Current glucose monitoring methods for the ever-increasing number of diabetic people around the world are invasive, painful, time-consuming, and a constant burden for the household budget. The non-invasive glucose monitoring technology overcomes these limitations, for which this topic is significantly being researched and represents an exciting and highly sought after market for many companies. This review aims to offer an up-to-date report on the leading technologies for non-invasive (NI) and minimally-invasive (MI) glucose monitoring sensors, devices currently available in the market, regulatory framework for accuracy assessment, new approaches currently under study by representative groups and developers, and algorithm types for signal enhancement and value prediction. The review also discusses the future trend of glucose detection by analyzing the usage of the different bands in the electromagnetic spectrum. The review concludes that the adoption and use of new technologies for glucose detection is unavoidable and closer to become a reality.

A wideband microwave system for head imaging is presented. The system includes an array of 16 corrugated tapered slot antennas that are installed on an adjustable platform. A switching device is used to enable the antennas to sequentially send a wideband 1-4 GHz microwave signal and capture the backscattered signals. Those signals are recorded using suitably designed virtual instrument software architecture. To test the capability of the system to detect brain injuries, a low-cost mixture of materials that emulate the frequency-dispersive electrical properties of the major brain tissues across the frequency band 1-4 GHz are used to construct a realistic-shape head phantom. A target that emulates a realistic hemorrhage stroke is fabricated and inserted in two different locations inside the fabricated head phantom. A preprocessing algorithm that utilizes the symmetry of the two halves of human head is used to extract the target response from the background reflections. A post-processing confocal algorithm is used to get an image of the phantom and to accurately detect the presence and location of the stroke.

This paper presents a simple design method for a class of compact couplers, which offer coupling in the range of 3-10 dB over an ultra-wide frequency band from 3.1 to 10.6 GHz. The proposed couplers are formed by two elliptically shaped microstrip lines, which are broadside coupled through an elliptically shaped slot. Their design is demonstrated for a 3-, 6-, and 10-dB coupling assuming a 0.508-mm-thick Rogers RO4003C substrate. Results of simulation and measurements show that the designed devices exhibit a coupling of 3plusmn1 dB, 6plusmn1.4 dB and 10plusmn1.5 dB across the 3.1-10.6-GHz band. This ultra-wideband coupling is accompanied by isolation and return loss in the order of 20 dB or better. The manufactured devices including microstrip ports occupy an area of 25 mm times 15 mm

A portable microwave system to detect traumatic brain injuries is described. The wideband system utilizes a unidirectional antenna, microwave transceiver, and processing and image reconstruction algorithms. The utilized antenna is designed to have a compact three-dimensional (3-D) structure using a slotted dipole element and a folded parasitic structure. It attains directional radiation patterns with an average 9-dB front-to-back ratio and 102.2% fractional bandwidth covering the band 1.1–3.4 $~$ GHz, which is suitable for head imaging. To test the system, a realistic head phantom, which attains accurate internal and external anatomical structure and electrical properties, is fabricated by a 3-D printer using a detailed numerical model. Targets imitating the properties of bleeding are inserted at different positions in the fabricated head phantom to emulate brain injury scenarios. The integrated system is used in a virtual arrayed monostatic radar approach to detect the injuries. Using data sets recorded at 32 antenna positions around the head, a back projection algorithm is used to generate images of the scanned head. The achieved results demonstrate the feasibility of such a system as a portable module for brain injuries detection.

An efficient approach is described for designing ultrawideband (UWB) antennas in the form of planar monopoles of elliptical and circular shape. To avoid the time consuming trial-and-error approach presented in other works, simple design formulas for this type of radiators are described and their validity is tested via electromagnetic analysis and measurements. Full electromagnetic wave investigations are performed assuming three types of substrates with wide range of dielectric constant and thickness. The presented results show that the proposed method can be applied directly to design planar antennas that cover the ultrawide frequency band from 3.1 GHz to more than 10.6 GHz. Four types of monopole antennas were manufactured using RT6010LM substrate and their operation was tested in terms of return loss, radiation pattern characteristics, gain, and time domain response. The developed antennas feature UWB behavior with near omnidirectional characteristics and good radiation efficiency. The time domain transmission tests between two identical elements show that the manufactured circular monopoles offer better performance in terms of distortionless pulse transmission than their elliptically shaped counter parts. These antennas are also assessed in terms of fidelity factor. The manufactured antennas show a high fidelity factor which is more than 90% for the face-to-face orientation.

Given the increased interest in a fast, portable, and on-spot medical diagnostic tool that enables early diagnosis for patients with brain stroke, a new approach of wearable electromagnetic (EM) head imaging system based on polymer material is proposed. A flexible low profile, wideband, and unidirectional antenna array with electromagnetic band gap (EBG) and metamaterial unit cells reflector is utilized. The designed antenna consists of a 4×4 radiating patch loaded with symmetrical extended open-ended U-slots and fed by combination of series and corporate transmission lines. A mushroom-like 10-EBG unit cell arrays are arranged around the feeding network to reduce surface waves, whereas 4×4 metamaterial (MTM) unit cells are placed on the back-side of the antenna to enable unidirectional radiation. The antenna is designed and embedded on a multi-layer low cost, low loss, transparent and robust polymer poly-di-methyl-siloxane (PDMS) substrate and optimized to operate in contact with the human head. The simulated and measured results show that the antenna has a fractional bandwidth of 53.8% (1.16 GHz - 1.94 GHz), more than 80% of radiation efficiency, and satisfactory field penetration in the head tissues with a safe specific absorption rate (SAR). An eight-element array is then configured on 300 × 360 × 4.1 mm3 PDMS material covering an average human head size and used as a worn part of the imaging system. A realistic-shaped 3D SAM head phantom is used to verify the performance of the designed array. The imaging results indicate the possibility of using the designed conformal array to detect a bleeding inside the brain using a confocal image algorithm.