Northern Canada AP/MTT Jt. Chapter


Student Seminar Series 2017 – Seminar #3

We are pleased to announce the first session in our student seminar series 2017. Two of our students will be presenting on  WednesdayMarch 29 from 12:00 pm – 1:00 pm in ICE 8-207. 

Speaker #1: David Sawyer – “Choke Ring Structures for Ground Penetrating Radar

Background: Ground penetrating radar (GPR) is a mature and successful technology that replaces expensive excavation and prospecting with simple scanning and imaging. Due to the high degree of loss in the ground at microwave frequencies, GPR systems are extremely susceptible stray reflections and interference (known as clutter), which can overwhelm signals of interest. For common GPR antennas such as dipoles, shielding, such as with a metallic cavity, is an attractive way to isolate the antenna from the above-ground environment. However, currents induced on the shield by the antenna can travel around the shield and re-radiate, acting as a source of clutter and offsetting these benefits. Choke rings are a well-known structure used for global positioning systems that reduce multi-path interference that work by suppressing currents along a plane. This work presents choke-ring structures as a way to suppress these currents for GPR and demonstrates that good bandwidth and time-domain performance may be achieved through the use of resistive, rather than perfectly metallic structures.

Biography: David Sawyer graduated from the University of Alberta with a B.Sc. in engineering physics in 2015, and as of 2017 is currently in the process of his M.Sc. in the area of microwave circuits. His current work is involved in the areas of metamaterial surfaces, small antennas, and ground penetrating radar, considering both frequency and time domain results. His work in this area has recently been accepted for publication at the AP-S Symposium on Antennas and Propagation. Some of David’s interests include fundamental limitations in electromagnetics, as well as numerical and mathematical methods in electromagnetics. David’s interests also extend to the arts. He currently helps run the University of Alberta Mixed Chorus as part of their executive, and is also a member of a local dance performance team.

Speaker #2: Mitchell Semple – “Optical Implementation of a Miniaturized ENNZ-Metamaterial-Lined Aperture Array


Abstract: Aperture arrays have been used as frequency selective surfaces and to demonstrate extraordinary transmission, and have been proposed for a multitude of applications. The operation of these devices requires large areas as they depend on either aperture size or array periodicity, respectively, on the order of a wavelength. It has recently been demonstrated that lining each circular aperture in an array with a thin epsilon-negative and near-zero (ENNZ) metamaterial dramatically lowers its resonance frequency while the aperture itself remains largely empty, obviating the need for both large apertures and large aperture spacing. Thus, aperture-array-based devices could be miniaturized in the microwave regime (E. Baladi, J. G. Pollock, and A. K. Iyer, Opt. Express, vol. 23, no. 16, 2015).
An optical implementation of the ENNZ-metamaterial-lined aperture array, simulated using COMSOL Multiphysics, will be presented. Challenges in achieving an optical implementation included the reliance of the microwave design on lumped circuit elements and near-ideal conductor properties, which cannot be reproduced directly at optical frequencies. The proposed optical aperture array was designed to improve transmission at optical-telecommunications wavelengths of λ = 1.55 μm (f = 193 THz) through apertures of size λ/5 and spacing λ/4. For a patterned gold surface with minimum feature size of 10 nm, an 8.7 dB transmission improvement over the unlined case was realized.

Biography: Mitchell graduated from the University of Alberta in 2016 with a B.Sc. in Electrical Engineering. He has previously worked on integrating molecular junctions into guitar distortion pedals as amplifier feedback elements and is currently an M.Sc. student working on plasmonic metamaterials.

Free pizza and refreshments will be served.

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