End-fire Antenna Array Research Articles

Low profile cavity-embedded ultra-wideband UHF array antenna with end-fire beams

A low profile, vertically polarized, ultra-wideband array antenna with end-fire beams operating in an ultra-high frequency (UHF) band is developed in this paper. The array antenna consists of 1×16 log-periodic top-hat loaded monopole antenna arrays and is feasible to embed into a shallow cavity to further reduce the array height. Capacitance is introduced in the proposed antenna element to reduce profile height and the rectangular top hats are carefully designed to minimize the transverse dimension. Simulated results show that when the antenna array operates in a frequency range of 300 MHz–900 ​MHz, the end-fire radiation pattern achieves ±45° scanning range in the horizontal plane. Then prototypes of the proposed end-fire antenna element and a uniformly spaced linear array (1×2) are fabricated and validated. The end-fire antenna array should be suitable for airborne applications where low profile and conformal scanning phased antenna arrays with end-fire radiations are required. This design is attractive for airborne platform applications that are used to search, discover, identify, and scout the aerial target with vertically polarized beams.

High-Gain and Wideband Circularly Polarized Endfire Leaky-Wave Antenna Array Based on the Complementary Dipole

A circularly polarized (CP) endfire leaky-wave antenna (LWA) array with the merits of high-gain and broad operation band is proposed in this communication. This array configuration is composed of double-row antenna cells arranged linearly, which derives from the performance of the complementary dipole (loop and electric dipole). By introducing the coupling loop and the electric dipole along both side of a metallic parallel strip line (PSL), the effective radiation is generated from this structure due to the periodic perturbation. Based on the intrinsic 90° phase differences of the complementary dipole, CP performance is easily achieved by turning the antenna unit size reasonably. Similar to the yagi antenna, this linearly antenna array achieves an endfire radiation. A fabricated prototype has verified the design concept, which shows that the proposed antenna has a relative impedance bandwidth of 51.1%, 3dB axial ratio (AR) bandwidth of 25%, and the gain of 1.1-13.59dBi within the operation band.

Beamforming Network Design Utilizing Node Microstrip Architectures for Dual-Polarized Endfire Millimeter-Wave Antenna Arrays

A node microstrip architecture is proposed for designing a compact Butler Matrix (BM) that is integrated with a dual-polarized endfire antenna array. The node microstrip architecture can be used to form a variety of compact 2 × 2 port networks including, but not limited to, couplers and crossovers. By concatenating the 2 × 2 port networks together, a compact BM with any number of ports can be formed. Using the proposed method, a compact 4 × 4 port BM operating in the millimeter wave band is designed and integrated with a dual-polarized endfire antenna array. The size of the compact BM is 2.1λ × 2λ and the size of the whole dual-polarized endfire antenna array with BM is 2.6λ × 4.8λ, which is smaller than traditional structures. The measured radiation pattern of the dual-polarized antenna array can achieve beam-scanning up to ±38° in the azimuth plane. The two beams in the dual-polarized endfire antenna array can also be independently steered. The optimized compact BM is potentially suitable for use in 5G wireless communication handsets.

A Compact Dual-Polarized Endfire Antenna Array for 5G Millimeter-Wave Terminal

This paper proposes a compact dual-polarized end-fire antenna array for 5G millimeter-wave (mmWave) application. The dual-polarized antenna unit is constructed by an open-ended substrate integrated waveguide (SIW) cavity for vertically polarized (VP) radiation and a broadband electric dipole for horizontally polarized (HP) radiation. By sharing the side walls of two neighboring SIW channels of the VP elements, the substrate integrated coaxial line (SICL) feeding structure for the HP element is achieved, thus a compact size of the final antenna array can be accomplished. To extend the bandwidth of the VP element, the quasi-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode of the cavity and the slot mode of the end-fire aperture are adopted for the VP element. A corresponding linear array with four units is designed and fabricated. The common -10-dB impedance bandwidth covers from 24.8 GHz to 29.2 GHz. The maximum gain is 10.0 dBi for both polarizations, with an overlapped scanning coverage ranging from -41.5º to 45.5º at 27 GHz. The proposed design has a compact configuration, and a wide scanning range, which is alternative for 5G mmWave terminal application.

A New Metasurface End-Fire Antenna Array Based on Yagi for 5G Applications

A novel end-fire wide-scanning metasurface antenna array for a millimeter wave operating at 28 GHz is proposed in this paper. The suggested antenna is considered as a low-cost device since it is printed on both sides of a single-layer FR-4 substrate with a thickness of 0.5 mm and a size of 44×13 mm2. On the top side of the cell phone PCB, eight Yagi antenna elements fed by microstrip lines have been used to form a linear array. The antenna gain and impedance matching are increased by placing a 5×5 metasurface composed of metallic H-shapes right in front of the Yagi array. This technique achieves a large bandwidth of 3.5 GHz from 26.2 to 29.7 GHz, and a high gain of 15.5 dBi, which is almost stable over a wide scanning angle. Finally, in order to understand the integration impact, the proposed antenna phased array has been covered by a casing. The simulation result demonstrates that there is no degradation effect for the entire assembly.

High power handling GaAs SP4T Switch-based Beam-Switching planar antenna module for 5G New-Radio FR2 applications

In this paper, a beam-switching antenna module for 5G New-Radio (NR) frequency range 2 (FR2) applications is proposed. The module is constructed with a single-pole-quadruple-throw (SP4T) switch featuring high power handling capability, low insertion loss, and higher isolation, which is integrated with a 4 × 4 Butler matrix and an end-fire antenna array for achieving beam switching characteristics. The system is realized on the Rogers RO3010 substrate which achieved a compact size of 4.67λ0 × 2.06λ0 × 0.031λ0 (f0 = 38 GHz) due to a higher integration level and demonstrated a decent impedance bandwidth of (15.78 %) 35–41 GHz with four beam patterns directing along + 14°, −40°, +49°, and −16°, respectively. The experimental results show an advantage in RF performance with high integration level which is promising for 5G NR n260 band communication applications.

Millimeter-Wave Endfire Wide-Angle Scanning Circularly Polarized Antenna Array

Because the width of antenna elements exceeds half of the air wavelength, resulting in too large element spacing, the scanning angle of traditional endfire circularly polarized (CP) antenna array is usually less than 60°. In order to solve the above problem, a CP quasi-Yagi antenna element is proposed in this letter, whose width is less than half of the air wavelength. Further, an 1 × 8 endfire CP antenna array is designed. Because the element spacing is about half a wavelength, the scanning angle of the proposed endfire CP antenna array can reach 60°. Moreover, the axial ratios of all beams are less than 3 dB in the scanning angle range of (0°, 60°). The final measured results are basically consistent with the simulated results

Millimeter-Wave ±45° Dual Linearly Polarized End-Fire Phased Array Antenna for 5G/B5G Mobile Terminals

In this article, a millimeter-wave (mmWave) endfire phased array antenna with ±45° linear polarizations is proposed for fifth generation (5G)/B5G mobile communications. The proposed antenna achieves ±45° polarizations by utilizing a modified substrate integrated waveguide (SIW) slot polarizer. The polarizer generates dual orthogonal modes with equal amplitudes and a 0°/180° phase difference, thereby yielding <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$+ 45^{\circ }/- 45^{\circ }$ </tex-math></inline-formula> -polarization radiated waves in the far field. In a practical metal-framed mobile phone environment, the ±45 polarizations are verified to provide more balanced radiation patterns and, consequently, a higher polarization-multiple input multiple output (MIMO) efficiency. A prototype of the proposed 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 4 array is fabricated and measured, achieving a −10 dB impedance bandwidth of 23.4–30.0 GHz (covers 5G band of n257/n258), with an isolation better than 15.6 dB and a realized gain above 8.9 dBi in the operating bandwidth. A peak gain of 11.4 dBi and a 3 dB scanning range of 87° can be observed at 27.0 GHz. Furthermore, the prototype is characterized on a metal-framed mobile phone platform, experimentally demonstrating its superiority to conventional vertical/horizontal polarized (V-/H-pol) arrays. The validated advantages of the balanced radiation patterns and robust impedance matching make the proposed ±45°-polarization endfire antenna array a promising candidate for mobile terminals in the era of 5G/B5G.

Switched and Steered Beam End-Fire Antenna Array Fed by Wideband Via-Less Butler Matrix and Tunable Phase Shifters Based on Liquid Crystal Technology

This article presents the design of a Ka-band beam-switchable and beam-steerable endfire planar Yagi–Uda antenna array fed by a wideband Butler matrix, combining continuously tunable phase shifters based on a liquid crystal (LC) technology. The proposed array consists of four wideband 3 dB 90° branch-line couplers, two novel wideband via-less crossovers, LC-based 135° microstrip (MS) delay line phase shifters, and planar endfire Yagi–Uda antennas. The Butler matrix realizes beam switching, while LC phase shifters enable continuous beam steering inbetween the discrete beam positions. In this way, long delay line phase shifters are avoided for achieving 360°, reducing the phase shifter insertion losses (IL). Besides, such a hybrid beam steering method is expected to respond faster and more accurate. The array has two metallized layers, which can be easily fabricated by standard photolithography procedures. The fabricated array demonstrator is measured in terms of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -parameters and far-field patterns. The measured return loss and isolation of the array are both ≥15 dB from 26 to 30 GHz. The beam is switchable among ±15° and ±45° in E-plane. By applying bias voltage up to 5 V to the LC phase shifters, the beam can be further continuously steered, covering almost −60° to +60° with acceptable sidelobe level. The maximum gain of the array is estimated to be 5.6 dBi. The radiation efficiency is 12%.

Design of Zero Clearance SIW Endfire Antenna Array Using Machine Learning-Assisted Optimization

In this communication, a substrate integrated waveguide (SIW) end-fire antenna array with zero clearance is proposed for fifth-generation (5G) mobile applications using machine learning-assisted optimization. In particular, a novel impedance matching architecture that involves three arbitrary pad-loading metallic vias is investigated and adopted for the antenna element. Due to the stringent design requirements, the locations and sizes of the vias and pads are obtained via a state-of-the-art machine learning assisted antenna design exploration method, parallel surrogate model-assisted hybrid differential evolution for antenna synthesis (PSADEA). Keeping a very low profile, the array optimized by PSADEA covers an operating frequency bandwidth from 36 to 40 GHz. The in-band total efficiency is generally better than 60&#x0025; and the peak gain is above 5 dBi. The beam scanning range at 39 GHz covers from &#x2212;20&#x00B0; to 35&#x00B0;.

Wideband Dual-Polarized Endfire Antenna Based on Compact Open-Ended Cavity for 5G Mm-Wave Mobile Phones

This article describes a compact dual-polarized endfire antenna array for fifth-generation (5G) millimeter-Wave (mm-Wave) mobile application. The dual-polarized endfire antenna element is constructed by a compact open-ended cavity with cavity mode for vertical polarization (VP) radiation and open-slot mode for horizontal polarization (HP) radiation. With the integrated design of VP and HP elements, the proposed antenna shows a much more compact size compared to existing schemes. To enhance the bandwidth of low-profile VP radiation, a slot is etched on the cavity to create a new mode for dual-resonance response, realizing a wide bandwidth of 24.5&#x2013;29.5 GHz for both polarizations. In addition, radiation pattern modification techniques are employed to achieve good endfire beams with a high front-to-back ratio for both polarizations, thus enabling a high peak gain of 10.3 and 11.3 dBi for VP and HP, respectively. A wide beam scanning range of &#x00B1;50&#x00B0; with realized gain above 7 dBi is realized at 27 GHz for both polarizations. In virtue of compact size, wide bandwidth, high gain, and good spatial coverage, the proposed design strategy is promising for future 5G mm-Wave mobile phones.

Millimeter-Wave Dual-Polarized Multibeam Endfire Antenna Array With a Small Ground Clearance

A dual-polarized multibeam endfire antenna array is presented for 5G millimeter-wave applications. The antenna element employs double-layer stack-up substrate integrated waveguides (SIWs) and stepped slot to serve as a polarizer. Dual-linear polarization can be generated when the two SIWs are fed with in-phase and out-of-phase signals. A resonated metallic loop and two pairs of bilateral connecting lines are loaded in front of the antenna aperture to improve impedance matching and enhance gains. The ground clearance is only 1.5 mm, thus is attractive to be applied for mobile terminals. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 \times 4$ </tex-math></inline-formula> multibeam array is constructed to evaluate the beamforming capability. Butler matrix and 180° hybrid couplers are used to provide the required feeding signals. The measured bandwidth is larger than 10% for both polarizations, capable of covering n257 and n261 bands. The measured peak gains of vertical and horizontal polarizations are 9.38 and 9.51 dBi, with an overlapped 3 dB azimuthal range covering ±48°.

Design of Millimeter-Wave Circularly Polarized Endfire Antenna and Multibeam Antenna Array for Wireless Applications

A broadband stepped tapered slots’ endfire circularly polarized (CP) antenna and a multibeam antenna array are proposed for millimeter-wave (mmWave) applications. First, a modified tapered slot endfire antenna element is designed. Compared with the normal antipodal linearly tapered slot (ALTSA) endfire antenna, the performance of the stepped tapered slots’ antenna shows remarkable improvement, and the size of the antenna reduces effectively. The simulation and measurement results of the proposed endfire antenna show that an impedance bandwidth of 63.5% (75.1–145 GHz), an AR < 3 dB bandwidth of 50% (75.9–125.3 GHz), and a max gain of 8.8 dBic are realized, respectively. Second, to reduce fabrication and assembly requirements, a groove gap waveguide (GWG) feeding network is designed for multibeam array applications. The broadband 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 2 GWG network, interconnections, and transitions are designed and applied in the antenna array. Finally, a multibeam array based on the proposed endfire antenna is designed, fabricated, and measured. An impedance bandwidth up to 37.7% and a wide axial ratio bandwidth of 38.7% with a max LHCP gain of 12.8 dBic are achieved by the proposed 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 2 multibeam antenna array. The proposed multibeam endfire CP antenna array would be an attractive candidate for mmWave wireless applications.

Design of Wideband Antenna Array with Dielectric Lens and Defected Ground Structure

In order to increase the gain of an end-fire antenna array and improve its broadband characteristics, techniques using a dielectric lens and defected ground structure have been investigated in this paper. The element of the array was constructed using an antipodal tapered slot, and two pairs of U-slots were symmetrically cut on the edges of the two antipodal fins to obtain better performance regarding impedance and radiation in the wider band. While loading an ellipse dielectric lens onto each element, the direction and gain were enhanced at the higher frequency. Meanwhile, a defected ground structure was added on the ground plane to decline the mutual coupling of adjacent radiation arms. This design method was verified by a four-element array and a four-way Wilkinson power divider was used as a feed network. Finally, a fabricated sample was tested. Experimental results showed the designed array was available.

A New and Simple Design Method for End-Fire Dipole Antenna Array and Three Two-Element 24 GHz Planar End-Fire Dipole Antenna Arrays

For an RF system, a high-gain antenna helps to improve the equivalent isotropic radiated power (EIRP) of the transmitter and an end-fire antenna array helps to improve the directivity (D) and half power beam width (HP) of the antenna. This work presents a new and simple design method for end-fire antenna array design. The method states that when antenna elements are λ/2 apart, a simple end-fire antenna array could be designed and constructed easily without matching networks between antenna elements. Utilizing Rogers 4350 PCB technology, three 24 GHz high-gain, compact planar two-element end-fire dipole antenna arrays are designed to verify this new design method. The achieved results are three two-element end-fire antennas with gains of 8.8, 9.9 and 9.1 dBi. These antenna arrays are characterized by high gain and simplicity in design. They are also very compact in size, with an area of about 1.9 × 1.7 cm2. The benefit of this work is that a new and simple design for end-fire antenna design is suggested, and three two-element end-fire dipole antenna arrays in planar technology which adopt the design method are presented. A utility model patent was granted for this end-fire dipole array antenna topology, ZL 202022106332.1.

A W-Band High-Efficiency Multibeam Circularly Polarized Antenna Array Fed by GGW Butler Matrix

In this letter, a high-efficiency multibeam circularly polarized (CP) antenna array with the groove gap waveguide (GGW) feeding technology for W-band application is proposed. First, a wideband CP septum antenna element based on GGW structure is proposed. The antenna has a simple structure with high tolerance, and the GGW technology reduces the machine difficulty, making the antenna easier to work in the higher frequency. Next, a 4 × 4 GGW Butler matrix is designed to feed the antenna array. Finally, a high-efficiency W-band four-beam CP endfire antenna array is fabricated and measured. Measured results verify that the antenna has a wider impedance bandwidth of 17.6% from 77.5 to 92.5 GHz for |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB. The measured AR values of the main lobe range of four beams are almost less than 3 dB. Also, stable radiation patterns are obtained. The maximum gain and radiation efficiency are 15.29 dBic and 89.6%, respectively.

A dual‐polarized end‐fire mmWave antenna array without ground clearance for 5G mobile terminals

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.

Three-dimensional aperture principle for end-fire radiation antenna array

According to the two-dimensional aperture principle, directivity and gain are expected to be proportional to the aperture area of an antenna or antenna array. Our simulations and measurements of an end-fire radiation antenna array overturn this conventional wisdom. The gain of an end-fire antenna array is found to be much higher than that calculated by the two-dimensional aperture principle. We introduce a length component into the two-dimensional aperture principle and propose a three-dimensional aperture principle. A four-element end-fire antenna array is designed and measured to verify the correctness of this new principle. The three-dimensional aperture principle opens a pathway to novel types of aperture utilization.

Performance Enhancement of 5G Millimeter Wave Antenna Module Integrated Tablet Device

This article describes the design and considerations for millimeter-wave (mmWave) 5G antenna modules embedded in a tablet device. The antenna module consists of eight-chain broadside antenna array and two pairs of four-chain endfire antenna array. A dual-polarized air-filled stacked patch antenna is designed for the broadside patch antenna. Although the performance can be deteriorated due to a plastic cover, the proposed antenna enables an adaptable design for a dielectric cover. A novel surface-mountable chip antenna is also proposed, to implement a vertical polarized (V-pol.) endfire antenna on a low-profile substrate. To integrate a dual-polarized endfire antenna in a confined space, a horizontal polarized (H-pol.) mesh grid antenna and a V-pol. chip antenna are collinearly integrated. In addition, a plastic cover on the tablet is modified to enhance the performance of the endfire antenna array. The cumulative distribution function (cdf) of effective isotropic radiated power (EIRP) is utilized to evaluate spherical coverage, based on the 5G standard of 3rd Generation Partnership Project (3GPP). The spherical coverages are presented by varying the types of plastic cover, the effects of the blockage, and the number of mmWave 5G modules.

Compact Millimeter-Wave Endfire Dual-Polarized Antenna Array for Low-Cost Multibeam Applications

A compact multibeam endfire dual-polarized antenna array for low-cost millimeter-wave (mmWave) applications is proposed in this letter. Multimode substrate-integrated waveguide (SIW) section with interactions is applied as the basic beamformer. The dual-mode SIW is used in the beamforming network to support dual-polarization application without occupying an extra area. The printed dipole antenna with integrated balun and the open-ended SIW antenna with metallic strips are integrated to realize an endfire dual-polarized antenna element. Based on this endfire antenna element, a multibeam dual-polarized antenna array is developed. The proposed antenna array includes a four-element antenna array, an SIW beamforming network, and transitions. Additional air gaps between antenna elements are designed for mutual coupling reduction. The fabricated multibeam endfire dual-polarized antenna array achieves an impedance bandwidth of 11.3%, and the overlapped 3 dB beamwidth of the four generated beams in two polarizations are able to cover a wide range between ± 41°. The proposed low-cost multibeam antenna array can be a good candidate for 5G mmWave wireless applications.