Low Cross-polarization Radiation Research Articles

Direct Metal Laser Sintering Conformal Waveguide Array Antenna for Millimeter-Wave 5G Communications

An omnidirectional conformal array antenna has been implemented in air-filled waveguide technology for the 37–40 GHz band. The input port of the antenna is a standard WR28 rectangular waveguide. The TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode excited in the rectangular waveguide is used to generate the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode inside a circular waveguide by means of a TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> –TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode converter. The circular waveguide section is progressively widened, forming a radial waveguide structure, where the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode propagates radially through several radiating apertures. Due to the rotational symmetry of the structure, an omnidirectional radiating performance with low ripple can be achieved. This structure has been three-dimentional (3-D) manufactured using the direct metal laser sintering technology. A good agreement between simulations and measurements has been found. A reflection coefficient of below −15 dB, a low-ripple omnidirectional performance in a conical cut plane, a low cross-polar radiation, and a total efficiency higher than 83% are obtained. This conformal antenna design is proposed for fifth generation (5G) New Radio indoor applications.

Developing Broadband Microstrip Patch Antennas Fed by SIW Feeding Network for Spatially Low Cross-Polarization Situation.

A stacked multi-layer substrate integrated waveguide (SIW) microstrip patch antenna with broadband operating bandwidth and low cross-polarization radiation is provided. A complete study on the propagating element bandwidth and cross polarization level is presented to demonstrate the importance of the design. The proposed antenna includes three stacked printed circuit board (PCB) layers, including one layer for the radiating 2 × 2 rectangular patch elements and two SIW PCB layers for the feeding network. There are two common methods for excitation in cavity-backed patch antennas: probe feeding (PF) and aperture coupling (AC). PF can be used to increase the bandwidth of the antenna. Although this method increases the antenna’s bandwidth, it produces a strong cross-polarized field. The AC method can be used to suppress cross-polarized fields in microstrip patch antennas. As microstrip patch antennas are inherently narrowband, the AC method has little effect on their bandwidth. This paper proposes an antenna that is simultaneously fed by AC and PF. As a result of this innovation, the operating bandwidth of the antenna has increased, and cross-polarization has been reduced. Actually, the combination of probe feeding and aperture coupling schemes leads to achieving a broadband operating bandwidth. The arrangement of radiator elements and cavities implements a mirrored excitation technique while maintaining a low cross-polarization level. In both numerical and experimental solutions, a less than −30 dB cross-polarization level has been achieved for all of the main directions. A fractional impedance bandwidth of 29.8% (10.55–14.25 GHz) for < −10-dB is measured for the proposed array. Simulated and measured results illustrate good agreement. Having features like low cost, light weight, compactness, broadband, integration capabilities, and low cross-polarization level makes the designed antenna suitable for remote-sensing and satellite applications.

A Comparative Study in Different Structures of Microstip Patch Antenna Design

Microstrip antenna consists of a metallic patch on a grounded substrate. It may be rectangular or circular patches. MSA become very popular for its ease of analysis and in fabrication, attractive radiation characteristics and low cross polarization radiation. In this paper, the proposed antennas are selected as UWB self-complementary Monopole antennas. I represent here the comparative study of Microstrip rectangular and hexagonal Patch antenna and their characteristics like Radiation pattern, VSWR vs. frequency, s-parameter vs. frequency, Impedance vs. frequency, current density etc.

Planar Broadband Higher-Order Mode Millimeter-Wave Microstrip Patch Antenna Array With Low Sidelobe Level

AbstractIn this letter, a planar broadband higher-order mode millimeter wave (MMW) microstrip patch antenna array with low sidelobe level (SLL) is presented. For the antenna element, antiphase-TM30 mode is excited by unequally etching the radiating patch with two transverse slots. Meanwhile an SIW-based pin-loaded slot coupling feeding structure is introduced to achieve merits of broadband, low cross polarization and low backward radiation. Then a one-eight power divider with in-phase unequally tapered amplitude distribution is adopted to excite an eight-element array with SLL. The GCPW-SIW transition structure is also selected to achieve broadband impedance matching. Finally, both element and array antenna are optimized and fabricated for verification. For the antenna array, the measured -10 dB impedance bandwidth is from 25.1 to 31.3 GHz (22%) with a maximum gain of 14.6 dBi at 29.5 GHz and a 3dB gain bandwidth of 27.9%. And the measured SLL at 26, 28 and 30 GHz are all less than 20 dB. Index TermsMillimeter-wave (MMW), broadband, higher-order mode, low sidelobe level (SLL).

A 3-D Printed Waveguide-Based Linearly Polarized Magnetoelectric Dipole Antenna

This letter presents a waveguide-based linearly polarized magnetoelectric (ME) dipole antenna. The magnetic and electric dipoles are realized by a waveguide aperture and a pair of rectangular patches, respectively. The antenna employs a 3-D printing technique as the manufacturing method. Compared to the conventional ME dipole designs that operate in microwave band, the proposed antenna has a novel structure and exhibits simplified fabrication process. In order to realize the metallic walls of the waveguide structure, a two-step metal deposition technique (sputtering and electroplating) is used to coat the dielectric with copper. To validate the design idea, a prototype is designed and fabricated in X-band for demonstration. Through experiments, it is found that the proposed antenna can achieve a wide impedance bandwidth of 46.8 ${\%}$ from 7.2 to 11.6 GHz and a stable gain of 5.4 $\pm$ 1.2 dBi. While the antenna has stable patterns, low cross-polarization and backlobe radiation over the operating frequency band as well.

Vivaldi antennas: a historical review and current state of art

AbstractThe progressions in the field of wireless technology can be highly attributed to the development of antennas, which can access high data rates, provide significant gain and uniform radiation characteristics. One such antenna called the Vivaldi antenna has attracted the utmost attention of the researchers owing to its high gain, wide bandwidth, low cross-polarization, and stable radiation characteristics. Over the years, different procedures have been proposed by several researchers to improve the performance of the Vivaldi antennas. Some of these different approaches are feeding mechanisms, integration of slots, dielectric substrate selection, and radiator shape. Correspondingly, the performance of a Vivaldi antenna can be increased by including dielectric lens, parasitic patch in between two radiators, corrugations, as well as metamaterials. This paper gives a systematic identification, location, and analysis of a large number of performance enhancement methods of Vivaldi antenna design depicting their concepts, advantages, drawbacks, and applications. The principal emphasis of this article is to offer an outline of the developments in the design of Vivaldi antennas over the last few years, where the most important offerings, mostly from IEEE publications, have been emphasized. This review work aims to reveal a promising path to antenna researchers for its advancement using Vivaldi antennas.

High-Gain SIW Filtering Antenna With Low H-Plane Cross Polarization and Controllable Radiation Nulls

In this communication, a high-gain substrate-integrated waveguide (SIW) filtering patch antenna with low H-plane cross-polarization (cross-pol) and controllable radiation nulls is proposed. The antenna is composed of a radiation patch integrated with three pairs of shorting pins and a single layer SIW cavity with two transverse slots. The shorting pins loaded on the patch can improve the gain and reduce the H-plane cross-pol of the antenna. The long slot on the middle layer can not only split the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> -mode resonator into two half-mode resonators but also generate magnetic coupling between half-mode resonators and the patch. Another short slot achieves mixed electric and magnetic coupling between the left half-mode resonator and the patch that introducing controllable radiation nulls to improve the selectivity. By adjusting the parameters of the short slot, the positions of two radiation nulls can be easily controlled. Finally, one prototype filtering antenna is fabricated and measured for demonstration. Experimental results show that the proposed SIW filtering antenna achieves a high gain of 9 dBi with only one radiator and has the merit of high-frequency selectivity as well as low H-plane cross-pol of lower than -43 dB.

Design of a single-layer broadband reflectarray using circular microstrip patch loaded with two unequal slots

A linearly polarized single-layer single-resonator reflectarray, which is designed using a simple circular patch loaded with two unequal rectangular slots, is investigated for the first time. For the proposed design, the linearity and sensitivity of the phase curve (S-curve) can be easily optimized by adjusting the ratio of the two unequal slots changeable according to a simple design equation. Here, the patch radius serves as a phase-shifting geometrical parameter and it is able to achieve a wide phase range of more than 458° with low phase sensitivity and a low reflection loss of less than 0.5 dB. With the use of the optimized phase curve, an offset-fed 13 × 13 full-fledged reflectarray with a square aperture is designed, fabricated and measured. Measurement results show that a −1-dB gain bandwidth of 11.8% and an antenna gain of 23.4 dBi are realizable at the center frequency of 9.3 GHz. Also, the proposed reflectarray has an aperture efficiency of 42% and a radiation efficiency of 98%. The proposed reflectarray has a simple structure and it is able to achieve smooth phase curve, low cross-polarized radiation field and low sidelobes.

A High Gain Series-Fed Circularly Polarized Traveling-Wave Antenna at W-Band Using a New Butterfly Radiating Element

We propose a novel series-fed circularly polarized (CP) traveling-wave antenna known as the “Butterfly” antenna suitable for operation at the millimeter-wave frequencies. The Butterfly unit-cell consists of a sequentially rotated series-fed linear array of four microstrip patch antennas. The proposed CP Butterfly structure offers low cross-polarization radiation and wide axial ratio (AR) beamwidth. A periodic leaky-wave antenna (LWA) analysis provides insights into the radiation characteristics of the Butterfly series-fed linear array antenna, which is validated by the full-wave electromagnetic simulations. The open-stopband (OSB) is suppressed in the broadside direction due to the cancellation of the internal reflections within each cell of the sequential-phase fed linear array. The measured and the simulated AR, radiation patterns, and gain are presented for the broadside radiation of the parallel–series fed $8\,\,\times24$ and $32\times24$ planar array antenna at 86 GHz. The average measured 3 dB gain beamwidths are 9.5° and 2.9° along the $\phi = 0^{\circ }$ plane of the $8\,\,\times24$ and $32\times24$ planar array antenna, respectively.

A wideband folded magnetoelectric dipole antenna with miniaturized integration for 5G applications

A 3-layer substrate integrated folded magnetoelectric dipole antenna is presented in this paper. The folded metal vias are proposed to broaden bandwidth and miniaturized antenna. Furthermore, the double-arc-edged patch, the single-arc-edged metal plane, side wall and removing shorted end are designed to improve the impedance matching and reduce the operating frequencies. The structure and parameters of the antenna are analyzed, especially the bandwidth blending and the current paths. A prototype was fabricated and measured. The presented antenna obtains a wide impedance bandwidth of 34.2% for VSWR≤2 from 4.88 to 6.89 GHz and a stable gain ranging from 6.0 to 7.5 dBi. Moreover, nearly identical unidirectional radiation patterns, low cross-polarization and low back radiation are achieved. The parameter of d s even can realize a lower operating frequency. The presented antenna is suitable for mass production with low cost by the printed circuit board technology, and promising for 5th Generation (5G) applications.

Mutual Coupling Reduction of ±45° Dual-Polarized Closely Spaced MIMO Antenna by Topology Optimization

A hybrid topology optimization (HTO) method is adopted to reduce the mutual coupling of a ±45° dual-polarized closely spaced MIMO antenna. In order to shorten the optimization time, only the isolation structure region of the two-element MIMO antenna is selected for optimization. More importantly, by exploiting the symmetry of both the MIMO antenna and the isolation structure, only a quarter of the isolation structure needs to be optimized to achieve good antenna performance. In this way, not only the optimization variables, but also the optimization sub-objectives are greatly reduced, and the optimization time is further diminished. The performance of the dual-polarized MIMO antenna with the optimized isolation structure (OIS) is validated by both simulation and measurement. The OIS resonates in both polarizations, thus lowering the mutual coupling between co-polarization ports ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{31}\vert $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{42}\vert$ </tex-math></inline-formula> ) and between cross-polarization ports ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{41}\vert $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{32}\vert$ </tex-math></inline-formula> ) simultaneously. With the center distance of only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.35\lambda _{0}$ </tex-math></inline-formula> , the measured mutual coupling between different ports are reduced by 6~11 dB within the 10-dB impedance bandwidth (Reflection coefficients < −10 dB) by adding the OIS, and the highest mutual coupling between different ports is reduced from −15 to −21 dB. Besides, the antenna maintains a low profile ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.026\lambda _{0}$ </tex-math></inline-formula> ), low cross-polarization and excellent radiation pattern performance.

Design &amp; Analysis of Multiband Sierpenski Gasket Fractal Antenna using Iteration Method

Wireless communication systems require antennas of multiband support,small design dimensions and higher gain. To provide size reduction and better impedance matching, geometrical interpreted fractal antenna is suitable. This allows the antenna to operate at different frequencies. To rise performances with respect to bandwidth, gain and multiband resonance, an array can fulfil the requirements. This paper shows the design and simulation of the Sierpinski Gasket array for multiband applications (4GHz to 8GHz, 8GHz to 12GHz) up to 4th iteration. The fractal geometry for patch antenna is selected due to low cross polarization radiation and ease of fabrication. Sierpinski gasket is known by the name, Sierpinski triangle having triangular slots using mid-point geometry of the triangle. This array makes use of micro strip feed where FR4 epoxy is used as the dielectric substrate. A low profile dielectric is used to get the radiation in maximum amount. This antenna finds its uses in satellite communications and transmissions,Wi-Fi. The simulation is carried out by using High Frequency Structure Simulator HFSS V13 software for the proposed antenna.

Frequency Tunable Differentially Fed Inverted Microstrip Patch Antenna with Low Cross-Polarized Radiation

In this article tunable characteristic of differentially fed inverted microstrip patch antenna is presented for C-band operation. Differential feeding is applied through a unilayer integrated coupler feed. Near the operating frequency of the designed antenna the fabricated coupler shows that the amplitude imbalance is 0.3 dB and phase imbalance corresponds to 3.2°. Tuning is achieved by changing the air gap height in the antenna structure from 1 to 4 mm. Proposed concept of tunablity is verified for two different patch geometries (circular and rectangular) and three different patch dimensions through analysis and experiments. Closed form expressions are proposed to predict the tuning frequency. This design offers low cross-polarized radiation in the H-plane and symmetric co-polarized radiation in both principal planes. Fabricated prototype is measured and compared with simulated and theoretical values. The comparison among the simulated values, theoretically computed values and the measured values for different air gap heights of 2, 3, and 4 mm, shows an error less than 1%.

Waveguide-Based Differentially Fed Dual-Polarized Magnetoelectric Dipole Antennas

This paper proposes a concept of waveguide-based dual-polarized magnetoelectric (ME) dipole antenna. Based on this concept, two antenna designs with rectangular and triangular-shaped E-dipoles are studied and presented. The former is differentially fed by $four$ probes and the latter by a turnstile junction orthomode transducer feed. Using 3-D printing technique, the corresponding prototypes are fabricated for demonstration. Experimental results show that the rectangular-shaped E-dipole design has a wide impedance bandwidth of 55.1% from 7.5 to 13.2 GHz and a stable gain of 6 ± 1.5 dBi. On the other hand, the triangular-shaped E-dipole design can achieve 62.8% impedance bandwidth from 7 to 13.4 GHz and 5.15 ± 0.95 dBi gain over the operating frequencies. Furthermore, it is found that both antennas have low cross polarization and backlobe radiation, both characteristics of ME dipoles. Due to the waveguide configuration, the proposed antennas have good mechanical and electrical performances. They can be easily implemented and applied for various high power capacity applications. With these advantages, the proposed antennas are good candidates for the satellite and other wireless communication systems.

Substrate Integrated Magneto–Electric Dipole for UWB Application

In this letter, a new substrate integrated magneto–electric dipole (ME) antenna has been proposed for ultrawideband application. The proposed antenna is composed of a bowtie patch functioning as an electric dipole and a pair of circular vertical shorted vias that are equivalent to a magnetic dipole. A Γ-shaped probe feed is employed to excite the ME antenna, and some planar metal reflectors with shorted via holes are located at the corner of the antenna to improve matching and radiation pattern of the antenna. A prototype was fabricated and measured. The simulation and measurement results demonstrate an impedance bandwidth of 110% with SWR≤2 from 3.1–10.66 GHz and a stable gain of 8.4 ± 2.5 dBi. Good unidirectional radiation patterns with low back radiation and low cross-polarization radiation are achieved across the operating bandwidth. With the use of multilayer printed circuit board technology, the proposed ME antenna is low-cost and easy to fabricate.

A Differential-Fed UWB Antenna Element With Unidirectional Radiation

A new differential-fed broadband antenna element with unidirectional radiation is proposed. This antenna is composed of a folded bowtie, a center-fed loop, and a box-shaped reflector. A pair of differential feeds is developed to excite the antenna and provide an ultrawideband (UWB) impedance matching. The box-shaped reflector is used for the reduction of the gain fluctuation across the operating frequency band. An antenna prototype for UWB applications is fabricated and measured, exhibiting an impedance bandwidth of 132% with standing wave ratio ≤ 2 from 2.48 to 12.12 GHz, over which the gain varies between 7.2 and 14.1 dBi at boresight. The proposed antenna radiates unidirectionally with low cross polarization and low back radiation. Furthermore, the time-domain characteristic of the proposed antenna is evaluated. In addition, a $2 \times 2$ element array using the proposed element is also investigated in this communication.

Low Side-Lobe Substrate-Integrated-Waveguide Antenna Array Using Broadband Unequal Feeding Network for Millimeter-Wave Handset Device

A low side-lobe substrate-integrated-waveguide (SIW) antenna array is presented at the 28-GHz band using broadband unequal feeding network for millimeter-wave (mm-wave) handset devices. The ground-plane size of the proposed antenna is fixed to half of the size of the Samsung Galaxy Note 4. The antenna array has been implemented with a multilayer structure created by stacking three substrates and a copper plate. An 8-way SIW feeding network with broadband 4-stage T-junction dividers and a cavity-backed antenna are investigated to obtain broadband performance. The proposed unequal T-junction dividers with phase compensation are introduced and designed for various output ratios. Applying Taylor beam-pattern synthesis in the 8-way SIW feeding network, low side-lobe performance is achieved. The measured result of the fabricated antenna has 2.3 GHz bandwidth within $\text{S}_11\,{ . The fabricated antenna can be performed with a gain up to 13.97 dBi with a low cross-polarization and symmetrical fan beam radiation patterns with low side-lobe levels. Most of the measured results are validated with the simulated results. The proposed antenna array provides low cost, broadband performance, and good radiation performances with low side-lobe levels for mm-wave handset devices.

A New Dual Circularly Polarized Feed Employing a Dielectric Cylinder-Loaded Circular Waveguide Open End Fed by Crossed Dipoles

This paper presents a new dual circularly polarized feed that provides good axial ratio over wide angles and low cross-polarized radiation in backward direction. A circular waveguide open end is fed with two orthogonally polarized waves in phase quadrature by a pair of printed crossed dipoles and a compact connectorized quadrature hybrid coupler. The waveguide aperture is loaded with a dielectric cylinder to reduce the cross-polarization beyond 90 degrees off the boresight. The fabricated feed has, at 5.5 GHz, 6.33-dBic copolarized gain, 3-dB beamwidth of 106°, 10-dB beamwidth of 195°, 3-dB axial ratio beamwidth of 215°, maximum cross-polarized gain of −21.4 dBic, and 27-dB port isolation. The reflection coefficient of the feed is less than −10 dB at 4.99–6.09 GHz.

Wideband Magneto-Electric Dipole Antenna for 60-GHz Millimeter-Wave Communications

A new wideband magneto-electric dipole antenna is proposed for 60-GHz millimeter-wave applications. This antenna features wideband and stable gain characteristics. The low cross polarization and low back radiation are obtained owing to its complementary antenna structure. The prototype of the single element was built using the low-cost single-layer printed circuit board (PCB) technology. The proposed antenna exhibits an impedance bandwidth of 51% (SWR ≤ 2) and a gain of approximately 8 dBi.

Substrate Integrated Magneto-Electric Dipole Antenna for 5G Wi-Fi

In this communication, a new technique-tapered H-shaped ground, is proposed to reduce the thickness of a magneto-electric (ME) dipole antenna. By employing the proposed technique, the antenna height of the ME dipole antenna is reduced from 0.25 to 0.11 λ0 (where λ0 is the wavelength of 5.5 GHz). This new antenna structure can be easily realized by the multi-layer printed circuit board (PCB) technology, which is low cost and easy to fabricate. Measured results show that this antenna has an impedance bandwidth of 18.74% for VSWR ≤ 2 (4.98 to 6.01 GHz). Stable radiation patterns with low back radiation and low cross polarization radiation are achieved across the entire operating bandwidth for 5G Wi-Fi.