Otman Aghzout

Apodization Optimization of FBG Strain Sensor for Quasi-Distributed Sensing Measurement Applications

A novel optimized apodization of Fiber Bragg Grating Sensor (FBGS) for quasi-distributed strain sensing applications is developed and introduced in this paper. The main objective of the proposed optimization is to obtain a reflectivity level higher than 90% and a side lobe level around −40 dB, which is suitable for use in quasi-distributed strain sensing application. For this purpose, different design parameters as apodization profile, grating length, and refractive index have been investigated to enhance and optimize the FBGS design. The performance of the proposed apodization has then been compared in terms of reflectivity, side lobe level (SLL), and full width at half maximum (FWHM) with apodization profiles proposed by other authors. The optimized sensor is integrated on quasi-distributed sensing system of 8 sensors demonstrating high reliability. Wide strain sensitivity range for each channel has also been achieved in the quasi-distributed system. Results prove the efficiency of the proposed optimization which can be further implemented for any quasi-distributed sensing application.

Design of compact multiband bandpass filter with suppression of second harmonic spurious by coupling gap reduction

In this paper, we describe a method to implement compact multiband bandpass filters with suppression of second harmonic frequency. This filter design approach is based on decreasing the coupling gap between adjacent resonators of a parallel-coupled-line bandpass filter in order to achieve both the desired multiband frequency response and the spurious suppression. We present the theoretical analysis of the proposed structure that consists of modeling the frequency dependence of the even- and odd-mode characteristic impedances as well as due to the different phase velocities of the parallel-coupled microstrip lines. As an example, a compact tri-band parallel-coupled-line bandpass filter with suppression of second harmonic frequency was implemented operating at 1.9/3.2/4.6 GHz to cover PCS1900, WiMAX, and C-band applications. A three-pole Chebyshev parallel-coupled microstrip bandpass filter was designed at a center frequency of 3.2 GHz and used as the basis to validate the gapping effect on the filter response which also achieves a narrower bandwidth for the second harmonic. Finally, the filter performance with minimized coupling gap is compared to a filter enhanced by the insertion of apertures in the ground plane. Generally speaking, good agreement was accomplished between simulated, calculated, and measured results.

Development of a calculator for Edge and Parallel Coupled Microstrip band pass filters

This paper presents an implemented calculator tool for the design of Edge/ Parallel Coupled Microstrip Band Pass Filters (PCMBPF) that makes use of the MATLAB software. This calculator allows estimating both the parameters required for the design of the PCMBPF and the electrical response which is obtained by means of the equivalent circuit of this type of filters. Based on the transmission line theory approach (TLTA), the calculator herein proposed is a good solution to simply obtain the design parameters of this type of filters given that all formulas required for the PCMBPF design are programmed using close-form mathematic expressions and the coupling matrix concept. In order to validate our calculator performance, we implemented the proposed filter in a commercial electromagnetic simulator CST MWs that considers a set of electromagnetic effects, and accurately determine the final filter design. Secondly, we compared these simulation outcomes with the measurement results, achieving a reasonable agreement.

A compact UWB sub-nanosecond pulse generator for microwave radar sensor with ringing miniaturization

This paper presents a compact ultra-wideband (UWB) microwave radar transmitter. The developed design presents low-power and low-cost ultra-short pulse with a minimum of the ringing in the output waveform. Ultra-short pulse has been generated by avalanche pulse generator and sharpened with a step recovery diode (SRD). In order to improve the simulation response and to increase the rise-time of the pulses, a new model of a step recovery diode (SRD) was used as a sharpener circuit. Making the discharge path as short as possible, a minimum of the ringing has been obtained in the output pulse, around 3,6% in overshoot. Compact pulse generator circuit structure is completely fabricated using low-cost microstrip technology characteristic. The measurement results present generator Gaussian wave form pulses over 6.4 V in amplitude and 440 fall time at 100 KHz. Good Agreements between the measured and calculated result are achieved.

Single notched-band UWB antenna for WLAN environment using complementary split ring resonators CSRR and spiral resonator CSR

Ultra-wide band (UWB) technology has become more popular due to various applications such as ground penetrating radar, medical imaging and sensor networks. The antenna is one of the key components of UWB systems and has drawn much attention in recent years. In this paper we propose the design of UWB monopole antenna, providing single notched-band for WLAN (5–6) GHz to avoid interference signals, using complementary split ring resonators CSRR and spiral resonator CSR. It consists of a microstrip patch with modified radiating element and ground plane, while the desired notch-band characteristic is achieved by etching separately CSRR and SCR in the radiating patch, in Fig.1. Investigations on the parameters of the CSRR were performed to obtain the same performance of CSR in high frequency keeping away it second resonance. Fig.2 shows simulated and measured return loss of proposed single notched-band UWB monopole antennas, compared to the antenna without filtering property. It can be seen that the monopole antenna covers the whole UWB band (3–11 GHz) with a good rejection of WLAN band for notched-band antennas. Also a good response is observed in high frequency of UWB band. for the antennas gain, it varies between 3dBi and 5 dBi. From it performances, The proposed antennas are a good candidate for UWB applications where notch-band for WLAN is required. All results indicate that the investigated CSSR works effectively to introduce a single notch-band characteristic for the UWB antenna, like CSR performances.

Ultra wideband and tri-band antennas for satellite applications at C-, X-, and Ku bands

In this paper, a low-cost compact microstrip ultra wideband antenna for satellite and radar communication systems with filtering properties resulting multiband characteristics is presented. The ultra wideband antenna consists of a modified rectangular radiating element with deformed ground plane which provides a wide bandwidth from 5 to 16 GHz. The U-shaped slots are introduced in the radiating patch to obtain the tri-band frequency response covering C, X and Ku bands separately. The frequency bands achieving are 4.9-7 GHz, 7.92-11.08 GHz and 11.85-15.94 GHz. The proposed antennas are successfully simulated and performed using CST MWs and experimental validation are presented to demonstrate the performance of these antennas.

Narrowband Characterization of Near-Ground Radio Channel for Wireless Sensors Networks at 5G-IoT Bands

In this contribution, a narrowband radio channel model is proposed for rural scenarios in which the radio link operates under near-ground conditions for application in wireless sensor networks dedicated to smart agriculture. The received power attenuation was measured for both transmitter and receiver antennas placed at two different heights above ground: 0.2 and 0.4 m. Three frequency ranges, proposed for future 5G-IoT use case in agriculture, were chosen: 868 MHz, 2.4 GHz and 5.8 GHz. Three ground coverings were tested in a rural scenario: soil, short and tall grass fields. The path loss was then estimated as dependent of the radio link range and a three-slope log-normal path loss model was tailored. Results are explained in terms of the first Fresnel zone obstruction. Commercial Zigbee sensor nodes operating at 2.4 GHz were used in a second experiment to estimate the link quality from the experimental Radio Signal Strength Indicator (RSSI) received values. Two sensor nodes were placed at the same elevation above ground as in the previous experiment, only for short grass field case. The Quality of Service performance was determined in terms of theoretical bit error rate achieved for different digital modulations—BPSK, 8PSK and 16QAM—concluding remarkable results for an obstructed radio link.

Graphical User Interface Calculator for FBGS Performance Optimization Based on New Window Formulas

In this research paper, we develop on one hand a novel theoretical approach to optimize the performance of Fiber Bragg Grating Sensor (FBGS) based on an automated MATLAB-based program, and on the other hand, we propose a new graphical user interface including all design parameters of the FBGS to optimize automatically its window profile based on the sensing system requirement. The main objective of this approach is to obtain the higher reflected power from the FBGS as long as side lobes are kept below the required level. All formulas of the proposed method of optimization are programmed using the Coupled Matrix Theory (CMT) and the Transfer Matrix Method (TMM), which describe the light behavior within the FBGS. The proposed easy-to-use graphical interface allows also researchers to determine easily all parameters required for high FBGS performance providing a high precision and accuracy of numerical results. The proposed theoretical approach has been compared with the window profiles proposed by other authors. All results demonstrate the efficiency of the proposed method.

Experimental frequency dispersion study of the vehicular-to-vehicular propagation channel

In this work, we perform an experimental study of the received envelope autocorrelation and the power spectrum density (PSD) of the vehicular-to-vehicular (V2V) propagation channel. The coherence time and Doppler spread have been derived from narrowband channel measurements at 5.9 GHz. The measurements have been collected in urban and highway environments under real road traffic conditions. The relationship of the coherence time and Doppler spread between the effective speed of the Tx and Rx is investigated. The values of the coherence time and Doppler spread reported here can be useful for protocols evaluation and future vehicular networks design.

Chromatic Dispersion Compensation Effect Performance Enhancements Using FBG and EDFA-Wavelength Division Multiplexing Optical Transmission System

An optical transmission system using Fiber Bragg Grating (FBG) and Erbium Doped Fiber Amplifier (EDFA) with new proposed model has been analyzed to overcome chromatic dispersion and attenuation phenomena. To evaluate the transmission system performance of the received signals, a simple model of one channel transmission has been developed in the first step. Also, optical fiber length and attenuation coefficient parameters have been investigated in detail to deal with the optimized corresponding parameter values. Results show that the performance of the optimized design parameters is very efficient in terms of output power (dBm), noise figure (dB), gain (dB), and -Factor. The model of one channel developed previously has been adapted to a complex model of four optical channels multiplexing with different wavelengths. FBG and EDFA have been also added to WDM technology system to enhance the chromatic dispersion and the signal attenuation. Results show that the new model is more efficient in terms of -Factor and eye diagrams.