Research Report - 2001
Communications
Academic Staff
A/Prof Marek E. Bialkowski
Dr Marian L. Majewski
Dr Vaughan Clarkson
Dr John Homer
Dr Aleksandar D. Rakic
Research Students
Mr Novak Petrovic
Mr Atul Kuver
Mr Rong Wang
Mr Sorachet Mitched
Mr Henry Shih-Hong Yang
Mr Vince Boros
Mrs Lidia Donskoi
Mrs Yuan Li
Mr Januar Janapsatya
Mr Salman Durrani
Mr Eddie Tsai
Mr Richard Taylor
Mr Chun-Wing Li
Miss Faith Choi
Mr Bruce Piper
Mr Hyok Jae Song
Mr Shaokang Chen
Research and Technical Staff
Mr Russell Clarke
Contact Details
A/Prof Marek Bialkowski
Email: meb@csee.uq.edu.au
Tel: 3365 3563
Dr Marian Majewski
Email: mlm@csee.uq.edu.au
Tel: 3365 4133
Dr Aleksandar D. Rakic
Email: rakic@csee.uq.edu.au
Tel: 3365 3569
Dr Vaughan Clarkson
Email: vaughan@csee.uq.edu.au
Tel: 3365 8834
Dr John Homer
Email: homerj@csee.uq.edu.au
Tel: 3365 4139
Research Summary
The Communications group is engaged in research topics spanning both microwave, wireless and photonic communications engineering. Much of the research of the group involves development of novel communications hardware such as antennae for microwave communications (including low profile antenna arrays, smart antennae) and design and optimisation of photonic communications devices and subsystems (including ultra-high bandwidth optical interconnects, and optical data links based on Vertical-Cavity Surface-Emitting Lasers and Tunable In-Plane Semiconductor lasers). Almost all of the projects undertaken in the group involve extensive collaboration with research groups from Australia and overseas including University of California Santa Barbara USA, The University of Hong Kong, China, City University of Hong Kong, China, National University of Singapore, Singapore, Federal Technical Institute (ETH) Zurich, Switzerland and the Australian National University, Canberra. The groups research performance in 2000 is measured by a significant number of high quality refereed journal articles and conference papers and success with competitive ARC and other grants.
Antenna Systems
Radial Line Slot Array Antennas for Wireless Communications Applications
A single layer Radial Line Slot Array (RLSA) antenna is attractive for point-to-point communications as well as for receiving Direct-to-Home television programs. This antenna is formed by a thin circular disk-shaped plastic body, which is enclosed in a conductive coating or foil material. In the standard RLSA design, the upper circular conductive surface carries a defined distribution of radiating slots, while the rear conductive surface is devoid of any slots. This rear surface incorporates a coaxial feeding element at its centre. Much interest has developed over recent years in this antenna because of its potential to overcome a number of the problems associated with its competitors, such as a parabolic reflector antenna or a planar microstrip patch array. Investigations are performed both into linearly and circularly polarised antennas. A simple but impressively accurate model for obtaining the radiation pattern of the RLSA antenna has been developed. In addition to the modelling of radiation mechanism, the research performed also covers the development of computer software packages that cater for the RLSA antenna design manufacture and test processes.
Davis, P.W. and Bialkowski, M.E., "Linearly Polarised Radial Line Slot Antennas with Improved Return Loss Performance", IEEE Antennas and Propagation Magazine, vol. 41, No 1, pp. 52-61, February 1999.
Active Reflect-Arrays
In recent years, in the search for alternatives of parabolic reflector antennas a microstrip reflect-array antenna has been devised. In this new arrangement, a horn antenna illuminates a planar array of microstrip patches, which are suitably phased to convert a spherical wavefront, produced by the feed, into a planar wavefront. In our work, a new configuration of a reflect-array is proposed so that the transistor amplifiers can be included making this antenna active. Initially an X-band passive reflect-array consisting of dual-feed aperture coupled microstrip patches fed by an off-set horn is designed and built. Each patch of this array includes two orthogonal apertures that are coupled via a section of a microstrip transmission line. Next, transistor amplifiers are designed for inclusion with each patch. At the present stage of research, we developed a 137-element active array with MESFET amplifiers. The array operates properly, although it shows significantly high sidelobes that can be due to phase errors caused by manufacturing tolerances.
Robinson, A.W., Bialkowski, M.E. and Song, H.J., "A Passive Reflect-Array with Dual-Feed Microstrip Patch Elements", Microwave and Optical Technology Letters, December 1999.
Spatial Power Combiners using Active Microstrip Patch Transmit-Arrays
Spatial power combining is a power combining method to overcome the limited output power level of solid-state devices by exploring open space as a power combining medium. In the research on spatial power combiners, most efforts were exercised to achieve active stages exhibiting good power combining efficiency under the assumption of uniform excitation. In order to achieve such uniform excitation, the active radiating structures were placed in a far field region of transmitting/ receiving devices. Unfortunately, the far-field arrangement is not suitable for its ultimate application in power combiners due to the large free-space loss. To eliminate this shortcoming, in the current work on spatial combiners active stages are placed in a reactive near-field region of the illuminating or receiving device. In our work we propose the use of a planar patch array as an illuminating device for a transmit-array of transistor amplifiers. Investigations are carried out into spacing between an illuminating patch and a passive transmit-array to achieve optimal power combining efficiency. The results obtained so far indicate high power combining efficiency of the developed amplifiers when illuminated by passive arrays and their suitability for future monolithic integration due to the planar format of the entire power combining structure.
Bialkowski, M.E. and Song, H.J., "Investiga- tions into Power Combining Efficiency of Microstrip Patch Transmit Arrays", Micro- wave and Optical Technology Letters, Vol. 22, Issue 4, 1999, pp.284-287, August 1999.
Spatial Power Combiners Using Tile and Tray Configurations of Microstrip Antennas.
This project will investigate tile and tray configurations of active planar arrays, which combine a signal from a two-dimensional distribution of transistor amplifiers equipped in receiving and transmitting antennas. Optimal conditions concerning insertion losses, power combining efficiency and operational bandwidth of these structures will be studied when a pyramidal horn or a corporate-fed array antenna is used to distribute an input signal. The results of these investigations are expected to significantly contribute to the development of novel configurations of solid-state power amplifiers for applications such as microwave and millimetre-wave satellite transponders, Local Multi-Point Video Distribution systems, and transportable radar systems. This project is funded via the Large ARC grants scheme. The project has received funding of $137,000 for 2001-2003.
Airborne Radar Antenna
Modules using Temperature Resistant Substrate Materials In airborne radar, advanced power dividing and phasing networks together with digital signal processors should be located close to transmitting and receiving antennas preferably using multi-layer architectures. Such architectures put stringent requirements on electrical and mechanical properties of dielectric substrates. This research concerns the design and development of multi-layer antenna elements and the associated power dividing and phasing networks using honeycomb and quartz-fibre composite materials. These substrates are resistant to large temperature changes and hence the developed prototypes show great promise to meet sophisticated requirements of airborne radar.
Kabacik, P. and Bialkowski, M.E., "The Temperature Dependence of Substrate Parameters and Their Effect on Microstrip Antenna Performance", IEEE Trans. Antennas and Prop., vol. 47, No. 6, pp. 1042-1049, June 1999.
Smart Antennas for Mobile Communications Applications
Initial investigations are conducted into the application of Smart Antennas to CDMA mobile communications. Smart antenna is the term given to an antenna array system that uses fast DSP to adaptively alter the beam-pattern to maximise signal to interference ratio. The design of the system borrows heavily from the signal processing and estimation theory areas since the beam-forming processing is closely linked to the CDMA processing. Steps are undertaken to perform theoretical studies using Matlab. Experimental investigations are envisaged using a collection of laptops equipped with wireless PCMCIA cards.
Novel Technologies and Signal Processing Techniques for Smart Antennas
This multidisciplinary research proposal aims at investigating novel technologies and signal processing techniques for cellular base stations. In particular, it aims at using honeycomb and quartz composites to design and develop smart flat-panel antennas. The proposed composite technology enables integration of antenna elements with active stages, optoelectronically controlled beamforming networks and signal processing modules. At the same time it offers a very light and strong construction that is capable of withstanding heavy winds and rains and extreme temperature variations. Using suitable signal processing algorithms the developed antenna system will facilitate a significant increase of the cellular system capacity. The signal processing techniques being developed are focusing on robust adaptive direction finding (or angle-of-arrival) methods, which enable detection and tracking of mobile units, within the multi-path environment of urban cellular systems. Techniques based on MUliple SIgnal Classification (MUSIC) have been investigated, but their success is limited in the harsh multi-path urban cellular environment. Current attention is being given to more recent adaptive multi-direction finding algorithms as well as to two-dimensional STAP (space-time adaptive processing) based techniques. This project is funded by the University of Queensland small grant scheme ($53,000 for 2001).
J. Homer, "Quantifying the convergence speed of the LMS adaptive FIR filter with autoregressive inputs", Electronics Letters, Vol. 36, pp.585-6, 2000.
J. Homer, "Detection guided NLMS estimation of sparsely parametrised channels", IEEE Trans. Circuits and Systems II, Vol. 47, pp. 1437-42, 2000.
Wideband Array Antennas with an Optical Beamforming
This research is concerned with broadband microwave array antennas for applications such as radar and multi-band wireless communications. In order to obtain broadband operation, tapered slot antennas (TSA) are considered. In order to achieve broadband beam steering, conventional phase shifters including PIN diodes or FETs can not be used with these antennas, as they are narrow-band in operation. One possible solution to that problem is the true-time delay (TTD) circuit, which is realized using a microwave optical link. This link consists of a laser diode, a photo diodes and sections of fibre or free space as a delay line. At the transmit side of the module, light signal is directly modulated by a microwave signal and transmitted through the free space/fiber. The differential phase shift required for beam steering is obtained using different length of transmission line in free space or a fiber. The research work aims at the design and manufacturing of a small array of tapered slot antennas that are steered using photonic means.
Wang, Q. and Bialkowski, M.E., "An Antipodal Tapered Slot Antenna on a High Dielectric Constant Substrate", Proc. APCC/ICCS98, pp. 604-607, 23-27 November 1998, Singapore.
Antennas for Mobile Satellite Communications
Mobile satellite communications is an emerging technology which is shaping the planet by putting people in remote areas in touch with the rest of the world. Examples of such satellite systems include the Australian MobilesatTM, North American AMSC/MSAT and Japanese NSTAR. These systems require antennas with about 10 dBi gain to establish voice, data, and facsimile communications via the satellites. Due to the high gain, the antennas have narrow beams and therefore, they need to track the satellite if they are installed on a moving vehicle. All these conditions make antenna design a real technologically challenging task. This project concerns antenna systems that are suitable for land mobile satellite communications (LMSS). Two low cost and compact designs, an 8-element switched-beam array and a 2-ring circular phased array, have been developed and fully tested indoors and outdoors. The outdoor field trials with an NEC S1 transceiving terminal demonstrated very good quality voice communications via Optus B-series satellites. Since using low cost components and easy manufacturing techniques substantially reduces the development cost, the antennas can find commercial markets in the mobile satellite communications arena.
Bialkowski, M.E. and Karmakar, N.C.,"A Two-Ring Circular Phased Array for Mobile Satellite Communications", IEEE Antennas and Propagration Magazine, Vol 41, No 3, pp.14-23, June 1999.
Optoelectronics & Microwaves
Several of our current research projects (including VCSEL design and characterisation, high speed operation of tunable 1.55 micrometer semiconductor lasers and modelling of optical properties of materials) have been conducted in collaboration with the Department of Electrical and Computer Engineering (Optoelectronic Technology Center), University of California at Santa Barbara USA, Australian National University, Canberra and The University of Hong Kong, China.
Vertical-Cavity Surface-Emitting Lasers for Optical Signal Processing
This project is concerned with the design and modelling of novel semiconductor laser diode structures, namely the Vertical-Cavity Surface-Emitting Lasers (VCSELs) including their applications to 2D optical signal processing. These devices are of particular importance to optical high speed access networks, 10-gigabit Local Area Networks (LANs)and optical interconnects. The outcome of this project will be to design VCSEL (single devices and arrays) for operation at 850 nm. They will be fabricated using MOCVD facilities at ANU.
A. D. Rakic and M. L. Majewski, Cavity and mirror design for VCSELs, Chapter 8 in E. H. Li and K. Iga (Eds.) Vertical-Cavity Surface-Emitting Laser Devices, Springer-Verlag Berlin 2001.
A. D. Rakic, M. L. Majewski, A. B. Djurisic, E. Herbert Li and J. M. Elazar Design of wide bandwidth, flat phase AxOy-GaAs DBR mirrors for Vertical-Cavity Surface-Emitting Lasers. In 22nd International Conference on Microelectronics MIEL 2000, 243-246, IEEE Press, 2000.
Modelling of Optical Properties of Semiconductor Materials used for Optoelectronic Device Manufacturing
The major task of this project is accurate and comprehensive modelling of semiconductor materials for optoelectronic devices: semiconductor lasers, photodiodes and modulators for applications in communication systems. The composition changes in group III-V and group II-VI semiconductor ternary and quaternary alloys allow for engineering of material properties in order to produce the semiconductor with the desired optical and electrical characteristics. Accurate models for the optical properties of semiconductors are needed for optoelectronic device design purposes and also for the real-time monitoring and control during the growth of these materials. Currently, there are two advanced methods that allow engineering of optoelectronic materials, namely Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapour-Deposition (MOCVD), both requiring growth monitoring. In this project we have developed comprehensive models that can be readily used for this purpose. Thus far our models have been widely cited in the literature and have been used for modelling of a large number of materials including the first successful model for a quaternary semiconductor alloy.
A. B. Djurisic, E. Herbert Li, A. D. Rakic, and M. L. Majewski. Modeling the optical constants of AlSn, GaSb and InSb. Appl. Phys. A, 70 (1): 29-32, 2000.
A. B. Djurisic, A. D. Rakic, E. Herbert Li, M. L. Majewski, and J. M. Elazar. Modeling the optical constants of AlxGa1-xAs alloys. J. Appl. Phys., 86 (1):445-451, 1999.
A. B. Djurisic, A. D. Rakic, P. C. K. Kwok, E. Herbert Li, and M. L. Majewski. Optical constants of GaP, InP and InAs. J. Appl. Phys., 85 (7):3638-3642, 1999.
A. D. Rakic, A. B. Djurisic, J. M. Elazar, and M. L. Majewski. Optical properties of metallic films for vertical-cavity optoelectronic devices. Appl. Opt., 37(22):5271-5283, 1998.
Global Optimisation Algorithms for Computer Aided Design of Optoelectronic Devices and Systems
This project is concerned with the development of two classes of global optimisers: Simulated Annealing Algorithms and Genetic Algorithms. Both algorithms, by simulating some natural processes, enable effective optimisation of engineering designs and in some cases the design of the system by the computer, in a globally optimal way. Our applications include the modelling of optical materials, optoelectronic and optical devices and systems.
A. B. Djurisic, A. D. Rakic, E. Herbert Li, M. L. Majewski, N. Bundaleski, and B. V. Stanic. Continuous optimization using elite genetic algorithms with adaptive mutations. In X. Yao, R. I. McKay, C. S. Newton, J.-H. Kim and T. Furujashi, Editors, Simulated Evolution and Learning, volume 1585 of Lecture Notes on Artificial Inteligence, pages 365-372. Springer Verlag, Berlin, 1999.
A. B. Djurisic, A. D. Rakic and J. M. Elazar. Modeling the optical constants of solids using acceptance-probability-controlled simulated annealing with an adaptive move generation procedure. Phys. Rev. E, 55(4):4797-4803, 1997.
Automated Techniques for Optical and Electrical Characterisation of Vertical-Cavity Surface-Emitting Lasers (VCSELs) and 2D VCSEL Arrays
In the course of this project we have developed a sophisticated novel system for comprehensive testing of light emitters used in optical communication systems. Our system allows for standard electrical (DC and RF) and optical measurements on semiconductor lasers such as Light-Current, Current-Voltage, optical spectrum, intensity noise spectrum and CCD camera beam profiling. In addition to these measurements our system allows for spectrally, spatially and polarization resolved imaging of coexisting transverse modes in VCSELs. When this is combined with high resolution spectral measurements and phase retrieval methods we are able to investigate the modal behavior in gain-guided VCSELs, and in particular the fine structure of the transverse modes. The addition of a new group of RF measurements to this system is currently underway.
Optical Interconnects using Optoelectronic Arrays
This project is concerned with the design and implementation of free-space optical interconnects instead of conventional copper wire type interconnects commonly used in the current computer technology. The advantage of optical interconnects investigated in this project is that they would allow higher operational speed (GBps), better Bit-Error-Rate (BER), and reduced power consumption in comparison with the existing electrical interconnects in current computer systems. The outcome of this project is to develop design oriented models for optical interconnects using Vertical-Cavity Surface-Emitting Laser (VCSEL) arrays, microlenses and photodetector arrays. Finally, these models will be verified experimentally in our Optical Laboratory.
Rong Wang, A. D. Rakic, and M. L. Majewski. Design of free-space optical interconnects based on arrays of vertical-cavity surface-emitting lasers (VCSELs), microlenses, and photodetectors. Appl. Opt. 2001, to be published
V. E. Boros, A. D. Rakic and S. Parameswaran, High-Level Model of a WDMA Passive Optical Bus for a Reconfigurable Multiprocessor System, In Proceedings of the 37th Design Automation Conference DAC 2000, Los Angeles, 221-226, Association for Computing Machinery, 2000.
Investigation of Multimode Band-Pass Filters using High Temperature Superconductor (HTS) Devices for Microwave Communication
Integrated Band-Pass (BP) filters are essential components of multichannel communication systems as they play a major role in signal mutiplexing and demultiplexing. Of particular significance to efficient realisation of integrated RF and microwave mobile communication systems based on either the satellite or cellular approach is to develop reliable multichannel low-noise receivers. In this project we introduce a novel approach to building these receivers by using for the first time multimode BP filter structures deposited with High Temperature Superconductor (HTS) material on dielectric substrates. The outcome of this project will be to design filters for the wireless RF cellular system and also to build prototype devices in collaboration with the Telecommunications and Industrial Physics Division of the CSIRO, Sydney.
Microwave Characterisation of Active and Passive Devices using Automated Vector Network Analyser
Typically, all RF, microwave and optoelectronic devices for high-speed operation in modern communication systems are characterised in terms of their scattering matrix parameters. This approach is commonly applied to both passive and active devices used for communication systems (satellite, wireless, fibre-optic networks, etc). Therefore we routinely use the HP 8510C Network Analyser to measure the scattering matrix parameters of high-speed electronic and optoelectronic devices in conjunction with the circuit modelling method (when applicable) using a commercial software package ADS in an effort to optimise the design of the circuit/system layout.
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