Yes / A novel wideband printed monopole antenna is proposed covering frequency spectrum of wireless local area network (WLAN) and the Worldwide Interoperability for Microwave Access (WiMAX). The total antenna size is 30 × 48 × 1.6 mm³ in which it consists of a G-shaped slotted printed antenna and a defected ground plane. Theoretical and experimental characteristics are presented and compared. The antenna yields an achieved impedance bandwidth of 95.1% between 2.374 GHz and 6.682 GHz at a reflection coefficient |S11| ≤ -10 dB.The results including S-parameters, surface current distribution, VSWR, radiation patterns and antenna gains; in addition to a reasonable and stable radiation pattern and power gain.

 This thesis focuses on three research topics on the design about planar ultrawide-band (UWB) monopole antennas, namely, the design of band notches for UWB monopole antennas, the ground-plane and cable effects on the measurement of compact UWB monopole antennas, and the design of a chipless UWB radio-frequency-identification (UWB-RFID) system. The designs of single, dual, triple and quadruple band-notched UWB monopole antennas using coplanar waveguide (CPW) resonators, quarter-wavelength (λ/4)-resonators and meander lines (MLs) are presented. The center frequencies and bandwidths of the individual notches in all these designs can be adjusted independently by varying the dimensions of the resonators. Studies of the designs are carried out by computer simulations using the EM software tool, CST MWS. For verification of the simulation results, these antennas are fabricated and measured using the antenna measurement system, Satimo Starlab. The frequency-domain performances, in terms of return loss, peak gain, efficiency and radiation pattern, and the time-domain performances, in terms of pulse responses and fidelity, are investigated by simulation and measurement. Results show that these UWB antennas have approximately omnidirectional radiation patterns with good band-notched characteristics and fidelities of more than 85% in the pulse responses. Results of studies show that, using a small ground plane in the design of the compact UWB antennas, there will be larger discrepancies between the measured and simulated radiation patterns, radiation efficiencies and peak gains at low frequencies. The discrepancies are due to diffraction of the electric fields at the edges of the small ground plane, which leads to currents flowing back to the measuring cable and hence secondary radiation. Computer simulation and measurement are used to study the ground-plane effects using a group of nine UWB antennas. These antennas have the same radiator but with rectangular ground planes of different sizes. Results show that the width of the ground plane affects the efficiency more than the length, while the length affects the lower cut-off frequency. The cable effects are further studied by modeling the measuring cables. Results show that, by using the cable model, the simulation and measurement efficiencies agree extremely well. The design of a novel chipless UWB-RFID system is presented. The system employs uniplanar chipless tags and a pair of high-gain reader antennas. The chipless tag is composed of two UWB monopole antennas connected by a CPW. Tag identification (ID) is represented by a spectral signature in the UWB and created by using a multi-resonator embedded on the CPW. Detection of spectral signature is based on only the amplitude of the spectral signature. Vertically and horizontally polarized signals are used to reduce mutual coupling between the uplink and downlink signals. Further reduction of the mutual coupling is achieved by using a copper plate in the reader to separate the uplink and downlink signals. Results of studies in an anechoic chamber show that the proposed RFID system can achieve a read range larger than 30 cm, indicating that the proposed system has great potentials for short-range item tracking at low-cost. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Richard Wolff. Includes bibliographical references (leaves 109-112).

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (p. 51-53 ). Also available in electronic version.

Thesis (Ph.D.)--Syracuse University, 2008. / "Publication number: AAT 3333567."

A unique property of spherical and hemispherical helical antennas is that they provide very broad half-power beamwdiths and circular polarization over a narrow bandwidth. In this thesis, new designs for hemispherical helical antennas are introduced that provide significant improvement in bandwidth, while maintaining the directivity and half-power beamwidth of the basic design. In the basic design, a simple wire of circular cross section is wound on the surface of a hemisphere, whereas in the proposed new designs a metallic strip forms the radiating element. Furthermore, the metallic strip may be tapered and tilted relative to the hemispherical surface, allowing wider bandwidth to be achieved. The antenna is fed by a coaxial cable with the inner conductor connected, through a matching section, to the radiating strip and its outer conductor connected to a ground plane. Radiation properties of the proposed hemispherical helical antennas are studied both theoretically and experimentally. A commercial software, based on the method of moments, is used to perform the numerical analysis of these helices. Three-dimensional far-field patterns, axial ratio, directivity, and voltage standing-wave ratio (VSWR) are calculated for several designs. The impacts of tapering as well as tilting of the metallic strip on radiation characteristics are examined. Also, matching of the proposed hemispherical antennas to 50â ¦ transmission lines is addressed. A 4.5-turn hemispherical helix with tapered radiating element and zero degree tilt angle, (metallic strip is perpendicular to the hemisphere axis of symmetry) provides the largest overall bandwidth. A nonlinearly tapered matching section is incorporated into the design in order to reduce the VSWR. For this design, an overall measured bandwidth of about 24% at a center frequency of 3.35 GHz is achieved. Over this bandwidth, the axial ratio remains below 3 dB, the VSWR is less than 2, and the directivity is about 9 ±1 dB. A half- power beamwidth of 70° is also obtained. A prototype of the best design was fabricated and tested using the VT indoor antenna range. Radiation patterns, the scattering parameter S₁₁, and the axial ratio were measured. The measured and simulated results agree reasonably well. In particular, agreements between measured and calculated far-field patterns and VSWR are quite remarkable. This compact, low profile antenna might find useful applications in avionics, global positioning systems (GPS), and high data rate wireless communication systems. / Master of Science

Yes / Two miniature low profile PIFLA antennas with a compact volume size of 30mm × 15mm × 8mm has presented in this paper. By applying the magnetic wall concept a reduced size dual-band and a wideband half PIFLAs for WLAN (2.4GHz/5.2GHz) and UWB applications are achieved. The dual-band antenna shows a relative bandwidth of 12% and 10.2% at ISM2400 and IEEE802.11a frequency bands respectively for input return loss less than 10dB. By carefully tuning the geometry parameters of the dual-band proposed antenna, the two resonant frequencies can be merged to form a wide bandwidth characteristic, to cover 3000MHz to 5400 MHz bandwidth (57%) for a similar input return loss that is fully covering the lower band UWB (3.1-4.8GHz) spectrum. The experimental and simulated return losses on a small finite ground plane of size 30mm × 15mm show good agreement. The computed and measured radiation patterns are shown to fully characterize the performance of the proposed two antennas. / MSCRC

The thesis report presents the designs of compact planar ultra-wideband (UWB) antennas for wireless devices applications. Three main designs of UWB antennas are studied, namely, single UWB antennas, UWB multiple-input-multiple-out(MIMO)antennas, and transparent UWB antennas on the screens of mobile phones. For single UWB antennas, the designs of two compact planar monopole antennas with compact sizes of 26×28 mm2and 30×39.3mm2are presented. The UWB operations of the antennas are achieved using a ground slot under the feed line, offsetting the feed line and the radiator from the middle of the ground plane and smoothly transforming the feed line. Simulation and measurement show that the two antennas can achieve an ultra-wide bandwidth with approximately omnidirectional patterns. A deep notch-band in5.1-5.85 GHz is created in one of the UWB antennas by employing two pairs of meander lines (MLs), one pair being close to the feed line and the other pair along the upper edge of the ground plane. At the notch frequency, the simulated efficiency is only 4%. Three compact UWB-MIMO antennas with very compact sizes of 26×40 〖mm〗^2, 21×38 〖mm〗^2, and 22×36 〖mm〗^2 are designed. Each of them is designed using two UWB antenna elements perpendicularly or symmetrically placed. Different techniques such as using ground stubs besides the radiators, cutting inclined slots on the ground, and adding a T-shaped protruding from ground are proposed to lower mutual coupling between the two antenna elements. One of the antennas is designed to generate a notched band in 5.15-5.85 GHz using two ground strips. Simulation and measurement results show that these antennas can cover the entire UWB of 3.1-10.6GHz with mutual coupling of less than -15 dB, and envelope correlation coefficient of less than 0.1. An UWB antenna is designed using a transparent conductive film for applications on mobile phone screens. The effects of a finger touching the screen are studied. Results show that, with the radiator on the bottom side of the screen and a thin film with a thickness of 0.05 mm on the top side to separate the finger and the antenna, the effects of the finger can be minimized. In measurement of monopole antennas with small ground planes, due to the feeding cable used, there are always discrepancies between the simulated and measured results in radiation patterns, efficiencies, and gains at lower frequencies. To verify that the discrepancies in the results of these studies are indeed due to the feeding cable used in measurement, the models of the feeding cables are developed and used for simulation. Results show that, by using the cable model, the simulated and measured results in radiation patterns, efficiencies, and gains agree very well. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 215-220).

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (p. 59-63). Also available in electronic version.