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A wearable, continuous electromagnetic sensing system provides 96% glucose estimation accuracy when tested on healthy individuals., Painless, needle-free, and continuous glucose monitoring sensors are needed to enhance the life quality of diabetic patients. To that extent, we propose a first-of-its-kind, highly sensitive, noninvasive continuous glycemic monitoring wearable multisensor system. The proposed sensors are validated on serum, animal tissues, and animal models of diabetes and in a clinical setting. The noninvasive measurement results during human trials reported high correlation (>0.9) between the system’s physical parameters and blood glucose levels, without any time lag. The accurate real-time responses of the sensors are attributed to their unique vasculature anatomy–inspired tunable electromagnetic topologies. These wearable apparels wirelessly sense hypo- to hyperglycemic variations with high fidelity. These components are designed to simultaneously target multiple body locations, which opens the door for the development of a closed-loop artificial pancreas.

This letter proposes a new matching technique that is based on a network of dual line topology with different characteristic impedances. The purpose of this network is to match the Schottky diode’s input impedance in a rectifying circuit with the 50 $\Omega $ source impedance. The strength of the proposed technique is based on the fact that it enables a stable efficiency response for different input power levels. It also forces the rectifier to exhibit an almost flat efficiency curve over a wide range of load variations. The proposed circuit is built and measured, where an agreement is attained between simulations and measured results over the IEEE 802.11 b/g bands.

This paper presents a new radio frequency (RF) rectifying design that is based on a tapered matching network. The rectifier operates over the Wi-Fi 802.11 b/g bands. The tapered matching network aims at transforming the Schottky diode's impedance into the input impedance of the circuit by resorting to dual transmission lines. Each line is designed with a different characteristic impedance. The rectifier topology is then integrated into a multiport RF energy harvesting system that relies on RF combining. The multi-port rectifier system shows excellent harvesting capabilities with an increased output DC voltage.

This paper proposes a new radio frequency (RF) energy harvesting system that operates over the Wi-Fi 802.11 b/g band at low input power levels. The system presented herein achieves good power conversion efficiencies (PCEs) over a power range that extends from (−20 dBm) to (3 dBm). A directive slot antenna is incorporated to drive the rectification process of the designed rectenna. The rectenna system is measured and tested, along with a power management circuitry, for design validation purposes. A good agreement between simulated and measured results is attained.

The corrosion process of mild steel in the presence of benzoate-doped polyaniline coatings exposed to different environments (3% NaCl, atmosphere, and the Sahara sand) has been investigated. This system was also tested for cathodic protection and it has proven more efficient comparing to mild steel alone. Possible mechanisms of the corrosion protection of mild steel in the presence of a polyaniline-based coating in different corrosion media were also proposed. This is the peer-reviewed version of the article: Elkais, A.R., Gvozdenović, M.M., Jugović, B.Z., Grgur, B.N., 2013. The influence of thin benzoate-doped polyaniline coatings on corrosion protection of mild steel in different environments. Progress in Organic Coatings 76, 670–676. [https://doi.org/10.1016/j.porgcoat.2012.12.008]

In this paper, a new reliable radio frequency (RF) rectifier topology with an enhanced operating power range is proposed. The presented RF harvester possesses an efficient RF to DC conversion ratio over an enhanced power range. A typical RF rectifier is initially optimized, and then the RF input is equally split into two branches. Splitting the input RF power improved the reliability and breakdown performance of the rectifier. This has the effect of increasing the power rectification range by approximately a factor of three. The design presented herein aims at avoiding any efficiency degradation in scenarios, where the RF power fed into a typical harvesting circuit varies. The proposed rectifier circuit is fabricated and the measured results show good agreement with simulated data.

This paper proposes a new RF rectifier with a dynamically extendable RF-DC power conversion (> 50%) range. Compared to typical rectifiers, the adopted power combining topology extends the dynamic efficient range by ∼ 3 dB, while maintaining acceptable performance at low powers. A 1.84 GHz rectifier with the proposed topology is designed. A prototype of the designed rectifier is fabricated and tested. It is shown that the proposed rectifier maintains acceptable conversion efficiency over a power range extending from 2 dBm to 11 dBm. The performance of such rectifier is to be assessed using different antenna configurations dedicated to harvest RF and/or solar energy to power battery-less devices.

In this paper, a reconfigurable cognitive radio receiver for autonomous spectrum sensing is presented. A reconfigurable antenna, low-noise amplifier, reconfigurable bandpass filter, single-ended balanced mixer, voltage-controlled oscillator (VCO), and variable gain amplifier (VGA) build up the chain of the proposed receiver. This receiver targets the WLAN IEEE 802.11WLAN IEEE 802.11 g commercial wireless standard. The receiver performance is demonstrated with a 20-MHz down-converted signal at its output.

This paper presents a frequency reconflgurable cedar- shaped fractal antenna. The special shape of the patch makes it simpler to integrate RF switches to connect consecutive branches. The proper activation/deactivation of the switches alters the current ∞ow and changes the resonance frequency. Simulated and measured results show the characteristics of the presented design.

The electrochemical synthesis of polyaniline (PANI) on mild steel, aluminum and copper from the sodium benzoate solutions has been investigated. It has been shown that thin, highly adherent, polyaniline films on the investigated metals could be obtained by anodic oxidation with current densities in the range of 0.5 and 1.5 mA cm-2. The corrosion behavior of mild steel, aluminum and copper with polyaniline coating in 0.5 mol dm-3 NaCl (pH 3) solutions, has been investigated by polarization technique. The corrosion current densities, porosity and protection efficiency was determined. It has been shown that polyaniline coating provided corrosion protection of all mentioned metals. U radu je ispitivana elektrohemijska sinteza polianilina (PANI) na mekom čeliku, aluminijumu i bakru iz rastvora natrijum-benzoata i monomera anilina. Ustanovljeno je da se tanki, dobro adherentni, filmovi polianilina mogu formirati na svim ispitivanim metalima pri anodnim gustinama struja od 0,5-1,5 mA cm-2. Ispitivano je koroziono ponašanje metala sa prevlakom polianilina u rastvoru 0,5 mol dm-3 NaCl (3%). Ustanovljeno je da ove prevlake pružaju korozionu zaštitu svim ispitivanim metalima u datoj korozionoj sredini.

Comparative studies have been carried out on two axial flow fan rotors of controlled vortex design (CVD), at their design flowrate, in order to investigate the effects of circumferential forward skew on blade aerodynamics. The studies were based on computational fluid dynamics (CFD), validated on the basis of global performance and hot wire flow field measurements. The computations indicated that the forward-skewed blade tip modifies the rotor inlet condition along the entire span, due to its protrusion to the relative inlet flow field. This leads to the rearrangement of spanwise blade load distribution, increase of losses along the dominant part of span, and converts the prescribed spanwise blade circulation distribution towards a free vortex flow pattern. Due to the above, reduction in both total pressure rise and efficiency was established. By moderation of the radial outward flow on the suction side, being especially significant for non-free vortex blading, forward sweep was found to be particularly useful for potential reduction of near-tip loss in CVD rotors. Application of reliable CFD-based design systems was recommended for systematic consideration and control of both load- and loss-modifying effects due to non-radial blade stacking.

In this paper, a wide power range RF energy harvesting circuit is presented. The proposed idea is based on optimizing the performance of the contained Schottky diodes, while considering their built-in potential, breakdown voltage and variable impedance properties. The carried out analysis revealed a greater than 50% RF-to-DC conversion efficiency over a wide range of input power extending from −10 to 8.5 dBm. The proposed design is suitable for ambient RF energy harvesting applications, where the received RF signals undergo an abrupt variation of power level.

This paper presents an agile tight feeding technique for use in highly integrated front-end architectures of mobile radios. This reconfigurable technique adjusts the operation of mounted antennas without installing switching components on their radiating surfaces. The proposed feeding technique is designed to feed two radiating structures on demand. The reconfiguration is achieved by resorting to two PIN diodes that are integrated within the feeding network whose operation ranges between 4 GHz and 6 GHz. A prototype is fabricated as a proof of concept. A good agreement is found between the simulated and measured results.

This letter introduces a DGS slot with an interdigital shape. The resonant frequency of the slot can be easily controlled by changing the length of the metal fingers, without changing the area taken by the structure. Using this slot, two quasi-elliptic low-pass filters were designed, fabricated and tested. The filters have a cut-off frequency of about 3 GHz.

Frequency-tunable microstrip antennas, for cognitive radio applications, are proposed herein. The approach is based on tuning the operating frequency of a bandpass filter that is incorporated into a wideband antenna. The integration of an open loop resonator- (OLR-) based adjustable bandpass filter into a wideband antenna to transform it into a tunable filter-antenna is presented. The same technique is employed to design a cognitive radio pattern diversity tunable filter-antenna. A good agreement between the simulated and measured results for the fabricated prototypes is obtained. The radiation characteristics of each designed tunable filter-antenna are included herein.

In this paper, a simple method to estimate the relative permittivity er and the tangential loss tan(δ) of wearable textiles is presented. Quarter-wavelength stub-line band-stop filters, based on jeans and cordura textiles, are designed assuming reasonable initial values of er and tan(δ), fabricated and experimentally tested. The filter designs are then re-simulated, by tweaking the values ofer and tan(δ), until the computed results are matched to the already obtained measured ones. The parameters er and tan(δ) of the jeans textile are studied in the 800MHz band. Results indicate that the difference between their initial values and the obtained actual estimates is large in this band. The study is repeated for both jeans and cordura textiles in the 2.4 GHz band. In this band of interest, the deviation of the initial er and tan(δ) from their actual values is small. To verify the reliability of the obtained estimates, jeans- and cordura-based wearable antennas are designed for operation in the 2.4 GHz band. Prototypes of these antennas are fabricated. A good agreement between measured and simulated results is revealed, thus verifying the correctness of the proposed electrical characterization method.

In this paper, a novel printed-circuit-board (PCB) antenna that employs electronic tunability is presented. The antenna is based on a 10mm × 25mm × 1.6mm FR4-epoxy substrate, is microstrip-line fed and has a partial ground plane. The proposed antenna is designed and simulated using the Finite-Element Method (FEM) and the Method of Moments (MoM) for two different switching conditions. The impedance bandwidth, gain, efficiency and radiation patterns of the antenna are demonstrated. It is shown that the antenna is suitable for WiMAX, C-band and X-band operation.

Sensing the communication channel is an essential task in wireless communication systems. This is necessary for retrieving the sent information from the received signal. In stationary (time-invariant) channels, this task is accomplished once by transmitting a series of training symbols at the beginning of a transmission phase. In time-varying channels, so called pilot symbols are transmitted regularly. This decreases the effective channel capacity. The capacity loss is the ratio between pilot and information symbols sent in a certain time frame. It increases as the channel time variation becomes faster. In this paper, an adaptive technique is introduced, which is based on tracking the time variation of the channel in order to adapt the number and distribution of the pilot symbols aiming at maximizing the capacity.