Showing papers on "Coaxial antenna published in 2016"

4G/5G Multiple Antennas for Future Multi-Mode Smartphone Applications

Abstract: A hybrid antenna is proposed for future 4G/5G multiple input multiple output (MIMO) applications. The proposed antenna is composed of two antenna modules, namely, 4G antenna module and 5G antenna module. The 4G antenna module is a two-antenna array capable of covering the GSM850/900/1800/1900, UMTS2100, and LTE2300/2500 operating bands, while the 5G antenna module is an eight-antenna array operating in the 3.5-GHz band capable of covering the $C$ -band (3400–3600 MHz), which could meet the demand of future 5G application. Compared with ideal uncorrelated antennas in an $8 \times 8$ MIMO system, the 5G antenna module has shown good ergodic channel capacity of $\sim 40$ b/s/Hz, which is only 6 b/s/Hz lower than ideal case. This multi-mode hybrid antenna is fabricated, and typically, experimental results such as S-parameter, antenna efficiency, radiation pattern, and envelope correlation coefficient are presented.

Wideband RCS Reduction of a Slot Array Antenna Using Polarization Conversion Metasurfaces

Abstract: A new approach to reducing the monostatic radar cross section (RCS) and preserving the radiation characteristics of a slot array antenna by employing polarization conversion metasurfaces (PCMs) is presented in this communication. The PCM is arranged in a chessboard configuration consisting of fishbone-shaped element. It is placed on the surface of the slot array antenna. The characteristics and mechanism of the RCS reduction are analyzed. Simulated and experimental results show that the monostatic RCS reduction band of the antenna with PCM ranges between 6.0 and 18.0 GHz for normally impinging both $x$ - and $y$ -polarized waves. The radiation characteristics of the antenna are well preserved simultaneously in terms of the impedance bandwidth, radiation patterns, and realized boresight gains.

A 60-GHz Wideband Circularly Polarized Aperture-Coupled Magneto-Electric Dipole Antenna Array

Abstract: A novel circularly polarized (CP) aperture-coupled magneto-electric (ME) dipole antenna is proposed. The CP ME-dipole antenna fed by a transverse slot etched on the broad wall of a section of shorted-end substrate integrated waveguide (SIW) is convenient to integrate into substrates. An impedance bandwidth of wider than 28.8%, a wide 3-dB axial ratio (AR) bandwidth of 25.9%, and gain of $7.7 \pm 1.4\,{\text{dBic}}$ over the operating band are achieved. Additionally, since the CP radiation is generated by the combination of two orthogonal ME-dipole modes, the antenna element has stable unidirectional radiation patterns that are almost identical in two principle planes throughout the operating band, which is desirable to array applications. By employing the proposed CP ME-dipole as radiating elements, an $8 \times 8$ high-gain wideband planar antenna array is proposed for 60-GHz millimeter-wave applications. A fabrication procedure of using conductive adhesive films to bond all print circuit board (PCB) layers together is successfully implemented to realize the array design with a three-layered geometry, which has advantages of low costs and possibility of large-scale manufacture. The measured impedance bandwidth of the fabricated prototype is 18.2% for $\vert{\rm S}_{11}\vert . Because of the wide AR bandwidth of the new antenna element, a wide AR bandwidth of 16.5% can be achieved by this array without the use of sequential feed. Gain up to 26.1 dBic and good radiation efficiency of around 70% are also obtained due to the use of a full-corporate SIW feed network with low insertion loss at millimeter-wave frequencies.

A Multibeam End-Fire Magnetoelectric Dipole Antenna Array for Millimeter-Wave Applications

Abstract: A novel substrate integrated waveguide (SIW)-fed end-fire magnetoelectric (ME) dipole antenna is proposed. The antenna consisting of an open-ended SIW and a pair of electric dipoles has a simple structure that can be integrated into substrates conveniently. Both the open-ended SIW and the electric dipoles are effectively radiated together. Excellent performance, including a bandwidth of 44%, symmetrical radiation patterns that are almost identical in two orthogonal planes, low backward radiation, low cross polarizations, stable gain of around 5 dBi, and wide beamwidth of around 110°, are also obtained. An $8 \times 8$ SIW Butler matrix is then designed. Modifications to the geometry of the matrix provide more spacing to locate SIW phase shifters and phase compensation structures with wide bandwidth. By employing the proposed end-fire ME-dipole antenna array and the $8 \times 8$ Butler matrix, an eight-beam antenna array is realized. The fabricated prototype demonstrates that wide bandwidth, stable radiation patterns with cross polarizations of less than −28 dB and gain varying from 9 to 12 dBi can be obtained. The proposed multibeam end-fire ME-dipole antenna array would be an attractive candidate for millimeter-wave wireless applications due to its good performance, ease of integration, and low fabrication cost.

Radiation Pattern-Reconfigurable Wearable Antenna Based on Metamaterial Structure

Abstract: A pattern-reconfigurable wearable antenna is designed based on a metamaterial structure. By reconfiguring the dispersion curve of the transmission line, the patch antenna can resonate at the zeroth-order mode or the +1 mode, yielding a broadside or an omnidirectional radiation pattern, respectively. The antenna is fabricated with textile material targeting wearable applications. The impedance bandwidth covers the 2.4 GHz Industrial, Scientific, and Medical (ISM) band in both operating states. The antenna is also simulated on a human tissue model, illustrating that the specific absorption rate is well below the European standard threshold. The bending configurations are also discussed for the proposed antenna.

60-GHz Dual-Polarized Two-Dimensional Switch-Beam Wideband Antenna Array of Aperture-Coupled Magneto-Electric Dipoles

Abstract: A dual-polarized aperture-coupled magneto-electric (ME) dipole antenna is proposed. Two separate substrate-integrated waveguides (SIWs) implemented in two printed circuit board (PCB) laminates are used to feed the antenna. The simulated $- {10}$ -dB impedance bandwidth of the antenna is 21% together with an isolation of over 45 dB between the two input ports. Good radiation characteristics, including almost identical unidirectional radiation patterns in two orthogonal planes, front-to-back ratio larger than 20 dB, cross-polarization levels less than $- {23}\;{\text{dB}}$ , and a stable gain around 8 dBi over the operating band, are achieved. By employing the proposed radiating element, a ${2} \times {2}$ wideband antenna array working at the 60-GHz band is designed, fabricated, and tested, which can generate two-dimensional (2-D) multiple beams with dual polarization. A measured $- {10}\;\text{dB}$ impedance bandwidth wider than 22% and a gain up to 12.5 dBi are obtained. Owing to the superiority of the ME dipole, the radiation pattern of the array is also stable over the operating frequencies and nearly identical in two orthogonal planes for both of the polarizations. With advantages of desirable performance, convenience of fabrication and integration, and low cost, the proposed antenna and array are attractive for millimeter-wave wireless communication systems.

Compact Dual-Polarized UWB Quasi-Self-Complementary MIMO/Diversity Antenna With Band-Rejection Capability

Abstract: A novel compact ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna system with dual polarization and band-rejection capabilities is proposed. The proposed MIMO antenna system consists of two quasi-self-complementary (QSC) antenna elements. The elements are arranged orthogonally and fed perpendicularly to obtain polarization diversity. High isolation can be achieved without additional decoupling structure owing to the inherent advantage of the self-complementary structure. Notched band at WLAN system can be realized by etching a bent slit in each of the radiating elements. Moreover, a four-element MIMO system is also proposed and investigated to fully reveal its potential use. Diversity performance in terms of envelope correlation coefficient (ECC) and the mean effective gain (MEG) ratio are studied. Measured results show that the proposed antenna has a wide bandwidth ranging from 3 to 12 GHz with band rejection at WLAN system and high port isolation (S 12 ≤ -20 dB at most of the band), which demonstrate the proposed MIMO/diversity antenna system can be a good candidate for UWB applications.

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

Abstract: 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.

Design and Fabrication of a High-Gain 60-GHz Corrugated Slot Antenna Array With Ridge Gap Waveguide Distribution Layer

Abstract: A wideband high-gain high-efficiency $16 \times 16$ -element slot antenna array is presented for 60-GHz band applications. The antenna is designed based on gap waveguide technology. The most important advantage of using this technology is its ability to decrease complexity and cost of fabrication because there is no requirement of electrical contact between the three layers of the antenna structure. The three layers are a corrugated metal plate with radiating slots, a subarray cavity layer, and a ridge gap waveguide (RGW) feed network layer. The corporate feed network is realized by a texture of pins and guiding ridges in a metal plate. Also, in order to excite the antenna with a standard V-band rectangular waveguide, a transition from RGW to WR-15 is designed. The radiating elements, corrugations, cavity layer, power dividers, and transition are designed and optimized to suppress the reflection coefficient at the input WR-15 port over the desired frequency range from 57 to 66 GHz. Finally, the $16 \times 16$ -element slot antenna array is fabricated by the standard milling technology. The measured results demonstrate about 16% of reflection coefficient bandwidth ( $\vert S_{11}\vert dB) covering the 56–65.7-GHz frequency range, and the measured gain is larger than 32.5 dBi over the band with more than 70% antenna efficiency.

Metasurface Superstrate Antenna With Wideband Circular Polarization for Satellite Communication Application

Abstract: A new wideband circularly polarized antenna using metasurface superstrate for C-band satellite communication application is proposed in this letter. The proposed antenna consists of a planar slot coupling antenna with an array of metallic rectangular patches that can be viewed as a polarization-dependent metasurface superstrate. The metasurface is utilized to adjust axial ratio (AR) for wideband circular polarization. Furthermore, the proposed antenna has a compact structure with a low profile of 0.07λ 0 ( λ 0 stands for the free-space wavelength at 5.25 GHz) and ground size of 34.5×28 mm 2 . Measured results show that the -10-dB impedance bandwidth for the proposed antenna is 33.7% from 4.2 to 5.9 GHz, and 3-dB AR bandwidth is 16.5% from 4.9 to 5.9 GHz with an average gain of 5.8 dBi. The simulated and measured results are in good agreement to verify the good performance of the proposed antenna.

Stacked Patch Antenna With Dual-Polarization and Low Mutual Coupling for Massive MIMO

Abstract: Massive multiple input and multiple output (MIMO) has attracted significant interests in both academia and industry. It has been considered as one of most promising technologies for 5G wireless systems. The large-scale antenna array for base stations naturally becomes the key to deploy the Massive MIMO technologies. In this communication, we present a dual-polarized antenna array with 144 ports for Massive MIMO operating at 3.7 GHz. The proposed array consists of 18 low profile subarrays. Each subarray consists of four single units. Each single antenna unit consists of one vertically polarized port and one horizontally polarized port connected to power splitters, which serve as a feeding network. A stacked patch design is used to construct the single unit with the feeding network, which gives higher gain and lower mutual coupling within the size of a conversional dual-port patch antenna. Simulation results of the proposed single antenna unit, sub-array, and Massive MIMO array are verified by measurement.

Compact Multimode Multielement Antenna for Indoor UWB Massive MIMO

Abstract: In this paper, we present a concept for a compact ultra-wideband multielement antenna (MEA) for massive MIMO indoor base stations. The antenna concept is based on the simultaneous excitation of different characteristic modes on each element of the MEA. This enables an effective 484 port antenna using only 121 physical antenna elements. Thereby, a size reduction of 54% compared to a generic MEA based on crossed dipoles is achieved. The antenna operates in the ultra-wide frequency band of 6–8.5 GHz with a reflection coefficient of $\text{s}_{\text{ii}} and the interelement and intraelement mutual coupling of the antenna ports is $\text{s}_{\text{ji}} \le -\text{20 dB}$ .

Bandwidth Enhancement of a Single-Feed Circularly Polarized Antenna Using a Metasurface: Metamaterial-based wideband CP rectangular microstrip antenna.

Abstract: Wireless systems manufacturers desire a low-profile, wideband, circularly polarized (CP) antenna. Generally, a single-feed CP microstrip antenna (CPMA) has a simple configuration but is hindered by a narrow, 3-dB axial ratio (AR) bandwidth. The bandwidth of a multiple-feed CPMA can be enhanced but requires a complicated and larger feeding network. Many techniques have been employed to improve AR bandwidth, such as using dual-feed, network-based structures [1], stacked patches [2]?[3], array antennas with sequential feeding network [4], and multilayered structures [5]. However, these CP antennas are based on multiradiating patches or complicated feeding structures.

Graphene Nanoflakes Printed Flexible Meandered-Line Dipole Antenna on Paper Substrate for Low-Cost RFID and Sensing Applications

Abstract: In this letter, a graphene nanoflakes printed antenna is presented Graphene nanoflakes conductive ink has been screen-printed on paper substrate and compressed to achieve the conductivity of $\text{043} \times {\text{10}^{\text{5}}} \hbox{\,S/m}$ Low-profile meandered-line dipole antenna has been fabricated as a proof of concept due to its electrically small size and simple structure The maximum gain is measured to be ${-}\hbox{4 dBi}$ , the ${-} \hbox{10-dB}$ bandwidth ranges from 984 to 1052 MHz (667%), and the radiation pattern is verified as being typical radiation patterns of a dipole-type antenna The radiation efficiency is 32% The measurement results reveal that graphene nanoflakes printed antenna can provide practically acceptable return loss, gain, bandwidth, and radiation patterns for mid- and short-range RFID, and sensing applications Furthermore, screen-printing technique employed in this work is of extremely low cost and capable of producing antennas in mass production

Bending and On-Arm Effects on a Wearable Antenna for 2.45 GHz Body Area Network

Abstract: Three types of flexible textile antennas for 2.45 GHz body area network (BAN) are compared in this letter. Two types of conducting materials are used to form radiation patch and ground plane; they are called copper foil tape (CFT, 0.05 mm thickness) and Shieldex (SH, 0.13 mm thickness, 0.009 Ohm surface resistivity). The substrate is a thin felt with relative permittivity of 1.2 and the thickness of 2 mm. In order to satisfy these requirements of small frequency shifting when the antenna is bent and placed on human body, two shorting probes are used to connect the radiation patch and ground plane. Compared to the antenna without shorting probes, the size of proposed antenna is reduced from 96 ×47 to 70 ×25 mm 2 , and the measured minimum value of S11 in free space is also decreased from -14.59 to -33.30 dB. Furthermore, an antenna with smaller size of 46 ×25 mm 2 is designed by modifying the proposed structure, and it can act as a wearable antenna as well.

A Novel Simple and Compact Microstrip-Fed Circularly Polarized Wide Slot Antenna With Wide Axial Ratio Bandwidth for C-Band Applications

Abstract: This communication presents a design of a new compact circularly polarized (CP) slot antenna fed by a microstrip feedline. The 3-dB axial ratio band can be achieved by simply protruding a horizontal stub from the ground plane toward the center of the wide slot (WS) and then feeding the WS with a microstrip feedline positioned to the side of the WS, underneath the protruded stub. The feedline and metallic stub are perpendicular to each other, and they resemble a T shape when viewed from the top. The proposed antenna is fabricated with an area of $25 \times 25\;{\rm mm}^{2}$ . Measurement results show that the antenna attains an ${\rm S}_{11}\le-10\;{\rm dB}$ impedance matching bandwidth of 90.2%, from 3.5 to 9.25 GHz, and a broadband 3 dB-AR bandwidth of 40%, ranging from 4.6 to 6.9 GHz. A peak gain of 0.8–4.5 dBi is achieved within the AR band. The proposed antenna is suitable for circular polarization applications in C band.

Compact MIMO Slot Antenna for UWB Applications

Abstract: A compact four-element multiple-input–multiple-output (MIMO) antenna for portable wireless ultrawideband (UWB) applications is presented in this letter. The proposed UWB MIMO antenna has the compact size of $ 42 \times 25 ~\hbox{mm}^2$ . The microstrip-fed stepped-slot antenna acts as a single UWB antenna element. The UWB antenna covers the wide frequency band from 3.1 to 12 GHz. High isolation ( $ \geq 22~\hbox{dB}$ ) is achieved between the UWB antenna elements without any decoupling network. It is due to inherent directional radiation properties of slot antennas (SAs) and their asymmetrical placements. The measured impedance bandwidth of UWB MIMO antenna is from 3.2 to 12 GHz with the isolation better than 22 dB over the entire UWB spectrum. The envelope correlation coefficient (ECC) as well as channel capacity loss (CCL) are investigated, and they are within their acceptable limits.

Broadband Bent Triangular Omnidirectional Antenna for RF Energy Harvesting

Abstract: In this letter, a broadband bent triangular omnidirectional antenna is presented for RF energy harvesting. The antenna has a bandwidth for ${\hbox {VSWR}}\leq2$ from 850 MHz to 1.94 GHz. The antenna is designed to receive both horizontal and vertical polarized waves and has a stable radiation pattern over the entire bandwidth. Antenna has also been optimized for energy harvesting application and it is designed for $100~\Omega $ input impedance to provide a passive voltage amplification and impedance matching to the rectifier. A peak efficiency of 60% and 17% is obtained for a load of $500~\Omega $ at 980 and 1800 MHz, respectively. At a cell site while harvesting all bands simultaneously a voltage of 3.76 V for open circuit and 1.38 V across a load of $4.3~\hbox{k} \Omega $ is obtained at a distance of 25 m using an array of two elements of the rectenna.

Closely packed millimeter-wave MIMO antenna arrays with dielectric resonator elements

Abstract: The design of a millimeter-wave (mm-wave) dielectric resonator (DR) multiple-input-multiple-output (MIMO) antenna system is presented. The MIMO structure consists of four arrays each radiating in one of four opposite directions. Each array is composed of four cylindrical DR antenna elements (cDRAs) operating at 30 GHz with a fractional bandwidth of at least 6.7%. The elements are fed via slot coupling which isolates the radiating elements from the feeding network. Also, each array in the MIMO system has a fixed and tilted beam enabling good MIMO operation which results from a passive microstrip-based feed network. The four arrays are closely packed in two pairs with each pair occupying only 20 × 10 × 3.1 mm3 on the top layer of the PCB. The proposed antenna can be used for compact mobiles that support 5G data links.

Wearable AMC Backed Near-Endfire Antenna for On-Body Communications on Latex Substrate

Abstract: A near-endfire, artificial magnetic conductor (AMC) backed wearable antenna is proposed in this paper for wireless body area networks operating in the 2.4-GHz industrial, scientfic and medical (ISM) radio band. The latex substrate permittivity has accurately been characterized for realizing a flexible planar Yagi-Uda antenna printed on it using a large-area screen-printing process. The bidirectional-endfire radiation of Yagi-Uda antenna is changed to an off-axis near-endfire radiation using an AMC reflector also printed on latex. The antenna is separated from the upper AMC surface using flexible Styrofoam of thickness $0.044\lambda _{o}$ at 2.4 GHz for the best compromise between keeping the antenna structure low profile and achieving an off-axis beam-tilt radiation of $\sim 74^{\circ }$ toward the endfire direction. The 0° reflection phase single-layered AMC and double-layered AMC (D-AMC) surfaces are proposed to reduce the body-absorbed radiation and, consequently, minimize the peak specific absorption rate (SAR) level for 2.4-GHz frequency band. Antenna performance in terms of return loss, radiation efficiency, extent of frequency detuning, gain, and SAR level is studied for free space as well as the CST MWS tissue-equivalent voxel model for all the proposed antenna designs. Antenna deformation bending study when placed on the human body is also performed in this paper. The antenna design is first optimized and fabricated on printed circuit board to verify the concept and then designed over the latex for actual human on-body all-flexible configuration. The Yagi-Uda antenna backed with D-AMC reflector demonstrates the measured return loss bandwidth of 45 MHz (2.425–2.47 GHz) and the gain of 0.12 dBi in the endfire direction with an improved on-body (chest) radiation efficiency of 78.97% and a reduced peak SAR level of 0.714 W/kg (average over 10-g tissue) for the compact overall flexible latex antenna volume of $0.4\lambda _{o} \times 0.4\lambda _{o} \times 0.076\lambda _{o}$ at 2.4 GHz. To the best of our knowledge, this is the first latex-based endfire antenna for on-body 2.4-GHz wireless communications backed with an AMC periodic metamaterial surface.

A Compact High-Gain and Front-to-Back Ratio Elliptically Tapered Antipodal Vivaldi Antenna With Trapezoid-Shaped Dielectric Lens

Abstract: A modified compact antipodal Vivaldi antenna is proposed with good performance for different applications including microwave and millimeter wave imaging. A step-by-step procedure is applied in this design including conventional antipodal Vivaldi antenna (AVA), AVA with a periodic slit edge, and AVA with a trapezoid-shaped dielectric lens to feature performances including wide bandwidth, small size, high gain, front-to-back ratio and directivity, modification on E-plane beam tilt, and small sidelobe levels. By adding periodic slit edge at the outer brim of the antenna radiators, lower-end limitation of the conventional AVA extended twice without changing the overall dimensions of the antenna. The optimized antenna is fabricated and tested, and the results show that S 11 <; -10 dB frequency band is from 3.4 to 40 GHz, and it is in good agreement with simulation one. Gain of the antenna has been elevated by the periodic slit edge and the trapezoid dielectric lens at lower frequencies up to 8 dB and at higher frequencies up to 15 dB, respectively. The E-plane beam tilts and sidelobe levels are reduced by the lens.

Three dimensional (3d) antenna structure

Abstract: An apparatus includes a substrate package and a three dimensional (3D) antenna structure formed in the substrate package. The 3D antenna structure includes multiple substructures to enable the 3D antenna structure to operate as a beam-forming antenna. Each of the multiple substructures has a slanted-plate configuration or a slanted-loop configuration.

A Compact Quad Element Slotted Ground Wideband Antenna for MIMO Applications

Abstract: A compact planar quad element wideband antenna for multiple-input-multiple-output (MIMO) system is proposed in this communication. A single element consists of a partially grounded printed monopole antenna loaded with a split ring resonator. The bandwidth of the antenna is from 2.2 to 6.28 GHz (96.2%), which covers LTE (2.2–3.8 GHz), Bluetooth (2.4 GHz), WLAN (2.4 and 5.1–5.8 GHz), WiMAX (2.3–5.7 GHz), and ISM bands (2.4/5.2/5.8 GHz). The fabricated antenna has an isolation greater than 14 dB between its elements, with a peak gain of 4 dBi and a peak efficiency of 91%. Polarization diversity is employed to accommodate four elements in an FR4 substrate, with an overall dimension of $0.33\lambda \times 0.33\lambda \times 0.01\lambda $ . The antenna has a simple planar design which is easy to fabricate with no intricate process involved.

S-shaped periodic defected ground structures to reduce microstrip antenna array mutual coupling

Abstract: A novel S-shaped periodic defected ground structure (PDGS) is proposed to reduce mutual coupling between antenna elements. Coplanar placed antenna elements work at the same frequency band with centre frequency 2.57 GHz. Centre-to-centre distance between the antenna elements is 50 mm which is ~0.43λ. The PDGS is three S-shaped defected ground structure units placed between microstrip antenna elements. By using the proposed PDGS, more than 40 dB mutual coupling reduction between microstrip antenna elements is achieved.

A Broadband Dual Circularly Polarized Square Slot Antenna

Abstract: A novel coplanar waveguide-fed broadband dual circularly polarized square slot antenna is presented. The antenna consists of a square slot, two asymmetric T-shaped feed lines in orthogonal direction protrude from signal lines, and an inverted-L grounded strip with three straight strips at the corner of the slot adjacent to both the feed lines. The circular polarization is obtained due to orthogonal feed lines. Axial ratio (AR) bandwidth is significantly enhanced because of inverted-L grounded strip with attached three straight strips. The 3-dB AR bandwidth of the antenna is about 60% in which return loss, and isolation are better than 10 and 15 dB, respectively.

Design of a Low-Profile Dual-Polarized Stepped Slot Antenna Array for Base Station

Abstract: In this letter, a microstrip-fed dual-polarized stepped-impedance (SI) slot antenna element with a low profile is first proposed. The antenna is composed of two pairs of SI slots excited by two orthogonal stepped microstrip feedlines. The broadband characteristic is achieved by combining the fundamental and spurious resonances of the SI slot resonators, while the good cross polarization is mainly due to the introduction of the shorting pins. Secondly, based on the proposed antenna, a four-element antenna array is designed, constructed, and measured for base-station applications. Measured results demonstrate the bandwidths (return loss ) of the antenna array are 46.9% (1.55-2.5 GHz) and 38.7% (1.69-2.5 GHz) for Port 1 and Port 2, respectively. The isolation between the two ports is greater than 35 dB, whereas the cross-polarization level maintains lower than -27 dB across the entire operating band. In addition, the antenna array prototype achieves average gains of 13.5 and 13.9 dBi for horizontal polarization and vertical polarization, respectively.

Conformal Array Antenna Theory And Design

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Compact-Size Low-Profile Wideband Circularly Polarized Omnidirectional Patch Antenna With Reconfigurable Polarizations

Abstract: A compact-size low-profile wideband circularly polarized (CP) omnidirectional antenna with reconfigurable polarizations is presented in this communication. This design is based on a low-profile omnidirectional CP antenna which consists of a vertically polarized microstrip patch antenna working in $\text{TM}_{01}/\text{TM}_{02}$ modes and sequentially bended slots etched on the ground plane for radiating horizontally polarized electric field. The combined radiation from both the microstrip patch and the slots leads to a CP omnidirectional radiation pattern. The polarization reconfigurability is realized by introducing PIN diodes on the slots. By electronically controlling the states of the PIN diodes, the effective orientation of the slots on ground plane can be changed dynamically and the polarization of antenna can be altered between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). The proposed antenna exhibits a wide-operational bandwidth of 19.8% (2.09–2.55 GHz) with both axial ratio below 3 dB and return loss above 10 dB when radiates either LHCP or RHCP waves. Experimental results show good agreement with the simulation results. The present design has a compact size, a thickness of only $0.024\lambda$ and exhibits stable CP omnidirectional conical-beam radiation patterns within the entire operating frequency band with good circular polarization.

Polarization conversion of metasurface for the application of wide band low-profile circular polarization slot antenna

Abstract: In this letter, based on a corner-cut square metasurface, a planar polarization conversion structure is presented and the application for wide band low-profile circular polarization (CP) slot antenna is proposed. The mechanisms for achieving the CP state from a linearly polarized incident wave and for broadening the working bandwidth of conventional slot antenna are analyzed theoretically. The wide band low-profile CP slot antenna is achieved with numerical optimizations and parameter studies. Both simulations and measurements are performed to demonstrate the proposed antenna, and good agreements are obtained. Such results will open the path for polarization conversion metasurfaces used in the CP antenna area.