School of Electronic and Communications Engineering

Sat, 18 Nov 2017 - DIT week 12

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Prof. Max Ammann, Assistant Head of School

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Research Interests

Current Research Projects

Compact and High-Performance Circularly Polarized Antennas for the Integration of Wireless Positioning, Communications and Asset Tracking Systems

Balancing the antenna performance across competing parameters is a key enabler for microwave communications as it evolves from established social telephony uses to linking advanced wireless networks. Circularly polarized radio propagation links in satellite communications, satellite positioning and radio frequency identification (RFID) systems are preferred to linear schemes which are subject to losses when arbitrary polarization misalignment occurs between the transmitter and receiver. With CP antennas at both radios, the enhanced gain and cross-polar discrimination improve the systems' resilience to multipath propagating effects. While antenna miniaturization is desirable for small and portable devices, radio links are dependent on a balance of antenna bandwidth, efficiency or polarisation quality which are inherently compromised by size reduction. The challenges are particularly acute in adverse environments due to congestion and variable propagation conditions.

In recent decades, several techniques have been used in various types of circularly polarized antennas to create broader operating bandwidths but with the sacrifice of the antenna profile being greater than a quarter-wavelength. Alternatively, lower profile slot antennas have achieved wideband CP characteristics, but equally, the antenna dimensions defy reduction to satisfy miniaturized device requirements and groundplane shapes and sizes are critical. The project involves antenna design which can support circular polarisation across unprecedentedly broad bandwidths which can lead to viable design solutions for integration with miniaturised radio systems of the future.

Antenna Time-Domain Optimization Technique for a Miniaturised Antenna Design

This project centres on antenna optimisation for signals that exploit time-domain characteristics in communications and ranging systems. Multi-jurisdictional ultra wideband standards (IEEE 802.15.4a) have been allocated frequency spectra for short range, low-powered applications that are sensitive to impulse distortion. Impulse Radio - Ultra Wideband (IR-UWB) use signals in the pico- to nano-second range. To preserve signal quality, it is essential that the antenna does (1) not add significant distortion to the transmitted or received signal and (2) the radiated energy pattern does not introduce significant variation to the signal time of arrival at different angles. In general, the miniaturisation of antennas compromises several of the radiating performances that reduce the communications range or data throughput performances. Fidelity metrics to quantify these effects will be used to optimise the miniaturisation of single-ended and balanced-feed antenna geometries for time-domain-based applications.

Directive Ultra Wideband Radar Antenna for Wireless Sensor Networks

This project involves research on Ultra Wideband (UWB) directive antennas for close proximity, penetrating radar object sensing. The topologies investigates will suit applications for Wireless Sensor Networks (WSN), where the small dimensions will facilitate ergonomic handheld investigation systems or discrete sub-surface monitoring networks. With materials in its near-field, the design will seek out a stable matched bandwidth and a low distortion of the pulsed radar signals due to the antenna transient time performance. The work is funded by Enterprise Ireland and capitalises on the group’s leading research expertise in UWB and medical applicator antennas and its advanced measurement equipment to create a pre-production prototype demonstrator.

Antennas for Medical Applications

Sergio Curto is part of an investigative group on adjuvant cancer therapy using electromagnetic energy who are investigating the relationship between radiowaves and cancer cell activity. He is investigating the use of various antennas for the delivery of RF power to the human body as an adjunct to cancer therapy. Numerical analyses is also carried out on in-vitro Specific Absorption Rate (SAR), internal magnetic and electric field components, and temperature rise due to exposure to electromagnetic energy at 434 MHz. He is funded by the Irish Research Council for Science, Engineering and Technology. Experimental validation and SAR measurements were carried out using the DASY4 system in the Institute for Infocomm Research, Singapore, under the guidance of Professor Zhi Ning Chen where he spent 3 months. www1.i2r.a-star.edu.sg/~chenzn

Combined PV and Cellular Antenna Panel for Building Façade Integration

The Science Foundation Ireland (SFI) funded project aims to realise autonomous solar powered communications networks, providing a rigorous practically-oriented understanding of the interactions between antenna theory and design, photovoltaic characteristics and non-imaging optics to optimise new generic forms of combined photovoltaic, cellular antenna panel, battery and base station for building façade integration.

Low cost, high performance antennas for UWB systems

This Enterprise Iireland funded project builds upon the technical expertise in the antenna research group in DIT to develop a prototype antenna that will provide best-in-class performance coupled with low cost planar fabrication technology. The antenna research group in DIT has been involved in antenna research with a particular focus on low cost planar antenna technologies for the past 7 years. The group is a partner in the CTVR, working on the fundamental antenna design issues related to wideband systems. This has highlighted the need for antennas with largely omni-directional behaviour over the frequency bands 3.1 GHz to 10.5 GHz. Preliminary studies have shown that the antenna technologies used to date cannot provide suitable performance in this respect in a small footprint, low cost device. Existing products in this area suffer primarily from nulls in the radiation pattern at certain parts of the frequency band. The technology normally used to make these antennas is an inherently narrow band technology that be made wideband by overlapping multi resonant modes and provide quasi-omnidirectional patterns over part of the bandwidth. The techniques that will be used here are inherently naturally wideband and can be tuned to achieve an acceptable trade-off between all design parameters across the full bandwidth required. This provides good performance in both the frequency and time domain and guarantees low pulse distortion.

Optical Spectrum Analysis, Slow and Fast Light Effects and Fibre Optic Sensor Technologies

are being researched by PhD students Kai-Uwe Lauterbach, Ronny Henker and Andrzej Wiatrek. This work is being carried out in the Institut fuer Hochfrequenz Technik, Deutsche Telekom University of Applied Sciences, Leipzig. The project, which is co-supervised by Dr Thomas Schneider and Dr Andreas Schwarzbacher, involves the use of stimulated Brillouin scattering

Design Principles of Antennas for Multiband Reconfigurable Wireless Systems

Centre for Telecommunications Value-chain Research (CTVR) (CTVR Antenna Group).
The Science Foundation Ireland (SFI) funded antenna group is based in the School of Electronic and Communications Engineering in Kevin St and led by Dr Max Ammann. It is part of the larger RF strand, based in NUI, Maynooth with Dr Ronan Farrell as strand leader. This strand is aimed at realizing the next generation of fully reconfigurable radio transceivers and associated intelligent antenna systems.

Ultrawideband antennas

are being developed and modelled using computational electromagnetic methods such as MoM/UTD, FI and TLM. Members of the group are working on novel low-profile wideband designs covering many octaves of bandwidth and are also examining the limitations of various feed, modelling and measurement techniques. Ph.D students Jonathan Evans, Giuseppe Ruvio and Matthias John are driving this project.

Electromagnetic BandGap Techniques

Circularly polarised microstrip patch antenna performance is being improved using soft and hard bandgap techniques including fractal hi-impedance surfaces. Dr Xiulong Bao and Giuseppe Ruvio are leading this work. Significant gain enhancement has been achieved as well as improving the axial-ratio bandwidth using various techniques.

Genetic Algorithm Optimisation

of wide-band printed monopoles and feed systems employing arrays of overlapping sub-patches and quadratic Bezier splines are being developed by Matthias John. Optimisation and miniaturisation techniques for multi-band printed elements are also developed.

Multi-polarised crossed-dipoles

using printed technologies have been developed. Applications include wireless LANs and other applications where polarization agility is required. Novel wideband matching and baluning techniques have been developed, with improved isolation, gain and polarization purity. Francisco Leon Lerma has completed this project in collaboration with Dr Tuli Herscovici.