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Modeling Liquid-Crystal Devices With The Three-Dimensional Full-Vector Beam Propagation Method, Qian Wang, Gerald Farrell, Yuliya Semenova Aug 2006

Modeling Liquid-Crystal Devices With The Three-Dimensional Full-Vector Beam Propagation Method, Qian Wang, Gerald Farrell, Yuliya Semenova

Articles

Simulation of light propagation within nematic liquid-crystal (LC) devices is considered, of which the director is aligned normal to the z axis. A three-dimensional full-vector finite-difference beam propagation method for an anisotropic medium is presented and an alternating direction implicit scheme is adopted. Simulations of light propagation in a bulk polarization converter, a waveguide with a LC covering layer, and an integrated polarization splitter and optical switch are presented. Comparison with an existing simulation method is carried out for beam behavior within the bulk polarization converter. The effect of strong surface anchoring of a LC cell on the beam behaviors …


Low-Cost Wavelength Measurement Based On A Macrobending Single-Mode Fiber, Qian Wang, Gerald Farrell, Thomas Freir, Ginu Rajan, Pengfei Wang Jun 2006

Low-Cost Wavelength Measurement Based On A Macrobending Single-Mode Fiber, Qian Wang, Gerald Farrell, Thomas Freir, Ginu Rajan, Pengfei Wang

Articles

A low-cost all-fiber wavelength measurement technique is proposed and demonstrated. A macrobending standard single-mode fiber is developed as an edge filter with an optimal design and simple surface processing. A ratiometric wavelength measurement system employing the developed macrobending fiber filter demonstrates a resolution of ∼10 pm in a wavelength range from 1500 to 1560 nm with ease of assembly and calibration.


Preliminary Results For A Monocular Marker-Free Gait Measurement System, Jane Courtney, Annraoi Depaor May 2006

Preliminary Results For A Monocular Marker-Free Gait Measurement System, Jane Courtney, Annraoi Depaor

Articles

This paper presents results from a novel monocular marker-free gait measurement system. The system was designed for physical and occupational therapists to monitor the progress of patients through therapy. It is based on a novel human motion capture method derived from model-based tracking. Testing is performed on two monocular, sagittal-view, sample gait videos – one with both the environment and the subject’s appearance and movement restricted and one in a natural environment with unrestricted clothing and motion. Results of the modelling, tracking and analysis stages are presented along with standard gait graphs and parameters.


A New Eccentric Geomagnetic Dipole To Give The Correct Dip Pole Locations, Annraoi De Paor, Ted Burke May 2006

A New Eccentric Geomagnetic Dipole To Give The Correct Dip Pole Locations, Annraoi De Paor, Ted Burke

Articles

In this paper, we describe a new eccentric dipole model of the Earth’s magnetic field. The constraints under which the conventional eccentric dipole model is defined result in predicted dip pole locations that differ significantly from the measured locations. Here, we give a preliminary exposition of a new dipole model which, because it is constrained by the observed dip pole locations, overcomes this problem.


Integrated Antenna For Multiband Multi-National Wireless Combined With Gsm1800/Pcs1900/Imt2000 + Extension, Matthias John, Max Ammann Mar 2006

Integrated Antenna For Multiband Multi-National Wireless Combined With Gsm1800/Pcs1900/Imt2000 + Extension, Matthias John, Max Ammann

Articles

A printed triple-band monopole antenna appropriate for use as a terminal antenna in modern wireless multiband systems is proposed. The impedance bandwidth of each band has been optimised using a quasi-Newton technique and the bandwidth includes virtually all wireless bands. Various parameter sweeps are presented which improve our understanding of the antenna, in particular, the effect of groundplane-size and branch-off point on impedance bandwidth and radiation pattern.


A Novel Gps Patch Antenna On A Fractal Hi-Impedance Surface Substrate, Xiulong Bao, Giuseppe Ruvio, Max Ammann, Matthias John Jan 2006

A Novel Gps Patch Antenna On A Fractal Hi-Impedance Surface Substrate, Xiulong Bao, Giuseppe Ruvio, Max Ammann, Matthias John

Articles

A compact high-performance circularly-polarized microstrip antenna for the global positioning system application is proposed. It comprises a fractal hi-impedance surface electromagnetic bandgap (EBG) structure printed on a high permittivity substrate. Measurements and simulation of return loss and axial ratio are in good agreement. It is shown that the proposed Global Positioning System antenna has good axial ratio performance in the upper half-plane, an improvement in gain and a significantly wider axial ratio bandwidth when compared to the same antenna without EBG


From L-Shaped Planar Monopoles To A Novel Folded Antenna With Wide Bandwidth, Giuseppe Ruvio, Max Ammann Jan 2006

From L-Shaped Planar Monopoles To A Novel Folded Antenna With Wide Bandwidth, Giuseppe Ruvio, Max Ammann

Articles

A novel folded monopole antenna is investigated numerically and experimentally. The proposed antenna comprises a short folded monopole suitably shaped at the base with two vertical grounding probes. This small antenna is shown to have a fractional impedance bandwidth up to 125% (1.6 GHz to 7.5 GHz) for a 10 dB return loss. An interesting compromise between impedance bandwidth and pattern control is found by tuning a double side bevel at the base of the monopole, the position of the feeding point and its distance from the ground plane. Measurements and simulations are in good agreement and show a dramatic …


Design Of Integrated Polarization Beam Splitter With Liquid Crystal, Qian Wang, Gerald Farrell, Yuliya Semenova Jan 2006

Design Of Integrated Polarization Beam Splitter With Liquid Crystal, Qian Wang, Gerald Farrell, Yuliya Semenova

Articles

An integrated polarization beam splitter based on a directional coupler (DC) with an etched slot and filled-in liquid crystal covering layer, which utilizes the birefringence of liquid crystal materials, is proposed. A supermode solution for the DC involving birefringence materials and the corresponding full-vector anisotropic beam propagation method are employed as modeling tools. A numerical design of the proposed structure is presented. Beam propagation behavior along the whole structure involving curved input and output regions and central coupling region is simulated. Simulation result shows an extinction ratio of 25.3 and 41.9 dB for the TE and TM mode, respectively.


Compact Annular-Ring Embedded Circular Patch Antenna With Cross-Slot Ground Plane For Circular Polarisation, Xiulong Bao, Max Ammann Jan 2006

Compact Annular-Ring Embedded Circular Patch Antenna With Cross-Slot Ground Plane For Circular Polarisation, Xiulong Bao, Max Ammann

Articles

A dual-frequency dual-circularly polarised patch antenna with wide beamwidth is proposed. The two-layer structure comprises circular patches with offset circular slots connected to rectangular slots. They provide orthogonal perturbations realising RHCP and LHCP for the lower and upper bands, respectively. The wide beamwidth is realised by extending the substrate beyond the groundplane. Measurements show a maximum beamwidth of 180deg and gains of 3.9 and 0.5 dBic for zenith and 10deg elevation, respectively, for the upper band. The measured beamwidth for the low band is 130deg with a maximum gain of 3.9 and -0.7 dBic for zenith and 10deg elevation, respectively. …


All-Fiber Multimode-Interference-Based-Refractometer Sensor:Proposal And Design, Qian Wang, Gerald Farrell Jan 2006

All-Fiber Multimode-Interference-Based-Refractometer Sensor:Proposal And Design, Qian Wang, Gerald Farrell

Articles

A novel all-fiber refractometer sensor is proposed, which is based on multimode interference in the multimode fiber core section sandwiched between two single-mode fibers. A wide-angle beam propagation method in the cylindrical coordinate is employed as the modeling tool for simulation and design of the proposed refractometer sensor. The design for a refractometer is presented that shows that the refractometer would have an estimated resolution of 5.4×10−5 for refractive indices from 1.33 to 1.45 and of 3.3×10−5 for refractive indices from 1.38 to 1.45 through the choice of an appropriate length of the multimode fiber core section.


Low-Cost Wavelength Measurement Based On A Macrobending Single-Mode Fiber, Qian Wang, Gerald Farrell, Thomas Freir, Ginu Rajan, Pengfei Wang Jan 2006

Low-Cost Wavelength Measurement Based On A Macrobending Single-Mode Fiber, Qian Wang, Gerald Farrell, Thomas Freir, Ginu Rajan, Pengfei Wang

Articles

A low-cost all-fiber wavelength measurement technique is proposed and demonstrated. A macrobending standard single-mode fiber is developed as an edge filter with an optimal design and simple surface processing. A ratiometric wavelength measurement system employing the developed macrobending fiber filter demonstrates a resolution of∼10 pmin a wavelength range from1500to1560 nmwith ease of assembly and calibration.


Analysis Of Strain And Intermixing In Single-Layer Ge/Si Quantum Dots Using Polarized Raman Spectroscopy, Anna Baranov, A. V. Federov, Tatiana Perova, R. A. Moore, V. Yam, D. Bouchier, V. Le Thanh, Kevin Berwick Jan 2006

Analysis Of Strain And Intermixing In Single-Layer Ge/Si Quantum Dots Using Polarized Raman Spectroscopy, Anna Baranov, A. V. Federov, Tatiana Perova, R. A. Moore, V. Yam, D. Bouchier, V. Le Thanh, Kevin Berwick

Articles

The built-in strain and composition of as-grown and Si-capped single layers of Ge∕Si dots grown at various temperatures (460–800 °C) are studied by a comparative analysis of the Ge-Ge and Si-Ge modes in the polarized Raman spectra of the dots. A pronounced reduction of the strain and Ge content in the dots after deposition of the cap layer at low temperatures is observed, indicating that strain-induced Si diffusion from the cap layer is occurring. For large dots grown at 700–800 °C the observations are in agreement with a model of the Ge∕Si dot consisting of a Si-rich boundary region and …


Synthesis Of High-Temperature Stable Anatase Tio2 Photocatalyst, Suresh Pillai, Declan Mccormack, Michael Seery, Pradeepan Periyat, Steven Hinder, John Colreavy, Reenamol George, Hugh Hayden Jan 2006

Synthesis Of High-Temperature Stable Anatase Tio2 Photocatalyst, Suresh Pillai, Declan Mccormack, Michael Seery, Pradeepan Periyat, Steven Hinder, John Colreavy, Reenamol George, Hugh Hayden

Articles

In the absence of a dopant or precursor odification, anatase to rutile transformation in synthetic TiO2 sually ccurs at a temperature of 600 700 °C. Conventionally, metal oxide dopants (e.g., Al2O3 nd SiO2 are used o tune the anatase to rutile transformation. A simple methodology is reported here to extend the anatase utile transformation by employing various concentrations of urea. XRD and Raman spectroscopy were used uring thermal treatment. A significantly higher anatase phase (97%) as been obtained at 800 C with use of a 1:1 Ti(OPr)4 urea composition and 11% anatase composition is etained even after calcining …


Quarter-Wave Metal Plate Solar Antenna, S. Shynu, Max Ammann, Brian Norton Jan 2006

Quarter-Wave Metal Plate Solar Antenna, S. Shynu, Max Ammann, Brian Norton

Articles

A novel design of a quarter-wave shorted trapezoidal metal plate solar antenna using high efficiency polycrystalline silicon solar cells is presented. Using the DC conductive parts of the cell as RF antenna elements as well as choosing the radiating element to be a small base trapezoid, better coupling between the the feed and shorting plates is ensured and 40.3% size reduction compared to a conventional shorted quarter-wave patch is obtained. The trapezoidal radiating element covers merely 2.7% of the total available illumination area of the solar cell, leaving its efficiency essentially unaffected. The proposed design strategy has been verified by …


Planar Antennas, Zhi Ning Cheng, Max Ammann, Xianming Qing, Xuan Hui Wu, T. S.P. See, A. Cai Jan 2006

Planar Antennas, Zhi Ning Cheng, Max Ammann, Xianming Qing, Xuan Hui Wu, T. S.P. See, A. Cai

Articles

This article reviews the state of the art in broadband antennas for emerging UWB applications and addresses the important issues of the broadband antenna design for UWB applications. First, a variety of planar monopoles with finite ground planes are reviewed. Next, the roll antennas with enhanced radiation performance are outlined. After that, the planar antennas printed on PCBs are described. A directional antipodal Vivaldi antenna is also presented for UWB applications. Last, a UWB antenna for wearable applications is exemplified


Compact Concentric Annular-Ring Patch Antenna For Triple Frequency Operation, Xiulong Bao, Max Ammann Jan 2006

Compact Concentric Annular-Ring Patch Antenna For Triple Frequency Operation, Xiulong Bao, Max Ammann

Articles

A novel single-layer, single-feed concentric annular-ring microstrip patch antenna providing triple-frequency operation is proposed and experimentally studied. This is achieved by embedding a small circular patch into a dual stub-loaded concentric annular-ring structure and by employing a cross-slot in the ground plane. The proposed technique can provide triple-band operation and reduce the antenna size by over 50% compared to the conventional annular-ring patch antenna for a given frequency. Experimental results show the proposed antenna to have impedance bandwidths of 6.38, 6.30 and 35% for the three bands, at 1.17, 1.428 and 1.9 GHz, respectively. The proposed structure is capable of …


Design Of One-Dimensional Composite Photonic Crystals With An Extended Photonic Band Gap, Vladimir Tolmachev, Kevin Berwick Jan 2006

Design Of One-Dimensional Composite Photonic Crystals With An Extended Photonic Band Gap, Vladimir Tolmachev, Kevin Berwick

Articles

A technique for photonic band gap (PBG) extension based on mixing photonic crystals with different lattice constants or filling factors is suggested. For the design of photonic crystals with maximal PBG extension the gap map imposition method is utilized. Gap maps for composite photonic crystals based on Si-air structures are calculated and used to predict optimal structures for fabrication.