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Showing papers in "IEEE Antennas and Wireless Propagation Letters in 2019"


Journal ArticleDOI
TL;DR: In this paper, an antenna element that has not only the self-isolated property but also a compact size is proposed for the fifth-generation MIMO system in mobile phone applications.
Abstract: An antenna element that has not only the self-isolated property but also a compact size is proposed for the fifth-generation multiple-input and multiple-output (MIMO) system in mobile phone applications. In particular, the size reduction is done by introducing two vertical stubs into the original self-isolated antenna element. It is demonstrated that very good isolation and antenna efficiency for an 8-antenna MIMO system can be obtained without using any additional isolation elements or decoupling techniques. An antenna prototype is fabricated and measured; and a quite good agreement between simulation and measurement is obtained.

205 citations


Journal ArticleDOI
Yin Zhang1, Jing-Ya Deng1, Ming-Jie Li1, Dongquan Sun1, Lixin Guo1 
TL;DR: In this paper, a multiple-input-multiple-output (MIMO) dielectric resonator antenna with enhanced isolation is proposed for future 5G millimeter (mm)-wave applications.
Abstract: A multiple-input–multiple-output dielectric resonator antenna with enhanced isolation is proposed in this letter for the future 5G millimeter (mm)-wave applications. Two rectangular dielectric resonators (DRs) are mounted on a substrate excited by rectangular microstrip-fed slots underneath DRs. Each DR has a metal strip printed on its upper surface moving the strongest part of the coupling field away from the exciting slot to improve the isolation between two antenna elements. The proposed antenna obtains a simulated impedance bandwidth ( S 11 ≤ –10 dB) from 27.25 to 28.59 GHz, which covers the 28 GHz band (27.5–28.35 GHz) allocated by the Federal Communications Commission for the 5G applications. A maximum improvement of 12 dB on the isolation over 27.5–28.35 GHz is achieved. The mechanism of the isolation improvement and the design procedure are given in this letter. A prototype is manufactured and measured as a validation of the proposed decoupling method.

197 citations


Journal ArticleDOI
TL;DR: In this article, a low-profile wearable antenna is presented for on-body wireless body area network (WBAN) applications, which combines the Koch fractal geometry, meandering slits, and defected ground structure to achieve a novel hybrid structure with compact footprint, good structural conformability, and enhanced impedance bandwidth.
Abstract: A compact and low-profile wearable antenna is presented for on-body wireless body area network (WBAN) applications. The proposed triangular patch antenna is designed using low-cost widely available vinyl polymer-based flexible substrate. The final antenna topology is obtained by the combination of the Koch fractal geometry, meandering slits, and defected ground structure, to achieve a novel hybrid structure with compact footprint, good structural conformability, and enhanced impedance bandwidth (BW) to operate in the Industrial, Scientific, and Medical band with center frequency at 2.45 GHz. The fabricated prototype of the antenna has shown a good agreement between numerical and experimental results. In comparison to state-of-the-art prototypes, our design has more compact form factor of 0.318λo × 0.318λo × 0.004λo, along with 7.75% impedance BW, a peak gain of 2.06 dBi, and overall radiated efficiency of 75%. For the assessment of a specific absorption rate (SAR) performance of our design, it is tested on realistic heterogeneous HUGO voxel model. Both numerical and experimental investigations revealed extremely good robustness to both human body loading and structural deformation, making it an ideal candidate for flexible and body-worn devices.

179 citations


Journal ArticleDOI
TL;DR: In this paper, a compact self-decoupled antenna structure is proposed for the fifth-generation MIMO operation in mobile terminals, which consists of two adjacent antenna elements, which are placed very close (1.2 mm or 0.014λ) to each other and located on the same side of the system ground plane.
Abstract: In this letter, a compact self-decoupled antenna structure is proposed for the fifth-generation multiple-input--multiple-output (MIMO) operation in mobile terminals. The antenna structure consists of two adjacent antenna elements, which are placed very close (1.2 mm or 0.014λ) to each other and located on the same side of the system ground plane. By sharing one common grounding branch for the two adjacent antenna elements, a compact self-decoupled antenna pair can be obtained. The MIMO antenna system is optimized to operate in the 3.5 GHz (3.4–3.6 GHz) band with isolation better than –17 dB. An antenna prototype is fabricated, and good agreement between simulation and measurement is obtained.

158 citations


Journal ArticleDOI
TL;DR: A review of the most recent advances in deep learning as applied to electromagnetics, antennas, and propagation is provided, aimed at giving the interested readers and practitioners in EM and related applicative fields some useful insights on the effectiveness and potentialities of DNNs as computational tools with unprecedented computational efficiency.
Abstract: A review of the most recent advances in deep learning (DL) as applied to electromagnetics (EM), antennas, and propagation is provided. It is aimed at giving the interested readers and practitioners in EM and related applicative fields some useful insights on the effectiveness and potentialities of deep neural networks (DNNs) as computational tools with unprecedented computational efficiency. The range of considered applications includes forward/inverse scattering, direction-of-arrival estimation, radar and remote sensing, and multi-input/multi-output systems. Appealing DNN-based solutions concerned with localization, human behavior monitoring, and EM compatibility are reported as well. Some final remarks are drawn along with the indications on future trends according to the authors’ viewpoint.

149 citations


Journal ArticleDOI
Jiaqi Han1, Long Li1, Guangyao Liu1, Zhao Wu2, Yan Shi1 
TL;DR: In this paper, a 1-bit 12 × 12 reconfigurable beam-scanning reflectarray is designed, fabricated, and measured, and a control board that can display phase shift distributions in real time is designed to regulate all PIN diodes.
Abstract: In this letter, a wideband 1 bit 12 × 12 reconfigurable beam-scanning reflectarray is designed, fabricated, and measured. The 1 bit reconfigurable element is realized by soldering PIN diode into a slotted metallic square patch. To enhance the bandwidth of 1 bit reconfigurable reflectarray, we choose the central frequency at 5.0 GHz whose phase shift is 200° where the maximum phase shift occurs. Phase difference within 180° ± 20° is realized from 4.7 to 5.3 GHz. Utilizing this wideband element, the 12 × 12 reconfigurable reflectarray antenna is fabricated and measured. A control board that can display phase shift distributions in real time is designed to regulate all PIN diodes independently. Experimental results show that beam scanning within ±50° can be achieved both in xoz and yoz plane at 5.0 GHz. Also, the measured results present that −1 dB gain bandwidth is 8.4% from 4.85 to 5.275 GHz.

116 citations


Journal ArticleDOI
TL;DR: In this paper, a reconfigurable rasorber based on switching activity of frequency selective surface (FSS) and resistive FSS was designed for radar cross section reduction applications.
Abstract: In this letter, a reconfigurable rasorber has been designed based on switching activity of frequency selective surface (FSS) and resistive FSS. The proposed design consists of two periodic layers separated from each other by an air spacer. The upper layer comprising lumped resistors assists wide absorption band (above 90% absorption) from 3.8 to 10.3 GHz (entire C and partial X Band), whereas PIN diodes are mounted in the bottom layer to enable the switching operation of the rasorber at S-Band. The novelty of the proposed design lies in its reconfigurable transmission/reflection band, which switches from a bandpass response (at around 2.88 GHz) to perfect reflection, with the control of the biasing states of the diode. A sample prototype is also fabricated and experimentally verified. Wide absorption band along with switchable transmission/reflection band characteristics have made the proposed rasorber an excellent choice for various radar cross section reduction applications.

111 citations


Journal ArticleDOI
Guoping Gao1, Chen Yang1, Bin Hu1, Rui-Feng Zhang1, Shaofei Wang1 
TL;DR: In this letter, a wearable all-textile metasurface antenna for 5 GHz wireless body area network (WBAN) applications is proposed and on-body studies show that the MSA is suitable for wearable applications.
Abstract: In this letter, a wearable all-textile metasurface antenna (MSA) for 5 GHz wireless body area network (WBAN) applications is proposed. All the components of the proposed MSA are made of the comfort textile materials. A metasurface with high permittivity values is placed right above a wide-bandwidth planar inverted-F antenna to realize size miniaturization and gain enhancement. The proposed MSA has a profile of 4 mm (0.07 λ 0) and occupies an area of 42 mm × 28 mm (0.77 λ 0 × 0.51 λ 0). Moreover, this antenna realizes a measured peak gain of 6.70 dBi, an average efficiency of 77%, and an operating band from 4.96 to 5.90 GHz that covers the 5 GHz WBAN band. In addition, the on-body studies show that the MSA is suitable for wearable applications.

111 citations


Journal ArticleDOI
TL;DR: In this article, an ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna using a novel fence-type decoupling structure, which has high isolation in the UWB, is presented.
Abstract: In this letter, an ultrawideband (UWB) multiple-input–multiple-output (MIMO) antenna using a novel fence-type decoupling structure, which has high isolation in the UWB, is presented. The MIMO design consists of two half-cutting UWB antenna units that have good low-frequency impedance-matching performance because of the use of a rectangular slot on the radiation patch. Meanwhile, the isolation in the operating band is enhanced by introducing the fence-type decoupling structure at the ground of the antenna. Furthermore, the L-shaped parasitic branches are designed to heighten the impedance bandwidth and isolation in the low-frequency band, i.e., 3–3.4 GHz. The simulation and experiments show that the antenna has low mutual coupling ( S 21 < –25 dB) and a low envelope correlation coefficient (ECC < 0.004) in the UWB.

100 citations


Journal ArticleDOI
TL;DR: A new two-step machine learning based approach is proposed to solve the electromagnetic inverse scattering (EMIS) problems, which serves a new path for realizing real-time quantitative microwave imaging for high-contrast objects.
Abstract: In this letter, a new deep learning (DL) approach is proposed to solve the electromagnetic inverse scattering (EMIS) problems. The conventional methods for solving inverse problems face various challenges including strong ill-conditions, high contrast, expensive computation cost, and unavoidable intrinsic nonlinearity. To overcome these issues, we propose a new two-step machine learning based approach. In the first step, a complex-valued deep convolutional neural network is employed to retrieve initial contrasts (permittivities) of dielectric scatterers from measured scattering data. In the second step, the previously obtained contrasts are input into a complex-valued deep residual convolutional neural network to refine the reconstruction of images. Consequently, the EMIS problem can be solved with much higher accuracy even for high-contrast objects. Numerical examples have demonstrated the capability of the newly proposed method with the improved accuracy. The proposed DL approach for EMIS problem serves a new path for realizing real-time quantitative microwave imaging for high-contrast objects.

91 citations


Journal ArticleDOI
TL;DR: An 8-element dual-band multiple-input–multiple-output (MIMO) antenna operating in the 5G New Radio band n77 (3300–4200 MHz) and 5 GHz band (4800–5000 MHz) in mobile handsets is presented.
Abstract: An 8-element dual-band multiple-input–multiple-output (MIMO) antenna operating in the 5G New Radio band n77 (3300–4200 MHz) and 5 GHz band (4800–5000 MHz) in mobile handsets is presented. The 8-element MIMO antenna is formed by employing four sets of dual-antenna arrays (DAAs) that are symmetrically printed along the two long side–edge frames of the smartphone. Each DAA is composed of two double-branch monopoles and a T-shaped decoupling stub, in which good mutual coupling reduction can be realized via the decoupling structures. Furthermore, the decoupling structures can also aid in improving the impedance matching of the array units for achieving wideband operation.

Journal ArticleDOI
TL;DR: In this article, a flexible mmWave antenna array for 5G wireless networks operating at Ka-band (26.5-40 GHz) was proposed, which is comprised of a coplanar-waveguide-fed rectangular patch tapered at its sides with two vertically oriented slots.
Abstract: This letter presents the design, fabrication, and performance evaluation of a flexible millimeter-wave (mm-wave) antenna array for the fifth generation (5G) wireless networks operating at Ka -band (26.5–40 GHz). The single element antenna is comprised of a coplanar-waveguide-fed rectangular patch tapered at its sides with two vertically oriented slots. The ground is designed with L-shaped stubs to converge the dispersed radiation pattern for improving the directivity and gain. The antenna fabrication is accomplished by two advanced methods of laser-milling and inkjet printing on a thin film of flexible liquid crystal polymer. A novel and time-efficient method for postprinting sintering is also proposed in this letter. The design is extended in a two-element array for the gain enhancement. Measurements have validated that the proposed antenna array exhibits a bandwidth of 26–40 GHz with a peak gain of 11.35 dBi at 35 GHz, and consistent high gain profile of above 9 dBi in the complete Ka -band. These features recommend the proposed antenna array as an efficient solution for integration in future flexible 5G front ends and mm-wave wearable devices.

Journal ArticleDOI
TL;DR: In this paper, a closely coupled dual-band multiple-input-multiple-output (MIMO) patch antenna that resonates at 3.7 and 4.1 GHz was presented.
Abstract: This letter presents a closely coupled dual-band multiple-input–multiple-output (MIMO) patch antenna that resonates at 3.7 and 4.1 GHz. The MIMO antenna is composed of two mirror-symmetrical single-feed patch antennas that are closely placed with approximately 0.034 λ0 (where λ0 is the wavelength at 3.7 GHz). The decoupling structure consists of the modified array antenna decoupling surface (MADS) and H-shaped defect ground structures for the lower band and upper band, respectively. Through simulation and measurement, the isolation is determined to be greater than 30 dB in both frequency bands, showing a noticeable improvement compared to the original antenna array. Under the effect of the MADS, the measured gain increases by 2.2 and 0.8 dB at the resonance frequencies of 3.7 and 4.1 GHz, respectively. The measured results indicate that the proposed decoupling structure is quite suitable for closely spaced dual-band MIMO antennas.

Journal ArticleDOI
TL;DR: In this paper, an optically transparent broadband microwave absorber has been developed, which is constructed of the patterned resistive films of an indium-tinoxide on flexible substrates, such that the structure exhibits broadband absorptivity (above 90%) from 4 to 17.20 GHz (covering C, X, and Ku bands).
Abstract: In this letter, an optically transparent broadband microwave absorber has been developed. The proposed geometry is constructed of the patterned resistive films of an indium-tin-oxide on flexible substrates, such that the structure exhibits broadband absorptivity (above 90%) from 4 to 17.20 GHz (covering C, X, and Ku bands). The novelty of the design lies in leveraging the properties of interdigital capacitance to achieve wide absorption (fractional bandwidth of 124.53%), angular stability, as well as optical transparency compared to the earlier reported broadband absorbers. Moreover, the structure has been extensively investigated through deriving an equivalent circuit model and studying surface current distributions. Experimental validation of the fabricated prototype has also confirmed the potential use of resistive film based broadband absorbers in several applications.

Journal ArticleDOI
TL;DR: In this article, a frequency-selective rasorber (FSR) with dual-band transmission and wideband absorption property is proposed, which is a two-layer structure composed of a lossy resistive sheet at the top and a lossless bandpass frequency selective surface (FSS) at the bottom, separated by an air spacer.
Abstract: A novel frequency-selective rasorber (FSR) with dual-band transmission and wideband absorption property is proposed in this letter. The FSR is a two-layer structure composed of a lossy resistive sheet at the top and a lossless bandpass frequency-selective surface (FSS) at the bottom, separated by an air spacer. The element of the resistive sheet is a lumped-resistor-loaded metallic dipole with a dual-resonance structure inserted in the center. The dual-resonance structure is realized by three different series LC structures in parallel, based on the Foster reactance theorem. There are two impedance poles between the three impedance zeros of the series LC circuits, where two transparent windows can be obtained for the lossy resistive sheet. The bandpass FSS is a simple dual-band FSS by etching two slots with different shapes and dimensions in a metallic plane. The FSR has realized two transmission bands at 7.7 and 12.6 GHz, and the band with | S 11| < −10 dB is 3.7–11.1 GHz. The design has been validated by full-wave simulation and experimental measurement.

Journal ArticleDOI
TL;DR: In this paper, a miniaturized two-element microstrip antenna array is proposed for the millimeter-wave band of 5G wireless communication systems, where a surface of electromagnetic bandgap structures (EBG) is applied as the ground for two closely packed patch antennas operating in 5G New Radio (26,500, 29,500) frequency band.
Abstract: A miniaturized two-element microstrip antenna array is proposed for the millimeter-wave band of fifth generation (5G) wireless communication systems. A surface of electromagnetic bandgap structures (EBG) is applied as the ground for two closely packed patch antennas operating in 5G New Radio (26 500–29 500 MHz) frequency band. With the help of the proposed EBG ground, the two E-shaped microstrip antenna elements can be placed in close proximity to each other by 0.3 wavelength center to center distance in free space at the center frequency, yet the mutual coupling between them can still reach to more than 23 dB within the whole band of interest, which is about 10 dB larger than that on normal ground. All major radiation characteristics of the two-element array are well reserved with the EBG ground. The proposed design can be used in multiple-input-multiple-output applications or as the building subarray of larger phased arrays at millimeter-wave bands for mobile communication systems.

Journal ArticleDOI
TL;DR: In this article, an 8 × 8 dual-band shared-aperture array antenna operating in K-(19.5)-21.5 GHz and Ka-band (29-31 GHz) using gap waveguide technology is presented.
Abstract: This letter presents an 8 × 8 dual-band shared-aperture array antenna operating in K-(19.5–21.5 GHz) and Ka-band (29–31 GHz) using gap waveguide technology. Radiating elements consist of circular apertures located on the top plate of the antenna and excited by two stacked cavities with different diameters for dual-frequency operation. A waffle grid is used on top to increase the effective area of apertures and reduce grating lobes. Each stacked cavity is fed by its appropriate corporate-feeding network: The upper feeding layer operates at 20 GHz band, and the lower one at 30 GHz band. As a result, the antenna presents two ports, one for each band, which radiate a directive far-field pattern with linear polarization, orthogonal to each other. Experimental results show impedance and radiation pattern bandwidths larger than 1.5 GHz in both bands.

Journal ArticleDOI
TL;DR: In this paper, two parasitic mushroom-type arrays are incorporated along with the two radiating edges of a main radiating patch, and the current distributions on those metal patches are nearly uniform so that high gains are achieved over the entire operating bandwidth.
Abstract: This letter presents a novel broadband microstrip patch antenna with a simple geometry. Two parasitic mushroom-type arrays are incorporated along with the two radiating edges of a main radiating patch. First, thanks to the mushroom-type structure, a new resonant mode, characterized as quasi-TM $_{30}$ mode, is generated. Besides, the main radiating patch produces the original TM $_{10}$ mode. Thus, wideband performance is realized on the basis of the two combined modes. Second, the current distributions on those metal patches are nearly uniform so that high gains are achieved over the entire operating bandwidth. Measured results indicate that the enhanced impedance bandwidth is from 11.9 to 18.2 GHz, which covers the whole Ku-band. Meanwhile, a nearly constant peak-radiating gain between 10 and 10.5 dBi at broadside radiation is obtained. The proposed antenna maintains the advantages of wide bandwidth, ease of fabrication, flat and high gains, and a low profile less than ${\lambda _0}$ /13 thickness substrate.

Journal ArticleDOI
TL;DR: In this article, a dual-band and dual-circular polarization (CP) stacked patch antenna is investigated for the BeiDou navigation satellite system, which employs a single coaxial probe to feed two layers of patches simultaneously, realizing dualband operation.
Abstract: A compact dual-band and dual-circular polarization (CP) stacked patch antenna is investigated for BeiDou navigation satellite system. The proposed antenna employs a single coaxial probe to feed two layers of patches simultaneously, realizing dual-band operation. The bottom patch with symmetrical slant corner-cuts and the top one with two rectangular stubs on the diagonal produce a pair of degenerated modes, achieving CP radiation. Furthermore, two L-shaped stubs are loaded on the top patch to widen impedance bandwidth. A prototype operating at the bands of 1.615/2.492 GHz was fabricated and measured. Both the left- and right-handed CP radiations are obtained concurrently in the dual bands. The proposed antenna has a profile of 4.6 mm $({{{\bf 0}}.{{\bf 024}}{{{\bf \lambda }}_0}})$ and occupies an area of $\text{70}\;{\text{mm}} \times \text{70}\;{\text{mm}}\;({0.38{\lambda _0} \times 0.38{\lambda _0}})$ . The measured impedance bandwidth with | S 11| < –10 dB is 9.1% and 5.1% for the lower and upper bands, respectively. The measured 3 dB axial-ratio bandwidth is more than 1% for both bands.

Journal ArticleDOI
TL;DR: In this article, a wide-angle narrowband leaky-wave antenna (LWA) based on substrate integrated waveguide-spoof surface plasmon polariton (SIW-SSPP) structure is proposed.
Abstract: In this letter, a wide-angle narrowband leaky-wave antenna (LWA) based on substrate integrated waveguide-spoof surface plasmon polariton (SIW-SSPP) structure is proposed. Periodic slots are etched on both the top and bottom surfaces of SIW to introduce an SSPP mode. The periodic slots on the top surface are sinusoidally modulated to realize bidirectional LWA radiation. The problem of open stopband is solved by the asymmetrical design of the top and bottom slots. Thus, a wide bidirectional scanning range from −60° to +63° is achieved. Besides, the relative bandwidth of the fabricated antenna is reduced to only 9% by introducing the slow-wave effect of SSPP. It means the proposed antenna has a large scanning rate, or equivalently beam scanning range/bandwidth ratio.

Journal ArticleDOI
TL;DR: In this article, a substrate integrated waveguide-based leaky-wave antenna with wide beam scanning is presented to mitigate open stopband (OSB), which can scan from −49° to +69° through broadside because of wide impedance matching.
Abstract: In this letter, a substrate integrated waveguide-based leaky-wave antenna with wide beam scanning is presented to mitigate open stopband (OSB). The unit cell of this proposed antenna consists of a longitudinal slot and a post placed oppositely offset from the center line. By introducing inductive post along with the longitudinal slot in each unit cell, the OSB is suppressed resulting in continuous beam scanning. An equivalent circuit of the proposed unit cell is developed to explain the impedance matching technique used here to suppress OSB. Dispersion diagram is also used to analyze this seamless scanning. This antenna can scan from –49° to +69° through broadside because of wide impedance matching. Finally, the antenna is prototyped and experimentally verified. Measured results are in accord with simulated results. This antenna provides maximum gain of 14.2 dBi and low level of cross polarization.

Journal ArticleDOI
Zhenghang Nie1, Huiqing Zhai1, Longhua Liu1, Jiaxu Li1, Diwei Hu1, Junhao Shi1 
TL;DR: In this article, a dual-polarized frequency-reconfigurable low profile antenna with harmonic suppression for 5G application is presented, which consists of a pair of ±45° polarized frequency reconfigurable dipole antennas, two vertically placed feeding structures with filtering branches, and an artificial magnetic conductor (AMC) surface.
Abstract: A dual-polarized frequency-reconfigurable low-profile antenna with harmonic suppression for 5G application is presented in this letter. The proposed design consists of a pair of ±45° polarized frequency-reconfigurable dipole antennas, two vertically placed feeding structures with filtering branches, and an artificial magnetic conductor (AMC) surface. By introducing the U-shaped structure, a better impedance matching performance is achieved in two bands. Measured results show that the proposed antenna can operate at 3.24–4.03 and 4.44–5.77 GHz by controlling the on–off of PIN diodes, and port isolation of two bands is greater than 25 dB. What is more, two-octave harmonic suppression is realized by loading the filtering branches. In order to obtain stable unidirectional radiation pattern in the operating bands and low-profile characteristic, a dual-band 4 × 4 AMC reflector is fabricated. Finally, a maximum gain of 6.86 dBi in low frequency band and 8.14 dBi in high frequency band are obtained. Besides, the height of the proposed antenna is 0.1 λ at 3.3 GHz. Experimental results show that the antenna can meet the needs of the 5G communication.

Journal ArticleDOI
TL;DR: In this paper, a dual-polarized frequency-selective rasorber/absorber at low microwave frequency based on double-layered metallic resonant structure array loaded with lumped elements is presented.
Abstract: This letter presents a switchable dual-polarized frequency-selective rasorber/absorber at low microwave frequency based on double-layered metallic resonant structure array loaded with lumped elements. It consists of an absorbing layer and a bandpass frequency-selective surface layer loaded with PIN diodes, sandwiched with an air-spacer between them. The operating principle is analyzed with the help of an equivalent circuit model. By biasing the PIN diodes on or off , it can be easily switched between the rasorber and absorber modes. When in the rasorber mode, it exhibits a passband at 1.6 GHz with 1.7 dB insertion loss between two neighboring absorption bands. While switched to the absorber mode, it achieves more than 80% absorptivity ranging from 0.8 to 3.4 GHz, corresponding to a fractional bandwidth of 124%. The total thickness is less than 8% of the free-space wavelength at the lowest operating frequency. A prototype of the proposed structure is fabricated and measured, where reasonable agreements between simulations and measurements are observed.

Journal ArticleDOI
TL;DR: In this article, a series-fed single-layer, dual circularly polarized (CP) seriesfed antenna based on the sequential rotation technique for millimeter-wave (MM-wave) applications is presented.
Abstract: This letter presents a low-cost, single-layer, dual circularly polarized (CP) series-fed antenna based on the sequential rotation technique for millimeter-wave (MM-wave) applications. The series-fed working form endows the proposed antenna with more compact structure and lower ohmic, dielectric losses caused by the feeding network compared with parallel-fed antennas. The curved microstrip transmission lines are adopted as radiation elements; therefore, the whole antenna can be etched on a single-layer laminate using standard printed circuit board technology. These characteristics make the antenna a competitive candidate for MM-wave applications. To validate the proposed design, a dual-CP antenna operating at 30 GHz is fabricated. Based on the measurement, the proposed antenna has a 3 dB gain bandwidth of 1.97 GHz, the measured $| {{S_{21}}} |$ is lower than −20 dB, and the axial ratios are lower than 3 dB in the aforementioned frequencies.

Journal ArticleDOI
TL;DR: In this article, a truly all dielectric metamaterial absorber, made of subwavelength water-based resonators and free of metallic ground, is designed, fabricated, and characterized.
Abstract: A truly all-dielectric metamaterial absorber, made of subwavelength water-based resonators and free of metallic ground, is designed, fabricated, and characterized. We demonstrate theoretically and experimentally that our metamaterial features a highly uniform perfect absorption for frequencies between 7.74 and 23.56 GHz, perfect thermal stability for temperatures from 0 to 100 $^\circ$ C, and excellent absorption performance for large angles of oblique incidence. The proposed metamaterial absorber can be fabricated at low cost, is environment friendly, and may find potential applications in broadband scattering reduction and electromagnetic energy harvesting.

Journal ArticleDOI
TL;DR: In this article, a reconfigurable unitcell for transmitarray antenna working at X-band is presented, which is designed to provide 1-bit phase quantization using p-i-n diodes.
Abstract: In this letter, a reconfigurable unit-cell for transmitarray antenna working at X-band is presented. It is designed to provide 1-bit phase quantization using p-i-n diodes. The unit-cell is based on multilayer frequency selective surfaces with the use of two substrates and a combination of a C-patch and a ring slot loaded by a rectangular gap. It is optimized using full-wave electromagnetic simulation and verified by using waveguide simulator. The experimental results show that the unit-cell provides two values of the transmission phase with a step of 180° at 11.5 GHz. Furthermore, the unit-cell has a low thickness of 0.19λ0, and is low-cost and easy to fabricate.

Journal ArticleDOI
TL;DR: A novel quasi-Yagi antenna is proposed for millimeter-wave (mmWave) 5G cellular handsets operating in the 28 GHz band and designed to be compact through modification of the planar folded dipole topology so that it can be mounted inside a compact mobile terminal.
Abstract: A novel quasi-Yagi antenna is proposed for millimeter-wave (mmWave) 5G cellular handsets operating in the 28 GHz band. The proposed antenna is designed to be compact through modification of the planar folded dipole topology so that it can be mounted inside a compact mobile terminal. A vertically stacked structure utilizing a multilayer printed circuit board (PCB) and via holes is applied to the antenna topology to minimize the antenna lateral width while maintaining the characteristics of the planar folded dipole antenna. A single antenna yields a $-$ 10 dB bandwidth for a return loss of 12.3% (26.3 to 29.75 GHz) and a gain of 5.51 dBi at 28 GHz. The change in beam patterns due to the chassis effect when four-element linear arrays are inserted into the upper and side edge inside the terminal is analyzed.

Journal ArticleDOI
TL;DR: In this article, a printed broadband metasurface (MTS) antenna fed by an aperture coupling through a coplanar waveguide (CPW) is introduced to achieve the wideband impedance matching.
Abstract: In this letter, a printed broadband metasurface (MTS) antenna fed by an aperture coupling through a coplanar waveguide (CPW) is introduced. To achieve the wideband impedance matching, a technique of loading an MTS radiator formed by nonuniform patch elements above a stair-shape aperture is applied. The stair-shape aperture is attached to the end of the CPW. The proposed antenna is simple and low-profile in structure, which can be realized by a single-layer printed circuit board (PCB) substrate. To verify the concept, a prototype with an overall size of 1.28 λ 0 × 1.28 λ 0 × 0.09 λ 0, where λ 0 is the free-space wavelength at 7 GHz, is fabricated. The proposed antenna realizes a wide impedance bandwidth of 67.3% with reflection coefficient ≤ −10 dB and peak gain of 9.18 dBi. The measurement results agree well with the anticipation.

Journal ArticleDOI
TL;DR: In this article, a single square cavity with a rectangular ring slot is used for both dual-mode excitation and radiation, which can be used for closely spaced radiating frequencies.
Abstract: This letter presents a substrate-integrated-waveguide-based compact, dual-mode self-diplexing antenna. A single square cavity with a rectangular ring slot is used for both dual-mode excitation and radiation. A prototype diplexing antenna is fabricated that radiates linear, orthogonal polarization at 9.5 and 10.5 GHz. The measured peak gains at the two frequencies are 5.75 and 5.95 dBi, respectively. Intermodal coupling between the modes provides two transmission zeros, which are utilized to achieve port isolation better than 29 dB. The proposed technique can be used for closely spaced radiating frequencies. As no external filter is used, the structure is compact. Furthermore, because of the slot loading effect, the antenna is smaller than a recently published antenna claimed as the most compact antenna. Its working principle is discussed in detail. Finally, design guidelines are suggested.

Journal ArticleDOI
TL;DR: In this article, a planar reflectarray with a small size of 3.87λ0 × 3.38 λ 0 × 0.38 ρ is designed, which can effectively convert arbitrary polarized waves to orbital angular momentum (OAM) waves with a desired mode number and a beam direction.
Abstract: In this letter, a high-efficiency planar reflectarray with a small size of 3.87λ0 × 3.87λ0 is designed, which can effectively convert arbitrary polarized waves to orbital angular momentum (OAM) waves with a desired mode number and a beam direction. The two concentric rings with a small size of 0.38 λ 0 × 0.38 λ 0 compose the unit, which can cover the phase-shifting range 360° by adjusting the ring radius. Though the developed reflectarray is much smaller than that of published ones, it can produce beams with the similar performance as large antennas. The advantages are as follows: high efficiency 22.6%, which is superior to published OAM reflectarrays, high gain 15.4 dBi, narrow divergence angle 9°, high purity, good stability, polarization insensitivity, planar structure, and easy fabrication. Using this reflective metasurface, we designed the following OAM beams: first, OAM mode l = 1, 2, 3, 4 at ( θ = 0°, ϕ = 0°); second, l = 1 at ( θ = 45°, ϕ = 180°); and third, l = 1 at ( θ = 45°, ϕ = 270°). The above advantages are proved by the following analysis: the magnitude and phase distributions in the near field, the purity analysis, and the radiation pattern in the far field.