Showing papers in "IEEE Antennas and Wireless Propagation Letters in 2017"
TL;DR: In this article, a dual-band inverted-F multiple-input-multiple-output (MIMO) antenna with improved isolation was proposed for the 2.4/5 GHz WLAN band.
Abstract: This letter presents a dual-band inverted-F multiple-input-multiple-output (MIMO) antenna with improved isolation, covering the 2.4/5-GHz wireless local networks (WLAN) band. The proposed MIMO antenna is composed of two symmetrical winding inverted-F antenna elements. The two antenna elements are closely spaced with about 0.115 λ
0
of the lower band. The high isolation is achieved by building two decoupling devices, a meandering resonant branch and an inverted T-shaped slot etched on the ground for the higher band and the lower band, respectively. Furthermore, two U-shaped slits achieving better impedance matching are etched on the 50-Ω feeding lines to broaden the bandwidth of the high band. The impedance bandwidth (S
11
<; -10 dB) of the proposed antenna covers 2.4-2.48 GHz in the lower band and 5.15-5.825 GHz in the upper band, and the proposed configuration obtains 15-dB isolation within the 2.4- and 5-GHz WLAN bands, which shows a significant improvement compared to the initial design of the MIMO antenna. The simulation and measurement results indicate that the proposed inverted-F MIMO antenna system is quite suitable for WLAN applications.
213 citations
TL;DR: In this paper, a broadband printed-dipole antenna and its arrays for 5G wireless cellular networks are proposed, which is fed by an integrated balun, which consists of a folded microstrip line and a rectangular slot.
Abstract: In this letter, we propose a broadband printed-dipole antenna and its arrays for fifth-generation (5G) wireless cellular networks. To realize a wide frequency range of operation, the proposed antenna is fed by an integrated balun, which consists of a folded microstrip line and a rectangular slot. For compactness, the printed dipole is angled at 45°. The single-element antenna yields an |S
11
| <;-10-dB bandwidth of 36.2% (26.5-38.2 GHz) and a gain of 4.5-5.8 dBi. We insert a stub between two printed-dipole antennas and obtain a low mutual coupling of <;-20 dB for a 4.8-mm center-to-center spacing (0.42-0.61 λ at 26-38 GHz). We demonstrate the usefulness of this antenna as a beamforming radiator by configuring 8-element linear arrays. Due to the presence of the stubs, the arrays resulted in a wider scanning angle, a higher gain, and a lower sidelobe level in the low-frequency region.
209 citations
TL;DR: In this article, a dual-port triple-band L-probe microstrip patch rectenna design for ambient RF energy harvesting using the GSM-900, GSM1800, and UMTS-2100 bands is described.
Abstract: A dual-port triple-band L-probe microstrip patch rectenna design for ambient RF energy harvesting using the GSM-900, GSM-1800, and UMTS-2100 bands is described. The compact dual-port L-probe patch antenna is implemented by stacking two single-port patch antennas back to back. Each port can independently harvest RF signal from a half-space with gain greater than 7 dBi, and together with both ports in a dc combining configuration, the antenna can acquire RF energy from nearly all directions. We also provide a design for a high-efficiency triple-band rectifier operating at GSM-900, GSM-1800, and UMTS-2100, which is replicated on each port and concatenated together to allow dc combining and near doubling of the output dc voltage. Measurement results show that our prototyped dual-port triple-band rectenna can receive RF power from nearly all directions with an efficiency of greater than 40% and an output voltage of more than 600 mV when the power density is greater than 500 $\mu \mathrm{W}/\mathrm{m}^{2}$ .
170 citations
TL;DR: In this paper, an efficient particle swarm optimization (PSO) algorithm was developed to design a near-field time-delay equalizer metasurface (TDEM) for the purpose of improving directivity and radiation patterns of classical electromagnetic band-gap resonator antennas.
Abstract: This letter presents an efficient particle swarm optimization (PSO) algorithm developed to design a near-field time-delay equalizer metasurface (TDEM) for the purpose of improving directivity and radiation patterns of classical electromagnetic band-gap resonator antennas. Triple layers of conductive printed patterns in the metasurface were optimized by the PSO algorithm to systematically design the TDEM. Predicted and measured results show a significant improvement in antenna performance including 9.6 dB enhancement in antenna directivity, lower sidelobes, and higher gain. The measured directivity of the prototype is 21 dBi, and 3-dB bandwidth is 11.8%.
165 citations
TL;DR: In this article, a fractal uniplanar compact electromagnetic bandgap (UC-EBG) structure and three cross slots are proposed to suppress the mutual coupling in a compact patch antenna array.
Abstract: A compact patch antenna array with high isolation by using two decoupling structures including a row of fractal uniplanar compact electromagnetic bandgap (UC-EBG) structure and three cross slots is proposed. Simulated results show that significant improvement in interelement isolation of 13 dB is obtained by placing the proposed fractal UC-EBG structure between the two radiating patches. Moreover, three cross slots etched on the ground plane are introduced to further suppress the mutual coupling. The design is easy to be manufactured without the implementation of metal vias, and a more compact array with the edge-to-edge distance of 0.22 λ0 can be facilitated by a row of fractal UC-EBG, which can be well applied in the patch antenna array.
160 citations
TL;DR: In this article, a compact wearable antenna with a novel miniaturized electromagnetic bandgap (EBG) structure at 2.4 GHz for medical application is presented, which demonstrates a robust, compact, and low-profile solution to meet the requirements of wearable applications.
Abstract: A compact wearable antenna with a novel miniaturized electromagnetic bandgap (EBG) structure at 2.4 GHz for medical application is presented in this letter. The design demonstrates a robust, compact, and low-profile solution to meet the requirements of wearable applications. The EBG structure reduces the back radiation and the impact of frequency detuning due to the high losses of human body. In addition, the structure improves the front-to-back ratio (FBR) by 15.5 dB. The proposed compact antenna with dimensions of ${\text{46}}\,\times \,{\text{46}}\,\times \,{\text{2.4 mm}}^{3}$ yields an impedance bandwidth of 27% (2.17–2.83 GHz), with a gain enhancement of 7.8 dBi and more than 95% reduction in the specific absorption rate. Therefore, the antenna is a promising candidate for integration into wearable devices applied in various domains, specifically biomedical technology.
148 citations
TL;DR: In this article, an absorptive frequency-selective transmission structure (AFST) is proposed, which is based on the design of a frequency-dependent lossy layer with square-loop hybrid resonator (SLHR).
Abstract: A novel design of an absorptive frequency-selective transmission structure (AFST) is proposed. This structure is based on the design of a frequency-dependent lossy layer with square-loop hybrid resonator (SLHR). The parallel resonance provided by the hybrid resonator is utilized to bypass the lossy path and improve the insertion loss. Meanwhile, the series resonance of the hybrid resonator is used for expanding the upper absorption bandwidth. Furthermore, the absorption for out-of-band frequencies is achieved by using four metallic strips with lumped resistors, which are connected with the SLHR. The quantity of lumped elements required in a unit cell can be reduced by at least 50% compared to previous structures. The design guidelines are explained with the aid of an equivalent circuit model. Both simulation and experiment results are presented to demonstrate the performance of our AFST. It is shown that an insertion loss of 0.29 dB at 6.1 GHz and a 112.4% 10 dB reflection reduction bandwidth are obtained under the normal incidence.
148 citations
TL;DR: In this paper, a dual-band antenna for off-and on-body communications in the 2.45- and 5.8-GHz Industrial, Scientific, and Medical bands is presented.
Abstract: A dual-band antenna for off- and on-body communications in the 2.45- and 5.8-GHz Industrial, Scientific, and Medical bands is presented. The two radiation characteristics, i.e., patch-like radiation for the off-body link and monopole-like radiation for the on-body link, are achieved by utilizing inherently generated TM $_{11}$ and TM $_{02}$ modes of a circular patch antenna. A shorting pin and two arc-shaped slots are employed to tune both modes to the desired operating frequencies. This approach allows a realization of a dual-band dual-mode antenna with a very simple structure, i.e., a single radiator with a simple feed. A further advantage of the proposed antenna is its realization using a silver fabric integrated onto a flexible polydimethylsiloxane substrate that makes it more practical for wearable applications. An experimental investigation of the antenna performance has been carried out in free space and on a semisolid human muscle equivalent phantom, which shows a robust performance against the human body loading effect. When placed on the phantom, the measured bandwidths of 84 and 247 MHz in the 2.45- and 5.8-GHz bands, respectively, are achieved with the corresponding peak gains of 4.16 and 4.34 dBi, indicating a promising candidate for body-centric communications.
146 citations
TL;DR: In this paper, a coding diffuse metasurface for radar cross section (RCS) reduction is designed, simulated, and measured, where two kinds of artificial magnetic conductor (AMC) unit cells are analyzed, and 5 × 5 AMC unit cells construct metamaterials block.
Abstract: In this letter, a coding diffuse metasurface for radar cross section (RCS) reduction is designed, simulated, and measured. First, two kinds of artificial magnetic conductor (AMC) unit cell are analyzed, and 5 × 5 AMC unit cells construct metamaterials block. A linear array factor is optimized by the ergodic algorithm, and the sequence is expanded from one-dimension code to two-dimension code. Then, the diffuse metasurface is constructed through the metamaterials blocks arrangement. Simulation results show that the bandwidth of RCS reduction is expanded compared to the classical chessboard arrangement. The diffuse characteristic of the metasurface is achieved under normal and oblique incidence wave. Experiment results verify the validity of the theoretical design and simulation. This letter provides a rapid design method to obtain diffuse metasurface, and this metasurface may achieve potential applications on low-scattering vehicle.
141 citations
Abstract: A wideband, pattern-reconfigurable antenna is reported that is, for example, a good candidate for ceiling-mounted indoor wireless systems. Switchable linearly polarized broadside and conical radiation patterns are achieved by systematically integrating a wideband low-profile monopolar patch antenna with a wideband L-probe fed patch antenna. The monopolar patch acts as the ground for the L-probe fed patch, which is fed with a coaxial cable that replaces one shorting via of the monopolar patch to avoid deterioration of the conical-beam pattern. A simple switching feed network facilitates the pattern reconfigurability. A prototype was fabricated and tested. The measured results confirm the predicted wideband radiation performance. The operational impedance bandwidth, i.e., |S
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| ≤ -10 dB, is obtained as the overlap of the bands associated with both pattern modalities. It is wide, from 2.25 to 2.85 GHz (23.5%). Switchable broadside and conical radiation patterns are observed across this entire operating bandwidth. The peak measured gain was 8.2 dBi for the broadside mode and 6.9 dBi for the conical mode. The overall profile of this antenna is 0.13λ 0 at its lowest operating frequency.
138 citations
TL;DR: A systematic study of phase quantization effects on the beam scanning performance of reconfigurable reflectarray antennas (RRAs) is presented and it is observed that thephase quantization does not affect the half-power beamwidth, but increases sidelobe levels.
Abstract: A systematic study of phase quantization effects on the beam scanning performance of reconfigurable reflectarray antennas (RRAs) is presented. The spatial feeding scheme of RRA introduces an intrinsic pseudorandom distribution of the phase quantization error, which effectively eliminates the grating lobes and high parasitic sidelobes. It is observed that the phase quantization does not affect the half-power beamwidth, but increases sidelobe levels. The gain loss due to phase quantization is computed for different quantization bit numbers and different scan angles, and the maximum aperture efficiencies are derived accordingly. Finally, the measured results of two 1-bit RRAs with ${1}0 \times {1}0$ and ${4}0 \times {4}0$ elements validate these observations.
TL;DR: In this paper, a broadband dual-polarized base station antenna with sturdy construction is presented, which mainly contains four parts: main radiator, feeding baluns, bedframe, and reflector.
Abstract: A broadband dual-polarized base station antenna with sturdy construction is presented in this letter. The antenna mainly contains four parts: main radiator, feeding baluns, bedframe, and reflector. First, two orthogonal dipoles are etched on a substrate as main radiator forming dual polarization. Two baluns are then introduced to excite the printed dipoles. Each balun has four bumps on the edges for electrical connection and fixation. The bedframe is designed to facilitate the installation, and the reflector is finally used to gain unidirectional radiation. Measured results show that the antenna has a 48% impedance bandwidth with reflection coefficient less than –15 dB and port isolation more than 22 dB. A four-element antenna array with 6° ± 2° electrical down tilt is also investigated for wideband base station application. The antenna and its array have the advantages of sturdy construction, high machining accuracy, ease of integration, and low cost. They can be used for broadband base station in the next-generation wireless communication system.
TL;DR: In this article, the authors proposed a hybrid isolation enhancing and miniaturization technique for UWB diversity antenna with a very low envelope correlation coefficient (ECC), which consists of two counter facing monopoles, and is miniaturized by using inverted-L stubs and a complementary split-ring resonator on the ground plane.
Abstract: The purpose of this letter is to introduce a compact ultrawideband (UWB) diversity antenna with a very low envelope correlation coefficient (ECC). The design employs a hybrid isolation enhancing and miniaturization technique. The antenna consists of two counter facing monopoles, and is miniaturized by using not only inverted-L stubs but also a complementary split-ring resonator (CSRR) on the ground plane. The added components enhance isolation and enable tighter packing of the antennas. The result is a very compact multiple-input–multiple-output (MIMO) array with an overall size of 23 $\times$ 29 mm2 , which covers the entire UWB spectrum from 3 to 12 GHz, with mutual coupling lower than –15 dB. Moreover, the CSRR unit that acts as a resonator is applied for the first time to suppress the interference of RF currents flowing through the ground plane of this UWB-MIMO/diversity antenna. The performance of the fabricated prototype in terms of scattering parameters, broadside (peak) gain, radiation patterns, efficiency, and ECC is presented and discussed.
TL;DR: In this article, a wearable flexible reconfigurable folded slot antenna is presented, where the antenna is composed of a folded slot and a stub where the reconfigurability is achieved by turning a p-i-n diode on and off, which alters the radiation characteristics of the stub.
Abstract: This letter presents a wearable flexible reconfigurable folded slot antenna. The antenna is composed of a folded slot and a stub where the reconfigurability is achieved by turning a p-i-n diode on and off , which alters the radiation characteristics of the stub. The operating frequency and polarization of the slot and stub are different. Hence, a polarization-dependent dual-band artificial magnetic conductor (AMC) surface is integrated with the antenna to improve its radiation performance and to reduce the specific absorption rate (SAR). The antenna is designed and fabricated on a flexible substrate, and its performance is measured for both flat and curved configurations. The measurements show an excellent agreement with the simulations. To examine its performance as a wearable antenna, it is measured on a human body. Simulations show that the SAR level is reduced when the AMC surface is used as an isolator. The proposed wearable antenna structure can be used for wireless body area network (WBAN) and Worldwide Interoperability for Microwave Access (WiMAX) body-worn wireless devices.
TL;DR: In this paper, a wide-angle beam-scanning antenna with circular polarization (CP) characteristic is proposed, where the antenna consists of two layers and a series of circular patches are placed on the top layer as radiating elements.
Abstract: In this letter, a wide-angle beam-scanning antenna with circular polarization (CP) characteristic is proposed. The antenna consists of two layers. Microstrip spoof surface plasmon polariton (SPP) is introduced on the bottom layer as a slow-wave feeding line. A series of circular patches are placed on the top layer as radiating elements. Simulated and measured results indicate that beam-scanning angle of the proposed antenna is improved and CP beam-scanning ability is obtained by introducing perturbation on the radiating elements. In the operating band of 11–15 GHz, measured scanning angle of the fabricated antenna is from –32° to +34°. The antenna axial ratio (AR) is below 3 dB at the corresponding beam direction, and gain is above 12.8 dBi over the whole band. It has potential applications in radar and wireless communication systems for simple structure, low-cost fabrication, wide beam-steering, and CP properties.
TL;DR: In this paper, an electric ring resonator (ERR) incorporated into the coplanar waveguide feedline is proposed for use in the planar configuration of the ultrawideband (UWB) antenna.
Abstract: The ultrawideband (UWB) planar antenna is designed as a circular metallic patch fed by a coplanar waveguide (CPW). This antenna provides the impedance bandwidth of the wideband response from 2.5 to 12 GHz. To achieve the notched characteristics at desirable frequencies, the electric ring resonator (ERR) incorporated into the CPW feedline is proposed for use in the planar configuration of the UWB antenna. The notched frequency band is controlled by dimensions of the ERR structure. The single-notched band can be obtained by placing a single ERR beneath the CPW structure. For implementation of the multinotch band, a modified multimode structure of the ERR is examined. Reconfigurability of the first notched band is provided by using a digital variable capacitor (DVC) instead of ERR's quasi-lumped capacitance. The results of simulations and measurements are in a good agreement.
TL;DR: In this article, a frequency selective surface absorber (FSSA) with bandpass characteristic between two neighboring absorption bands is proposed, which is implemented by loading lumped resistors and LC resonators in the FSSA structure.
Abstract: A novel method of designing a frequency selective surface absorber (FSSA) with bandpass characteristic between two neighboring absorption bands is proposed in this letter. This method is implemented by loading lumped resistors and LC resonators in the FSSA structure. An equivalent circuit model together with an analytical design method is developed for further illustration. The performance of the FSSA structure is tested using a free-space measurement system. Experiments show a bandpass response at the center frequency of 6.74 GHz with a fractional bandwidth of 5% and two absorption bands over 3.33–6.26 and 7.09–10.36 GHz with an absorption rate of more than 80%, which indicates a good agreement with the simulation results.
TL;DR: In this article, an effective technique for reducing the mutual coupling between millimeter-wave dielectric resonator antennas using a novel metamaterial polarization-rotator (MPR) wall is investigated and presented.
Abstract: An effective technique for reducing the mutual coupling between millimeter-wave dielectric resonator antennas (DRAs) using a novel metamaterial polarization-rotator (MPR) wall is investigated and presented. The mutual coupling is reduced by embedding an MPR wall between two DRAs, which are placed in the H-plane. Using this MPR wall, the TE modes of the antennas become orthogonal, which reduces the mutual coupling between the two DRAs. The proposed MPR wall is composed of 1 × 7 unit cells along the E-plane. The mutual coupling is reduced by more than 16 dB on average (8 dB at 57 GHz, 22 dB at 60 GHz, 14 dB at 62 GHz) when the MPR wall is placed between the antennas. The proposed MPR wall nearly has no effect on the antenna characteristics in terms of input impedance and radiation pattern. The radiation pattern is almost unchanged compared to a DRA multiple-input-multiple-output (MIMO) antenna array without MPR wall. The MIMO antenna array with MPR wall is fabricated and measured. The results give a low correlation coefficient (<;0.1e-6). This is due to the fact that the MPR wall makes the two antennas orthogonal in terms of mutual coupling. The measured and simulated results show a good agreement.
TL;DR: In this paper, a pair of parallel coupled-line resonators (PCRs) are used for isolation enhancement in planar microstrip patch array antennas. But the proposed antenna is deployed in a two-element antenna array, and the mutual coupling characteristics are studied.
Abstract: This letter presents the implementation of a pair of parallel coupled-line resonators (PCRs) for isolation enhancement in planar microstrip patch array antennas. Each PCR consists of three coupled lines separated by a small coupling distance. The attempted configuration provides band-reject characteristics at the design frequency of 3.5 GHz. Two such PCRs are replicated to provide higher order rejection that enhances the bandstop characteristics. The designed PCR is deployed in a two-element microstrip patch antenna array, and the mutual coupling characteristics are studied. The proposed PCR-based decoupling unit cell provides additional 12–26.2-dB coupling reduction with an enhancement of antenna gain up to 1.25 dB. The prototype antenna is fabricated, and the simulation results are validated using experimental measurements.
TL;DR: In this paper, an effective technique for reducing the mutual coupling between two dielectric resonator antennas (DRAs) operating at 60 GHz bands is presented by incorporating a metasurface between the two DRAs, which are arranged in the H-plane.
Abstract: An effective technique for reducing the mutual coupling between two dielectric resonator antennas (DRAs) operating at 60-GHz bands is presented. This is achieved by incorporating a metasurface between the two DRAs, which are arranged in the H-plane. The metasurface comprises an array of unique split-ring resonator (SRR) cells that are integrated along the E-plane. The SRR configuration is designed to provide bandstop functionality within the antenna bandwidth. By loading the DRA with 1 × 7 array of SRR unit cells, a 28-dB reduction in the mutual coupling level is achieved without compromising the antenna performance. The measured isolation of the prototype antenna varies from -30 to -46.5 dB over 59.3-64.8 GHz. The corresponding reflection coefficient of the DRA is better than -10 dB over 56.6-64.8 GHz.
TL;DR: In this paper, a single-fed miniaturized wide-beamwidth circularly polarized implantable antenna, operating in the Industrial, Scientific, and Medical band (2.40-2.48 GHz), is designed and experimentally verified for subcutaneous real-time glucose monitoring applications.
Abstract: A single-fed miniaturized wide-beamwidth circularly polarized implantable antenna, operating in the Industrial, Scientific, and Medical band (2.40–2.48 GHz), is designed and experimentally verified for subcutaneous real-time glucose monitoring applications. The proposed antenna features a very good miniaturization with the dimensions of ${\mathbf 8.5 \times 8.5 \times 1.27 \; \text{mm}^{3}}$ by employing four C-shaped slots and a complementary split-ring resonator (CSRR). Meanwhile, by adjusting the slits of CSRR, circular polarization is realized. The simulation results in a three-layer phantom demonstrate that the impedance bandwidth is 12.2% (2.32–2.62 GHz) with a peak gain of −17 dBi, and the 3-dB axial-ratio bandwidth is 2.4% (2.42–2.48 GHz) with a wide beamwidth of around 140°. An in vitro test was carried out in a pork slab, and the measured impedance bandwidth is 13% (2.31–2.63 GHz) with ${\boldsymbol S_{11} , confirming the simulated results. The specific absorption rate distribution has been evaluated for the consideration of health safety, and the calculated link margin shows that the reliable communication can be guaranteed within 10 m in free space.
TL;DR: In this article, a parasitic isolator is used to suppress mutual coupling between two patch antennas, and a defected ground structure is employed to suppress the cross-polarization (XP) level.
Abstract: A novel approach to suppress mutual coupling (MC) between two patch antennas is presented in this letter. A parasitic isolator, which is printed between the two patches, controls the polarization of the coupling field to reduce the antenna coupling. Furthermore, a defected ground structure is employed to suppress the cross-polarization (XP) level. There exists a tradeoff between the MC reduction and XP improvement in this approach. As an example, a two-element patch array with an optimized isolator is fabricated and measured. The measured results show that, at the resonant frequency, the achieved isolation enhancement and XP level are 19.6 dB and $-$ 13.2 dB, respectively.
TL;DR: In this paper, a high-gain, aperture-efficient cavity resonator antenna using metamaterial superstrate is reported, which shows calculated gain of 16.35 dB achieving 92.42% of maximum gain due to effective aperture area in H-plane.
Abstract: In this letter, a high-gain, aperture-efficient cavity resonator antenna using metamaterial superstrate is reported. Highly reflective compact metamaterial surface resonating at 10.15 GHz with measured 3-dB bandwidth stopband characteristic of 4.10 GHz from 8.1 to 12.2 GHz is proposed. Material property of the metasurface is studied by using the free-space technique. Next, the metasurface is used as a superstrate to a patch antenna operating at 10.09 GHz, forming Fabry-Perot cavity. Gain enhancement of 11.85 dB in H-plane and 12.5 dB in E-plane with improved cross-polarization level and front-to-back ratio is observed. The prototype cavity antenna shows calculated gain of 16.35 dB achieving 92.42% of maximum gain due to effective aperture area in H-plane.
TL;DR: In this article, a three-element compact multiple-input-multiple-output (MIMO) antenna system with both pattern and polarization diversity is proposed, which exhibits good isolation (>15 dB) without the use of any separate decoupling structure.
Abstract: In this paper, a three-element compact multiple-input-multiple-output (MIMO) antenna system having both pattern and polarization (linear/circular) diversity is proposed. The proposed MIMO system consists of a chamfered-edge square patch antenna with an offset feed that provides circular polarization in broadside direction. Furthermore, two printed dipole antennas are placed adjacent to it for providing linearly polarized endfire radiation. The three-element MIMO antenna system exhibits good isolation (>15 dB) without the use of any separate decoupling structure. The match between the simulated and measured results on fabricated antenna prototype suggests that the proposed antenna can be a good candidate for pattern-and polarization-diversity MIMO applications in the 5.8-GHz WLAN frequency range.
TL;DR: In this paper, a wearable antenna integrated into a military beret for an indoor/outdoor positioning system is proposed, which consists of a truncated patch and a circular ring patch with four conductive threads.
Abstract: A wearable antenna integrated into a military beret for an indoor/outdoor positioning system is proposed. The antenna consists of a truncated patch and a circular ring patch with four conductive threads. The truncated patch antenna is designed for the Global Positioning System (GPS) L1 band for use in outdoor situations, and the circular ring patch antenna with four conductive threads operates at the TM41 higher-order resonance mode (915 MHz) with a monopole-like radiation characteristic for indoor positioning systems. The antenna is fabricated using textile materials and is integrated into a military beret. The effects of the antenna deformation due to the shape of the military beret and the effects of the human head are analyzed via both simulation and measurement. The simulated and measured 10-dB return-loss bandwidths of the antenna on the head phantom fully cover the 915-MHz industrial, science, and medical band and the 1.575-GHz GPS L1 band.
TL;DR: In this paper, a wideband circularly polarized reconfigurable patch antenna with L-shaped feeding probes is presented, which can generate unidirectional radiation performance that is switchable between left-hand circular polarization (LHCP) and righthand circular polarization (RHCP).
Abstract: A wideband circularly polarized reconfigurable patch antenna with L-shaped feeding probes is presented, which can generate unidirectional radiation performance that is switchable between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). To realize this property, an L-probe fed square patch antenna is chosen as the radiator. A compact reconfigurable feeding network is implemented to excite the patch and generate either LHCP or RHCP over a wide operating bandwidth. The proposed antenna achieves the desired radiation patterns and has excellent characteristics, including a wide bandwidth, a compact structure, and a low profile. Measured results exhibit approximately identical performance for both polarization modes. Wide impedance, 31.6% from 1.2 to 1.65 GHz, and axial-ratio, 20.8% from 1.29 to 1.59 GHz, bandwidths are obtained. The gain is very stable across the entire bandwidth with a 6.9-dBic peak value. The reported circular-polarization reconfigurable antenna can mitigate the polarization mismatching problem in multipath wireless environments, increase the channel capacity of the system, and enable polarization coding.
TL;DR: In this paper, a dual-band and dual-sense circularly polarized coplanar-waveguide-fed monopole antenna with two rectangular parasitic elements and an I-shape grounded stub is presented.
Abstract: A novel design of a dual-band and dual-sense circularly polarized coplanar-waveguide-fed monopole antenna with two rectangular parasitic elements and an I-shape grounded stub is presented here. The monopole consists of a vertical and a horizontal section. Lower band is obtained due to 90° phase difference between currents in the two orthogonal branches of the monopole. Upper band is obtained due to the I-shape stub. Parasitic elements help in input impedance matching. The dual-band and dual-sense antenna provides wide 10-dB impedance bandwidth of 71.63% at 2.82 GHz. The 3-dB axial-ratio bandwidths are 27.45% at 2.55 GHz (right-hand circular polarization) and 7.1% at 3.53 GHz (left-hand circular polarization).
TL;DR: Numerical results show that the proposed method outperforms the existing method using logarithmically increasing frequency increments in suppressing undesired sidelobes, which implies that better target location performance can be achieved for the proposed methods.
Abstract: Due to its range-angle-dependent transmit beampattern, frequency diverse array (FDA) provides potential applications for joint range and angle estimation of targets and range-dependent interference suppression. However, a standard FDA using linearly increasing frequency increments will generate range- and angle-coupled S-shaped beampattern. This letter proposes a focused beampattern synthesis by optimizing the frequency increments with genetic algorithm. Both single-dot and multidot-shaped transmit beampatterns can be synthesized in this way. Numerical results show that the proposed method outperforms the existing method using logarithmically increasing frequency increments in suppressing undesired sidelobes, which implies that better target location performance can be achieved for the proposed method.
TL;DR: A very compact dual-band two-element multiple-input–multiple-output antenna for wireless local area network applications is presented, which uses a simple decoupling network to achieve good isolation between the ports.
Abstract: A very compact dual-band two-element multiple-input–multiple-output antenna for wireless local area network applications is presented in this letter. The antenna occupies an overall area of 24 × 25 mm2. A microstrip-line-fed antenna with two quarter-wavelength slots of different lengths, which radiate at 2.5 and 5.6 GHz, is used as an antenna element. The proposed antenna uses a simple decoupling network, based on a wide slot and a pair of narrow slots, to achieve good isolation (better than 20 dB) between the ports. Moreover, the envelope correlation coefficient of the proposed antenna is within the acceptable limit.
TL;DR: A new dielectric resonator antenna for a millimeter-wave (mm-wave) multiple-input–multiple-output system is presented, indicating that the proposed antenna can provide spatial or pattern diversity to increase the data capacity of wireless communication systems at mm-wave bands.
Abstract: A new dielectric resonator antenna (DRA) for a millimeter-wave (mm-wave) multiple-input–multiple-output system is presented. Two approaches are exploited to reduce the mutual coupling between two antenna elements. First, a frequency selective surface (FSS) wall is inserted between the DRAs to reduce the free-space radiation. Then, two slots with different size acting like an $LC$ resonator are etched from the common ground plane of the structure to reduce the surface current. The designed FSS has a wideband characteristic from 40 to 70 GHz. The FSS is optimized for the desired frequency of 57–63 GHz. A high isolation of −30 dB is achieved when both FSS wall and slots are used. A prototype of the structure is fabricated and measured. The results give a low correlation coefficient ( $e$ –6) and a good agreement with simulation ones, indicating that the proposed antenna can provide spatial or pattern diversity to increase the data capacity of wireless communication systems at mm-wave bands.