Showing papers in "IEEE Antennas and Wireless Propagation Letters in 2011"
Journal Article•
358 citations
TL;DR: In this article, the authors proposed the use of variable-impedance metasurfaces for transforming surface or guided waves into different wavefield configurations with desirable properties, referred to as "metasurfing".
Abstract: Metasurfaces constitute a class of thin metamaterials, which are used from microwave to optical frequencies to create new antennas and microwave devices. Here, we propose the use of variable-impedance metasurfaces for transforming surface or guided waves into different wavefield configurations with desirable properties. We will shortly refer to this metasurface-driven wavefield transformation as “metasurfing.” Metasurfing can be obtained by an appropriate synthesis of inhomogeneous metasurface reactance that allows a local modification of the dispersion equation and, at constant operating frequency, of the local wave vector. The general effects of metasurface modulation are similar to those obtained in solid (volumetric) inhomogeneous metamaterial as predicted by the transformation optics-namely, readdressing the propagation path of an incident wave. However, significant technological simplicity is gained. Several examples are shown as a proof of concept.
341 citations
TL;DR: A simple rectenna design ex ample containing a 2 × 2 planar antenna array will be presented to demonstrate such RF power harvesting technology and the parameter, Rectenna Topology Indicator (RTI), is introduced for performance comparison.
Abstract: RF power harvesting enables controllable and simultaneous wireless power delivery to many RF devices. Devices built with this unique technology can be sealed, embedded within structures, or made mobile, thus eliminating additional service for a battery. A key component of this technology is the "rectenna," which is composed of antennas and rectifying circuitry to convert RF energy into dc power. Typically, multiple rectenna elements are used to generate the dc power for reliable device operation. This letter compares two different rectenna architectures for maximum RF-to-dc power conversion efficiency. A simple rectenna design ex ample containing a 2 × 2 planar antenna array will be presented to demonstrate such RF power harvesting technology. The parameter, Rectenna Topology Indicator (RTI), is introduced for performance comparison.
321 citations
TL;DR: In this article, a miniaturized multifrequency antenna is proposed, which consists of a circular ring, a Y-shape-like strip, and a defected ground plane.
Abstract: A miniaturized multifrequency antenna is proposed. The proposed antenna can generate three separate impedance bandwidths to cover all the 2.4/5.2/5.8-GHz WLAN operating bands and the 2.5/3.5/5.5-GHz WiMAX bands. The proposed microstrip-fed antenna mainly consists of a circular ring, a Y-shape-like strip, and a defected ground plane. By adding a Y-shape-like strip in the circular ring, the antenna excites two resonant modes and is with miniaturization structure. Because of the introduction of the cambered ground plane with an isosceles triangle-defect, the third wide band with better impedance matching is obtained. A prototype is experimentally tested, and the measured results show good radiation patterns and enough gains across the operation bands.
251 citations
TL;DR: In this article, a compact microstrip line-fed ultrawideband (UWB) tapered-shape slot antenna is presented, which is fabricated onto an inexpensive FR4 substrate with an overall dimension of 22 × 24 mm2.
Abstract: A compact microstrip line-fed ultrawideband (UWB) tapered-shape slot antenna is presented. The proposed antenna comprises a tapered-shape slot and rectangular tuning stub. The antenna is fabricated onto an inexpensive FR4 substrate with an overall dimension of 22 × 24 mm2. The experiment shows that the proposed antenna achieves good impedance matching constant gain, stable radiation patterns over an operating bandwidth of 3-11.2 GHz (115.5%) that covers the entire UWB. The nearly stable radiation pattern with a maximum gain of 5.4 dBi makes the proposed antenna suitable for being used in UWB communication applications.
239 citations
TL;DR: In this article, the authors proposed a method based on the Nicolson-Ross-Weir (NRW) technique for extracting material parameters from samples thicker than λ/2, a measure that would otherwise cause problems in the NRW extraction technique.
Abstract: Approaches of automated evaluation of electromagnetic material parameters have received a lot of attention in the literature. Among others, one method is to retrieve the material parameters from the reflection and transmission measurements of the sample material. Compared to other methods, this is a rather wideband method, but suffers from an intrinsic limitation related to the electrical thickness of the measured material. In this letter, we propose a novel way to overcome this limitation. Although being based on the classical Nicolson-Ross-Weir (NRW) technique, the proposed extraction technique does not involve any branch seeking and is therefore capable of extracting material parameters from samples thicker than λ/2, a measure that would otherwise cause problems in the NRW extraction technique. The proposed derivative of the NRW extraction technique is then used to study the effect of thermal noise on the extracted material parameters.
232 citations
TL;DR: An efficient mutual coupling reduction method is introduced in this article for extremely closely placed dual-element microstrip antennas positioned on a finite-sized ground plane for WLAN MIMO application at 5.8 GHz.
Abstract: An efficient mutual coupling reduction method is introduced in this letter for extremely closely placed dual-element microstrip antennas positioned on a finite-sized ground plane for WLAN MIMO application at 5.8 GHz. High isolation can be achieved through a simple slot structure on the ground between the microstrip antennas. The position, length, and width of the slot have been optimized for maximizing the isolation. It is found that more than 40 dB isolation can be achieved between two parallel microstrip antennas sharing a common ground plane. The space distance of these antennas is 17.5 mm ≈ 0.33λ0 from element center to center (side by side of 1.6 mm ≈ 0.031λ0) when the ground plane size is 0.85λ0 × 0.55λ0. Along with this letter, several prototypes were fabricated, and their performances measured to validate the obtained IE3D moment method-based simulation results.
230 citations
TL;DR: In this paper, an efficiency analysis of a magnetic resonance wireless power transfer (WPT) system with an intermediate resonant coil is presented, and the power efficiency is calculated using the temporal coupled mode theory (CMT).
Abstract: This letter presents an efficiency analysis of a magnetic resonance wireless power transfer (WPT) system with an intermediate resonant coil. A helical coil and a spiral coil with an additional capacitor are considered as resonant coils for the WPT system. The intermediate resonant coil is set up coaxially and perpendicular to both the Tx and Rx resonant coils in order to observe the efficiency change according to the directions. The power efficiency is calculated using the temporal coupled mode theory (CMT). Impedance matching conditions are also shown by using the CMT. Analysis results show that using an intermediate coil properly improves efficiency and extends the distance between the transmitter and receiver. Both calculated and measured efficiencies are in good agreement. It is also shown that the intermediate resonant system has a good efficiency and is superior to nonintermediate systems.
214 citations
TL;DR: In this paper, a simple and intuitive metric of multiplexing efficiency is proposed for evaluating the performance of multiple-input-multiple-output (MIMO) antennas in the spatial multiple-access mode of operation.
Abstract: A simple and intuitive metric of multiplexing efficiency is proposed for evaluating the performance of multiple-input-multiple-output (MIMO) antennas in the spatial multiplexing mode of operation. Apart from gaining valuable insights into the impact of antenna efficiency, efficiency imbalance, and correlation on multiplexing performance, the metric is particularly useful for antenna engineers whose goal is to achieve the optimum antenna system design. Experimental results involving prototype mobile terminals highlight the effectiveness of our proposal.
207 citations
TL;DR: In this paper, a modified antipodal Vivaldi antenna is presented and a novel tapered slot edge (TSE) structure is employed in this design, which has the capacity to extend the low-end bandwidth limitation and improve the radiation characteristics in the lower frequencies.
Abstract: In this letter, a modified antipodal Vivaldi antenna is presented. A novel tapered slot edge (TSE) structure is employed in this design. The proposed TSE has the capacity to extend the low-end bandwidth limitation and improve the radiation characteristics in the lower frequencies. A prototype of the modified antenna is fabricated and experimentally studied as well. The measured results show reasonable agreement with the simulated ones that validate the design procedure and confirm the benefits of the modification.
202 citations
TL;DR: In this paper, two microstrip square open-loop resonators, a coupled line, and a Γ-shaped antenna are used and integrated to be a filter-antenna.
Abstract: Design, fabrication, and measurement of a new compact filter-antenna for modern wireless communication systems are presented in this letter. Two microstrip square open-loop resonators, a coupled line, and a Γ-shaped antenna are used and integrated to be a filter-antenna. The Γ-shaped antenna is excited by a coupled line that is treated as the admittance inverter in filter design. The Γ-shaped antenna performs not only a radiator, but also the last resonator of the bandpass filter. Therefore, near-zero transition loss is achieved between the filter and the antenna. The design procedure follows the circuit approach-synthesis of bandpass filters. Measured results show that the filter-antenna achieves an impedance bandwidth of 16.3% (over 2.26-2.66 GHz) at a reflection coefficient |S11 | <; - 10 dB and has a gain of 2.41 dBi.
TL;DR: In this paper, a novel triband square-slot antenna with symmetrical L-strips is presented for WLAN and WiMAX applications, which can yield three different resonances to cover the desired bands while maintaining small size and simple structure.
Abstract: A novel triband square-slot antenna with symmetrical L-strips is presented for WLAN and WiMAX applications. The proposed antenna is composed of a square slot, a pair of L-strips, and a monopole radiator. By employing these structures, the antenna can yield three different resonances to cover the desired bands while maintaining small size and simple structure. Based on this concept, a prototype of a triband antenna is designed, fabricated, and tested. The experimental results show the antenna has the impedance bandwidths of 480 MHz (2.34-2.82 GHz), 900 MHz (3.16-4.06 GHz), and 680 MHz (4.69-5.37 GHz), which can cover both WLAN in the 2.4/5.2-GHz bands and WiMAX in the 2.5/3.5-GHz bands.
TL;DR: In this article, a fractal monopole antenna is proposed for the application in the UWB frequency range, which is designed by the combination of two fractal geometries.
Abstract: A fractal monopole antenna is proposed for the application in the UWB frequency range, which is designed by the combination of two fractal geometries. The first iterations of Giusepe Peano fractal are applied on the edges of a square patch, and a Sierpinski Carpet fractal is formed on its surface. The feed circuit is a microstrip line with a matching section over a semi-elliptical ground plane. The presented antenna has an omnidirectional radiation pattern, a good gain, and high efficiency. The fabrication and measurement data attest to the satisfaction of the design specifications.
TL;DR: In this paper, a 2.45 GHz rectifying antenna (rectenna) using a compact dual circularly polarized (DCP) patch antenna with an RF-dc power conversion part is presented.
Abstract: A 2.45-GHz rectifying antenna (rectenna) using a compact dual circularly polarized (DCP) patch antenna with an RF-dc power conversion part is presented. The DCP antenna is coupled to a microstrip line by an aperture in the ground plane and includes a bandpass filter for harmonic rejections. It exhibits a measured bandwidth of 2100 MHz (10 dB return loss) and a 705-MHz CP bandwidth (3 dB axial ratio). The maximum efficiency and dc voltage are respectively equal to 63% and 2.82 V over a resistive load of 1600 Ω for a power density of 0.525 mW/cm2.
TL;DR: In this paper, a U-shape radiating patch is excited by a T-shape resonator through an inset coupling structure, which acts as a radiator as well as the last stage of the filter.
Abstract: Design, fabrication, and measurement of a compact filtering microstrip antenna with second-order quasi-elliptic broadside antenna gain response are presented. A U-shape radiating patch is excited by a T-shape resonator through an inset coupling structure. The U-shape patch acts as a radiator as well as the last stage of the filter, and the inset coupling structure can be treated as the admittance inverter in filter design. The design procedure follows the circuit approach-synthesis of bandpass filters. The broadside gain of the filtering antenna has two poles in passband and two broadside radiation nulls (zeros) at the band edges for improving selectivity. Compared to the conventional inset-fed microstrip antenna, with a little extra circuit area, the proposed filtering antenna has a flatter passband response, better frequency skirt selectivity, and almost twice wider bandwidth. The measurement result shows a good agreement with the simulations.
TL;DR: In this article, a high-gain Vivaldi antenna based on compactly anisotropic zero-index metamaterials (ZIM) was proposed to enhance the directivity.
Abstract: The traditional Vivaldi antenna has an ultrawide bandwidth, but low directivity. To enhance the directivity, we propose a high-gain Vivaldi antenna based on compactly anisotropic zero-index metamaterials (ZIM). Such anisotropic ZIM are designed and fabricated using resonant meander-line structures, which are integrated with the Vivaldi antenna smoothly and hence have compact size. Measurement results show that the directivity and gain of the Vivaldi antenna have been enhanced significantly in the designed bandwidth of anisotropic ZIM (9.5-10.5 GHz), but not affected in other frequency bands (2.5-9.5 GHz and 10.5-13.5 GHz).
TL;DR: In this paper, a single-layer antenna composed of a square ground plane embedded with two unequal-size inverted-L strips around two opposite corners is capable of generating a resonant mode for exciting two orthogonal E vectors.
Abstract: This letter presents a new design for a circularly polarized square slot antenna (CPSSA). The proposed single-layer antenna composed of a square ground plane embedded with two unequal-size inverted-L strips around two opposite corners is capable of generating a resonant mode for exciting two orthogonal E vectors. In this model, compared to the previous CPSSA structures, the impedance bandwidth and the axial ratio bandwidth of antenna are increased, which is four times wider than the impedance bandwidth of previous similar designs. The designed CPSS antenna with size 60 × 60 × 0.8 mm3 operates over the frequency band between 2.67 and 13 GHz (4.74:1, 132%) for VSWR <; 2, exhibiting a 32.2% (4.9-6.9 GHz, 1.5:1) circular polarization (CP) bandwidth. Throughout this letter, the improvement process of the axial ratio (AR) and S\\ properties are presented and discussed in detail.
TL;DR: In this paper, a planar microstrip-fed super wideband monopole antenna is proposed to cover DVB-H in L-band (for PMP), DCS, PCS, UMTS, Bluetooth, WiMAX2500, LTE2600, and UWB bands.
Abstract: A planar microstrip-fed super wideband monopole antenna is initially proposed. By embedding a semielliptically fractal-complementary slot into the asymmetrical ground plane, a 10-dB bandwidth of 172% (1.44-18.8 GHz) is achieved with ratio bandwidth >;12:1. Furthermore, the proposed antenna also demonstrated a wide 14-dB bandwidth from 5.4 to 12.5 GHz, which is suitable for UWB outdoor propagation. This proposed antenna is able to cover the DVB-H in L-band (for PMP), DCS, PCS, UMTS, Bluetooth, WiMAX2500, LTE2600, and UWB bands.
TL;DR: In this article, the authors discuss the connection between the surface susceptibilities of a metafilm and effective material properties of a thin material slab and discuss the sign conventions and nomenclature used for surface susceptibility and correct sign errors.
Abstract: A metafilm is a type of metasurface, a two-dimensional equivalent of a metamaterial, and is essentially a surface distribution of electrically small scatterers arranged in a judiciously chosen pattern. In previous work, we have shown that the most appropriate way to characterize a metafilm is by its effective electric and magnetic surface susceptibilities, and we discussed methods for retrieving these surface susceptibilities. Nevertheless, some researchers have continued to characterize metasurfaces in terms of bulk effective material properties. In this letter, we first clarify sign conventions (and nomenclature) used for surface susceptibilities and correct sign errors in previous publications. We then discuss the connection between the surface susceptibilities of a metafilm and effective material properties of a thin material slab. The two subtle but important aspects discussed here are: 1) the interpretation of a thin material slab by its surface susceptibilities, and 2) the equating of a metafilm (which has its own unique surface susceptibilities) to a thin material slab with effective material properties.
TL;DR: In this article, a new design for single-feed dual-band circularly polarized microstrip antennas is presented, where a stacked patch configuration is used for the antenna, and circular polarization is achieved by designing asymmetrical U-slots on the patches.
Abstract: In this letter, a new design for single-feed dual-band circularly polarized microstrip antennas is presented. A stacked- patch configuration is used for the antenna, and circular polarization is achieved by designing asymmetrical U-slots on the patches. The dimensions of the U-slots are optimized to achieve circular polarization in both bands. A prototype has been designed to operate at two frequencies with a ratio of 1.66. Both experimental and theoretical results are presented and discussed. The circularly polarized bandwidth of the antenna is 1.0% at 3.5 GHz (WiMax) and 3.1% at 5.8 GHz (HiperLAN).
TL;DR: In this article, the authors demonstrate the gain enhancement of an ultrawideband (UWB) antenna, achieved using an appropriately designed multioctave dual-layer frequency selective surface (FSS) reflector.
Abstract: In this letter, we demonstrate the gain enhancement of an ultrawideband (UWB) antenna, achieved using an appropriately designed multioctave dual-layer frequency selective surface (FSS) reflector. The proposed novel FSS reflects effectively in phase over a bandwidth of about 120%. Hence, significant enhancement in antenna gain has been achieved with a low-profile configuration without compromising the impedance bandwidth of the UWB antenna. The proposed FSS reflector has a low transmission coefficient and linearly decreasing phase over an ultra-wide frequency band, which is the key requirement for providing an effectively in-phase reflection at the antenna plane. The composite structure is compact, with a total height of λ/4, where λ is the free-space wavelength at the lowest operating frequency of 3 GHz. Experimental results show an impedance bandwidth of 122%. The antenna gain is maintained around 7.5 dBi from 3 to 7 GHz. Between 7-14 GHz, the antenna is more directive with a gain of about 9 dBi with ±0.5 dB variation. Experimental measurements con firm the predicted wideband antenna performance and gain enhancement due to the FSS reflector.
TL;DR: In this paper, a simple, low-cost, and compact printed dual-band fork-shaped monopole antenna for Bluetooth and ultrawideband (UWB) applications is proposed.
Abstract: A simple, low-cost, and compact printed dual-band fork-shaped monopole antenna for Bluetooth and ultrawideband (UWB) applications is proposed. Dual-band operation covering 2.4-2.484 GHz (Bluetooth) and 3.1-10.6 GHz (UWB) frequency bands are obtained by using a fork-shaped radiating patch and a rectangular ground patch. The proposed antenna is fed by a 50-Ω microstrip line and fabricated on a low-cost FR4 substrate having dimensions 42 (Lsub) × 24 (Wsub) × 1.6 (H) mm3. The antenna structure is fabricated and tested. Measured S11 is ≤ -10 dB over 2.3-2.5 and 3.1-12 GHz. The antenna shows acceptable gain flatness with nearly omnidirectional radiation patterns over both Bluetooth and UWB bands.
TL;DR: In this article, a single-feed circularly polarized (CP) patch antenna at L-band was designed and built using the recently developed U-slot loaded patch technique, which achieved a reasonable axial-ratio bandwidth.
Abstract: A single-feed circularly polarized (CP) patch antenna at L-band is designed and built using the recently developed U-slot loaded patch technique. With the presence of the U-slot, the antenna fabricated on a high-dielectric-constant (er = 10.02) substrate achieves a reasonable axial-ratio bandwidth. At the operating frequency of 1.575 GHz, the size of the patch is 0.13λo × 0.13λo, while the ground size is 0.315λo × 0.315λo and the thickness of the substrate is 0.05λo. The measured gain is 4.5 dBi, and axial-ratio bandwidth is 3.2%.
TL;DR: In this article, a phase-shifting cell for linearly polarized reflectarray applications is presented, which provides a nearly 360° phase range and naturally comes back to its initial geometry after the phase cycle has been achieved.
Abstract: This letter presents a new phase-shifting cell for linearly polarized reflectarray applications. It provides a nearly 360° phase range and naturally comes back to its initial geometry after the phase cycle has been achieved. A complete analysis of the resonating mechanism is given, and a low dispersion (<;30°/GHz) is demonstrated over a large bandwidth (18%) in simulation.
TL;DR: In this article, a coplanar waveguide (CPW)-fed antenna consisting of slot and monopole antenna for dual-band design is proposed, which can provide two separate impedance bandwidths of 124 MHz and 1124 MHz.
Abstract: A coplanar waveguide (CPW)-fed antenna consisting of slot and monopole antenna for dual-band design is proposed. The proposed antenna can provide two separate impedance bandwidths of 124 MHz (about 5.1% centered at 2.45 GHz) and 1124 MHz (about 22.4% centered at 5.5 GHz), making it easy to cover the specification for WLAN operation in the 2.45-GHz band (about 3.4% required bandwidth) and 5.2/5.8-GHz bands (about 13% required bandwidth). Furthermore, the proposed antenna has a low profile of 3.5 mm, making it suitable for installation in wireless handheld devices. Details of the proposed antenna design and experimental results are presented and discussed.
TL;DR: In this paper, a new ultra wideband circular monopole antenna with an acceptable band-rejection characteristic is investigated, which is created by means of an electromagnetic band-gap (EBG) structure.
Abstract: In this letter, a new compact ultra wideband circular monopole antenna with an acceptable band-rejection characteristic is investigated. This rejection band is created by means of an electromagnetic band-gap (EBG) structure. The EBG structure that is used here is a mushroom-like structure. An equivalent circuit model is employed to investigate the stopband characteristic of the EBG. The operation frequency band is 3.1-10.6 GHz with a rejection band of 0.7 GHz around 5.5 GHz. Accurate and high rejection is achieved. The proposed model is implemented, and the measured results are in good agreement with simulated ones.
TL;DR: In this paper, an empirical path loss model was proposed for high-speed railway viaduct scenarios, considering the influences of the height H and base station antenna relative height h, which are not well-covered by existing large-scale models.
Abstract: Based on the narrowband 930-MHz measurements taken along the “Zhengzhou-Xi'an” high-speed railway in China, an empirical path loss model is proposed. It is applicable to high-speed railway viaduct scenarios, considering the influences of viaduct height H and base station antenna relative height h, which are not well-covered by existing large-scale models. The path loss exponents are investigated, based on which the influence of viaduct on propagation is discussed. The fading depth up to 15.96 dB and the Ricean K -factor with mean value of 3.79 dB are obtained.
TL;DR: In this paper, two different designs of folded split-ring resonators (FSRRs), composed of single and double rows, etched into the ground plane are proposed for more reduction of the mutual coupling and spacing between antennas.
Abstract: This letter presents an efficient technique to reduce the mutual coupling between two 5.2-GHz probe-fed patch antennas in an array format. Two different designs of folded split-ring resonators (FSRRs), composed of single and double rows, etched into the ground plane are proposed for more reduction of the mutual coupling and spacing between antennas. Parametric studies show that by carefully adjusting the basic design parameters, and so equivalent capacitance and inductance of the FSRRs, a reduction of more than 30 dB in the mutual coupling between two antennas with a very close distance of about 0.039 λ0 (edge-to-edge distance) and 0.27 λ0 (center-to-center distance) can be obtained. Measured S21 of the array in the first and second designs of the FSRRs are about -56 and -45 dB, respectively. The features including very small occupied area, high performance, and noncomplex structure make the proposed FSRRs more useful for various related applications.
TL;DR: In this paper, a flexible SU-8/PDMS-based antenna has been demonstrated, not only targeting the wearable computing, but also fitting well in the RF system-on-package (RF SOP) applications.
Abstract: In this letter, a flexible SU-8/PDMS-based antenna has been demonstrated, not only targeting the wearable computing, but also fitting well in the RF system-on-package (RF SOP) applications. The characteristics of the proposed antenna fabricated on a flexible polymer substrate (SU-8/PDMS) with different bending angles have been successfully measured and characterized for the first time. The measured results have shown fairly good agreement with the simulation results. The measured bandwidth and maximum gain are 3% from 6.2 to 6.4 GHz and 2.17 dBi, respectively, when the antenna is flat. Moreover, related antenna fabrication process provides a practical approach to realize the flexible antenna for the portable wireless electronics applications.
TL;DR: In this paper, a simple and compact UWB printed monopole antenna with filtering characteristic is presented, which consists of a defected ground structure (DGS) and a radiating patch with arc-shaped step that is notched by removing two squares at the bottom.
Abstract: A simple and compact UWB printed monopole antenna with filtering characteristic is presented. The proposed antenna consists of a defected ground structure (DGS) and a radiating patch with arc-shaped step that is notched by removing two squares at the bottom. By using a modified shovel-shaped defected ground structure, band-notched characteristic that in volves both operating frequency band of Dedicated Short-Range Communication (DSRC) systems and WLAN is obtained. Omnidirectional H-plane radiation patterns and appropriate impedance characteristic are the main features of the proposed antenna that are achieved by designing the lower edges of the radiating patch in the form of arc-shaped step. The designed antenna has a small size of 15 × 18 mm2 and provides the impedance bandwidth of more than 128% between 3.1 and 14 GHz for VSWR <; 2, with notch frequency band at 5.13-6.1 GHz.