1 - EFFECTIVE MEDIUM THEORIES BACKWARD IN TIME: FROM THE 21ST TO THE 19TH CENTURY

2 - THE PHYSICS AND MATHEMATICS OF THE SIGNAL PROPAGATION MECHANISM IN CELLULAR WIRELESS COMMUNICATION SYSTEMS

3 - INTRODUCTION TO APERTURE ANTENNAS & ARRAYS

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EFFECTIVE MEDIUM THEORIES BACKWARD IN TIME: FROM THE 21ST TO THE 19TH CENTURY
Non-Asymptotic and Nonlocal Approximations, Finite Samples, Interface Boundaries

Instructor:
Prof. Igor Tsukerman
Department of Electrical and Computer Engineering, The University of Akron, OH 44325-3904, USA,
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http://blogs.uakron.edu/tsukerman/
(joint work with Vadim Markel, Institut Fresnel (Marseille, France); on leave from University of Pennsylvania, Philadelphia, PA, USA)

Duration: 4 hours (morning or afternoon)

SUMMARY: Electromagnetic metamaterials are artificial periodic structures engineered to control the propagation of waves and to achieve physical effects not attainable in natural materials – high-frequency magnetism, negative refraction, strong absorption, lensing, cloaking, and more. Research in metamaterials started three decades ago, if not earlier, and exploded in the 2000s as a quest for “perfect lenses,” “perfect absorbers,” etc. But, as the field of metamaterials matured, it became clear that ideal devices were not realizable because of losses, finite lattice cell sizes, and other factors. Undoubtedly, however, “imperfect” materials and devices will continue to be developed, and we can therefore expect a growing need for more sophisticated methods of their analysis and, more specifically, for accurate homogenization theories valid for any composition and size of the lattice cell.
The objective of homogenization (effective medium theory) is to describe a composite structure in terms of effective parameters accurately representing reflection, transmission and propagation of waves on the scale coarser than the lattice cell size.
The course introduces a homogenization methodology valid in both electrostatics and electrodynamics and applicable to an arbitrary size and composition of the lattice cell. Nonlocal effects can be included in the model, making order-of-magnitude accuracy improvements possible.
We then travel backward in time and explore the connection between the new framework and the classical 19th – early 20th century theories of Clausius-Mossotti, Lorenz-Lorentz, Maxwell Garnett.
A particularly challenging problem for future research is to determine what effective material tensors are attainable for given constituents of a metamaterial with their given properties, and how the lattice cell could be designed to produce such tensors. For example, what is the maximum effective permeability achievable? Bounds for effective parameters are currently known only for relatively simple settings, such as static dielectric permittivity of mixtures with two ingredients. The methodology developed in this course may help to make progress toward solving a much broader set of problems of this kind.

CONTENT:
• 21st century: metamaterials and homogenization.
• From asymptotic to non-asymptotic homogenization.
• The uncertainty principle in the homogenization of metamaterials.
• From non-asymptotic to nonlocal homogenization.
• Back to the 19th century: connection of classical effective medium theories with the new ones.
• Open problems.
• Conclusion.

 


  

THE PHYSICS AND MATHEMATICS OF THE SIGNAL PROPAGATION MECHANISM IN CELLULAR WIRELESS COMMUNICATION SYSTEMS

Instructor: 
Prof. Tapan K. Sarkar
Department of Electrical Engineering and Computer Science, Syracuse University, Syracuse, New York 13244-1240, USA
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Duration: 4 hours (morning or afternoon)

SUMMARY: The objective of this short course is to introduce a new physics based visualization of the Electromagnetic wave propagation mechanism in cellular wireless communication systems. We also illustrate from a mathematical point of view that an electromagnetic macro model can accurately predict the dominant component of the propagation path loss in a cellular wireless communication. The reason a macro model can provide accurate results that agree with experiments is because the trees, buildings, and other man made obstacles contribute second order effects to the propagation path loss as the dominant component is the free space propagation of the signal and the effect of the Earth over which the signal is propagating. It is demonstrated using both measurements and an analytical theoretical model that the propagation path loss inside a cellular communication cell is first about 30 dB per decade of distance and later on, usually outside the cell, it is about 40 dB per decade of distance between the transmitter and the receiver irrespective of their heights from the ground. This implies that the electric field decays first at a rate of ρ─1.5 inside the cell and later on, usually outside the cell, as ρ─2, where ρ stands for the distance between the transmitter and the receiver. It will also be illustrated that the so called slow fading is due to the interference between the direct wave and the ground wave as introduced by Sommerfeld over a hundred years ago. All these statements can be derived from the approximate integration of the Sommerfeld integrals using a modified path for the steepest descent method and also using an accurate purely numerical methodology. An optical analog model will be presented based on the image theory developed by Van der Pol to illustrate the mechanism of radio wave propagation in a cellular wireless communication system where the path loss is 30 dB per decade or the field decays as ρ─1.5. This macro model is used to refine the experimental data collection system for the propagation path loss and it is also illustrated how the antenna tilt both mechanical and electrical can be incorporated in the macro model to predict the propagation path loss. Finally, an observation is made on how to further improve the propagation mechanism by observing the second channel from the mobile to the base station. Numerical data will reveal that the proposed methodology is a much better way to deploy base station antennas.

 


  

INTRODUCTION TO APERTURE ANTENNAS & ARRAYS

Instructor:
Prof. Trevor S. Bird FTSE, LFIEEE
Macquarie University, Antengenuity, PO Box 306, Eastwood NSW 2122, Australia

Duration: 5 hours (morning or afternoon)

SUMMARY: The topic of aperture antennas includes many antennas in common daily use. Typical examples include waveguides, horns, reflectors, lenses, slits, slots and microstrip antennas. In this Workshop the underlying theory of these antennas is described as well of their applications. The intention is to provide an introduction to some basic aperture antennas and their design. It will be assumed that attendees are familiar with the basics of Maxwell’s equations, fields and waves. Aperture antennas are normally associated with directional beams and, indeed, this is their role in many applications. Aperture antennas can also occur on non‐planar or curved surfaces such as on aircraft or groundbased vehicles. These antennas may consist of a single radiator or in arrays. In this form they are often used to provide directional or shaped beams. A limitation of a directional planar antenna is that when it is scanned from broadside the beam broadens and the pattern deteriorates. When the antenna is conformal to a convex surface, such as a cylinder or a cone, the beam can be scanned in discrete steps through an arc while maintaining a constant pattern. Of importance in the design of low sidelobe antenna arrays, both planar and conformal, is predicting the effect of mutual coupling
between the array elements. Maximum performance is achieved from arrays when the coupling between elements is fully taken into account.
The cost of the Workshop is Euro 100. The fee includes:
- a copy of the book entitled ‘Fundamentals of Aperture Antennas and Arrays’- Trevor Bird (the book will be used as notes for the Workshop)
- lunch (Sept. 15  at 12:30).


Topics to be covered include:
1. Introduction (1 hr)
    a. ‐ definition of aperture antenna
    b. ‐ equivalent sources
    c. ‐ fields radiated by an aperture
    d. ‐ basic antenna parameters
2. Waveguide and horn antennas (1 hr)
3. Reflector antennas (1 hr)
4. Arrays of aperture antennas (1 hr)
5. Other aperture antennas (1 hr):
    a. ‐ reflectarrays
    b. ‐ lenses
    c. ‐ Fabry‐Perot resonators