Mohamed Dhieb

Correction applied to the propagation model of UWB wave in human biological tissue obtained by FDTD method for estimation of the wave form at the heart

This work studies the spread of a UWB pulse in biological tissue, which forms the propagation media to the electromagnetic waves to detect a heartbeat. This tissue is multiple Modeled as semi-infinite lossy and dispersive media. The study focused on the deformations at the interfaces between two successive layers. The FDTD method is an approach for solving Maxwells equations. However, we note at the interfaces, the distortion signal. This is observed in the attenuation of energy signal. In this article we try to understand the origins of these disturbances, to find a solution for these perturbations, and, to estimate the waveform by adding an adaptive mesh at the interfaces.

Wireless power transmission technologies and applications

In this paper, a review is given of present state of the art about the concept of wireless power transmission i.e., transmitting power as microwaves from one place to another in order to reduce losses during the transmission and distribution of electrical power or also to deliver energy in location where conventional wires are expensive, inconvenient or impossible. This concept is known as Microwave Power Transmission (MPT). We presented the technological of Wireless Power Transmission (WPT) and also its applications.

Mathematical approximation of the hyperbolic tangent

This paper presents an assimilation of the transfer function of a differential pair of MOS transistors to a hyperbolic tangent function. Also it prove, that the characteristic of transfer function of a MOS differential pair is symmetrical and that is close to the one of the bipolar transistors differential pair (It represent the transfer function of this differential pair; it describe the output signal in the form of a hyperbolic tangent of the input signal) with minor differences in our application. For this comparison, we use a MOS model transistor (0.35µm) resulting from the library of the AMS foundry and on other hand we use a perfect nonlinear model of the bipolar transistor resulting from the Agilent-ADS library.

3.1–10.6 GHz high linearity, excellent gain flatness CMOS power amplifier for UWB applications using stagger tuning technique

In this paper, an Ultra-Wide-Band (UWB) RF power amplifier (PA) which provides some great features such as high and flat gain, low power, small group delay variation and a greater stability across the entire spectrum from 3.1GHz to 10.6 GHz is proposed. The UWB PA that it is implemented in 0.18μm CMOS technology employs stagger tuning technique which incorporates two stage amplifier connected in cascode configuration to establish a wider bandwidth. Low power consumption is decreased by employing the current-reuse topology and high linearity is achieved by using the self-biased circuit. The simulation results show that the proposed UWB PA has an excellent gain flatness of 18±0.2 dB and flat and low noise figure (NF) of 2.63±0.29 over the frequency band of interest. The PA design realizes a good phase linearity property (group-delay-variation) of ±25 ps over the whole band, so it is unconditionally stable. An input return loss (S11) inferior to -10dB, output return loss (S22) smaller than -8.4dB and an excellent reverse isolation S12 less than -30 dB. The input third-order intermodulation point (IIP3) is 2.25 dBm at 7 GHz to ensure more linearity.

Maximization of the power “UWB” signal by random method while respecting official constraints

In this paper, we try to maximize the power of ultra-wideband signal “UWB” sent to the target without breaching the restriction limits of the Federal Communications Commission “FCC”. The signal is a series of monocycle Gaussian pulses, characterized by the frequency center “FC”, Pulse Repetition Interval “PRI”. And the amplitude “A”. Maximizing the signal power under the FCC constraints: get a PSD (Power Spectral Density) as close to the barrier −41.3 dB as possible in the frequency domain. The method of random variables can be used to determine the optimal characteristics of the signal. We will also impose 0,025 as a maximum ratio between the center frequency and the PRI to avoid overlap between pulses. This signal is used to be sent to the human body in order to detect heart beats. To see the waveform near the heart : Firstly, we modeled the human body as the consisting of four semi-infinite layers. These layers are characterized by their dielectric relative constant, thickness and electrical conductivity. Then, we use the Finite Difference Time Domain (FDTD) to model the UWB propagation channel. This method was an efficient tool to predict the distribution of electromagnetic field along the propagation channel.

Design of a high performance rectenna for wireless powering 2.45Ghz RFIDs

This paper describes the design and the optimization of a rectenna in ISM band, dedicated to wirelessly supplying RFIDs sensors, to replace or recharge existing batteries. The circuit is based on a double voltage rectifier designed and optimized at 2.45GHz with ADS software. We detail a new methodology to design and optimize a rectenna circuit. As a result, excellent performance is achieved in terms of both output voltage level and RF to DC conversion efficiency. The described rectenna reaches approximately a conversion efficiency of 90% and produces 6Volt at 8 dBm enabling hence some RFID chips.

UWB pulse propagation in human tissue: Comparison between Gaussian and square waves shape

The detection and the viewing by the radar waves in the opaque medium are going to establish in the coming years a strategic stake in the area of biomedical application. This work studies the performance of Ultra-Wide Band (UWB) signals. These signals have to be sent towards the human body to detect the heart beatings. In previous works, the estimation of UWB pulse attenuation in the human tissue was made by FDTD method or the Friis formula. This paper presents a comparison study between two waves shape; the first one is a Gaussian pulse wave and the second one is a square. These signals have the same central frequency. The comparison of performance of signal is done at the antenna level and the propagation medium. An impedance of 50 Ω characterizes the transmitter antenna. The propagation medium is modeled by four superimposing layers characterized by semi-infinite thickness, dielectric constant and conductivity. ULB wave propagation in such a medium is modeled by the “Finites Differences Time Domain method (FDTD)”. This method is a discretization in time and space of Maxwells equations in order to find a space-time evolution of the electromagnetic field.