Conference papers

Deploying a Context Aware Smart Classroom

Ciaran O'Driscoll et al. — Thu, 03 Mar 2011 04:02:02 PST

Context aware environments respond in a pseudo-intelligent manner depending on the identity of occupants, particular location, desired activity and specific time. The Context Aware Smart Classroom (CASC) is a classroom that responds to lecturers and student groups based on preset policies and the lecture timetable. The pervasive nature of personal mobile devices permits the investigation of developing low-cost location and identification systems that support development of a smart classroom. Material used during the teaching activity is distributed to students based on students’ policies using WLAN, LAN or email. The smart classroom CASC uses a central scheduling system to determine the teaching activity. In this paper we present CASCs’ system design and results from the trial deployment. In particular we review the issues related to using low-cost solutions such as existing communications infrastructure for developing large scale environments. Finally we present the plans for ongoing development of the Context Aware Smart Classroom.

RFID: an Ideal Technology for Ubiquitous Computing?

Ciaran O'Driscoll et al. — Mon, 31 Jan 2011 04:01:37 PST

This paper presents a review of RFID based approaches used for the development of smart spaces and smart objects. We explore approaches that enable RFID technology to make the transition from the recognized applications such as retail to ubiquitous computing, in which computers and technology fade into the background of day to day life. In this paper we present the case for the use of RFID technology as a key technology of ubiquitous computing due to its ability to embed itself in everday objects and spaces. Frameworks to support the operation of RFID-based smart objects and spaces are discussed and key design concepts identified. Conceptual frameworks, based on academic research, and deployed frameworks based on real world implementations are reviewed and the potential for RFID as a truly ubiquitous technology is considered and presented.

A Novel Hybrid Inverted-L Antenna with Wide Bandwidth

Max Ammann et al. — Tue, 28 Apr 2009 10:40:40 PDT

The paper describes a novel inverted-L antenna which comprises a short planar monopole loaded with two linear elements. This small antenna is shown to have impedance bandwidth up to 100 % for 6 dB return loss. Antenna parameters such as impedance bandwidth, gain and pattern stability are examined and the measured data are in good agreement with a MoM/UTD analysis.

Optimization of the Brillouin Spectrum for Fiber Based Slow Light Systems

Ronny Henker et al. — Tue, 28 Apr 2009 10:40:38 PDT

This article shows simulation results and first practical investigations of the optimization of a Brillouin spectrum with the natural bandwidth superimposed with two losses for fiber based slow light systems.

Spline Based Geometry for Printed UWB Antenna Design

Matthias John et al. — Tue, 28 Apr 2009 10:40:37 PDT

This paper presents a geometry for ultra-wideband (UWB) antennas which is based on quadratic Bezier spline curves. A genetic algorithm (GA) is used to optimise the geometry. The search space for the GA is minimised in order to improve the performance and computational efficiency of the algorithm. The optimised antenna covers the entire UWB bandwidth.

Square Planar Monopole Antenna

Max Ammann — Tue, 28 Apr 2009 10:40:36 PDT

A planar monopole may be realised by replacing the wire element of a conventional monopole with a planar element. In this case, the planar element which is square, is located above a groundplane and fed using an SMA connector as illustrated. The square monopole has a simple geometry and a smaller bandwidth compared to the circular-disc monopole. However, it is still a broadband antenna with a typical impedance bandwidth of 75 % at S band. This broadband antenna shows a constant radiation pattern over the impedance bandwidth. A simple formula for the frequency corresponding to the lower edge of the impedance bandwidth, which has an accuracy of ±8.5 % over the frequency range 1 GHz to 6 GHz, is proposed. The effect of the feedgap distance is also examined

On Surface Currents in a Polycrystalline Solar Cell Acting as Ground Plane for Microstrip Patch Antennas

Maria J. Roo Ons et al. — Tue, 28 Apr 2009 10:40:35 PDT

The integration of communication devices with photovoltaic (PV) technology leads to the development of autonomous communication systems distinguished by immunity to grid breakdowns and eco-friendliness.

UWB Vivaldi Antenna Based on a Spline Geometry with Frequency Band-notch

Matthias John et al. — Tue, 28 Apr 2009 10:40:35 PDT

A printed UWB Vivaldi antenna is presented in this paper. Its geometry is based on a novel spline shape and optimised by an efficient global optimisation algorithm. A U-shaped slot is introduced into the geometry to notch out the 5.1 GHz to 5.8 GHz WLAN band. This can be used to mitigate interference between WLAN and UWB systems.

Wideband Directional Base-station Antenna with Dual-linear and Circular-polarization Capabilities

Francisco Lerma et al. — Tue, 28 Apr 2009 10:40:34 PDT

A crossed-dipole antenna providing polarization diversity is presented. The antenna which employs a planar reflector yields high directivity and good isolation between ports over a wide impedance bandwidth, suitable for polarization-agile wireless base-station use. The dipole wing shape is optimised, which yields the wide bandwidth. Matching is achieved using a quarter-wave balanced-to-unbalanced section which also improves the port-to-port isolation. Radiation characteristics for linear and circular polarizations are presented

A Wideband Monopole for Reconfigurable Multiband Radio Terminals

Max Ammann — Tue, 28 Apr 2009 10:40:33 PDT

A wideband planar monopole employing two broadbanding techniques is investigated, and is shown to yield an impedance bandwidth ratio of 10:1 or greater for a return loss of 8 dB. The radiation pattern bandwidth is also investigated

Slow and Fast-light in Optical Fibers: an Overview

Ronny Henker et al. — Tue, 28 Apr 2009 09:13:10 PDT

Slow- and fast-light is the control of the velocity of light in a medium by light. As a fascinating new field in physics there is a fundamental interest on this effect on the one side, but on the other side there exist a lot of practical applications for telecommunication and information systems. Among these are optical signal processing, the radio frequency-photonics, nonlinear optics and spectroscopy in time domain. Furthermore, the slow- and fast-light effect can be seen as a key technology for optical delay lines, buffers, equalizers and synchronizers in packed switched networks. To realize the effect there are different methods and material systems possible. Beside these especially the nonlinear effect of stimulated Brillouin scattering (SBS) is of special interest because it has several advantages. This article gives an overview about the fundamentals and limits of the slow-and fast-light effect in general and based on the SBS in optical fibers. Some experimental results which were achieved so far are shown.

Some Techniques to Improve Small Groundplane Printed Monopole Performance

Max Ammann et al. — Tue, 28 Apr 2009 09:13:09 PDT

Printed planar monopole antennas are enjoying considerable popularity and publicity to their low-profile, wide bandwidth, quasi-omnidirectional radiation characteristics and their ease of integratability into devices. The impedance bandwidth and radiation properties of a strip monopole have been shown to be heavily dependent on groundplane size. The groundplane (GP) is of primary importance and when miniaturised, the antenna properties change significantly. Techniques to improve the performance of printed antennas on small groundplanes are presented.

Spatial Group Delay Patterns for three Ultra Wideband Spline Antennas

Patrick McEvoy et al. — Tue, 28 Apr 2009 09:13:08 PDT

The IEEE ultra wideband (UWB) standard includes both a multiple frequency carrier (MB-OFDM) and an impulse spectrum (DS-UWB) method, for which application antennas should be appropriately optimized. Small printed monopoles with outline features that can be defined by a Bezier-spline [1] have good matched impedance performance across the 3.1 - 10.6 GHz band. For communications applications, an omni-directional pattern, where the gain pattern varies by less than plusmn5 dBi, and a stable frequency-gain profile in the azimuth plane, allow for an even spatial coverage in all directions. In the case of an impulse system, any non-linear phase transfer performance in the antenna adds distortion to the transieved pulses therefore reducing the data rates. Contemporary UWB antenna gain performances are often presented across the whole spectrum using contour plots. This discloses more details and compliments the conventional sampled frequency polar plots that are more suited to narrow bandwidth antennas. In this paper, the approach is extended to a group delay pattern measurement which is more comprehensive than the traditional and limited boresight-only approach.

Performance characterization for patch antenna systems with a limited number of EBG cells using the mushroom-like structure as benchmark.

Giuseppe Ruvio et al. — Tue, 28 Apr 2009 09:13:07 PDT

The effect of one, two and three lines of EBG mushroom-like cells on the coupling of two different 2-element arrays was analyzed and described. It was demonstrated that a certain surface waves attenuation is already achievable with just one row of cells, even though a better performance is obtained when more lines are added. A bandgap investigation technique based on the analysis of the transmission coefficient of a two-patch antenna array separated by one, two and three lines of EBG cells was used throughout the paper. e analyze two types of antennas (monopole and square patch) both resonating at 15 GHz but with different radiation mechanisms in order to isolate the contribution of the EBG and better understand its effect on different polarized surface waves.

Printed Planar Monopole Antenna with Electromagnetically Coupled Elements

Jonathan Evans et al. — Tue, 28 Apr 2009 09:13:06 PDT

In this paper, the addition of an EM-coupled element to the printed planar monopole antenna is investigated. While remaining simple to construct, modifications to the EM-coupled element are shown to reduce the lower edge frequency of the 10 dB impedance bandwidth by up to ∼19% (280 MHz at 1.5 GHz). The radiation patterns for these antennas are characteristic of monopole antennas - i.e. omnidirectional in the azimuth plane with a at the zenith - and are consistent within +/- 2 dB across their useful impedance bandwidths. By optimizing the feed arrangements on these antennas a 10 dB impedance bandwidth ratio of over 3:1 can be achieved. This technique yields the ability to construct a smaller antenna, in comparison to a simple printed planar monopole antenna, for a given frequency range. The antennas considered in this paper operate between 1.3 and 5.5 GHz, making them suitable for numerous mobile and portable applications. Measured results are compared to antenna simulations using transmission line modelling.

Printed Band-rejection UWB Antenna with H-shaped Slot

Xiulong Bao et al. — Tue, 28 Apr 2009 09:13:04 PDT

The development of the high data rate wireless communication systems, has placed significant demands on antenna designers, in particular, the requirement for smaller elements with broader bandwidths. In this paper, a novel UWB antenna with notch-band frequency is studied. Effects of the various parameters for antenna performances are also discussed. An optimized compact UWB antenna with notch-frequency function is fabricated and experimentally examined. The measured results show the proposed UWB antenna can achieve a return loss greater than 10 db over an ultrawide bandwidth, of 9.8 GHz, from 2.97 GHz to 12.77 GHz with a tunable notch-frequency band of 5.15 GHz to 5.825 GHz

High Performance Circularly Polarized Antenna Based on Fractal EBG Structure

Xiulong Bao et al. — Tue, 28 Apr 2009 06:42:23 PDT

Circularly polarized patch antennas have been widely applied in wireless communication system, global positioning system, etc., because of their low-profile, lightweight, ease of fabrication and low lost [1,2]. To achieve high performance for circularly polarized patch antennas, some new structures were reported in the literature, such as antennas array, stack layer antennas, using periodic structures [3-7], etc. In this paper, a high performance circularly polarized low frequency patch antenna based on the compact fractal high-impedance surface EBG structure has been fabricated and experimented. The measured results show that the proposed circularly polarized patch antenna has good performance in impedance bandwidth, axial ratio (AR) bandwidth, and gain.

High Quality Millimeter Wave Generation via Stimulated Brillouin Scattering

Marcus Junker et al. — Tue, 28 Apr 2009 06:42:22 PDT

A new and simple method for the generation and modulation of Millimeter waves is presented. Based on frequency upconversion via Stimulated Brillouin Scattering, it is very flexible in its output frequency and modulation bandwidth.

1 Gbit/s Radio Over Fiber Downlink at a 32 GHz Carrier

Marcus Junker et al. — Tue, 28 Apr 2009 06:42:21 PDT

The carrier frequency of the presented radio over fiber downlink at 32 GHz is generated by stimulated Brillouin scattering and an error free 1 Gbit/s data transmission is realized.

Improved Pattern Stability for Monopole Antennas with Ultrawideband Impedance Characteristics

Max Ammann — Tue, 28 Apr 2009 06:42:20 PDT

The requirement of future software defined and reconfigurable radio networks to operate in multiple, wide-ranging, frequency bands places heavy demands on antenna designs. Rather than using antennas tuned at the time of manufacture to operate in certain predefined frequency bands under predefined radio systems, which limits the possibilities of implementing new radio systems on a reconfigurable terminal, a wideband antenna is proposed. The use of a single antenna which can operate over many octaves is very desirable for future wireless communications systems. We discuss the characteristics of the planar monopole, an antenna with wideband properties. The addition of a second planar element orthogonal to a planar monopole improves the radiation pattern stability without degrading the ultrawideband impedance characteristics.