De-embedding method for a sensing area characterization of planar microstrip sensors without evaluating error networks.

A de-embedding method for determining all scattering (S-) parameters (e.g., characterization) of a sensing area of planar microstrip sensors (two-port network or line) is proposed using measurements of S-parameters with no calibration.

Simple and inexpensive microwave setup for industrial based applications: Quantification of flower honey adulteration as a case study.

A simple and inexpensive microwave measurement setup based on measurements of magnitudes of transmission properties ( ) is proposed for industrial-based microwave aquametry (moisture or water content) applications. An easy-to-apply calibration procedure based on normalization is implemented to eliminate systematic errors in the measurement system. As a case study, we applied this setup for the quantification of water-adulteration in flower honey.

A Microwave Differential Dielectric Sensor Based on Mode Splitting of Coupled Resonators.

This study explores the viability of using the avoided mode crossing phenomenon in the microwave regime to design microwave differential sensors. While the design concept can be applied to any type of planar electrically small resonators, here, it is implemented on split-ring resonators (SRRs). We use two coupled synchronous SRRs loaded onto a two-port microstrip line system to demonstrate the avoided mode crossing by varying the distance between the split of the resonators to control the coupling strength.

Simulation and optimization of rectenna systems.

In this paper, we present an entirely simulation-based method to predict the performance of a complete rectenna system that includes all its components: the receiving antenna, the matching circuits between the antenna and the rectification circuit, and the load circuit. Whereas previous efforts to predict the performance of a rectenna system subdivided the system into the antenna part (radiation to AC power conversion) and the circuit part (AC power to DC power conversion), and made assumptions about the performance of the non-linear part of the rectenna based on a specified power level and frequency, in this method, the radiation part of the system is incorporated into the simulation by using Thevenin theorem. The method proposed in this work enables the rectenna designer to predict the performance of the complete rectenna system, at the design stage, for variation in the incident field's power density, angle of incidence, and operating frequency.

Microwave bone fracture diagnosis using deep neural network.

This paper studies the feasibility of a deep neural network (DNN) approach for bone fracture diagnosis based on the non-invasive propagation of radio frequency waves. In contrast to previous "semi-automated" techniques, where X-ray images were used as the network input, in this work, we use S-parameters profiles for DNN training to avoid labeling and data collection problems. Our designed network can simultaneously classify different complex fracture types (normal, transverse, oblique, and comminuted) and estimate the length of the cracks.

Mammography using low-frequency electromagnetic fields with deep learning.

In this paper, a novel technique for detecting female breast anomalous tissues is presented and validated through numerical simulations. The technique, to a high degree, resembles X-ray mammography; however, instead of using X-rays for obtaining images of the breast, low-frequency electromagnetic fields are leveraged. To capture breast impressions, a metasurface, which can be thought of as analogous to X-rays film, has been employed.

A Highly Sensitive 3D Resonator Sensor for Fluid Measurement.

Planar sub-wavelength resonators have been used for sensing applications, but different types of resonators have different advantages and disadvantages. The split ring resonator (SRR) has a smaller sensing region and is suitable for microfluidic applications, but the sensitivity can be limited. Meanwhile, the complementary electric-LC resonator (CELCR) has a larger sensing region and higher sensitivity, but the topology cannot be easily designed to reduce the sensing region.

Surface plasmon resonance biosensor based on graphene layer for the detection of waterborne bacteria.

As a result of the risks that waterborne bacteria bring to the human body, identifying them in drinking water has become a global concern. In this article, a highly sensitive surface plasmon resonance (SPR) biosensor consisting of prism, Ag, graphene, affinity layer and sensing medium is proposed for rapid detection of the waterborne bacteria. Four SPR-based sensors are first studied with the structures prism/Ag/sensing medium, prism/Ag/affinity layer/sensing medium, prism/Ag/graphene/sensing medium, and prism/Ag/graphene/affinity layer/sensing medium.

Cancer cell detector based on a slab waveguide of anisotropic, lossy, and dispersive left-handed material.

Cancer is a disease that takes place when human cells grow uncontrollably. When detected and cured early, it can be non-life-threatening. It becomes life-threatening in case of late discovery where it affects the ability of an organ to function.

Ternary optimization for designing metasurfaces.

A fully automated approach for designing metasurfaces whose unit cell may include metallic vias is proposed. Towards this aim, a ternary version of the particle swarm optimization (PSO) algorithm is employed in order to find the optimal metallic pattern and via-hole positions simultaneously. In the proposed design method, the upper surface of the unit cell is first pixelated.

Real-time multi-functional near-infrared wave manipulation with a 3-bit liquid crystal based coding metasurface.

We propose a new generation of reprogrammable multi-functional bias encoded metasurfaces for dynamic wave manipulation using liquid crystals (LC). This metadevice is an array of unit-cells based on LCs to provide the desired phase steps based on its large birefringence property. The presented 3-bit coding metasurface (CM) use 8 states of "000"-"111" to control and manipulate the scattered wave at λ=1.

A Pixelated Microwave Near-Field Sensor for Precise Characterization of Dielectric Materials.

A highly sensitive microwave near-field sensor based on electrically-small planar resonators is proposed for highly accurate characterization of dielectric materials. The proposed sensor was developed in a robust complete-cycle topology optimization procedure wherein first the sensing area was pixelated. By maximizing the sensitivity as our goal, a binary particle swarm optimization algorithm was applied to determine whether each pixel is metalized or not.

Unconditionally stable FDTD algorithm for 3-D electromagnetic simulation of nonlinear media.

For the first time, an unconditionally stable finite-difference time-domain (FDTD) method for 3-D simulation of dispersive nonlinear media is presented. By applying a new adopted alternating-direction implicit (ADI) time-splitting scheme and the auxiliary differential equation (ADE) technique, the time-step in the FDTD simulations can be increased much beyond the Courant-Friedrichs-Lewy (CFL) stability limit. Thus, in comparison to the classical nonlinear FDTD method, the computational time for the proposed approach is decreased significantly while maintaining a reasonable level of accuracy.

Pixelated Metasurface for Dual-Band and Multi-Polarization Electromagnetic Energy Harvesting.

A 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.

Near Field Breast Tumor Detection Using Ultra-Narrow Band Probe with Machine Learning Techniques.

In this work, we propose a near-field microwave sensing modality that uses a single probe combined with a classification algorithm to help in detecting the presence of tumors in the human female breast. The concept employs a near-field resonant probe with an ultra-narrow frequency response. The resonant probe is highly sensitive to the changes in the electromagnetic properties of the breast tissues such that the presence of the tumor is gauged by determining the changes in the magnitude and phase response of the sensor's reflection coefficient.

Harvesting the Energy of Multi-Polarized Electromagnetic Waves.

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.

Pixelated Checkerboard Metasurface for Ultra-Wideband Radar Cross Section Reduction.

In this paper we designed and fabricated a metasurface working as a radar cross section (RCS) reducer over an ultra wide band of frequency from 3.8 to 10.7 GHz.

Spherical aberration in electrically thin flat lenses.

We analyze the spherical aberration of a new generation of lenses made of flat electrically thin inhomogeneous media. For such lenses, spherical aberration is analyzed quantitatively and qualitatively, and comparison is made to the classical gradient index rod. Both flat thin and thick lenses are made of gradient index materials, but the physical mechanisms and design equations are different.

A Non-Invasive Phase Sensor for Permittivity and Moisture Estimation Based on Anomalous Dispersion.

The traditional microwave resonance sensors are based on the measurement of the frequency shift and bandwidth of a resonator's amplitude spectrum. Here we propose a novel sensing scheme in which the material properties are estimated by determining the changes in the phase spectrum of an anomalous-phase resonator. In the proposed phase sensing, we exploit the unique double phase reversal which takes place on the edges of the anomalous dispersion region as a signature to detect the resonance.

Portable Automated Oxygen Administration System for hypoxaemic patients.

Oxygen is a lifesaving medication that should be offered with an administration to a patient who suffers from oxygen deficiency to avoid toxic effects of excessive oxygen supplement as well as to minimize the exposure to hypoxaemia. This work aims to automate the process of administering oxygen delivery in order to extend the continuous oxygen administration process beyond the IC units, reduce the cost of oxygen administration in terms of well-trained health care providers and equipment, prolong the lifetime of oxygen supplement, and help in the process of weaning patient from oxygen. In this work, a prototype model for a Portable Automated Oxygen Delivery System that consists of two subsystems: an Oxygen Reader Subsystem and an Automated Adjustment Oxygen Delivery Subsystem, both communicating wirelessly, has been developed.

Refraction in electrically thin inhomogeneous media.

This work presents a new formulation for refraction from flat electrically thin lenses and reflectors comprised of inhomogeneous material. Inhomogeneous electrically thin flat lenses and reflectors cannot make use of the Snell law since this classical formulation works solely at interfaces of planar homogeneous media. The refraction of a perpendicularly incident plane wave at a planar interface is physically explained through the phase advance of the rays within the medium.

Reducing Sweeping Frequencies in Microwave NDT Employing Machine Learning Feature Selection.

Nondestructive Testing (NDT) assessment of materials' health condition is useful for classifying healthy from unhealthy structures or detecting flaws in metallic or dielectric structures. Performing structural health testing for coated/uncoated metallic or dielectric materials with the same testing equipment requires a testing method that can work on metallics and dielectrics such as microwave testing. Reducing complexity and expenses associated with current diagnostic practices of microwave NDT of structural health requires an effective and intelligent approach based on feature selection and classification techniques of machine learning.

A True Metasurface Antenna.

We present a true metasurface antenna based on electrically-small resonators. The resonators are placed on a flat surface and connected to one feed point using corporate feed. Unlike conventional array antennas where the distance between adjacent antennas is half wavelength to reduce mutual coupling between adjacent antennas, here the distance between the radiating elements is electrically very small to affect good impedance matching of each resonator to its feed.

Electrically thin flat lenses and reflectors.

We introduce electrically thin dielectric lenses and reflectors that focus a plane wave based on the principles of phase compensation and constructive wave interference. Phase compensation is achieved by arranging thin rectangular slabs having different dielectric permittivity according to a permittivity profile obtained through analytic design equations. All incident rays parallel to the optical axis converge to a focal point with equalized optical paths resulting in constructive interference.