Telecommunications and electromagnetics
Major fields of research include radio systems, and microwave engineering and electromagnetics.
The major focus of the research in this area is mobile radio systems, and a core activity has been the characterisation of the radio channel in a broad range of physical environments. In general, the radiowave propagation process is complicated as propagation characteristics are both environment and frequency dependent. The team has undertaken extensive experimental investigation, analysis and modelling of a range of typical New Zealand environments including outdoor propagation at frequencies used for mobile radio, cellular radio and personal communications systems (PCS), and the penetration of radio signals into and within buildings.
This propagation research, while valuable in itself, is also used to underpin a range of additional activities including systems planning and reliability/capacity estimation research. Accurate propagation data is needed in order to permit, for example, reliable coverage assessments and interference calculations in cellular radio and PCS systems. With the widespread introduction of such systems and the need to achieve a high level of spectrum utilisation by frequency reuse, there is considerable outside interest in research in these and related topics. An example of this is the research in outage probability assessment which has been recognised internationally.
Current research is largely focused on the engineering of personal communications systems (PCS) operating at frequencies at 2GHz and above. Examples of current topics include:
- Improved propagation models (particularly for micro-cellular and pico-cellular/indoor environments)
- Development of planning tools for estimating interference and reliability (including the extension of earlier work for narrowband analogue systems to broadband digital systems)
- Various issues concerning the deployment of wireless systems within buildings
- Issues related to CDMA and PRMA systems
- Aspects of the co-existence of CDMA mobile radio systems with existing fixed services
- Design of patch antennas for PCS applications and the implementation of advanced receiver structures using FPGA and DSP technologies
Microwave engineering and electromagnetics
A major focus of research by this team has been the analysis and modelling of complex excitation and coupling structures in rectangular and radial waveguides. This has included the analysis and modelling of coaxial line /waveguide junctions, probe couplers, and various waveguide post-mounting structures used in solid-state amplifiers, oscillator and switching elements. This work has application in the design of various subsystems, and is a continuation of a theme of work for which we have established an international reputation. Recent work has included the theoretical analysis, characterisation and modelling, and experimental study of dielectrically sheathed junctions.
Attention is also being directed at the electromagnetic modelling of propagation. This work was originally concerned with modelling propagation over multiple rows of buildings (as might be encountered in cellular environments) and has recently been extended to consider propagation through steel reinforced concrete structures. This recent work has application in the deployment of broadband indoor communication services, and illustrates one of the valuable linkages between the research activities of the two teams in the Telecommunications Research Group. An exciting new development in this area is the design of frequency selective surfaces which are expected to find applications controlling interference in high density wireless systems. Some attention is also being directed at the analysis of bioelectromagnetic effects, especially in the beneficial uses of electromagnetic energy in, for example, hyperthermia and bone union therapy.