Showing papers in "Progress in Electromagnetics Research C in 2008"

Curvelet fusion of mr and ct images

Abstract: This paper presents a curvelet based approach for the fusion of magnetic resonance (MR) and computed tomography (CT) images. The objective of the fusion of an MR image and a CT image of the same organ is to obtain a single image containing as much information as possible about that organ for diagnosis. Some attempts have been proposed for the fusion of MR and CT images using the wavelet transform. Since medical images have several objects and curved shapes, it is expected that the curvelet transform would be better in their fusion. The simulation results show the superiority of the curvelet transform to the wavelet transform in the fusion of MR and CT images from both the visual quality and the peak signal to noise ratio (PSNR) points of view.

Improved adaptive bacteria foraging algorithm in optimization of antenna array for faster convergence

Abstract: This paper proposes an improved adaptive approach involving Bacterial Foraging Algorithm (BFA) to optimize both the amplitude and phase of the weights of a linear array of antennas for maximum array factor at any desired direction and nulls in specific directions. The Bacteria Foraging Algorithm is made adaptive using principle of adaptive delta modulation. To show the improvement in making the algorithm adaptive, results for both adaptive and nonadaptive algorithms are given. It is found that Adaptive Bacteria Foraging Algorithm (ABFA) is capable of improving the speed of convergence as well as the precision in the desired result.

Improvement in the analytical calculation of the magnetic field produced by permanent magnet rings

Abstract: In this paper, we present an improved Coulombianbased analytical calculation of magnetic fields created by permanentmagnetic rings. The 3 dimensional (3D) components of two types of magnetized rings (axially and radially) were analytically evaluated. The obtained components of the magnetic field are expressed over complete elliptical integrals of the first and second kind, as well as by Heuman’s Lambda function. These expressions permit fast and accurate calculations of the magnetic field at any point of interest, for both regular and singular cases. The presented method gives an improvement of already known expressions for calculating the magnetic fields of the aforementioned magnetized rings, and we consider that these improved analytical expressions are more extendable to numerical applications.

Linear Antenna Array Design with Use of Genetic, Memetic and Tabu Search Optimization Algorithms

Abstract: Antenna array design techniques are focused on two main classes: uniformly spaced antenna arrays and the non-uniform spacing case. These include techniques based on mathematical programming, such as constrained programming and non-linear programming. More recently, meta-heuristics approaches have been successful at designing antenna arrays (5). In this work, this paper presents efficient methods of genetic algorithm (GA), memetic algorithm (MA) and tabu search algorithm (TSA) for the synthesis of linear antenna design. We present three examples of antenna array design to compare the efficiency of the algorithms through simple design to complex design. The GA, TSA and MA has been used to optimize the spacings between the elements of the linear array to produce a radiation pattern with minimum SLL and null placement control.

Small Size Edge - Fed Sierpinski Carpet Microstrip Patch Antennas . Doc

Abstract: In this paper, we present a novel technique to reduce the size of edge-fed microstrip patch antenna. By etching the patch as the Sierpinski carpet, the resonant frequency can be lowered to lower values, and this property can be employed to reduce the size of the conventional patch antenna. The measurement results show, the patch achieved a maximum 33.9% size reduction by the edge-fed Sierpinski Carpet microstrip patch antenna (SCMPA) of the second iteration order, and other performances, such as return loss bandwidth and radiation patterns, were virtually unchanged.

Wireless Bio-Radar Sensor for Heartbeat and Respiration Detection

Abstract: In this study, a wireless bio-radar sensor was designed to detect a human heartbeat and respiration signals without direct skin contact. In order to design a wireless bio-radar sensor quantitatively, the signal-to-noise ratio (SNR) in the baseband output of a sensor should be calculated. Therefore, we analyzed the SNR of the wireless bio-radar sensor, considering the signal power attenuation in a human body and all kinds of noise sources. Especially, we measured a residual phase noise of a typical free-running oscillator and used its value for the SNR analysis. Based on these analysis and the measurement results, a compact, low-cost 2.4 GHz direct conversion bio-radar sensor was designed and implemented in a printed circuit board. The demonstrated sensor consists of two printed antennas, a

Designs on cpw-fed aperture antenna for ultra-wideband applications

Abstract: A novel co-planar waveguide (CPW) ultra-wideband (UWB) aperture antenna is presented. The antenna consists of a rectangular aperture on a printed circuit board ground plane and a mushroom-shaped exciting stub. The mushroom-shaped stub is simple and has less parameter, which is convenient to analyze and optimize. The antenna has a compact aperture size 22 × 13 mm 2 , fabricated on FR4 substrate with dielectric constant of 4.3, thickness of 1.5 mm. The antenna is successfully implemented and measured, which has 8.3 GHz match bandwidth (VSWR < 2), and stable radiation patterns.

Investigating the interaction between a human head and a smart handset for 4g mobile communication systems

Abstract: In this paper we evaluate the potential of a 5-element monopole array incorporated into a handheld device for beamforming in the 5.0-GHz band. The geometry of the handset consists of a 5-element array: four elements located at the handset corners and the fifth-element located at the center. Also, the interaction of the antenna array, mounted on a mobile handset, with a human head phantom is investigated. Firstly, the spatial peak specific absorption rate (SAR) values of 5-element array antennas for mobile handsets in the vicinity of a spherical phantom of a human head are evaluated numerically as a function of the distance between the handset and the head phantom for two different scenarios. Next, the effect of the human head on the handset radiation pattern is studied. The effect of different handset positions on the radiation pattern is also considered. The particle swarm optimization (PSO) algorithm is used to optimize the complex excitations of the adaptive arrays elements in a mutual coupling environment for beamforming synthesis. All numerical simulations are performed using the FEKO Suite 5.3

Homomorphic Enhancement of Infrared Images Using the Additive Wavelet Transform

Abstract: This paper presents a new enhancement technique for infrared images. This technique combines the benefits of homomorphic image processing and the additive wavelet transform. The idea behind this technique is based on decomposing the image into subbands in an additive fashion using the additive wavelet transform. This transform gives the image as an addition of subbands of the same resolution. The homomorphic processing is performed on each subband, separately. It is known that the homomorphic processing on images is performed in the log domain which transforms the image into illumination and reflectance components. Enhancement of the reflectance reinforces details in the image. So, applying this process in each subband enhances the details of the image in each subband. Finally, an inverse additive wavelet transform is performed on the homomorphic enhanced subbands to get an infrared image with better visual details.

Design of a novel monopole uwb antenna with a notched ground

Abstract: In this paper,a novel compact monopole ultra-wideband (UWB) antenna with a notched ground is presented. To increase the impedance bandwidth,a notched ground is introduced. The parameters and the characteristics of the antenna are given. It shows good characteristics for UWB,and it satisfies the VSWR requirement of less than 2.0 in the frequency band from 2.55 GHz to more than 13 GHz. The measured radiation patterns show good omnidirectional performance and antenna gains across the operation bandwidth.

Circular polarized dielectric resonator antennas using a single probe feed

Abstract: In this paper six novel Dielectric Resonator Antennas (DRAs) providing Circular Polarization (CP) using single probe feeds are proposed. By splitting the fundamental mode of conventional rectangular or cylindrical DRA into two near-degenerate orthogonal resonant modes, CP is obtained. The proposed antennas are numerically investigated using Finite Element Method (FEM). Parametric study on all antennas is carried out. The results show that the impedance bandwidth (S11 < −10 dB) of all reported antennas is in the range of 112–140 MHz. Also, the Axial Ratio bandwidth (AR < 3 dB) range of presented antennas is 28–33 MHz. The investigation shows radiation patterns of all proposed antennas are remaining broadside throughout the bandwidth. † Also with Electrical Engineering Department, Ferdowsi University of Mashhad, Mashhad, Iran. 82 Malekabadi, Neshati, and Rashed-Mohassel

Nonuniform transmission lines as compact uniform transmission lines

Abstract: In this paper, we propose a new way to compact the transmission lines, which has a general application to miniaturization of RF and microwave circuits. In this way, we use Nonuniform Transmission Lines (NTLs) instead of Uniform Transmission Lines (UTLs). To synthesize the desired Compact Length Transmission Lines (CLTLs), the characteristic impedance function of the NTLs is expanded in a truncated Fourier series. Then, the optimum values of the coefficients of the series are obtained through an optimization approach. The usefulness of the proposed structures is verified using some examples.

Broadband and high-gain e-shaped microstrip antennas for high-speed wireless networks

Abstract: New electromagnetically coupling fed low profile broadband high gain E-shaped microstrip antennas (MSA) were proposed for high speed wireless networks in IEEE 802.11 a and j standards. The proposed antenna uses an E-shaped microstrip patch covered by a radome and fed by an electromagnetically coupled strip. To validate this concept, a single antenna element and a sub-array were designed, built and measured. The measured results indicate that the element and the sub-array cover the band from 4.8 to 6.0 GHz (return loss < −10 dB) and produce a gain of 8 dBi and 11 dBi, respectively. The developed prototypes may find their applications in wireless communication networks as mobile or base antennas.

On Examining the Influence of a Thin Dielectric Strip Posed Across the Diameter of a Penetrable Radiating Cylinder

Abstract: A thin rectangular dielectric strip is located along the horizontal diameter of a penetrable rod, while the whole structure is illuminated by a plane wave at an arbitrary angle. The unknown field on the slab-sided scatterer is determined by dividing it into a large number of square pixels and thus the problem is solved via analytical integration. A quantity expressing the effect of the strip in the far region is defined and graphically represented with respect to the problem parameters. The attached diagrams are examined and discussed.

High resolution doa estimation in fully coherent environments

Abstract: A novel method for direction-of-arrival (DOA) estimation is proposed. This technique employs the excellent performance of Bartlett method in coherent environments as well as high resolution and low computational complexity of Beamspace MUSIC. Simulation results show that the use of Beamspace MUSIC with Bartlett yields significantly improved performance compared to the original MUSIC especially in highly correlated situations.

A novel broadband fractal sierpinski shaped, microstrip antenna

Abstract: As wireless communication applications require more and more bandwidth, the demand for wideband antennas increases as well. One of the most applicable frequency bands is X-band (8–12 GHz). X-band frequencies are used in satellite communications. Radar applications, terrestrial communications and networking, motion detection and etc. Fractal passive Microstrip antennas are simple and novel structures that attract much attraction recently. In this paper, new Microstrip sierpinski modified and fractalized antenna using multilayer structure for achieving wideband behavior in X-band which in 7–10.6 GHz portion overlaps UWB working range. Using fractal defection in patch, multi higher order modes are inspired for coupling a much wider bandwidth. Roggers TMM3 (er = 3.38) is used in this antenna as substrate. Working range for this antenna is from 7.7 GHz to 16.7 GHz (BW = 9 GHz). This antenna has simple structure, small size and 4 resonance frequencies. This fabricated and tested antenna is designed by Ansoft Designer software. 180 Pilevari Salmasi, Kashani, and Azarmanesh

A Novel Wideband Bandpass Filter Based on Complementary Split-Ring Resonator

Abstract: This paper presents a novel wideband bandpass filter making use of complementary split-ring resonator (CSRR) as the basic resonant unit. The resonant characteristic of CSRR is carefully studied through full wave analysis. The coupling of CSRR structure is very strong that can be used to realize wideband filter with small insertion loss. A filter with center frequency at 3.5 GHz, passband from 3.1 GHz to 3.8 GHz is designed and fabricated. The measured results are in good consistent with simulated results.

Analysis of a rectangular waveguide using finite element method

Abstract: The characteristics impedance of the fundamental mode in a rectangular waveguide is computed using finite element method. The method is validated by comparison with the theoretical results. In addition to this, we have considered the problem of determining the modes of propagation of electromagnetic waves in a rectangular waveguide for the simple homogeneous dielectric case. The starting point is Maxwell's equations with an assumed exponential dependence of the fields on the Z-coordinates. From these equations we have arrived at the Helmholtz equation for the homogeneous case. Finite- element-method has been used to derive approximate values of the possible propagation constant for each frequency. The finite element method (FEM) has been widely used during the last two decades in the analysis of waveguide components. With this method propagation characteristics of arbitrarily shaped waveguides of different composition are easily attainable. The finite element method is based on a spatial discretization (1). This approximation allows one to handle waveguide cross section geometries which are very similar to the real structures employed in practical devices. These complex structures do not lend themselves to analytical solutions. As a consequence, the FEM constitutes a promising tool to characterize such problems (2, 11). Modern phased array radars imply the requirements for polarization agility of wideband array elements. One possible choice for a radiating element with this property is the rectangular waveguide. In this paper a formulation is proposed to solve waveguides problems. A numerically efficient finite element formulation is presented that shows propagation modes and which may be used to analyze problems

Analysis of Nonlinear Oscillators with U Force by HE’SEnergy Balance Method

Abstract: In this letter, an application of energy balance method is applied to solve the nonlinear oscillators with un force. Comparison is made between the modification of harmonic balance method and energy balance method. The results reveal that the energy balance method is very effective and simple. Energy balance method is very effective and convenient and quite accurate to both linear and nonlinear physics and engineering problems.

Performance analysis of os structure of cfar detectors in fluctuating target environments

Abstract: This paper is intended to the analysis of adaptive radar detectors for partially correlated χ 2 targets. This important class of targets is represented by the so-called moderately fluctuating Rayleigh targets, which, when illuminated by a coherent pulse train, return a train of correlated pulses with a correlation coefficient in the range 0 < ρ< 1 (intermediate between SWII and SWI models). The detection of this type of fluctuating targets is practically of great importance. Since the CFAR detectors represent an attractive class of schemes that can be used to overcome the problem of clutter by adaptively setting their threshold based on local information of total noise power, they are commonly used to decide the presence or absence of the radar target of interest, which is of partially correlated χ 2 type. In addition, the OS based algorithms are chosen to carry out this task owing to their immunity to outlying targets which may be present amongst the contents of the reference window. Moreover, since the large processing time of the single-window OS detector limits its practical applications, our scope here is to analyze the performance of OS modified versions for moderately fluctuating Rayleigh targets in nonideal situations. This analysis includes the single-window as well as the double-window OS detection schemes for the case where the radar receiver postdetection integrates M square-law detected pulses and the signal fluctuation obeys χ 2 statistics with two degrees of freedom. These detectors include the mean-level (ML-), the maximum (MX-) and the minimum (MN-) OS algorithms. Exact formulas for their detection probabilities are derived, in the absence as well as in the presence of spurious targets. The primary and the secondary interfering targets are assumed to be of the moderately fluctuating Rayleigh targets. Swerling's well known cases I and II represent the cases where the signal is completely correlated and completely decorrelated, respectively, from pulse to

An Efficient Technique for Reducing Papr of OFDM System in the Presence of Nonlinear High Power Amplifier

Abstract: Peak to average power ratio (PAPR) is one of the serious problems in any wireless communication system using multicarrier modulation technique like OFDM, which reduces the efficiency of the transmit high power amplifier. In this paper, proposed scheme will be introduced that combines interleaving method with peak windowing method. With the proposed scheme, the simulation results show that, the PAPR is reduced by 3.5 dB. Moreover Eb/N0, is decreased more than 3 dB at bit error rate (BER)=10mnplus3 in the presence of nonlinear power amplifier.

Numerical Analysis of Combined Field Integral Equation Formulations for Electromagnetic Scattering by Dielectric and Composite Objects

Abstract: Numerical analysis of a generalized form of the recently developed electric and magnetic current combined field integral equation (JM-CFIE) for electromagnetic scattering by homogeneous dielectric and composite objects is presented. This new formulation contains a similar coupling parameter α as CFIE contains in the case of perfectly conducting objects. Two alternative JM-CFIE(α) formulations are introduced and their numerical properties (solution accuracy and convergence of iterative Krylov subspace methods) are investigated. The properties of these formulations are found to be very sensitive to the choice of α and to the permittivity of the object. By using normalized fields and currents the optimal value of α minimizing the number of iterations becomes only weakly dependent on the permittivity object. Using linear-linear basis functions instead of the more conventional constant-linear (RWG) basis functions the solution accuracy can be made less dependent on the choice of α.

Scattering properties of the strip with fractional boundary conditions and comparison with the impedance strip

Abstract: In this paper two-dimensional problem of plane-wave diffraction by a "fractional strip" is studied. "Fractional strip" is introduced as a strip with fractional boundary conditions (FBC) involving fractional derivatives of the field components. FBC describe intermediate boundary between perfect electric conductor (PEC) and perfect magnetic conductor (PMC). It is shown that "fractional strip" has scattering properties similar to the well-known impedance strip. For one important case of fractional order equal to 0.5 the solution of the wave diffraction problem by a "fractional strip" can be found analytically. Detailed comparison analysis of the physical characteristics of the scattered fields for both fractional and impedance strips is presented. The relation between the fractional order and the value of impedance is derived. It is shown that in a wide range of input parameters the physical characteristics of the "fractional strip" are similar to the strip with pure imaginary impedance. 1. FORMULATION OF THE PROBLEM Consider a two-dimensional problem of electromagnetic wave diffrac- tion by a strip located at the plane y = 0 and infinite along the axis z. The width of the strip is 2a. In this paper E-polarization case is discussed. An incident plane wave is described by the function � E i (x, y )= � i (x, y )= � −ik(xα0+y

Determination of the Frequency-Amplitude Relation for Nonlinear Oscillators with Fractional Potential Using HE's Energy Balance Method

Abstract: A He's Energy balance method (EBM) is used to calculate the periodic solutions of nonlinear oscillators with fractional potential. Some examples are given to illustrate the effectiveness and convenience of the method. We find this EBM works very well for the whole range of initial amplitudes, and the excellent agreement of the approximate frequencies and periodic solutions with the Exact or other analytical solutions has been demonstrated and discussed. Comparison of the result obtained using this method with that obtained by Exact or other analytical solutions reveal that the EBM is very effective and convenient and can therefore be found widely applicable in engineering and other science.

A Novel Compact and Wide-Band Uni-Planar EBG Structure

Abstract: A novel uni-planar electromagnetic Band Gap (EBG) structure incorporated with inter-digital capacitor and meandered line inductor (ML-ID-EBG) is presented, this novel structure significantly enlarges the fringe capacitance to reduce sized cells, as well as increases the equivalent inductance to widen the relative bandwidth. Its design is detailed in this paper, and several experimental results are presented, the improved properties of the proposed ML-ID-EBG are examined, as compared with a conventional UC-EBG and a novel EBG incorporated only with inter-digital capacitor (ID-EBG).

Microwave characterization of dielectric materials using bayesian neural networks

Abstract: This paper shows the efficiency of neural networks (NN), coupled with the finite element method (FEM), to evaluate the broad- band properties of dielectric materials. A characterization protocol is built to characterize dielectric materials and NN are used in order to provide the estimated permittivity. The FEM is used to create the data set required to train the NN. A method based on Bayesian regularization ensures a good generalization capability of the NN. It is shown that NN can determine the permittivity of materials with a high accuracy and that the Bayesian regularization greatly simplifies their implementation.

Analysis of cfar detection of fluctuating targets

Abstract: Our scope in this paper is to provide a complete analysis of CFARdetection of fluctuating targets when the radar receiver incoherently integrates M returned pulses from a chi-squared fluctuating targets with two and four degrees of freedom and operates in a multitarget environment. Since the Swerling models of fluctuating targets represent a large number of such type of radar targets, we restrict our attention here to this interesting class of fluctuation models. There are four categories of such representation; namely SWI, SWII, SWIII, and SWIV. SWI and SWIII represent scan- to-scan fluctuating targets, while SWII and SWIV represent fast pulse-to-pulse fluctuation. Exact expressions are derived for the probability of detection of all of these models. A simple and an effective procedure for calculating the detection performance of both fixed-threshold and adaptive-threshold algorithms is obtained. The backbone of this procedure is the ω-domain representation of the cumulative distribution function of the test statistic of the processor under consideration. In the CFARcase, the estimation of the noise power levels from the leading and the trailing reference windows is based on the OS technique. The performance of this detector is analyzed in the case where the operating environment is ideal and where it includes some of extraneous targets along with the target under test. The primary and the secondary outlying targets are assumed to be fluctuating in accordance with the four Swerling's models cited above. The numerical results show that, for large SNR, the processor detection performance is highest in the case of SWIV model while it attains its minimum level of detection in the case of SWI model. Moreover, SWII model has higher performance than the SWIII representation of fluctuating targets. For low SNR, on the other hand, the reverse of this behavior is occurred. This observation is common either for fixed-threshold or for adaptive-threshold algorithm.