Prof. Omar Ramahi
Electrical and Computer Engineering Department, University of Waterloo, Waterloo, ON N2L 3G1, Canada
'%3e%3cpath%20d='M22.1642%2019.0924C21.7317%2018.068%2021.1041%2017.1375%2020.3163%2016.3527C19.5309%2015.5656%2018.6006%2014.9381%2017.5766%2014.5048C17.5674%2014.5002%2017.5582%2014.4979%2017.5491%2014.4933C18.9774%2013.4616%2019.9059%2011.7811%2019.9059%209.88504C19.9059%206.74408%2017.3611%204.19922%2014.2201%204.19922C11.0792%204.19922%208.53429%206.74408%208.53429%209.88504C8.53429%2011.7811%209.46282%2013.4616%2010.8912%2014.4956C10.882%2014.5002%2010.8728%2014.5025%2010.8636%2014.5071C9.83652%2014.9404%208.91487%2015.5617%208.1239%2016.355C7.33685%2017.1404%206.70933%2018.0707%206.276%2019.0947C5.85031%2020.0972%205.62072%2021.172%205.59967%2022.2609C5.59905%2022.2853%205.60335%2022.3097%205.61229%2022.3325C5.62123%2022.3553%205.63465%2022.376%205.65174%2022.3935C5.66883%2022.4111%205.68926%2022.425%205.71182%2022.4345C5.73437%2022.444%205.7586%2022.4489%205.78308%2022.4489H7.15868C7.25956%2022.4489%207.3398%2022.3686%207.3421%2022.2701C7.38795%2020.5001%208.09868%2018.8425%209.35506%2017.5861C10.655%2016.2862%2012.3814%2015.5709%2014.2201%2015.5709C16.0588%2015.5709%2017.7852%2016.2862%2019.0852%2017.5861C20.3415%2018.8425%2021.0523%2020.5001%2021.0981%2022.2701C21.1004%2022.3709%2021.1807%2022.4489%2021.2815%2022.4489H22.6571C22.6816%2022.4489%2022.7058%2022.444%2022.7284%2022.4345C22.751%2022.425%2022.7714%2022.4111%2022.7885%2022.3935C22.8056%2022.376%2022.819%2022.3553%2022.8279%2022.3325C22.8369%2022.3097%2022.8412%2022.2853%2022.8406%2022.2609C22.8176%2021.165%2022.5907%2020.0989%2022.1642%2019.0924ZM14.2201%2013.8284C13.1678%2013.8284%2012.1773%2013.418%2011.4322%2012.6729C10.6871%2011.9278%2010.2767%2010.9374%2010.2767%209.88504C10.2767%208.83271%2010.6871%207.84227%2011.4322%207.09715C12.1773%206.35204%2013.1678%205.94165%2014.2201%205.94165C15.2724%205.94165%2016.2629%206.35204%2017.008%207.09715C17.7531%207.84227%2018.1635%208.83271%2018.1635%209.88504C18.1635%2010.9374%2017.7531%2011.9278%2017.008%2012.6729C16.2629%2013.418%2015.2724%2013.8284%2014.2201%2013.8284Z'%20fill='%238590A2'/%3e%3c/g%3e%3c/svg%3e)
Co-authors
Following
Followers
Research Focus & Metrics
Explore full metrics on Scilit
Academic Career Length
37Years (1990-Present)
(Calculated once Scilit publication data is synced: current year − year of first publication + 1)
Representative Publications
View All Publications13 April 2015 in Applied Physics Letters
Journal Article
TAThamer S. Almoneef
Thamer S. AlmoneefOmar RamahiWe present the design of a metamaterial medium for electromagnetic energy harvesting based on the full absorption concept. A metamaterial slab was designed comprising 13 × 13 electrically small cells, each loaded with an 82 Ω resistor which mimics the input impedance of a rectification circuitry. Unlike earlier designs of metamaterial absorbers, here the power absorption is mostly dissipated across a resistive load instead of the dielectric substrate. This implies that effective electromagnetic energy harvesting can be achieved. The power is channeled through a via connected to each cell. For a design optimized at 3 GHz, simulation and experimental results show power absorption efficiency of 97% and 93%, respectively.
Journal Article
MAMaged Aldhaeebi
Maged AldhaeebiKAKhawla Alzoubi
Khawla AlzoubiTAThamer Almoneef
Thamer AlmoneefSBSaeed M. Bamatraf
Saeed M. BamatrafHAHussein Attia
Hussein AttiaOmar RamahiConventional breast cancer detection techniques including X-ray mammography, magnetic resonance imaging, and ultrasound scanning suffer from shortcomings such as excessive cost, harmful radiation, and inconveniences to the patients. These challenges motivated researchers to investigate alternative methods including the use of microwaves. This article focuses on reviewing the background of microwave techniques for breast tumour detection. In particular, this study reviews the recent advancements in active microwave imaging, namely microwave tomography and radar-based techniques. The main objective of this paper is to provide researchers and physicians with an overview of the principles, techniques, and fundamental challenges associated with microwave imaging for breast cancer detection. Furthermore, this study aims to shed light on the fact that until today, there are very few commercially available and cost-effective microwave-based systems for breast cancer imaging or detection. This conclusion is not intended to imply the inefficacy of microwaves for breast cancer detection, but rather to encourage a healthy debate on why a commercially available system has yet to be made available despite almost 30 years of intensive research.
1 January 2019 in IEEE Transactions on Microwave Theory and Techniques
Journal Article
MSMaryam Saadat-Safa
Maryam Saadat-Safa
Vahid NayyeriMKMostafa Khanjarian
Mostafa Khanjarian
MSMohammad Soleimani
Mohammad Soleimani
Omar Ramahi5 September 2018 in Scientific Reports
Journal Article
BGBagher Ghaderi
Bagher Ghaderi
Vahid NayyeriMSMohammad Soleimani
Mohammad Soleimani
Omar RamahiA dual-band and polarization-independent electromagnetic energy harvester composed of an array of pixelated unit cells is proposed. The pixelated unit cell is basically a dual-band resonator loaded with two resistors which model the input impedance of a power combining circuit in a complete harvesting system. To design the unit cell, a topology optimization approach based on pixelization of the surface of the unit cell and application of a binary optimization algorithm is used. The optimization goal is set to maximize harvesting efficiency at 2.45 GHz and 6 GHz. In our design, full symmetry of the unit cell is considered to achieve insensitivity to the polarization of the incident wave. Once, the unit cell is designed, as a proof of the concept, a metasurface harvester composed of 9 × 9 pixelated cells is designed. The full-wave electromagnetic simulation results demonstrate that the proposed metasurface absorbs the incident electromagnetic wave energy with nearly unity efficiency at both frequencies of interest and irrespective the polarization of the incident field while simultaneously delivering the absorbed power to the loads. To validate the simulations, the metasurface harvester is fabricated and tested in an anechoic chamber. A strong agreement between the simulation results and measurements is observed.
7 November 2017 in Scientific Reports
Journal Article
We present the idea and design of a dual polarized metasurface for electromagnetic energy harvesting. A 4 × 4 super cell with alternating vias between adjacent cells was designed to allow for capturing the energy from various incident angles at an operating frequency of 2.4 GHz. The collected energy is then channeled to a feeding network that collects the AC power and feeds it to a rectification circuitry. The simulation results yielded a radiation to AC and an AC to DC conversion efficiencies of around 90% and 80%, respectively. As a proof of concept, an array consisting of 9 super cells was fabricated and measured. The experimental results show that the proposed energy harvester is capable of capturing up to 70% of the energy from a planewave having various polarizations and converting it to usable DC power.
8 March 2018 in IEEE Transactions on Microwave Theory and Techniques
Journal Article
We present a frequency-selective surface (FSS) that is specially designed and optimized for ambient RF energy harvesting. The unit cell geometry incorporates channeling features in order to combine the collected power from multiple unit cells, allowing for efficient operation under low-power conditions. To demonstrate its performance, we designed and fabricated a matched full-wave rectifier integrated with the absorber FSS. Radiated measurements for the complete rectenna system are included in this paper demonstrating strong agreement with the simulation results. The proposed periodic structure absorbs 97% of the available energy at its resistive load, thus making it an ideal candidate for energy harvesting and channeling applications. Overall Radiation-to-dc conversion efficiency of the fabricated prototype was measured to be 61% when the collected power at the rectifier was 15 dBm.
About Me
Omar M. Ramahi was born in Jerusalem, Palestine. He received his BS degrees in Mathematics and Electrical and Computer Engineering from Oregon State University, Corvallis, OR. He received his MS and PhD degrees in Electrical and Computer Engineering from the University of Illinois at Urbana–Champaign. From 1993 to 2000, he worked at Digital Equipment Corporation (presently, HP). In 2000, he joined the University of Maryland at College Park as an Assistant Professor and later as a tenured Associate Professor. Presently, he is a Professor at the Electrical and Computer Engineering Department. He is a coauthor of the book EMI/EMC Computational Modeling Handbook, 2nd Ed. Professor Ramahi has served as a consultant to several companies and cofounded Applied Electromagnetic Technology and Wave Intelligence Inc. He won the Excellent Paper Award in the 2004 International Symposium on Electromagnetic Compatibility, Sendai, Japan, and the 2010 University of Waterloo Award for Excellence in Graduate Supervision. In 2009, he was elected an IEEE Fellow, and in 2012, he was awarded the IEEE Electromagnetic Compatibility Society Technical Achievement Award. From 2007 to 2015, he served as an Associate Editor for the IEEE Transactions on Advanced Packaging. From 2010 to 2012, he served as an IEEE EMC Society Distinguished Lecturer. He has authored over 500 journal and conference papers. Professor Ramahi is the winner of the 2022 University of Waterloo Engineering Research Excellence Award.