Showing papers on "Patch 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.

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.

Optical Patch Antennas for Single Photon Emission Using Surface Plasmon Resonances

Abstract: Single photon sources can greatly benefit from specially designed structures that modify the properties of the photon emitter. Dielectric cavities are often discussed, but they require a compromise between the spectral width and Purcell factor. In this Letter, we introduce plasmonic cavities as promising alternatives. We first study how the emitter couples with the modes of such structures. We then show how a patch antenna configuration simultaneously presents a large Purcell factor, collection efficiency, and spectral width.

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.

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.

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.

HermesD: A High-Rate Long-Range Wireless Transmission System for Simultaneous Multichannel Neural Recording Applications

Abstract: HermesD is a high-rate, low-power wireless transmission system to aid research in neural prosthetic systems for motor disabilities and basic motor neuroscience. It is the third generation of our "Hermes systems" aimed at recording and transmitting neural activity from brain-implanted electrode arrays. This system supports the simultaneous transmission of 32 channels of broadband data sampled at 30 ks/s, 12 b/sample, using frequency-shift keying modulation on a carrier frequency adjustable from 3.7 to 4.1 GHz, with a link range extending over 20 m. The channel rate is 24 Mb/s and the bit stream includes synchronization and error detection mechanisms. The power consumption, approximately 142 mW, is low enough to allow the system to operate continuously for 33 h, using two 3.6-V/1200-mAh Li-SOCl2 batteries. The transmitter was designed using off-the-shelf components and is assembled in a stack of three 28 mm ? 28-mm boards that fit in a 38 mm ? 38 mm ? 51-mm aluminum enclosure, a significant size reduction over the initial version of HermesD. A 7-dBi circularly polarized patch antenna is used as the transmitter antenna, while on the receiver side, a 13-dBi circular horn antenna is employed. The advantages of using circularly polarized waves are analyzed and confirmed by indoor measurements. The receiver is a stand-alone device composed of several submodules and is interfaced to a computer for data acquisition and processing. It is based on the superheterodyne architecture and includes automatic frequency control that keeps it optimally tuned to the transmitter frequency. The HermesD communications performance is shown through bit-error rate measurements and eye-diagram plots. The sensitivity of the receiver is -83 dBm for a bit-error probability of 10-9. Experimental recordings from a rhesus monkey conducting multiple tasks show a signal quality comparable to commercial acquisition systems, both in the low-frequency (local field potentials) and upper-frequency bands (action potentials) of the neural signals. This system can be easily scaled up in terms of the number of channels and data rate to accommodate future generations of Hermes systems.

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.

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.

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.

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.

Compact Monopole Antenna With Band-Notched Characteristic for UWB Applications

Abstract: A compact planar monopole antenna with standard band-notched characteristic suitable for ultrawideband (UWB) applications is presented. This microstrip-fed antenna, consisting of a square slot patch with a vertical coupling strip, only occupies a small size of 15 (L) × 15 (W) × 1.6 (H) mm3. By properly designing the strip placed at the center of the patch, good frequency rejection performance of the antenna with a wide operating band from 3.05 to 11.15 GHz can be obtained. Compared to other designs, the antenna has a quite simple structure to make the band-notched property to reduce the effect caused by the frequency interference. Furthermore, fairly good omnidirectional radiation patterns and transmission responses both indicate that the proposed antenna is well suited to be integrated within various portable devices for UWB operation.

A Compact CPW-Fed Slotted Patch Antenna for Dual-Band Operation

Abstract: A compact coplanar waveguide (CPW)-fed patch antenna designed by simply embedding two types of shaped slots into a rectangular patch for achieving dual-band operation is presented. The use of embedded slots can effectively excite multiresonant modes together with good dual-impedance bandwidths, especially ultrawide for the upper bandwidth. By fabricating and measuring the prototype of the proposed optimal antenna, dual operating bands with 10-dB return-loss bandwidths of about 230 MHz centered at 2.42 GHz and of about 73% ranging from 4.8 to 9.62 GHz covering the required bandwidths of 2.4/5.2/5.8 GHz WLAN standards and the C-band satellite communication were obtained. Also, a stable monopole-like radiation pattern and an average antenna gain of 1.4 and 5.1 dBi, respectively, across the dual operating bands have been measured.

Planar Antenna Array and Article of Manufacture Using Same

Abstract: A planar antenna array and articles of manufacture using the same are disclosed. In one embodiment, close-packed antenna elements, disposed on a substrate, number N where N=3x and x is a positive integer. Each of the close-packed antenna elements includes a substantially continuous photonic transducer arranged as an outwardly expanding generally logarithmic spiral having six turns. Each of the outwardly expanding generally logarithmic spirals may be a golden spiral. As an article of manufacture, the planar antenna array may be incorporated into a chip, such as a cell phone, or an article of clothing, for example.

Reconfigurable Antenna With Elevation and Azimuth Beam Switching

Abstract: A reconfigurable microstrip antenna is proposed for low-cost adaptive beam-switching applications. A small patch-slot ring structure is used as the radiating element where an asymmetrical arrangement of p-i-n diodes is employed to switch the pattern in four directions. The antenna provides pattern switching of 65° and 45° in its fundamental mode for the elevation and azimuth planes, respectively. By maintaining the resonant frequency and beamwidth as relatively constant, beam switching is realized using a single feed point.

Ultrawideband Dielectric Resonator Antenna With Broadside Patterns Mounted on a Vertical Ground Plane Edge

Abstract: A novel portable dielectric resonator antenna (DRA) design with broadside radiation is presented for ultrawideband wireless applications and narrow pulse sensor for breast cancer detections. The antenna provides broadside radiation. By using a solid rectangular dielectric resonator mounted on a vertical ground plane edge, the total antenna volume is considered to be less than that with a perpendicular ground plane. A wide impedance matching bandwidth is achieved. In addition, a modified version of the rectangular dielectric resonator antenna, which has two dielectric pieces removed to have an A-shaped resonator, provides wider impedance matching bandwidth of around 93% with much better broadside radiation characteristics and lighter weight is also considered. Comparison between the two antennas is presented with parametric study. The modified antenna is built and tested and very good agreement between computed and measured results is obtained.

Bandwidth Enhancement Method for Low Profile E-Shaped Microstrip Patch Antennas

Abstract: A simple bandwidth enhancement method for low profile E-shaped patch antennas is presented. By introducing a distributed LC circuit to the E-shaped patch antenna, a new resonant frequency close to that of the E-shaped patch is obtained, thus the bandwidth is widened. Moreover, the air thickness of the E-shaped patch antennas is reduced to only 0.0344λ0. A prototype antenna operated at AMPS band (824-894 MHz) was fabricated and measured. Measured results show that the designed low profile antenna has an impedance bandwidth over 9% for VSWR<; 2, with a satisfactory radiation performance within the bandwidth. The proposed method is also applicable to the design of other types of low profile slot-loaded patch antennas.

Compact Elongated Mushroom (EM)-EBG Structure for Enhancement of Patch Antenna Array Performances

Abstract: A compact elongated mushroom electromagnetic band-gap (EM-EBG) structure, exploiting the thickness of the substrate to achieve higher isolation compared to the case of the conventional mushroom EBG (CM-EBG), is proposed for the enhancement of the performances of patch antenna arrays. Guidelines, based on fairly accurate formulas, are provided for the design of the stop-band of the structure. The compactness of the EM-EBG is investigated and shown to be superior to that of the CM-EBG in practical cases. The superior reduction of mutual coupling of the EM-EBG is demonstrated by full-wave and experimental results both for a pair of patches and for a 4-element patch array. Finally, the benefits of the EM-EBG in terms of array processing, specifically side-lobe level (SLL) control and direction of arrival (DOA) estimation, are presented.

E-Textile Conductors and Polymer Composites for Conformal Lightweight Antennas

Abstract: We present a conformal and lightweight antenna technology based on E-textile conductors and polymer-ceramic composites. Unique advantages of the proposed technology are its structural integrity, light weight and conformity to the platform. E-textile conductors are fabricated with single wall carbon nanotube (SWNT) and Ag coated textiles. They demonstrate good structural integrity with polymer composites due to their mechanical compatibility. Similarly, polymer composites demonstrate superior RF performance with permittivity ranging from 3 to 13. Fabrication process for E-textile conductors and integration process with polymer composites is described in detail. We also demonstrated merit of the proposed technology with a simple patch antenna whose radiation performance is measured when it was flat and conformed onto a cylindrical surface. We compared its performance with that of an ideal patch. Experiments suggested that the sample patch antenna based on the proposed technique achieved 6 dB gain, which is 2 dB below a patch which has the same dimensions and made of ideal lossless materials. When it is conformed onto a cylindrical surface, we achieved 2.5 dB less gain than that of antenna realized with a PEC surface. This clearly validates the merit of the proposed conformal antenna technique based on non-traditional materials.

Polymer-Carbon Nanotube Sheets for Conformal Load Bearing Antennas

Abstract: We propose a conductive carbon nanotube (CNT) sheet to realize conformal antennas on polymer substrates. Polymer-ceramic composites (rubber-like structures) have good RF (high dielectric constant and low loss tangent) and desirable mechanical properties (conformal, flexible and lightweight). However, there is a challenge in printing metallization circuits on polymer substrates due to their hydrophobic nature. Also, they are associated with low metal-polymer adhesion, causing peeling under stain or tensile stresses. To address these issues, in this paper, we consider the approach of embedding high density vertically-aligned carbon nanotubes within the polymer composite to achieve a CNT sheet having high structural compatibility. We present the fabrication process to achieve high conductivity CNT sheets and construct a sample polymer-CNT patch antenna, yielding a 5.6 dB gain. This is only 0.8 dB lower than that of an ideal patch made of perfect electric conductor (PEC). Strain and tensile tests are also carried out to evaluate electrical performance of the polymer-CNT sheet as it is bent and stretched. Our measurements show that the proposed conductive polymer-CNT sheet is highly flexible and preserves good conductivity under small bending and stretching. The CNT sheet retains acceptable performances even after 100° bending and 13% stretching. The proposed polymer-CNT sheets are well suited for load bearing antenna applications.