Showing papers on "Microstrip antenna published in 2010"

Invasive Weed Optimization and its Features in Electromagnetics

Abstract: A new numerical stochastic optimization algorithm, inspired from colonizing weeds, is proposed for Electromagnetic applications. This algorithm, invasive weed optimization (IWO), is described and applied to different electromagnetic problems. The linear array antenna synthesis, the standard problem used by antenna engineers, is presented as an example for the application of the IWO. Compared to the PSO, The features of the IWO are shown. As another application, the design of aperiodic thinned array antennas by optimizing the number of elements and at the same time their positions is presented. By implementing this new scenario, thinned arrays with less number of elements and lower sidelobes, compared to the results achieved by genetic algorithm (GA) for the same aperture dimensions, are obtained. Finally, the IWO is applied to a U-slot patch antenna to have the desired dual-band characteristics.

Mutual Coupling Reduction in Patch Antenna Arrays Using a UC-EBG Superstrate

Abstract: Reducing mutual coupling between elements of an antenna array is one of the main topics in array designs. The use of electromagnetic band-gap (EBG) structures built by microstrip technology is an attractive way to mitigate the mutual coupling problem. This letter describes a novel configuration of uniplanar compact electromagnetic band-gap (UC-EBG) structures to reduce mutual coupling between the radiating elements. The idea is to use the UC-EBG structures placed on top of the antenna layer. The main objective is to reduce both the element separation and the mutual coupling between the patch antennas, which in turn increases antenna directivity. The proposed configuration eliminates drawbacks of similar structures presented in previous works.

Mutual Coupling Reduction Between Microstrip Patch Antennas Using Slotted-Complementary Split-Ring Resonators

Abstract: A novel structure based on complementary split-ring resonators (SRRs) is introduced to reduce the mutual coupling between two coplanar microstrip antennas that radiate in the same frequency band. The new unit cell consists of two complementary SRR inclusions connected by an additional slot. This modification improves the rejection response in terms of bandwidth and suppression. The filtering characteristics of the band-gap structure are investigated using dispersion analysis. Using the new structure, it was possible to achieve a 10-dB reduction in the mutual coupling between two patch antennas with a separation of only 1/4 free-space wavelength between them. Since the proposed structures are broadband, they can be used to minimize coupling and co-channel interference in multiband antennas.

Microstrip Patch Antennas

Abstract: Introduction Review of Some Background Materials General Formulation of the Cavity Model Characteristics of the Rectangular Patch Characteristics of the Circular Patch The Annular-Ring and the Equilaterial Triangular Patch Introduction to Full Wave Analysis of Microstrip Antennas Some Methods of Tuning the Resonant Frequencies of Patch Antennas Broadbanding Techniques Size Reduction Techniques Dual and Multi-Band Designs Dual Polarized Patch Antenna Designs Circular Polarization Microstrip Arrays

Asymmetric-Circular Shaped Slotted Microstrip Antennas for Circular Polarization and RFID Applications

Abstract: Novel asymmetric-circular shaped slotted microstrip patch antennas with slits are proposed for circularly polarized (CP) radiation and radio frequency identification (RFID) reader applications. A single-feed configuration based asymmetric-circular shaped slotted square microstrip patches are adopted to realize the compact circularly polarized microstrip antennas. The asymmetric-circular shaped slot(s) along the diagonal directions are embedded symmetrically onto a square microstrip patch for CP radiation and small antenna size. The CP radiation can be achieved by slightly asymmetric (unbalanced) patch along the diagonal directions by slot areas. Four symmetric-slits are also embedded symmetrically along the orthogonal directions of the asymmetric-circular shaped slotted patch to further reduce antenna size. The operating frequency of the antenna can be tuned by varying the slit length while keeping the CP radiation unchanged. The measured 3-dB axial-ratio (AR) bandwidth of around 6.0 MHz with 17.0 MHz impedance bandwidth is achieved for the antenna on a RO4003C substrate. The overall antenna size is 0.27λo × 0.27λo × 0.0137λo at 900 MHz.

Microstrip and printed antennas : new trends, techniques, and applications

Abstract: Preface. List of Contributors. Acknowledgments. 1 Numerical Analysis Techniques (Ramesh Garg). 1.1 Introduction. 1.2 Standard (Yee s) FDTD Method. 1.3 Numerical Dispersion of FDTD Algorithms and Hybrid Schemes. 1.4 Stability of Algorithms. 1.5 Absorbing Boundary Conditions. 1.6 LOD-FDTD Algorithm. 1.7 Robustness of Printed Patch Antennas. 1.8 Thin Dielectric Approximation. 1.9 Modeling of PEC and PMC for Irregular Geometries. References. 2 Computer Aided Design of Microstrip Antennas (Debatosh Guha and Jawad Y. Siddiqui). 2.1 Introduction. 2.2 Microstrip Patch as Cavity Resonator. 2.3 Resonant Frequency of Circular Microstrip Patch (CMP). 2.4 Resonant Frequency of Rectangular Microstrip Patch (RMP) with Variable Air Gap. 2.5 Resonant Frequency of an Equilateral Triangular Microstrip Patch (ETMP) with Variable Air Gap. 2.6 Input Impedance of a Microstrip Patch. 2.7 Feed Reactance of a Probe-Fed Microstrip Patch. 2.8 Radiation Characteristics. 2.9 Radiation Efficiency. 2.10 Bandwidth. 2.11 Conclusion. References. 3 Generalized Scattering Matrix Approach for Multilayer Patch Arrays (Arun K. Bhattacharyya). 3.1 Introduction. 3.2 Outline of the GSM Approach. 3.3 Mutual Coupling Formulation. 3.4 Finite Array: Active Impedance and Radiation Patterns. 3.5 Numerical Example. 3.6 Conclusions. 3.7 References. 4 Optimization Techniques for Planner Antennas (Rabindra K. Mishra). 4.1 Introduction. 4.2 Basic Optimization Concepts. 4.3 Real Coded Genetic Algorithm (RCGA). 4.4 Neurospectral Design of Rectangular Patch Antenna. 4.5 Inset-fed Patch Antenna Design Using Particle Swarm Optimization. 4.6 Conclusion. References. 5 Microstrip Reflectarray Antennas (Jafar Shaker and Reza Chaharmir). 5.1 Introduction. 5.2 General Review of Reflectarrays: Mathematical Formulation and General Trends. 5.3 Comparison of Reflectarray and Conventional Parabolic Reflector. 5.4 Cell Elements and Specific Applications: A General Survey. 5.5 Wideband Techniques for Reflectarrays. 5.6 Development of Novel Loop-Based Cell Elements. 5.7 Conclusion. References. 6 Reconfigurable Microstrip Antennas (Jennifer T. Bernhard). 6.1 Introduction. 6.2 Substrate Modification for Reconfigurability. 6.3 Conductor Modification for Reconfigurability. 6.4 Enabling Reconfigurability: Considerations for Reconfiguration Mechanisms. 6.5 Future Trends in Reconfigurable Microstrip Antenna Research and Development. References. 7 Wearable Antennas for Body Area Networks (Peter S. Hall and Yang Hao). 7.1 Introduction. 7.2 Sources on the Human Body. 7.3 Narrowband Antennas. 7.4 Fabric Antennas. 7.5 Ultra Wideband Antennas. 7.6 Multiple Antenna Systems. 7.7 Conclusion. References. 8 Printed Antennas for Wireless Communications (Satish K. Sharma and Lotfollah Shafai). 8.1 Introduction. 8.2 Broadband Microstrip Patch Antennas. 8.3 Patch Antennas for Multiband Wireless Communications. 8.4 Enhanced Gain Patch Antennas. 8.5 Wideband Compact Patch Antennas. 8.6 Microstrip Slot Antennas. 8.7 Microstrip Planar Monopole Antenna. References. 9 UHF Passive RFID Tag Antennas (Daniel Deavours and Daniel Dobkin). 9.1 Introduction. 9.2 Application Requirements. 9.3 Approaches. 9.4 Fabrication. 9.5 Conclusion. References. 10 Printed UWB Antennas (Zhi Ning Chen, Xianming Qing and Shie Ping See). 10.1 Introduction. 10.2 Swan Antenna with Reduced Ground Plane Effect. 10.3 Slim UWB Antenna. 10.4 Diversity Antenna. 10.5 Printed Slot UWB Antenna and Band-Notched Solutions. References. 11 Metamaterial Antennas and Radiative Systems (Christophe Caloz). 11.1 Introduction. 11.2 Fundamentals of Metamaterials. 11.3 Leaky-Wave Antennas. 11.4 Resonant Antennas. 11.5 Exotic Radiative Systems. References. 12 Defected Ground Structure for Microstrip Antennas (Debatosh Guha, Sujoy Biswas, and Yahia M. M. Antar). 12.1 Introduction. 12.2 Fundamentals of DGS. 12.3 DGS for controlling Microstrip Antenna Feeds and Front-End Characteristics. 12.4 DGS to Control/Improve Radiation Properties of Microstrip Patch Antennas. 12.5 DGS for Reduced Mutual Coupling between Microstrip Array Elements and Associated Improvements. 12.6 Conclusion. Appendix: A Brief DGS Chronology. References. 13 Printed Leaky Wave Antennas (Samir F. Mahmoud and Yahia M. M. Antar). 13.1 Introduction. 13.2 The Leaky Wave as a Complex Plane Wave. 13.3 Radiation Pattern of a Leaky Wave. 13.4 Examples of Leaky Mode Supporting Structures. 13.5 The Excitation Problem. 13.6 Two-Dimensional Leaky Waves. 13.7 Further Advances on a Class of Periodic Leaky Wave Antennas. References. Appendix I Preliminary Ideas: PTFE-Based Microwave Lamiantes and Making Prototypes. Appendix II Preliminary Ideas: Microwave Connectors for Printed Circuits and Antennas. Index.

Graphene-based nano-antennas for electromagnetic nanocommunications in the terahertz band

Abstract: Nanotechnology is enabling the development of devices in a scale ranging from one to a few hundred nanometers. Coordination and information sharing among these nano-devices will lead towards the development of future nanonetworks, boosting the range of applications of nanotechnology in the biomedical, environmental and military fields. Despite the major progress in nano-device design and fabrication, it is still not clear how these atomically precise machines will communicate. Recently, the advancements in graphene-based electronics have opened the door to electromagnetic communications in the nano-scale. In this paper, a new quantum mechanical framework is used to analyze the properties of Carbon Nanotubes (CNTs) as nano-dipole antennas. For this, first the transmission line properties of CNTs are obtained using the tight-binding model as functions of the CNT length, diameter, and edge geometry. Then, relevant antenna parameters such as the fundamental resonant frequency and the input impedance are calculated and compared to those of a nano-patch antenna based on a Graphene Nanoribbon (GNR) with similar dimensions. The results show that for a maximum antenna size in the order of several hundred nanometers (the expected maximum size for a nano-device), both a nano-dipole and a nano-patch antenna will be able to radiate electromagnetic waves in the terahertz band (0.1–10.0 THz).

Determination of Dielectric Constant of Fabric Materials and Their Use as Substrates for Design and Development of Antennas for Wearable Applications

Abstract: A novel approach to measure the dielectric constant of fabric substrate materials used for the development of wearable antennas (also called textile antennas) is presented in this paper. The technique reported here is based on the resonance method and focused on the use of microstrip patch radiator, which contains fabric material as its substrate. The accurate value of the dielectric constant of the fabric material can easily be extracted from the measured resonant frequency of the patch radiator. The dielectric constant values of six fabric materials, including jeans cotton, polyester combined cotton, and polyester, have been determined by this way. As an extended objective of this paper, initial investigations are done to study the performance/behavioral characteristics of wearable antennas in the Bluetooth industrial, scientific, and medical band. Two of the six textile antenna structures, developed to meet out the primary objective of determining the dielectric constant of fabrics, are tested, and their performance characteristics, such as impedance bandwidth, gain, efficiency, etc., are measured. In addition, another Bluetooth antenna employing polyester fabric substrate is designed considering its measured accurate value of dielectric constant and subjected to radiation pattern measurements. In general, all the measured antennas yield very good results, fulfilling the requirements for practical applications, and in particular, the third fabric antenna utilizing the accurate value of the dielectric constant determined shows superior performance characteristics compared to others, indicating the correctness of our approach. Thus, the suitability of fabric substrate materials for the development of textile antennas with microstrip patch configuration is also well demonstrated.

A Printed, Broadband Luneburg Lens Antenna

Abstract: The design of a 2D broadband, Luneburg lens antenna implemented using printed circuit board techniques is detailed. The refractive index of the lens is controlled through a combination of meandering crossed microstrip lines and varying their widths. The 12.4λ° diameter lens is designed to operate in the transverse electromagnetic (TEM) mode at 13 GHz. The lens antenna was designed, fabricated, and measured. The measured half power beamwidth of the experimental antenna is 4.34°.

Polarization Reconfigurable U-Slot Patch Antenna

Abstract: A compact U-slot microstrip patch antenna with reconfigurable polarization is proposed for wireless local area network (WLAN) applications. PIN diodes are appropriately positioned to change the length of the U-slot arms, which alters the antenna's polarization state. Two antenna prototypes with identical dimensions are designed, fabricated and measured. The first antenna prototype enables switching between linear and circular polarization by using a PIN diode and a capacitor located on the U-slot. The second antenna prototype uses two PIN diodes to switch between the two circular polarization senses. A good impedance match (S11 ≤-10 dB) for both linear and circular polarization is achieved from 5.725 to 5.85 GHz, a band typically used for WLAN applications, and the 3 dB axial ratio bandwidth is greater than 2.8%. Details of the simulated and measured reflection coefficient, axial ratio, gain and radiation patterns are presented.

A broadband and high-gain metamaterial microstrip antenna

Abstract: A broad bandwidth and high gain rectangular patch antenna was specifically designed in this paper using planar-patterned metamaterial concepts. Based on an ordinary patch antenna, the antenna has isolated triangle gaps and crossed strip-line gaps etched on the metal patch and ground plane, respectively. Demonstrated to have left-handed characteristics, the patterned metal patch and finite ground plane form a coupled capacitive-inductive circuit of negative index metamaterial. It is shown to have great impact on the antenna performance enhancement in terms of the bandwidth significantly broadened from a few hundred megahertz to a few gigahertz, and also in terms of high efficiency, low loss, and low voltage standing wave ratio. Experimental data show a reasonably good agreement between the simulation and measured results. This antenna has strong radiation in the horizontal direction for some specific applications within the entire band.

A Simple Ultrawideband Planar Rectangular Printed Antenna With Band Dispensation

Abstract: A compact planar ultrawideband (UWB) antenna with band notched characteristics is presented. Modification in the shape of radiation element and ground plane with two symmetrical bevel slots on the lower edge of the radiation element and on the upper edge of the ground plane makes the antenna different from the rectangular printed monopole. These slots improve the input impedance bandwidth and the high frequency radiation characteristics. With this design, the reflection coefficient is lower than 10 dB in the 3.1-10.6 GHz frequency range and radiation pattern is similar to dipole antenna. With the inclusion of an additional small radiation patch, a frequency-notched antenna is also designed and good out of band performance from 5.0-6.0 GHz can be achieved. Measured results confirm that the antenna is suitable for UWB applications due to its compact size and high performance. Also an approximate empirical expression to calculate the lowest resonant frequency is proposed.

Dual-Band Circularly Polarized $S$ -Shaped Slotted Patch Antenna With a Small Frequency-Ratio

Abstract: A dual-band single-feed circularly polarized, S-shaped slotted patch antenna with a small frequency-ratio is proposed for GPS applications. An S-shaped slot is cut at the centre of a square patch radiator for dual-band operation. A single microstrip feed-line is underneath the center of the coupling aperture ground-plane. The frequency-ratio of the antenna can be controlled by adjusting the S-shaped slot arm lengths. The measured 10-dB return loss bandwidths for the lower and upper-bands are 16% (1.103-1.297 GHz) and 12.5% (1.444-1.636 GHz), respectively. The measured 3-dB axial-ratio (AR) bandwidth is 6.9% (1.195-1.128 GHz) for the lower-band and 0.6% (1.568-1.577 GHz) for the upper-band. The measured gain is more than 5.0 dBic over both the bands. The measured frequency-ratio is 1.28. The overall antenna size is 0.46 ?o × 0.46?o × 0.086?o at 1.2 GHz.

Rectenna design and optimization using reciprocity theory and harmonic balance analysis for electromagnetic (EM) energy harvesting

Abstract: A rectenna design methodology combining electromagnetic (EM) simulation and harmonic balance (HB) analysis is presented. It consists of applying reciprocity theory to calculate the Thevenin equivalent circuit of the receiving antenna and optimizing the rectifying circuit parameters using HB analysis. The method is demonstrated by designing a 2.45-GHz rectenna based on a square aperture-coupled patch antenna with dual linear polarization. A compact implementation is achieved by etching a cross-shaped slot on the patch surface leading to a 32.5% patch side reduction. Voltage-doubling circuits convert the received RF power from each port to dc permitting the rectenna to receive arbitrarily polarized signals. The circuit is optimized for low input power densities and a simulated maximum efficiency of 38.2% was obtained for 1.5 nWcm-2 input RF power density at 2.43 GHz.

Two-dimensional optical phased array antenna on silicon-on-insulator.

Abstract: Optical wireless links can offer a very large bandwidth and can act as a complementary technology to radiofrequency links. Optical components nowadays are however rather bulky. Therefore, we have investigated the potential of silicon photonics to fabricated integrated components for wireless optical communication. This paper presents a two-dimensional phased array antenna consisting of grating couplers that couple light off-chip. Wavelength steering of $0.24 degrees /nm is presented reducing the need of active phase modulators. The needed steering range is $1.5 degrees . The 3dB angular coverage range of these antennas is about $0.007pi sr with a directivity of more than 38dBi and antenna losses smaller than 3dB.

Broadband CPW-Fed Circularly Polarized Square Slot Antenna With Lightening-Shaped Feedline and Inverted-L Grounded Strips

Abstract: A novel design is described for a circularly polarized square slot antenna (CPSSA). Circular polarization (CP) operations can be attained using a lightening-shaped feedline protruded from the signal line of the feeding coplanar waveguide (CPW). The CP bandwidth can be significantly enhanced by implanting a pair of inverted-L grounded strips into the slot and adjusting the dimensions of the lightening-shaped feedline, whereas the impedance bandwidth can be greatly enlarged through tuning embedded vertical and horizontal stubs. The designed antenna was measured to exhibit a CP bandwidth of as high as 48.8%.

Investigation Into the Effects of the Patch-Type FSS Superstrate on the High-Gain Cavity Resonance Antenna Design

Abstract: Results of modeling, design, simulation and fabrication are presented for a high-gain cavity resonance antenna (CRA), employing highly-reflective patch-type superstrates. In order to determine the resonant conditions, the antenna is first analyzed using the transverse equivalent network (TEN) model, as well as the well known simple ray-tracing method. Prior to that, a highly-reflective patch-type frequency selective surface (FSS) is designed in order to be employed as the superstrate layer of the CRA. Next, a 2.5-D full-wave analysis software package, based on the method of moments (ANSOFT Designer v4.0), is utilized to analyze the antenna structure. Using this full-wave analyzer, the input impedance properties of an actual antenna are investigated as well. Then, a 3-D full-wave analyzer, based on the finite element method (ANSOFT HFSS), is used to extract the directivity and radiation patterns of the CRA, taking into account the finiteness of the substrate, superstrate and ground plane. Some previously unaddressed issues, such as the effects of the FSS superstrate on the input impedance characteristics of the probe-fed microstrip patch antenna, acting as the excitation source of the CRA are also studied. The effects of the highly-reflective FSS superstrate size on the CRA directivity, and explicitly its aperture efficiency, are investigated as well. A comparative study is also performed between CRAs with patch-type FSS and high permittivity dielectric superstrates. Measurement results are provided to support the modelings and simulations.

A Compact Microstrip Slot Triple-Band Antenna for WLAN/WiMAX Applications

Abstract: A compact triple-band microstrip slot antenna applied to WLAN/WiMAX applications is proposed in this letter. This antenna has a simpler structure than other antennas designed for realizing triple-band characteristics. It is just composed of a microstrip feed line, a substrate, and a ground plane on which some simple slots are etched. Then, to prove the validation of the design, a prototype is fabricated and measured. The experimental data show that the antenna can provide three impedance bandwidths of 600 MHz centered at 2.7 GHz, 430 MHz centered at 3.5 GHz, and 1300 MHz centered at 5.6 GHz.

A Focused Planar Microstrip Array for 2.4 GHz RFID Readers

Abstract: The specific problems encountered in the design of near-field focused planar microstrip arrays for RFID (Radio Frequency IDentification) readers are described. In particular, the paper analyzes the case of a prototype operating at 2.4 GHz, which has been designed and characterized. Improvements with respect to conventional far-field focused arrays (equal phase arrays) are discussed and quantified.

Electronically Reconfigurable Transmitarray at Ku Band for Microwave Applications

Abstract: An electronically reconfigurable transmitarray device at 12 GHz is presented in this work. This paper highlights the functioning of this kind of device and thoroughly examines the proposed reconfigurable transmitarray. The architecture is discussed along with the design and selection of all the constituting elements and the prototypes for all of them. In order to add reconfigurability to the transmitarray structure, 360° reflective phase shifters were designed, prototyped and validated for direct application. Eventually, a demonstrative prototype for an active transmitarray with phase shifters was assembled, and radiation pattern measurements were taken in an anechoic chamber to demonstrate the capabilities of this structure.

A Comparison of a Wide-Slot and a Stacked Patch Antenna for the Purpose of Breast Cancer Detection

Abstract: A wide-slot UWB antenna is presented for intended use in the detection scheme being developed at the University of Bristol, based on the principle of synthetically focused UWB radar using a fully populated static array. The antenna's measured and simulated, input and radiation characteristics are presented and compared to an existing, stacked patch antenna that has been designed for the same purpose. The results of this study show that the wide-slot antenna has excellent performance across the required frequency range. Compared to the stacked-patch antenna used in our previous array, the wide-slot antenna can be 3 times smaller (in terms of front surface). The compact nature of the slot antenna means that the detection array can be densely populated. Additionally, this new antenna offers better radiation coverage of the breast. For angles up to 60° away from bore-sight radiated pulses are almost identical (fidelity >95%), whereas for the patch antenna fidelity falls to 58% at the angular extremes. This uniform radiation into the breast should result in focused images with low levels of clutter.

Compact Dual Band-Notched Printed Monopole Antenna for UWB Application

Abstract: A compact printed ultrawideband (UWB) monopole antenna with dual band-notched characteristics is presented. By inserting two I-shaped notches in both sides of the microstrip feed line on the ground plane, additional resonances are excited, and hence the bandwidth is increased up to 123%. Two notched frequency bands are achieved by embedding a pair of Γ-shaped stubs in the radiation patch and a modified G-slot defected ground structure in the feeding line. The designed antenna has a small size of 20 × 18 mm2 and operates over the frequency band between 2.8 and 11.8 GHz for VSWR <; 2, with one notch frequency band at 3.3-3.8 GHz (WiMAX band) and the other at 5.1-6 GHz (WLAN band). The VSWR and radiation patterns of the fabricated antenna are presented, which prove that the designed antenna is a good candidate for various UWB applications.

RF MEMS Integrated Frequency Reconfigurable Annular Slot Antenna

Abstract: A new kind of double- and single-arm cantilever type DC-contact RF MEMS actuators has been monolithically integrated with an antenna architecture to develop a frequency reconfigurable antenna. The design, microfabrication, and characterization of this ?reconfigurable antenna (RA) annular slot? which was built on a microwave laminate TMM10i ( ?r = 9.8, tan ? = 0.002), are presented in this paper. By activating/deactivating the RF MEMS actuators, which are strategically located within the antenna geometry and microstrip feed line, the operating frequency band is changed. The RA annular slot has two reconfigurable frequencies of operation with center frequencies f low = 2.4 GHz and f high = 5.2 GHz, compatible with IEEE 802.11 WLAN standards. The radiation and impedance characteristics of the antenna along with the RF performance of individual actuators are presented and discussed.

Miniaturized Substrate Integrated Waveguide Slot Antennas Based on Negative Order Resonance

Abstract: Miniaturized waveguide slot antennas using negative order resonance are proposed and developed in this paper. The design of these novel resonant-type antennas is based on the study of a composite right/left-handed (CRLH) substrate integrated waveguide (SIW) starting from the dispersion diagram and the equivalent circuit. These proposed CRLH resonators are realized by etching the interdigital slot on the surface of the SIW. The slot acts as a series capacitor as well as a radiator leading to a CRLH antenna application. Two types of slot antennas, which are open-ended and short-ended, respectively, are proposed and discussed. The short-ended antenna, which represents a quasi-quarter-wavelength resonator, is characterized by a cavity-backed slot antenna thus providing a high gain. On the other hand, the open-ended antenna exhibits a small size owing to a quasi-half-wavelength operation in the left-handed (LH) region. Four antennas with one or two unit cells are fabricated and measured. Compared with the existing CRLH patch antennas and waveguide slot antennas, our antennas show advantages in terms of simplicity, low-profile, high efficiency, easy fabrication and integration with other circuits.

The Versatile U-Slot Patch Antenna

Abstract: The U-slot patch antenna was originally developed as a single-layer, single-patch wideband antenna. It has recently been shown that it can also be designed to perform a number of other functions. In this paper, a comprehensive account is given on the development of this antenna. Emphasis is placed on experimental and simulation results for various U-slot topologies, illustrating the antenna's versatility in several practical applications. These include wideband, dual- and triple-band operation with small and large frequency ratios, as well as for circular-polarization applications.

Development of textile antennas for body wearable applications and investigations on their performance under bent conditions

Abstract: Utilization of wearable textile materials for the develop- ment of microstrip antenna segment has been rapid due to the recent miniaturization of wireless devices. A wearable antenna is meant to be a part of the clothing used for communication purposes, which includes tracking and navigation, mobile computing and public safety. This pa- per describes design and development of four rectangular patch anten- nas employing difierent varieties of cotton and polyester clothing for on-body wireless communications in the 2.45GHz WLAN band. The impedance and radiation characteristics are determined experimentally when the antennas are kept in ∞at position. The performance deterio- ration of a wearable antenna is analyzed under bent conditions too to check compatibility with wearable applications. Results demonstrate the suitability of these patch antennas for on-body wireless communi- cations.

Wideband Circularly Polarized Trapezoidal Dielectric Resonator Antenna

Abstract: A wideband circularly polarized (CP) trapezoidal dielectric resonator antenna (DRA) is investigated in this letter. The DRA is simply excited by a single 45° inclined slot fed by a microstrip feed line. It is found that the 3-dB axial ratio (AR) bandwidth of the proposed antenna can be as wide as 21.5%. The antenna gain varies between 5.28 and 8.40 dBi across the antenna passband (3.11-3.86 GHz). This letter also presents a modified trapezoidal DRA that has a notch at its top. The modified version improves the impedance match, as the AR and gain remain almost unchanged. The reflection coefficient, AR, radiation pattern, and antenna gain of each proposed configuration are studied, and reasonable agreement between the measured and simulated results is observed.

A Broadband UHF Near-Field RFID Antenna

Abstract: A broadband segmented loop antenna is presented for ultra high frequency (UHF) near-field radio frequency identification (RFID) applications. Using a segmented line, the current distribution along the loop is kept in phase even though the perimeter of the loop is more than two operating wavelengths so that the proposed antenna generates strong and even magnetic field distribution in the near-field zone of the antenna. The antenna prototype, printed onto a piece of FR4 substrate, with an overall size of , achieves a large interrogation zone of with good impedance matching and uniform magnetic field distribution over the entire UHF RFID band of 840-960 MHz.

Bandwidth Enhancement of Printed E-Shaped Slot Antennas Fed by CPW and Microstrip Line

Abstract: Two printed wide-slot antennas with E-shaped patches and slots, for broadband applications, are proposed They are fed by a coplanar waveguide (CPW) and a microstrip line with almost the same performances Detailed simulation and experimental investigations are conducted to understand their behaviors and optimize for broadband operation Good agreement between the measurement and simulation has been achieved The impedance bandwidths, determined by 10-dB reflection coefficient, of the proposed slot antennas fed by microstrip line and CPW, from both measurement and simulation, are about 136% (285 to 1512 GHz) and 146% (283 to 182 GHz), respectively This large operating bandwidth is obtained by choosing suitable combinations of feed and slot shapes In order to achieve wider operation bandwidth both of the designed antennas have round corners on the wide slot and patch Meanwhile, the proposed antennas exhibit almost omnidirectional radiation patterns, relatively high gain, and low cross polarization A comprehensive numerical sensitivity analysis has been done to understand the effects of various dimensional parameters and to optimize the performance of the designed antennas Results for reflection coefficient, far-field E and H-plane radiation patterns, and gain of the designed antennas are presented and discussed

Design of a 2.45 GHz rectenna for electromagnetic (EM) energy scavenging

Abstract: A compact dual polarized rectenna operating at 2.45 GHz is presented. It consists of a square aperture coupled patch antenna with a cross shaped slot etched on its surface that permits a patch side reduction of 32.5%. The patch size is 3.4 cm by 3.4 cm. The antenna is dual linearly polarized with each orthogonal polarization received by an appropriately placed coupling slot. The received signal from each slot output is rectified by a voltage doubling circuit and the doubler DC output signals are combined allowing the rectenna receive signals of arbitrary polarization. The circuit is optimized for low input power densities using harmonic balance. Simulated rectifier maximum RF-to-DC conversion efficiency values of 15.7% and 42.1% were obtained for input available power levels of -20 dBm and -10 dBm respectively at 2.45 GHz. The measured results are in agreement with the simulation.