Radiation Beamwidth Research Articles

Omnidirectional Dual-Band Dual Circularly Polarized Microstrip Antenna Using ${\rm TM}_{01}$ and ${\rm TM}_{02}$ Modes

An omnidirectional dual-band dual circularly polarized (CP) antenna with wide beam radiation patterns using TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> modes is investigated. The proposed antenna is composed of a circular patch with eight curved slots and a disk-loaded coaxial probe. The horizontal and vertical polarizations are obtained by the currents flowing on the patch and on the coaxial probe, respectively. Omnidirectional CP fields can be achieved at both resonant modes when the two orthogonally polarizations are equal in amplitude and different in phase by 90°. With a low profile of 0.017 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , the proposed antenna exhibits a wide beamwidth of 100° in the elevation plane at both modes. The measured axial ratios (ARs) at the two resonant modes in the azimuth plane are 1.71 and 2.82 dB, respectively. The measured left-hand CP (LHCP) and right-hand CP (RHCP) gains in the azimuth plane are 0.1 dBic at the lower center frequency and -1.1 dBic at the upper center frequency, respectively. These measured results are congruent with the simulated data. In addition, the methods to broaden the bandwidth of the proposed antenna are given and discussed in details.

Wide-Beam Circularly Polarized Crossed Scythe-Shaped Dipoles for Global Navigation Satellite Systems

This paper describes composite cavity-backed crossed scythe-shaped dipoles with wide-beam circularly polarized (CP) radiation for use in Global Navigation Satellite Systems. Each branch of the dipole arm contains a meander line, with the end shaped like a scythe to achieve a significant reduction in the size of the radiator. For dual-band operation, each dipole arm is divided into two branches of different lengths. The dipoles are crossed through a 90° phase delay line of a vacant-quarter printed ring to achieve CP radiation. The crossed dipoles are incorporated with a cavity-backed reflector to make the CP radiation unidirectional and to improve the CP radiation beamwidth. The proposed antennas have broad impedance matching and 3-dB axial ratio bandwidths, as well as right-hand CP radiation with a wide-beamwidth and high front-to-back ratio.

Linearly polarised planar inverted F‐antenna for Global Positioning System and Worldwide Interoperability for Microwave Access applications

A compact dual-band planar inverted-F antenna in conjunction with an inverted L-shaped parasitic and reduced ground-plane structure working in the GPS (Global Positioning System) band (1565–1585 MHz) and Worldwide Interoperability for Microwave Access band (3300–3800 MHz) is presented. The antenna meets the strict space requirements of the portable devices and the final design fits a volume of 100 × 24 × 9.7 mm3 (L × W × H). It is composed of a series of branches, properly dimensioned and separated to generate the resonances at the desired frequencies. The antenna is fabricated using a 0.2 mm thick copper foil. The linearly polarised antenna exhibits good impedance matching performance, wide beam radiation pattern and high gain. Also, carrier-to-noise ratios for three different satellite locations, that is, 5°, 50° and 90° elevation are 47.58, 50.49 and 45.86 dB/Hz, respectively, at the centre frequency (1575 MHz) of GPS L1 band, which is well within the maximum allowable limit (50.5 dB/Hz) at room temperature.

SU‐E‐I‐40: Survey of Radiation Beam Width in CT According to ACR 2012 CT QC Manual

Purpose: To survey CT radiation beam width using in clinical protocols according to America College of Radiology (ACR) 2012 CT Quality Control Manual. We assessed the relationship between nominal collimated and radiation beam width. Methods: Radiation beam width was measured using a self‐developed film (GAFCHROMIC XR CT2) for 346 CT scanners. The film was placed at the isocenter of CT scanner. Nominal collimated beam widths (N×T) using for clinical examinations of routine adult head, adult abdomen, and 5‐years pediatric abdomen were measured. Results: The performance criteria set by ACR 2012 CT Quality Control Manual are that the measured radiation beam width should be accurate to within 3 mm or 30% of the nominal collimated beam width (NxT), whichever is less. According to our survey, the fail rates were 18.8% for adult head examinations, 15.0% for adult abdomen examinations 20.1% for 5‐years pediatric abdomen examinations. If the criteria were set to within 3 mm or 30% whichever is greater, the fail rates dropped to 8.2%, 0.6%, and 2.0%, respectively. Toshiba CT scanners have to pay more attention to meet ACR criteria because the fail rate was from 39% to 75%. Conclusion: This survey gave a view of relationship of nominal and radiation beam width in different protocols and manufacturers. About twenty percent of CT scanners cannot pass the ACR criteria of radiation beam width.

Compact Circularly Polarized Composite Cavity-Backed Crossed Dipole for GPS Applications

In this paper, we present a circularly polarized (CP) composite cavity-backed crossed dipole antenna for global positioning system (GPS) applications. We produce the CP radiation by crossing two dipoles through a <TEX>$90^{\circ}$</TEX> phase delay line of a vacant-quarter printed ring, which also has a broadband impedance matching characteristic. Two techniques, insertion of meander lines in the dipole arm and arrowhead-shaped trace at its end, are employed to reduce the sizes of the primary radiation element. The compact radiator is backed by a cavity reflector to achieve a wide CP radiation beamwidth. The proposed antenna exhibits a measured bandwidth of 1.450~1.656 GHz for a voltage standing wave ratio (VSWR) < 2 and 1.555~1.605 GHz for AR < 3-dB. At 1.575 GHz, the antenna has a gain of 7 dBic, a frontto-back ratio of 27 dB, AR of 1.18 dB, and 3-dB AR beamwidths of <TEX>$130^{\circ}$</TEX> and <TEX>$132^{\circ}$</TEX> in the x-z and y-z planes, respectively.

A Coplanar Waveguide Fed Two Arm Archimedean Spiral Slot Antenna With Improved Bandwidth

A compact wideband circularly polarized (CP) printed antenna design is presented in this communication. The proposed antenna consists of two Archimedean spiral slots, loaded with two chip resistors and fed by a coplanar waveguide (CPW) transmission line. The antenna is situated in one plane and fed without using an external balun or a matching network. The antenna has wideband input impedance bandwidth with circular polarization (CP), and broad beamwidth radiation pattern over 1.6:1 bandwidth. The study has shown that the proposed antenna is capable of improving the CP bandwidth and reducing the overall antenna size.

Frequency Selective Surfaces for Beam-Switching Applications

A novel design of a beam-switching antenna based on reconfigurable frequency selective surfaces (FSSs) is presented. The antenna is composed of a cylindrical FSS with PIN diodes and divided into six equal sectors by metallic sheets. Metallic cones at the top and bottom of the structure are used to create a directive beam. The antenna is fed by a simple dipole at its center. To switch the radiation pattern of the antenna, the diodes in one FSS-sector are set off to be transparent to the incident EM waves, whereas the diodes in other sectors are on to reflect the incident wave. The direction of the radiation pattern is defined by the off-state sector. In this design, the beam-switching is achieved with only one layer and minimum size of the cylindrical active FSS in order to decrease the number of active elements, and the amount of the power supply. The antenna can sweep the entire azimuth plane with 60° radiation beamwidth in six steps. The fabricated antenna prototype operates from 2.3 GHz to 3 GHz with maximum measured gain of 10 dBi and 3-dB beamwidth of 60°. This antenna can be used in the base station of the wireless communication systems.

PARASITIC PROBE FED MICROSTRIP ANTENNA FOR MULTI-CONSTELLATION GNSS

The design approach and development of a right hand circularly polarized wideband microstrip antenna for multi- constellation Global Navigation Satellite System (GNSS) is presented. The antenna is corner truncated square patch, parasitically excited by a dielectric covered straight probe. A thermacol layer of thickness ‚=14 at center frequency is used to support the microstrip over the ground plane substrate. The simulated and measured results are presented. The antenna shows wide beam radiation patterns with axial ratio less than §1dB. Its VSWR is better than 2.8 : 1 and the gain varies from 1.2dBi to 3.5dBi over the frequency band.

A small broadband switched-beam Cross-PIFA for m-WiMAX applications

A small broadband and low cost switched-beam smart antenna suitable for mobile WiMAX applications (band class 5–3.5 GHz) is presented in this paper. Present mobile terminal antennas are expected to show increased bandwidth as well as low-loss impedance matching while maintaining low-profile geometry. The proposed structure consists of four planar inverted-F antennas (PIFA) connected forming a cross, sharing the same ground plane, in a configuration designed for symmetrical coverage of the horizontal plane (Cross-PIFA). A custom genetic algorithm (GA) is used in order to optimize the proposed antenna parameters regarding resonant frequency and radiation pattern orientation angle and beamwidth. The optimized antenna exhibits small size (dimensions cm), satisfactory directivity for mobile terminal applications of 3.38 dB over an operation bandwidth of 120 MHz around the central frequency of 3.5 GHz. Simulation and measurement results and parameters range are exposed below followed by the according radiation pattern and variation of the VSWR indicating consistency between design and implementation.

Collimating lenses from non-Euclidean transformation optics

Based on non-Euclidean transformation optics, we design a thin metamaterial lens that can achieve wide-beam radiation by embedding a simple source (a point source in the three-dimensional (3D) case or a line current source in the 2D case). The scheme is performed on a layer-by-layer geometry to convert curved surfaces in the virtual space into flat sheets, which pile up and form the entire lens in the physical space. Compared to previous designs, the lens does not have extreme material parameters. Simulation results confirm its functionality.

Novel Directional Nanoantennas for Single-Emitter Sources and Wireless Nano-Links

Optical nanoantennas are emerging as one of the key components in the future nanophotonic and plasmonic circuits. The first optical nanoantennas were in a form of simple spherical nanoparticles. Recently more complex Yagi-Uda nanoantenna structures were demonstrated. These nanoantennas enhance radiation of single emitters and provide well-defined directional radiation. In this contribution, we present the novel design of the directional nanoantenna, which is excited from the propagating mode of the plasmonic waveguide. The nanoantenna design is based on thetravelling waveprinciple, well known at RF/microwave frequencies. By properly designing the propagating parts of the nanoantenna, a very efficient coupling to free space wave impedance can be achieved. Furthermore, the control over the radiation direction and beam width is relatively easy with this nanoantenna. Compared to the previously published Yagi-Uda designs, the new nanoantenna presented in this work has directivity three times higher.

SU-GG-I-73: CT Image Quality and Radiation Dose Survey in Taiwan

Introduction: The Standards for Medical Exposure Quality Assurance, derived from Ionizing Radiation Protection Act, was enforced in Taiwan since July 1, 2005. The first diagnostic facility, mammography, was included in the regulation since July 1, 2008. The Atomic Energy Council plans to include computed tomography(CT) in the next stage. Before that, the national survey for realizing the current level of CTquality assurance is necessary. The purpose of this study is to survey the image quality and patient doses for CT in Taiwan. Methods and Materials: Trained investigators conducted on‐site measurements, started from March 2009. An ACR CT accreditation phantom (Model 464, Gammex) was used to evaluate CTimage quality, including slice thickness accuracy, CT number accuracy, image uniformity, artifact, spatial resolution, and low contrast detectability. Computed tomography dose indexs(CTDI) in head and body phantoms were measured by a pencil‐type ionization chamber (10X6‐3CT, Radcal). Radiation beam width was assessed by chromic films (XR‐CT Dosimetry film, Gafchromic). Representative patient doses for adult head, adult abdomen, and 5‐years pediatric abdomen examinations were evaluated, including volume CTDI(CTDIvol). Results: There are 425 CT scanners, including CT, PET/CT, SPECT/CT, and CT simulator, in 241 hospitals in Taiwan. The preliminary results, obtained from March to December 2009, included 222 units in 142 hospitals. The fail rates of image quality items are low. The CTDIvol for adult head, adult abdomen, and 5‐years pediatric abdomen examinations are 58, 18, and 26 mGy. The rates of CTDIvol for adult head, adult abdomen, and 5‐years pediatric abdomen examinations over the ACR limits are 10%, 25%, and 32%. Conclusion: The preliminary results give us a view of current level in miniature of CTimage quality and patient doses in Taiwan. Once the survey is complete, final results will be useful and helpful references for the Atomic Energy Council.

A Low-Profile Linearly Polarized 3D PIFA for Handheld GPS Terminals

A 3D planar inverted F-antenna (PIFA) is proposed for a Global Positioning System (GPS) receiver. The antenna is designed to be integrated in a portable device and must meet compact size requirements. The 3D PIFA consists of a single metal sheet properly cut and bent in order to minimize costs for realization, materials and series production. The linearly polarized antenna exhibits good impedance matching performance, wide beam radiation patterns and a relatively high gain, which allow the reception from a wide angle toward the satellite constellation. An antenna prototype has been embedded in a commercial GPS receiver and an experimental measurement campaign has been carried out to evaluate the most important performance parameters. Measurements have been performed out by collecting time sweeps signal samples along urban and suburban routes. Time to first fix, carrier to noise ratio distribution and horizontal dilution of precision have been calculated; these parameters are shown and discussed. Comparisons with respect to some reference circularly polarized antennas (a nearly square patch and a quadrifilar helix antenna) and to a simpler inverted-F antenna printed on the receiver PCB have been performed and are shown in the paper.

Concurrent dual‐band six‐loop‐antenna system with wide 3‐dB beamwidth radiation for MIMO access points

AbstractA high‐gain, wide‐beamwidth, six‐loop‐antenna MIMO system suited for wireless access points in the concurrent WLAN 2.4 and 5 GHz bands is presented.The antenna system mainly comprises an antenna ground plane and single‐band loop antennas, among which the three antennas are designated for 2.4 and 5 GHz operation, respectively. The antennas are set in a sequential, rotating arrangement on the ground plane with an equal inclination angle of 60° to form a symmetrical structure, and the 2.4 and 5 GHz loops are facing each other one by one. The experimental results show that good port isolation can be obtained between antenna ports. High‐gain, directional radiation patterns with wide 3‐dB beamwidth in elevation planes are also observed. Details of a design prototype are described and discussed in the article. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1253–1258, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25208

다중센서를 이용한 이동표적의 위치추적시스템 설계

본 논문에서는 적외선 센서와 초음파 센서를 동시에 사용하여 이동하는 표적의 위치를 실시간으로 추적하는 위치추적 시스템을 설계하였다. 위치 추적 시스템은 2 개의 적외선 센서를 이용하여 표적이 감시영역에 침입하는 것을 확인하고, 4 개의 초음파 센서를 이용해서 각 센서에서 표적까지의 거리를 탐지하여 이동하는 표적의 위치좌표 (x,y)를 구하였다. 특히 초음파 센서가 가지고 있는 안테나의 빔폭 특성 때문에 4 개 센서 중 2개 센서에만 표적이 탐지될 경우에도 표적의 위치를 정확하게 결정하는 방법을 제시하였다. 또한 개발된 알고리즘을 설계된 시스템에 장착하여 시험한 결과 감시시스템이 실험실 내에서 실시간 정확하게 구동하는 것을 확인하였다. In this paper we present a position tracking system that checks the locations of moving targets in real-time. The system confirms that unknown object invades in watch area using 2 infrared sensors and detect the distance from each sensor to object using 4 ultrasonic sensors, and calculate the position of moving object in x-y coordinate. We specially present an algorithm that decide the location of target in case of target is detected in 2 sensors because of radiation beam width of ultrasonic sensor. We established the algorithm to hardware system and tested the system within a laboratory, and confirmed that the designed system tracked an object exactly in real-time.

A New Low-Profile and Cost SPA-PIFA for Mobile 2.4 GHz ISM Applications

A new low cost switched-beam antenna array suitable for 2.4 GHz ISM applications is presented in this paper. The proposed structure consists of four planar inverted-F antennas (PIFA), sharing the same ground plane, in a configuration designed for symmetrical coverage of the horizontal plane (Quad-PIFA). A custom Genetic Algorithm (GA) is used in order to optimize the array parameters regarding resonation frequency and radiation pattern orientation angle and beamwidth. The optimized Quad-PIFA exhibits low profile (size equal to 8 cm × 8 cm), high front to back ratio (15.6 dB), and satisfactory directivity (3.6 dB) over an operational bandwidth of over 200 MHz. Simulation and measurement results are presented indicating consistency between design and implementation and demonstrating the performance of the array.

Rectangular Microstrip Patch on a Composite Dielectric Substrate for High-Gain Wide-Beam Radiation Patterns

A rectangular microstrip patch on a composite substrate is theoretically and experimentally investigated. Considerably wide radiation beamwidth along with high gain is experimentally demonstrated. Compared to a conventional microstrip patch, the proposed configuration shows as much as 75% increment in beam width in its H-plane and nearly 10% in E-plane, indicating the peak gain of the order of 8 dBi.

Refinement of circular-polarization based on multilayer film structure

Circular-polarization discrimination appears in many antennas' applications. A compensation approach based on multilayer film structure is proposed to improve the axial ratio of the magnitude of the two perpendicular modes of the lump ports. The goal is to widen the beamwidth of radiation that has an axial ratio less than 3 dB and thus reducing the complexity at the receiver. A transfer matrix method was developed to represent the multilayer film and characterize its performance. Simulation using high frequency structure simulator shows that a crossed dipole, as an example, can achieve a beamwidth of more than 30° at the frequency of 12.45 GHz after compensation. Finally, conclusions and future work about this compensation method are presented.

Reconfigurable Beamwidth Antenna Based on Active Partially Reflective Surfaces

This letter presents a new method to design a new reconfigurable antenna by using an active cylindrical electromagnetic band-gap (EBG) structure for wireless communication systems. The antenna provides a reconfigurable elevation beamwidth while the azimuth radiation pattern maintained omnidirectional. The EBG structure that is composed of periodic discontinuous metallic strips and PIN diodes behaves as an active partially reflecting surface (PRS). By changing the diode states, the reflection coefficient of the structure is controlled so that the radiation beamwidth and directivity of the antenna can be reconfigured. To validate the proposed concept, the final prototype is fabricated, and measurement results are also presented and discussed.

OPTIMIZATION OF THREE-DIMENTIONAL (3-D) GROUND STRUCTURE FOR IMPROVED CIRCULARLY POLARIZED MICROSTRIP ANTENNA BEAMWIDTH

A novel circularly polarised (CP), single-fed widebeam microstrip antenna is presented. The antenna consists of a corner- truncated square patch and a three dimensional circular ground structure. Simulated and measured results show that, owing to the ground structure, the 3dB beamwidth of the CP radiation can reach more than 165 - , which is about 85 - greater than that of a corresponding regular microstrip antenna. It is also shown that experimental results were in good agreement with the simulated performance. Details of the proposed 3-D circular ground structure are described, and the efiects of various dimensions of the proposed ground structure on the beamwidth enhancement of CP radiation are studied.