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Wireless Communications Research Team

Electromagnetic and microwave engineering

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Analysis of Low-cost Original Holographic Antennas

Theoretical OveRvIew, NOtes, StudY, DesigN, and EasY Implementation (ALOHA TORINO-SYDNEY)

Researcher: Ladislau Matekovits (Politecnico di Torino, Italy)

Summary

The project involves the theoretical investigation, numerical study and experimental characterisation of holographic antennas (HA) based on microstrip technology.

Studies of holograms have been started at optical frequencies to obtain virtual images as a result of interference of two polarised electromagnetic waves. The first applications of holograms at microwave frequency date back to the 1970s, but the scientific community is showing new interest.

Research groups are studying antennas based on this principle, since holographic surfaces offer new potentials in this field. In HA the radiating aperture is formed by a conductive, metallic pattern on a surface-wave carrying grounded (multi)layer dielectric substrate.

The hologram is obtained by recording the resulting interference between two polarised electromagnetic waves at the air-substrate interface. By exciting the hologram with only one of these two waves, the second one is generated.

The hologram is viewed as a variable surface impedance: its synthesis is realised by width-modulated microstrip lines. The periodic arrangement of such structures allows the generation of a substrate that supports slow waves, mandatory for the coupling between the surface and space waves. Control of the phase velocity (the surface impedance) is achieved by adequately varying the width of a microstrip line inside the unit cells.

Plans

We will study analytic, numerical and experimental procedures and techniques.

Applications

This method has recently been submitted for patent. Antennas based on this principle present various advantages, notably the polarisation purity of the radiated field. The absence of a feeder in the front of the antenna eliminates the blockage, yielding a higher gain.

The proposed low-cost microstrip technology is widely used in aero spatial application as well, because of the reduced dimensions of the antennas and the possibility to build conformal configurations.

Progress

Analytical elaboration of the kernel of the EFIE

  • Integration of the structure with a surface wave launcher
  • Dinamically control of the dispersion diagram
  • Optimisation of the geometry
  • Preliminary study of conformal geometry.

Duration: 1 July 2009-30 June 2012 (last year at Politecnico di Torino)
Funding: European Commission (Marie Curie Actions - International Outgoing Fellowships (IOF)
Outcomes/outputs: 1 patent, 10 submitted articles - journal and conferences

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Beamforming and evaluation of focal plane arrays for radioastronomy

Researchers: Douglas Hayman (CSIRO ICT Centre), Trevor Bird, Karu Esselle, Peter Hall (International Centre for Radio Astronomy Research and Curtin University)

Summary

Focal plane arrays (FPAs) are a key technology for a new generation of radiotelescopes. Their primary benefit is the rapid survey speed facilitated by the wide field of view from multiple beams. Recent advances have brought this technology within reach for radio astronomy and a number of institutions have significant research programs in this field.

The size of the FPA required for a specified field of view is an important parameter for preliminary system design. This is examined by calculating the encircled power in the focal plane using physical optics.

Design data is provided relating the FPA size, dish size, focal length and field of view for practical prime focus dimensions. A broad minimum in the FPA size for a dish focal length and diameter ratio (F/D) of 0.4 was found and over practical geometries, the FPA size is dependent only on the F/D and the scan-angle-and-dish-diameter ratio.

In an operational radiotelescope, the parameters required to generate an optimum set of beamforming weights are not sufficiently well known to determine the weights a priori. This is because of component drift and the difficulty in accurately modelling all the effects in the system.

Therefore a black-box approach is used. The theoretical basis for the approach is detailed: the determination of the standard figures of merit, gain (G) and system temperature (T) is shown as well as the calculation of the maximum sensitivity (G/T) weighting.

A prototype interferometer-radiotelescope, built at CSIRO's Radiophysics Laboratory in Sydney, is used to demonstrate a suite of techniques for FPA beamforming and evaluation. The maximum G/T weighting can be calculated from readily measured parameters in an appropriately equipped radiotelescope.

The techniques canvassed enabled the ratio of G/T values for different weights to be determined an order of magnitude more accurately than the absolute values of G and T.

Duration: August 2003-August 2011
Funding: PGRF and support from CSIRO.
Progress: The investigation is complete and the thesis is being written.
Outcomes/outputs: 1 journal publication, 9 conference papers.

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Cloaking device

Researcher: Francesco Monticone, visiting student, Politecnico di Torino (Italy)
Supervisor:
Ladislau Matekovits, visiting academic, Politecnico di Torino 
Group leader:
Karu Esselle

Aims

The aim is to design a cloaking device for the microwave/millimetre-wave range. In particular, we intend to:

  • develop a novel, low-cost, easy-to-fabricate polymer shell
  • analyse its performance by means of full-wave electromagnetic simulators, compared to other solutions proposed in the literature.

Duration: July-October 2010
Funding: Scholarship, Politecnico di Torino 
Outcomes/outputs:

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Design and development of frequency selective surfaces (FSS) for energy-saving glass

Researcher: Syed Irfan Sohail (PhD student)

A drawback of energy-saving glass is that its coating reduces signals for computers and other devices. We aim to improve reception while retaining thermal efficiency.

Summary

Frequency selective surfaces (FSS) are periodic structures that behave like spatial filters. As spatial filters they are usually designed for transmitting low/high frequencies and also to allow/stop certain band of frequencies.

One interesting application is with energy-saving glass. This type of glass has a metallic coating, and is used as windows to keep heat or cold inside rooms or buildings. But the coatings affect useful microwave signals - for example from GSM(800-900MHz), GPS and PCs. This creates poor reception in rooms and buildings.

At the same time, coated glass has the advantage of keeping WLAN signals (2.45GHz/5GHz) secured within a building.

Aims

We intend to design, analyse and develop FSS filters for energy-saving coated glass that will work as spatial filters. The aim is to improve the transmission/reception of useful and desired microwave signals inside the rooms and buildings, while keeping the thermal effects within a comfortable range.

Progress

We are conducting the literature review of previous research in FSS, to get the research footings and an initial approach to our aims and objectives.

Duration: 1 July 2010-July 2014
Funding: iMQRES scholarship
Outcomes/outputs:

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Metalmaterials based on spiral resonators and their microwave applications

Researchers: Ozgur Isik (PhD student), Karu Esselle, Yuehe Ge

Duration: July 2005-April 2009
Funding: International Macquarie University Research Scholarship
Outcomes/outputs: 3 journal publications, 8 conference papers

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Tunable periodic structures

Researchers: Professor Karu Esselle, A/Professor Michael Heimlich, Dushmantha Thalakotuna (PhD student), Ladislau Matekovits (Visiting academic), Dr Stuart Hay (CSIRO)

Multi-state antennas for wireless body-area networks and other microwave/millimetre-wave systems

Summary

We will analyse and design electromagnetic-band gap-based dynamically controllable electromagnetic structures. These are formed by cascading multi-state electromagnetic elements (MSEEs). Advantages include dynamic control of the dispersion diagrams, transmission properties, and radiation properties. We will analyse, design and test microwave models.

The aim is to implement these in MMIC for millimetre-wave wireless networks and a range of other applications.

Plans

Dynamic tuning of the electromagnetic band gap is shown theoretically. Proof of concept on dynamic tuning of the band gap is to be validated by realising a prototype to function around 3-7 GHz on Alumina wafer.

Further study is needed for:

  • behaviour of this periodic structure as a leaky wave antenna
  • proper impedance matching in different regimes of frequency as a filter and antenna.

Practical application of these tunable structures as filters, sensors and antennas in body area networks will be studied in the future.

Progress

We have shown the possibility of dynamically tuning the electromagnetic band gap. This allows the change of cutoff frequency as well as size of the band gap.

In order for proof of concept, a proper CAD model is developed to accommodate switches in alumina wafer and change between different periodic structures in the 3-7 GHz frequency range.

Dates: September 2009-December 2012
Funding: iMQRES scholarships and CSIRO top-up scholarship, US Army Grant.
Outcomes/outputs: publications, patents, awards.
Patent from Torino

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Ultra-wideband and super-wideband planar antenna

Researchers: Jianjun Liu (PhD student), Karu Esselle, Shunshi Zhong (School of Communication and Information Engineering, Shanghai University), Stuart Hay (ICT Centre CSIRO)

Summary

High-speed and multiple band wireless communication systems are placing more requirements on antenna design. The preference is for a single antenna with a wide impedance bandwidth that can cover operating frequency bands of wideband and multiple wireless communication systems. We need techniques to:

  • broaden the bandwidth of printed antennas
  • optimise the antenna characteristics.

The project involves printed super-wideband antennas and wideband miniaturisation for ultra-fast wireless communication applications and extremely broadband RF energy scavenging.

It also relates to super-wideband antenna with multiple notch-bands to support multiple communication services, while avoiding interference from other selected systems.

Plans

  • Time domain characteristic research and radiation pattern improvement for SWB antenna
  • Energy harvesting with SWB antenna
  • UWB wearable antenna and UWB antenna for WPAN application
  • Dual-polarisation UWB antenna and UWB antenna array
  • Reconfigurable antenna integrated with wideband monopole for cognitive radio applications.

Progress

We have designed and developed:

  • six printed super-wideband antennas
  • one compact planar ultra-wideband antenna with band-notched function
  • and one super-wideband antenna with multiple band-notched character.

In consultation with Macquarie University, Shanghai University has submitted a Chinese patent application on extremely wideband antennas. The researchers are preparing another Chinese patent application for the super-wideband planar antenna project.

Duration: May 2009-present
Funding: Endeavour International Postgraduate Research Scholarship, iMQERS Macquarie University Postgraduate Research Fund and HDR project fund
Outcomes/outputs: 8 conference papers and 1 journal paper accepted

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Wideband and multiband antenna systems for ultra wideband (UWB) and global navigation satellite systems (GNSS)

Researcher: Yogesh

Ultra wideband systems (UWB)

Ultra wideband systems hold opportunities for high-definition home viewing and the smart office.

In this research we report on some novel techniques for enhancing the gain of printed antenna while maintaining the impedance bandwidth. Add more info about research focus aims and

Summary

Ultra wideband (UWB) communication systems offer an unprecedented opportunity to impact on the way people interact with communication systems. Advantages include:

  • enormous bandwidth
  • wide scope of data rate/range trade-off
  • low cost leading to pervasive use.

UWB systems require an antenna that can receive all frequencies at the same time. Antenna behaviour and performance must be consistent and predictable across the entire band.

In the past, UWB antennas have been developed for communication, impulse radio and microwave imaging, e.g. biomedical imaging, non-damage detection and ground-penetrating radar (GPR). Ideally, pattern and matching should be stable and preferentially non-dispersive, with a fixed phase centre.

The Federal Communications Commission's 2002 approval of 3.1 GHz-10 GHz license-free UWB band has given rise to several other candidates for UWB applications, such as:

  • high data rate terminals (fixed or movable) for multimedia
  • home entertainment like high-definition TV
  • blue ray
  • WLAN
  • video distribution within cars etc are also emerge as front candidates for UWB applications.

Techniques such as multi band-orthogonal frequency division multiplexing (MB-OFDM) have restricted UWB because of lower gain. To improve the link budget, the only way to proceed at RF hardware level at receiver side is either to reduce the noise figure or to introduce antenna gain.

To overcome the shortcomings of standard printed monopole antennas for UWB systems, it is important to design antenna systems with constant gain over the whole UWB band.

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Global navigation satellite systems (GNSS)

Compared to the US and Europe, we have very clear skies for watching satellites, from Australia to Singapore. If we set up base stations for next-generation GNSS, we will be able to track most of the satellites up there.

Summary

Next-generation multi-signal multiband GNSS are designed to provide precise position, velocity and timing information on a global, common coordinate system, for an unlimited number of suitably equipped users.

The first systems grew out of the Cold War: the US had GPS and the USSR (and later Russia) had Glonass. As it became clear that GPS in particular was outgrowing its military purpose, other nations began to join in.

  • The Europeans proposed Galileo.
  • China launched Beidou, the first regional navigation satellite system (RNSS), and then announced Compass, a GNSS.
  • Japan tried to solve the urban canyon problem by planning their own regional augmentation to GPS: the Quasi-Zenith Satellite System (QZSS).
  • India proposed the Indian RNSS (IRNSS).

Who knows who will propose a navigation satellite system (or NSS, which includes both GNSS and RNSS), but most of the big space players are now represented.

For instance, some systems, or at least their signals look very similar - GPS and QZSS. Others, such as IRNSS, are very different. However, they can all be seen from Australia.

There are a significant number of carriers and bandwidths. But from a receiver front end design point of view, where all signals must be received, they can be grouped into two bands:

  • from the bottom of the E5 band to the top of the E6 band (1.166-1.294 GHz, a 128MHz band)
  • from the bottom of the Compass L1 band to the top of the Glonass G1 band (1.559-1.616 GHz, a 57MHz band).

Designing antennas to cover this range with good 'isotropic' gain and phase centre behaviour is a real challenge.

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Wireless localisation projects (CSIRO PhDs)

We develop systems for accurate indoor localisation and tracking for a wide range of uses, including underground mining and indoor sports.

Wireless Ad-hoc System for Positioning (WASP)

Partners: The Wireless Communications 'localisation' team at Macquarie University collaborates with the CSIRO Wireless and Networking Technologies Laboratory.

Summary

WASP uses time-of-arrival localisation on a rugged custom software-defined radio platform. It provides accuracy down to 0.1 m and update rates up to 200 Hz. The team has built over 100 nodes and can deploy large networks of nodes in a mobile ad hoc network, in field and application trials.

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Advanced navigation through data fusion from inertial sensors and wireless ad-hoc positioning systems

Summary

Recently MEMS inertial sensors (such as the Analog Device's ADIS16405) have reached the accuracy where they can be used for inertial navigation.

The goal is to build a tightly integrated system to improve navigation by fusing data from the inertial sensor and WASP. The work involves:

  1. Measuring and modelling the error characteristics of the sensor
  2. Designing algorithms to stabilise the attitude of the platform
  3. Designing algorithms for optimal fusion of the sensor data to estimate inertial sensor bias
  4. Efficient real-time implementation of the algorithms.

This project can leverage prior research in the field of fusion of inertial and GPS sensors.

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Localisation algorithms and protocols in highly mobile ad hoc networks

In some applications it is not desirable to rely on any fixed infrastructure - a network will consist solely of mobile nodes forming a highly mobile ad hoc network. In such an environment, existing communication stacks from the physical layer through to the transport layer do not function well. Accurate localisation puts further requirements on the network protocols, and many of the applications have hard requirements for quality of service (QoS).

This research will:

  • look at the development of better protocols to support localisation in highly mobile ad hoc networks
  • evaluate their performance using large scale networks in real applications.

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Performance optimisation of cooperative localisation

Summary

Unlike conventional localisation, where nodes exchange signals with anchor nodes to determine their location, in cooperative localisation, nodes exchange signals with all neighbouring nodes. This allows simpler network setup with fewer anchor nodes, and localisation of nodes out of communication range of anchor nodes. But it comes at the cost of increased computational complexity and network communication overhead.

This project will explore the relationship between the amount of data exchanged between nodes and the performance of cooperative localisation.

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Low-complexity and low-power Bayesian localisation algorithms

Summary

Localisation in indoor environments is complicated by the fact that the distribution of range errors is biased and highly non-Gaussian. We have shown that Bayesian algorithms using a realistic model of the errors can produce substantially better localisation and tracking results than conventional algorithms. However, their computational complexity is a couple of orders of magnitude greater.

This project will explore:

  • developing a Bayesian localisation algorithm with excellent performance
  • optimally mapping this into a heterogeneous computation platform combining field programmable gate arrays (FPGA) and digital signal processors (DSP).

The objective is to run in real time with a low-power budget.

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Low-power management strategies for wireless ad hoc positioning systems

Summary

Battery life is the limiting factor in reducing the size of high-update rate wireless tracking hardware.

This project will examine how to substantially reduce the power of WASP, using aggressive power management strategies. The scope includes changes to the medium-access controller (MAC) algorithm, and selecting components in the hardware.

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