Showing papers on "Patch antenna published in 2012"

Graphene-based nano-patch antenna for terahertz radiation

Abstract: The scattering of terahertz radiation on a graphene-based nano-patch antenna is numerically analyzed. The extinction cross section of the nano-antenna supported by silicon and silicon dioxide substrates of different thickness are calculated. Scattering resonances in the terahertz band are identified as Fabry–Perot resonances of surface plasmon polaritons supported by the graphene film. A strong tunability of the antenna resonances via electrostatic bias is numerically demonstrated, opening perspectives to design tunable graphene-based nano-antennas. These antennas are envisaged to enable wireless communications at the nanoscale. # 2012 Elsevier B.V. All rights reserved.

Printed MIMO-Antenna System Using Neutralization-Line Technique for Wireless USB-Dongle Applications

Abstract: A printed two-multiple-input multiple-output (MIMO)-antenna system incorporating a neutralization line for antenna port decoupling for wireless USB-dongle applications is proposed. The two monopoles are located on the two opposite corners of the system PCB and spaced apart by a small ground portion, which serves as a layout area for antenna feeding network and connectors for the use of standalone antennas as an optional scheme. It was found that by removing only 1.5 mm long inwards from the top edge in the small ground portion and connecting the two antennas therein with a thin printed line, the antenna port isolation can be effectively improved. The neutralization line in this study occupies very little board space, and the design requires no conventional modification to the ground plane for mitigating mutual coupling. The behavior of the neutralization line was rigorously analyzed, and the MIMO characteristics of the proposed antennas was also studied and tested in the reverberation chamber. Details of the constructed prototype are described and discussed in this paper.

Flexible Liquid Metal Alloy (EGaIn) Microstrip Patch Antenna

Abstract: This paper describes a flexible microstrip patch antenna that incorporates a novel multi-layer construction consisting of a liquid metal (eutectic gallium indium) encased in an elastomer. The combined properties of the fluid and the elastomeric substrate result in a flexible and durable antenna that is well suited for conformal antenna applications. Injecting the metal into microfluidic channels provides a simple way to define the shape of the liquid, which is stabilized mechanically by a thin oxide skin that forms spontaneously on its surface. This approach has proven sufficient for forming simple, single layer antenna geometries, such as dipoles. More complex fluidic antennas, particularly those featuring large, co-planar sheet-like geometries, require additional design considerations to achieve the desired shape of the metal. Here, a multi-layer patch antenna is fabricated using specially designed serpentine channels that take advantage of the unique rheological properties of the liquid metal alloy. The flexibility of the resulting antennas is demonstrated and the antenna parameters are characterized through simulation and measurement in both the relaxed and flexed states.

Package structures to improve on-chip antenna performance

Abstract: A radio frequency integrated circuit (RFIC) chip package is provided having an RFIC chip and an integrated antenna structure. The integrated antenna structure includes an on-chip antenna having one or more radiator elements formed as part of a back-end-of-line structure of the RFIC chip. The antenna structure further includes a superstrate structure disposed on the back-end-of-line structure of the RFIC chip. The superstrate structure includes at least one substrate layer and a focusing metal element. The focusing metal element has a structure that is complementary to the on-chip radiator elements and which is configured to focus electromagnetic radiation to and from the planar antenna structure. The superstrate structure improves the performance (e.g., antenna gain and bandwidth) of the on-chip antennas for millimeter-wave applications.

Controlling spontaneous emission with plasmonic optical patch antennas

Abstract: We experimentally demonstrate the control of the spontaneous emission rate and the radiation pattern of colloidal quantum dots deterministically positioned in a plasmonic patch antenna. The antenna consists of a thin gold microdisk 30 nm above a thick gold layer. The emitters are shown to radiate through the entire patch antenna in a highly directional and vertical radiation pattern. Strong acceleration of spontaneous emission is observed, depending of the antenna size. Considering the double dipole structure of the emitters, this corresponds to a Purcell factor up to 80 for dipoles perpendicular to the disk.

A Pattern Reconfigurable U-Slot Antenna and Its Applications in MIMO Systems

Abstract: A new compact pattern reconfigurable U-slot antenna is presented The antenna consists of a U-slot patch and eight shorting posts Each edge of the square patch is connected to two shorting posts via PIN diodes By switching between the different states of the PIN diodes, the proposed antenna can operate in either monopolar patch or normal patch mode in similar frequency ranges Therefore, its radiation pattern can be switched between conical and boresight patterns electrically In addition, the plane with the maximum power level of the conical pattern can be changed between two orthogonal planes Owing to a novel design of the switch geometry, the antenna does not need dc bias lines The measured overlapping impedance bandwidth (|S11| <; -10 dB) of the two modes is 66% with a center frequency of 532 GHz The measured radiation patterns agree well with simulated results The antennas are incorporated in a 2 × 2 multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system to demonstrate the improvement in system capacity In the real-time MIMO-OFDM channel measurement, it is shown that compared to omnidirectional antennas, the pattern reconfigurable antennas can enhance the system capacity, with 17% improvement in a line-of-sight (LOS) scenario and 12% in a non-LOS (NLOS) scenario at a signal-to-noise ratio (SNR) of 10 dB

A High Gain Antenna With an Optimized Metamaterial Inspired Superstrate

Abstract: A metamaterial unit cell with a low refractive index over a wide frequency band is proposed and designed. The effective material parameters of the unit cell are extracted, and the unit cell forms a planar three-layer metamaterial structure used as a superstrate for broadside gain enhancement of a patch antenna at 10 GHz. The proposed superstrate is optimized along with the antenna to enhance its beam-focusing ability, taking into account the oblique wave incidence from the radiation source. Both simulation and measurement of the antenna with the optimized superstrate show that this configuration is able to achieve a broadside gain 70%-80% of the maximum gain from the ideal effective radiation surface.

Embroidered Conductive Fibers on Polymer Composite for Conformal Antennas

Abstract: We provide a novel class of conformal antennas based on embroidered conductive metal-polymer fibers (E-fiber) on polymer-ceramic composites. This new technology offers attractive mechanical and RF performance when compared to traditional flat and rigid circuits and antennas. The proposed E-fiber components are consisted of high strength and flexible polymer fiber cores and conductive metallic coatings. They were fabricated using automatic embroidery process, followed by assembly with polydimethylsiloxane and rare-earth titanate ceramic composites. Such composite substrates were tape-casted, and capable of providing tunable dielectric constant from 3 to 12 with a low tanδ <; 10-2 up to GHz frequencies. Basic RF prototypes, such as transmission lines (TL), patch antennas, and antenna arrays were fabricated for experimental evaluation. Measurement of the prototypes were conducted and compared to their copper counterparts. The RF characteristics of the E-fiber TLs exhibited an insertion loss of only 0.03 dB/cm higher than copper TLs up to 4 GHz . Also, the E-fiber patch antenna and antenna array exhibited 0.3 dB and 0.6 dB lower gains, respectively, than their copper counterparts. When applied onto a cylindrical surface, both the E-fiber patch antenna and antenna array only suffered 1 dB loss in realized gain, which is quite remarkable when compared with traditional antennas.

A Compact Wideband MIMO Antenna With Two Novel Bent Slits

Abstract: A compact wideband multiple-input- multiple-output (MIMO) antenna is presented. The MIMO antenna consists of two symmetric monopoles with edge-to-edge separation of nearly 0.083 λ0 at 2.5 GHz. Two novel bent slits are etched into the ground plane. At the lower frequencies, the bent slits can reduce the mutual coupling and have slight effect on the reflection coefficient. At the higher frequencies, the slits can be considered as slit antennas to widen the impedance bandwidth because the two slits are coupled fed by two 50-Ω microstrip lines, respectively. Two triangles are cut from the ground plane. In this way, the reflection coefficient and isolation of the two slit antennas can be improved. A bandwidth of 92.7% with |S11| ≤ -10 dB and |S21 | ≤ -18 dB from 2.4 to 6.55 GHz is achieved. In order to provide quantifications for the performance of the MIMO antenna in real-world usage conditions, the effects of human hand and head on the performance of the MIMO antenna are investigated. The results show that the MIMO antenna serving as a phone antenna can provide spatial and pattern diversity to combat multipath fading.

Wideband Dual-Polarized Patch Antenna With Low Cross Polarization and High Isolation

Abstract: A coax-feed wideband dual-polarized patch antenna with low cross polarization and high port isolation is presented in this letter. The proposed antenna contains two pairs of T-shaped slots on the two bowtie-shaped patches separately. This structure changes the path of the current and keeps the cross polarization under -40 dB. By introducing two short pins, the isolation between the two ports remains more than 38 dB in the whole bandwidth with the front-to-back ratio better than 19 dB. Moreover, the proposed antenna achieving a 10-dB return loss bandwidth of 1.70-2.73 GHz has a compact structure, thus making it easy to be extended to form an array, which can be used as a base station antenna for PCS, UMTS, and WLAN/WiMAX applications.

Closely-Packed UWB MIMO/Diversity Antenna With Different Patterns and Polarizations for USB Dongle Applications

Abstract: A closely-packed ultrawideband (UWB) multiple- input multiple-output (MIMO)/diversity antenna (of two elements) with a size of 25 mm by 40 mm is proposed for USB dongle applications. Wideband isolation can be achieved through the different patterns and polarizations of the two antenna elements. Moreover, the slot that is formed between the monopole and the ground plane of the half slot antenna is conveniently used to further enhance the isolation at the lower frequencies and to provide an additional resonance at one antenna element in order to increase its bandwidth. The underlying mechanisms of the antenna's wide impedance bandwidth and low mutual coupling are analyzed in detail. Based on the measurement results, the proposed antenna can cover the lower UWB band of 3.1-5.15 GHz, and within the required band, the isolation exceeds 26 dB. The gains and total efficiencies of the two antenna elements are also measured. Furthermore, a chassis mode can be excited when a physical connection is required between the ground planes of the two antenna elements. Without affecting the performance of the half slot element, the monopole can now cover the band of 1.78-3 GHz, apart from the UWB band. The proposed antenna structure is found to provide good MIMO/diversity performance, with very low envelope correlation of less than 0.1 across the UWB band.

Analysis and Design of a Compact Dual-Band Directional Antenna

Abstract: A new type of compact dual-band directional antenna is proposed for 2.4/5-GHz wireless access point and RFID reader applications. The dual-band antenna consists of a longer dipole for the lower band and a pair of shorter dipoles for the upper band. A simple coupling microstrip line is employed to excite the dipoles. Both the dual-band antenna and the feeding microstrip line are printed on the same substrate, leading to a fully planar structure. The length of the dipole for the lower band is shortened by a capacitive loading at each end of the dipole, offering a compact antenna configuration. The compact dual-band antenna achieves a desirable directional radiation pattern with an antenna gain of near 8 dBi for the lower band and 9-10 dBi for the upper band. An equivalent circuit analysis for the design of the dual-band directional antenna is presented.

Bandwidth Enhancement of a Microstrip Line-Fed Printed Wide-Slot Antenna With a Parasitic Center Patch

Abstract: A printed wide-slot antenna with a parasitic patch for bandwidth enhancement is proposed and experimentally investigated. A simple 50-Ω microstrip line is used to excite the slot. A rotated square slot resonator is considered as reference geometry. The rotated square slot antenna exhibits two resonances (f1 : lower resonant frequency, f2: higher resonant frequency). By embedding a parasitic patch into the center of the rotated square slot, the lower resonant frequency is decreased and the higher resonant frequency is increased. Thus, broadband characteristic of the wide-slot antenna is achieved. The measured results demonstrate that this structure exhibits a wide impedance bandwidth, which is over 80% for |S11| ≤ -10 dB ranging from 2.23 to 5.35 GHz. Also, a stable and omnidirectional radiation pattern is observed within the operating bandwidth. In this design, a smaller ground plane is considered compared to the reference antenna (rotated square slot antenna without the parasitic center patch).

A Reconfigurable Wideband and Multiband Antenna Using Dual-Patch Elements for Compact Wireless Devices

Abstract: A reconfigurable wideband and multiband C-Slot patch antenna with dual-patch elements is proposed and studied. It occupies a compact volume of 50 × 50 × 1.57 (3925 mm3), including the ground plane. The antenna can operate in two dual-band modes and a wideband mode from 5 to 7 GHz. Two parallel C-Slots on the patch elements are employed to perturb the surface current paths for excitation of the dual-band and the wideband modes. Two switches, implemented using PIN diodes, are placed on the connecting lines of a simple feed network to the patch elements. Dual-band modes are achieved by switching “ON” either one of the two patch elements, while the wideband mode with an impedance bandwidth of 33.52% is obtained by switching “ON” both patch elements. The frequencies in the dual-band modes can be independently controlled using positions and dimensions of the C-Slots without affecting the wideband mode. The advantage of the proposed antenna is that two dual-band operations and one wideband operation can be achieved using the same dimensions. This overcomes the need for increasing the surface area normally incurred when designing wideband patch antennas. Simulation results are validated experimentally through prototypes. The measured radiation patterns and peak gains show stable responses and are in good agreements. Coupling between the two patch elements plays a major role for achieving the wide bandwidth and the effects of mutual coupling between the patch elements are also studied.

A Novel UWB Antenna With Dual Notched Bands for WiMAX and WLAN Applications

Abstract: A novel planar ultrawideband (UWB) antenna with dual notched bands is proposed and investigated. The antenna consists of a square patch and a modified grounded plane. To realize dual notched bands characteristics, a T-shaped stub embedded in the square slot of the radiation patch and a pair of U-shaped parasitic strips beside the feed line is used. The advantage of this antenna is the high rejection level in the stopband. The measured results show that the proposed dual-notched-bands planar antenna shows a very wide bandwidth from 2.8 to 11.0 GHz defined by voltage standing wave ratio VSWR <; 2, with two notched bands of 3.3-4.0 GHz (WiMAX band) and 5.05-5.90 GHz (WLAN band), respectively. Both the experimental and simulated results of the proposed antenna are presented, indicating that the antenna is a good candidate for various UWB applications.

Microstrip Patch Antennas—Basic Characteristics and Some Recent Advances

Abstract: The basic geometry of a microstrip patch antenna (MPA) consists of a metallic patch printed on a grounded substrate. Three commonly used feeding methods are coaxial feed, stripline feed, and aperture-coupled feed. The patch antenna idea was first proposed in the early 1950s, but it was not until the late 1970s that this type of antenna attracted serious attention of the antenna community. The microstrip patch antenna offers the advantages of low profile, conformability to a shaped surface, ease of fabrication, and compatibility with integrated circuit technology, but the basic geometry suffers from narrow bandwidth. In the last three decades, extensive studies have been devoted to improve the performance of this antenna and the MPA has found numerous applications in both the military and the commercial sectors. This article begins with a brief description of the modeling techniques and basic characteristics of the MPA. Methods of broadbanding, dual and multiband designs, size-reduction techniques, and design for circular polarization are then reviewed. The paper ends with some concluding remarks.

Miniaturization of Patch Antennas Using a Metamaterial-Inspired Technique

Abstract: A new design methodology for producing highly miniaturized patch antennas is introduced. The methodology uses complementary split-ring resonators placed horizontally between the patch and the ground plane. By optimizing the geometry of the split rings, sub-wavelength resonance of the patch antenna can be achieved with a good impedance match and radiation characteristics comparable to those of a traditional patch antenna on a finite ground plane. Construction of the optimized antenna is straightforward, requiring only the sandwiching of two etched circuit boards. High levels of miniaturization are demonstrated through simulations and experiments, with reductions of a factor of more than four in transverse dimension achieved for a circular patch resonant at 2.45 GHz. Although miniaturization is accompanied by a decrease in antenna radiation efficiency and a loss of fractional bandwidth, antenna performance remains acceptable even for a 1/16 reduction in patch area.

A Polarization Reconfigurable Patch Antenna With Loop Slots on the Ground Plane

Abstract: This letter proposes a reconfigurable microstrip patch antenna with polarization states being switched among linear polarization (LP), left-hand (LH) and right-hand (RH) circular polarizations (CP). The CP waves are excited by two perturbation elements of loop slots in the ground plane. A p-i-n diode is placed on every slot to alter the current direction, which determines the polarization state. The influences of the slots and p-i-n diodes on antenna performance are minimized because the slots and diodes are not on the patch. The simulated and measured results verified the effectiveness of the proposed antenna configuration. The experimental bandwidths of the -10-dB reflection coefficient for LHCP and RHCP are about 60 MHz, while for LP is about 30 MHz. The bandwidths of the 3-dB axial ratio for both CP states are 20 MHz with best value of 0.5 dB at the center frequency on the broadside direction. Gains for two CP operations are 6.4 dB, and that for the LP one is 5.83 dB. This reconfigurable patch antenna with agile polarization has good performance and concise structure, which can be used for 2.4 GHz wireless communication systems.

Power combiner using tri-plane antennas

Abstract: A power combining apparatus includes a waveguide structure and a plurality of antenna elements arranged in the waveguide structure, wherein each of the antenna elements comprises a center planar antenna layer, two outer planar antenna layers arranged on opposite sides of the center planar antenna layer, a non-conductive layer between the center planar antenna layer and one of the outer planar antenna layers, and another non-conductive layer between the center planar antenna and the other one of the outer planar antenna layers. The power combining apparatus includes a waveguide structure having an input, an output, and a plurality of antenna elements arranged in the waveguide structure, wherein each antenna element is configured to transform an electric field direction of an electromagnetic field by substantially 90 degrees rotation about a longitudinal axis of the waveguide structure, wherein a bandwidth of the antenna is less than, equal to, or greater than a decade of frequency range.

Mutual Coupling Reduction Between Planar Antennas by Using a Simple Microstrip U-Section

Abstract: Mutual coupling is an inevitable phenomenon in multiantenna systems, usually reducing the system performance. Numerous works have focused on the reduction of this effect. The aim is maintaining the mutual coupling suppressing structure as simple as possible while having a high amount of mutual coupling reduction. This letter presents a novel structure suppressing the mutual coupling between nearby patches. It is composed of only a simple U-shaped microstrip, which reduces the mutual coupling considerably. The structure has been constructed and tested. The measurement results prove the high efficiency of this configuration.

Low Profile Fully Planar Folded Dipole Antenna on a High Impedance Surface

Abstract: A fully planar antenna design incorporating a high impedance surface (HIS) is presented. The HIS is composed by a periodic array of subwavelength dogbone-shaped conductors printed on top of a thin dielectric substrate and backed by a metallic ground plane. First, the characteristics of a dipole over PEC or PMC layers, a dielectric slab, and the HIS are compared and studied in detail, highlighting the advantages provided by the use of the HIS. Then, the design of a low profile folded dipole antenna working at 5.5 GHz on top of the HIS is described. The surface provides close to 6% antenna impedance bandwidth and increased gain up to 7 dBi, while shielding the lower half space from radiation. The antenna structure comprises three metal layers without any vias between them, and its overall thickness is 0.059λ0. The dipole is fed by a balanced twin lead line through a balun transformer integrated in the same antenna layer. A prototype has been built and measurements confirming simulation results are provided.

A Compact Circularly Polarized Cross-Shaped Slotted Microstrip Antenna

Abstract: A compact cross-shaped slotted microstrip patch antenna is proposed for circularly polarized (CP) radiation. A symmetric, cross shaped slot is embedded along one of the diagonal axes of the square patch for CP radiation and antenna size reduction. The structure is asymmetric (unbalanced) along the diagonal axes. The overall size of the antenna with CP radiation can be reduced by increasing the perimeter of the symmetric cross-shaped slot within the first patch quadrant of the square patch. The performance of the CP radiation is also studied by varying the size and angle variation of the cross-shaped slot. A measured 3-dB axial-ratio (AR) bandwidth of around 6.0 MHz is achieved with the CP cross-shaped slotted microstrip antenna, with an 18.0 MHz 10-dB return-loss bandwidth. The measured boresight gain is more than 3.8 dBic over the operating band, while the overall antenna volume is 0.273λo × 0.273λo × 0.013λo (λο operating wavelength at 910 MHz).

Reflector arrangement for attachment to a wireless communications terminal

Abstract: A reflector arrangement (20, 22) is configured for attachment to a wireless communications terminal (4) having a patch antenna. The patch antenna includes a patch radiator(28)in a substantially parallel relationship with a ground plane(42), and the patch antenna produces a radiation beam of a predetermined beamwidth. The reflector arrangement is configured, when attached to the terminal, to produce a radiation beam of reduced beamwidth relative to the predetermined beamwidth. The reflector arrangement comprises a main reflector(20)and a sub-reflector (22) for reflecting radiation towards the main reflector(20), and the reflector arrangement is configured such that, when attached to the terminal, the patch antenna acts as a feed antenna for the sub-reflector(22). The sub-reflector (22) is arranged to collect the radiation from the patch antenna and to reflect the beam towards the main reflector (20) such that the main reflector (20) produces the radiated beam of reduced beamwidth.

Planar Leaky-Wave Antenna With Flexible Control of the Complex Propagation Constant

Abstract: This communication demonstrates for the first time the capability to independently control the real and imaginary parts of the complex propagation constant in planar, printed circuit board compatible leaky-wave antennas. The structure is based on a half-mode microstrip line which is loaded with an additional row of periodic metallic posts, resulting in a substrate integrated waveguide SIW with one of its lateral electric walls replaced by a partially reflective wall. The radiation mechanism is similar to the conventional microstrip leaky-wave antenna operating in its first higher-order mode, with the novelty that the leaky-mode leakage rate can be controlled by virtue of a sparse row of metallic vias. For this topology it is demonstrated that it is possible to independently control the antenna pointing angle and main lobe beamwidth while achieving high radiation efficiencies, thus providing low-cost, low-profile, simply fed, and easily integrable leaky-wave solutions for high-gain frequency beam-scanning applications. Several prototypes operating at 15 GHz have been designed, simulated, manufactured and tested, to show the operation principle and design flexibility of this one dimensional leaky-wave antenna.

Design Criteria for Near-Field-Focused Planar Arrays

Abstract: A detailed performance analysis of near-field-focused planar arrays is addressed. Design curves and performance data are shown for planar square arrays as a function of the array size, the inter-element distance, and the focal distance. The performance curves are compared with results presented in earlier studies relevant to continuous-aperture antennas, as well as with numerical results obtained from a full-wave analysis of planar microstrip arrays.

Characteristic-Mode-Based Improvement of Circularly Polarized U-Slot and E-Shaped Patch Antennas

Abstract: Characteristic mode (CM) analysis is carried out to understand the underlying physics of two popular circularly polarized (CP) microstrip patch antennas, namely U-slot and E-shaped CP patch antennas, for achieving better performance. Modifications of these two CP antennas with optimal feed position and compact patch size are explicitly obtained through examining the CMs, modal significance, and characteristic angle. Compared to conventional designs, the two modified designs have better axial ratio (AR) and cross-polarization performance without introducing any additional design cost or complexity. It is also interesting to find that: 1) offset probe feed in CP U-slot patch antennas will provide excellent AR performance; 2) cutting off the redundant section from CP E-shaped patch antenna will yield low cross polarization and more compact configuration.

A Compact Frequency-Reconfigurable Narrowband Microstrip Slot Antenna

Abstract: A frequency-reconfigurable microstrip slot antenna is proposed. The antenna is capable of frequency switching at six different frequency bands between 2.2 and 4.75 GHz. Five RF p-i-n diode switches are positioned in the slot to achieve frequency reconfigurability. The feed line and the slot are bended to reduce 33% of the original size of the antenna. The biasing circuit is integrated into the ground plane to minimize the parasitic effects toward the performance of the antenna. Simulated and measured results are used to demonstrate the performance of the antenna. The simulated and measured return losses, together with the radiation patterns, are presented and compared.

Wideband Stacked Rectangular Dielectric Resonator Antenna at 5.2 GHz

Abstract: This paper presents a design of stacked rectangular dielectric resonator antenna (RDRA) with wide bandwidth, in the range of 13.56 % is described. The antenna exploits two low-Q modes with overlapping bandwidths to achieve a wide continuous bandwidth. This is achieved using low-permittivity DRA volume placed on high permittivity DRA volume. The antenna consists of dielectric constant of 10 and 32, stacked vertically to obtain improved bandwidth as compared to the conventional RDRA. A 50 Ω microstrip line is used in the proposed antenna as a feeding mechanism. Physical parameters of stacked RDRA have been optimized by extensive simulations using Ansoft HFSS. The parameters of antenna are 17x7x4.56 mm 3 with grounded substrate size: 80x50 mm 2 . The prototype is fabricated. Measured and simulated results are both in good agreement. The prototype antenna designed to operate in band from 5.0 to 5.7 GHz with measured gain at 5.2 GHz resonant frequency. The proposed antenna is suitable for wireless local area networks (WLAN) applications in 5 GHz frequency band (in the frequency range 5.15-5.35 GHz and 5.5-5.7 GHz). This stacked RDRA exceeds the bandwidth requirements for IEEE 802.11a WLAN applications within a required VSWR. Parametric studies of the stacked DRA are presented.

Bandwidth Enhancement of Cavity-Backed Slot Antenna Using a Via-Hole Above the Slot

Abstract: A novel technique for the bandwidth enhancement of a cavity-backed slot antenna is presented. A via-hole located above the slot creates an additional resonance at a higher frequency by shortening the effective length of the slot. The location of the via-hole can be changed to determine the second resonance frequency of the antenna. With proper placement of the via-hole, the bandwidth of cavity-backed slot antenna can be increased. The fabricated antenna has a 60% wider bandwidth than a cavity-backed slot antenna without a via-hole. The proposed antenna maintains high radiation efficiency and gain, which are characteristics of a conventional cavity-backed slot antenna. The proposed technique is especially useful for enhancing the bandwidth of a cavity-backed slot antenna in a limited area.

A Reconfigurable Microstrip Antenna With Radiation Pattern Selectivity and Polarization Diversity

Abstract: A novel reconfigurable microstrip antenna with radiation pattern selectivity and polarization diversity is presented in this letter. A four-way power divider made by three Wilkinson power dividers and interconnected with switches (currently copper strips for proof of concept) is designed to feed this antenna. By controlling the states of the switches, the antenna characteristics can be changed into two modes. When the four rectangular radiating patches are excited by four sources with equal amplitude and phase, a metamaterial antenna with conical beam and linear polarization (LP) is achieved, while four sources with equal amplitude but 90° phase difference for each adjacent output leads to a wideband antenna with broadside beam and circular polarization (CP). This single-port antenna is useful for terrestrial land-mobile or other wireless applications.