Ibrahim Elshafiey

A New Low SAR Antenna Structure for Wireless Handset Applications

This paper proposes a new mobile handset antenna structure to reduce the value of the speciflc absorption rate (SAR). The antenna is based on the PIFA structure and operates at dual-bands of 0.9GHz and 1.8GHz. The chassis current is reduced using a metallic shim-layer inserted between the patch and chassis. This shim-layer is connected to the handset chassis through posts whose number and positions are determined using optimization techniques. Sidewalls are attached to increase the gain of the antenna and reduce the radiation towards human head. Simulations in the cheek mode show that the SAR reduction factor (SRF) of the proposed structure averaged over 10-g is more than 75% at 0.9GHz and 46% at 1.8GHz. The SRF values obtained using simulations and measurements are found to be better than 51% and 76% at 0.9GHz and 1.8GHz, respectively.

Adaptive UWB-OFDM Synthetic Aperture Radar

This paper presents an empirical study of high resolution potentially jamming-resistant Synthetic Aperture Radar (SAR) system based on UWB-OFDM architecture. The Range-Doppler Algorithm (RDA) was used to construct a high resolution SAR image for simulation purpose. Suitable waveforms to achieve high resolution SAR imaging are proposed for both friendly and hostile environments. The proposed waveforms were tested for a point scatterer and for full 2-D SAR image construction. Simulation results demonstrate the benefits of using UWB-OFDM waveforms for SAR system, such as dynamic spectrum allocation, antijamming potential through pulse diversity-while having a potential to produce high resolution target images. The use of UWB-OFDM waveform for SAR system proves useful for high resolution image data collection for civilian purposes and provides significant anti-jamming capabilities for military purposes.

Multi user detection for SDMA OFDM communication systems

This paper investigates the implementation scenario of Space Division Multiple Access(SDMA) which is a notable application of Multiple Input Multiple Output(MIMO) system. SDMA is one of the most promising techniques aiming at solving the capacity problem of wireless communication systems and achieving higher spectral efficiency, depending on multiplexing signals based on their spatial signature. This paper presents of combining SDMA combined with the Orthogonal Frequency Division Multiplexing (OFDM). Various SDMA techniques are investigated including linear detection schemes, minimum mean square error, ordered successive cancellation, and maximum likelihood methods. Promising results are obtained to enhance spectral efficiency on the expense of computational complexity which needs to be addressed.

Genetic algorithm implementation of multi-user detection in SDMA-OFDM systems

Number of supported users in the orthogonal frequency division multiplexing (OFDM) systems can be increased considerably using powerful multi-user detector (MUD) combined with space division multiple access (SDMA) techniques. This paper presents the results of implementing MUD in SDMA-OFDM systems based on an advanced genetic-algorithm (GA) optimization tool. The hardware implementation is performed using Field Programmable Gate array (FPGA) devices which allow the real time performance of the proposed tool. Results show that the GA scheme enhances the performance and provides BER near to that attained using maximum likelihood (ML) detector at considerably lower computation complexity. Investigation of the GA population size is presented and FPGA implementation is described based on the shared memory approach.

Optimization of UWB antenna array for hyperthermia treatment of brain tumor

A study is presented to implement ultra wide-band (UWB) Vivaldi antenna array for hyperthermia treatment of brain tumors. A human head phantom is used to develop a hyperthermia treatment model. Design parameters are optimized to focus the energy inside the tumor location, by controlling the excitation of phased antenna array. Results are presented, showing the effect of the optimization process on the distribution of the specific absorption rate SAR inside the head phantom.

Optimization of UWB Vivaldi Antenna for Tumor Detection

An UWB Vivaldi Antenna structure is presented and analyzed for tumor detection of brain cancer. Various antenna configurations are considered in this analysis. The radiation is investigated inside a human head phantom with a tumor model. The antenna is designed with FR-4 substrate, and is tested when immersed in background of relative permittivity 40 to achieve good matching with the head tissue. Results show that good performance is obtained for the design size of 329.25×153×1.6 mm, and the antenna is found to operate in the range 100 Mhz to 1.4 GHz.

Image Fusion Based Enhancement of Nondestructive Evaluation Systems

Advantages and limitations associated with each nondestructive evaluation (NDE) modality raises a tradeoff in which no single modality can be identified for a particular application. Techniques are presented here that can be used to enhance inspection process based on multi-spectral, multi-temporal, and multi-resolution image fusion. The necessary elements for building an intelligent NDE system based on image fusion are introduced. An application is presented considering the fusion of optical and eddy current images. Developed image evaluation measures (quality metrics) are adopted to cross the gap between subjective and objective evaluation, which is essential to automate NDE systems in industrial environments.

GMR- AND GMI-BASED SYSTEMS FOR NONDESTRUCTIVE EVALUATION OF PRINTED CIRCUIT BOARD

Advances in magnetoresistive type sensors provide a new technique for nondestructive evaluation of metal structures. Giant magnetoresistive and giant magnetoimpedance sensors provide high sensitivity and reduced size with GMI sensors also adding capabilities of high frequency range of measurements. Being produced with thin film processing techniques, the manufacturing cost of these sensors is low. An example is considered of detecting defects in printed circuit boards. System details and experimental results are provided. Computational modeling validation is introduced based on finite element as well as method of moments analysis.

Efficient techniques to enhance nearfield imaging of human head for anomaly detection

This paper proposes efficient algorithms to enhance the nearfield electromagnetic imaging of human head. Forward problem is modeled using SAM head phantom with brain tumor anomalies, surrounded by a circular applicator antenna array. Scattered signals are compressively sensed (CS) at a limited number of sensing positions, and the sensed signals are preprocessed efficiently using a proposed novel technique to maximize information extraction. A dictionary is formed and then implemented in CS based inverse problem analysis. Reconstructed images are enhanced using new post-processing techniques to improve the spatial resolution. Image quality is analyzed using the quality metric in terms of peak signal-to-noise ratio (PSNR). The quality of the reconstructed images and the corresponding PSNR values reveals the validity of the imaging techniques.

Compressed sensing based nearfield electromagnetic imaging

This paper proposes a novel method of nearfield electromagnetic imaging using compressed sensing technique. Orthogonal matching pursuit (OMP) reconstruction algorithm is implemented for reconstruction of the target space. A dictionary is tested considering head imaging of single and multiple brain tumor targets. The received scattered time-domain signals are captured using spatial compressed sensing and later interpolated for full target space. These signals are also processed for temporal compressed sensing using background subtraction. Simulation of the forward problem it is conducted using CST Microwave Studio using frequency range of 300-3000 megahertz. The quality of reconstructed images reveals the potential of the proposed method.