antenna With Low Profile

A polarization reconfigurable magneto-electric (ME) dipole antenna with broad bandwidth is proposed and investigated. Two crossed dipoles through a 90° phase delay line, constituting a sequentially rotated configuration, is used to feed the ME dipole. By manipulating the states of four p-i-n diodes which are inserted in the crossed dipoles, the antenna is able to switch the polarization between two orthogonal circularly polarized states. To verify the performance, the proposed antenna is designed, constructed, and tested. Measurements reveal the design obtains an effective bandwidth of 33.3% and a gain of approximately 8.2 dBic for both polarization states. Besides, stable unidirectional radiation patterns with front-to-back ratios higher than 25 dB are also achieved.

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A Magneto-Electric Dipole Antenna With Switchable Circular Polarization

In this letter, a wideband water patch antenna with polarization diversity is proposed. Simultaneously, different polarization states are realized by changing the operation modes between TM11 and TM02 modes of a circular water patch and switching the feeding ports. To obtain an overlapped frequency band between these two modes, a size-changeable water patch is used. An adjustable plexiglass container is used to contain water and change the size of the water patch, while a disk-loaded probe and two pairs of L-probes are applied as the switchable feeding ports and also support wide bands. A fully functional prototype was fabricated and tested to verify the proposed design. The measured results show that all three polarization states can work well with a high isolation level. The overlapped −10 dB impedance bandwidth of three polarizations is 23.40% (2.34 GHz∼2.95 GHz). With the advantages of multipolarization states, ease of fabrication, and high optical transparency, the proposed antenna is suitable for various applications, such as indoor communications.

Shuai Gao

Papers

Low-Profile Dual-Band Stacked Microstrip Monopolar Patch Antenna for WLAN and Car-to-Car Communications

A Low-Profile Dual-Band Antenna With Different Polarization and Radiation Properties Over Two Bands for Vehicular Communications

Magnetoelectric Dipole Antenna With Low Profile

A Magneto-Electric Dipole Antenna With Switchable Circular Polarization

A Wideband Water Patch Antenna With Polarization Diversity