Efthymios Kallos

Detection of glucose variability in saline solutions from transmission and reflection measurements using V-band waveguides

This paper presents experimental results that demonstrate the correlation of glucose concentration in water and saline solutions with transmitted electromagnetic (EM) energy in the frequency range of 50–75 GHz. The system is based on placing the aqueous solutions in acrylic holding tanks sandwiched between two open V-band waveguides. The measured samples have clinically relevant range of glucose concentrations, as low as 0.025 wt%. Our measurements show for the first time that it is possible to establish an approximately linear relationship between the signals transmitted through this simple waveguide-based system and the glucose content in the samples. Accurate full-wave EM simulations confirm this linear correlation. The results suggest the possibility of developing a miniaturized non-invasive glucose sensing device based on the transmission of radio waves in this frequency range.

Study of a small printed quasi-self-complementary ultra wideband antenna for on-body applications

In this paper, the performance parameters of a small printed quasi-self-complementary ultra wideband (UWB) antenna in close proximity to the human body is investigated. The return loss response, impedance, radiation pattern and gain are investigated. The antenna shows good on-body performance, and therefore it will be suitable for on-body applications in UWB wireless body area networks.

Glucose sensing in saline solutions using V-band waveguides

We present results from an experimental system employed to study the impact of glucose content on measured transmission data. The measurements have been performed at frequencies between 50 GHz and 75 GHz using V-Band waveguides, and the measured samples consisted of saline solutions with glucose concentrations down to 0.025 wt%. The performed transmission measurements show that it is possible to establish an approximately linear relationship between the transmission coefficient and the glucose content in the samples. This linear dependence is also verified via simulations. The results are of interest for developing a miniaturized mobile glucose sensing system.

A Glucose Sensing System Based on Transmission Measurements at Millimetre Waves using Micro strip Patch Antennas

We present a sensing system operating at millimetre (mm) waves in transmission mode that can measure glucose level changes based on the complex permittivity changes across the signal path. The permittivity of a sample can change significantly as the concentration of one of its substances varies: for example, blood permittivity depends on the blood glucose levels. The proposed sensing system uses two facing microstrip patch antennas operating at 60u2009GHz, which are placed across interrogated samples. The measured transmission coefficient depends on the permittivity change along the signal path, which can be correlated to the change in concentration of a substance. Along with theoretical estimations, we experimentally demonstrate the sensing performance of the system using controlled laboratory samples, such as water-based glucose-loaded liquid samples. We also present results of successful glucose spike detection in humans during an in-vivo Intravenous Glucose Tolerance Test (IVGTT). The system could eventually be developed into a non-invasive glucose monitor for continuous monitoring of glucose levels for people living with diabetes, as it can detect as small as 1.33u2009mmol/l (0.025u2009wt%) glucose concentrations in the controlled water-based samples satisfactorily, which is well below the typical human glucose levels of 4u2009mmol/l.

Balanced antipodal Vivaldi antenna array for microwave tomography

This paper presents simulation studies for an array comprised of twelve balanced antipodal Vivaldi antennas for microwave tomography in the presence of a simple numerical breast phantom. This type of antennas bas been proposed previously in UWB breast imaging, but their use is a microwave tomographic setup is studied for the first time. The coupling effect of array elements and the electric field patterns are investigated with and without the phantom in the frequency range of interest between 0.5 and 5 GHz.

Design and Experimental Validation of a Multiple-Frequency Microwave Tomography System Employing the DBIM-TwIST Algorithm

We present a first prototype of a wideband microwave tomography system with potential application to medical imaging. The system relies on a compact and robust printed monopole antenna which can operate in the 1.0–3.0 GHz range when fully immersed in commonly used coupling liquids, such as glycerine–water solutions. By simulating the proposed imaging setup in CST Microwave Studio, we study the signal transmission levels and array sensitivity for different target and coupling liquid media. We then present the experimental prototype design and data acquisition process, and show good agreement between experimentally measured data and results from the CST simulations. We assess imaging performance by applying our previously proposed two-dimensional (2-D) DBIM TwIST-algorithm to both simulated and experimental datasets, and demonstrate that the system can reconstruct simple cylindrical targets at multiple frequencies.

Balanced Antipodal Vivaldi Antenna for microwave tomography

Balanced Antipodal Vivaldi Antennas (BAVAs) have been recently proposed for ultra-wideband (UWB) microwave imaging in medical applications such as breast cancer detection. This paper presents a modified design that allows the use of wideband BAVAs in microwave tomography, where the frequency range of interest is significantly lower than the UWB range down to 1 GHz. The performance of the antenna is evaluated using full-wave electromagnetic simulations.

Finite-Difference Time-Domain Modeling of Electromagnetic Cloaks

A radially dependent dispersive finite-difference time-domain (FDTD) method is proposed to simulate electromagnetic cloaking devices. The Drude dispersion model is applied to model the electromagnetic characteristics of the cloaking medium. Both lossless and lossy cloaking materials are examined and their operating bandwidth investigated. It is demonstrated that the perfect “invisibility” of electromagnetic cloaks is only available for lossless metamaterials and within an extremely narrow frequency band. Spherical cloaks are simulated and investigated with a parallel dispersive FDTD technique. Finally, ground-plane cloaking devices are examined and analyzed with non-orthogonal and orthogonal FDTD methods.