For a cellular mobile communication system in narrow streets of urban areas, blind spots caused by shadowing of high buildings are a significant problem. In this research, a new dual-antenna system (DAS) is proposed, including a power transmission network, a receiving and a reradiating antenna to realize a broad-angle beam control. An equivalent bi-static radar cross section (BRCS) is deduced to present a theoretical explanation to the operating principles of the DAS. The main advantage of this design over ordinary reflectarray antenna as a passive RF booster is its flexible beam control capabilities. The simulated BRCS of the proposed DAS, composed of a microstrip patch array and a planar Yagi-Uda antenna, is given along with that of a metal plate of identical dimensions for comparison. purposes.

The corrected dispersion relation governing the linear interaction of a TE mode in a circular cylindrical wave guide with an annular beam of gyrating electrons in a gyro-TWT configuration is derived. The derivation of the correct dispersion relation no longer involves any integration with respect to the radial coordinate r_o. of the electron guiding center as the relevant equilibrium distribution function turns out to be independent of r_o. When the cyclotron resonance condition is satisfied by the TE mode for a positive s-number, the small-signal theory is shown to predict an initial exponential growth of the mode with interaction length over a small but finite band of frequencies around the design frequency.

In this paper spatial-band pass filters consisting of frequency selective surfaces (FSSs) are designed in order to realize both the desired transfer function of the filter in the frequency domain and drastic size reduction. Each FSS is made of aperture elements and patch elements. In this design method, the shape of each FSS is designed by a genetic algorithm (GA) so that the resonant curve of each FSS fits to the resonant curve which can be obtained from an equivalent circuit approach. By locating these designed FSSs at the intervals of quarter wavelength a spatial band pass filter is realized. Furthermore, a technique which controls the frequency response of each FSS has been applied to reduce the longitudinal size of filter. By this technique the FSSs are located at the intervals which are much shorter than a quarter wavelength, keeping the desired transfer function. Through a designed example it is shown that the half longitudinal length of a typical spatial filter can be obtained without any additional structure. Magnetic type spectral domain dyadic Green's functions are derived, and the characteristics of a spatial band-pass filter are calculated by means of the coupled magnetic filed integral equation which accurately takes higher order mode interactions. Derived linear matrix equations are solved using method of moment (MoM). The effectiveness of the proposed structure and its performance are verified and validated by designing and simulating an equal ripple spatial band pass filter at X-band.

In this paper we analyze the electromagnetic response of a metamaterial slab in the case of normal incidence using the point-dipole interaction model and an expansion of polarization by eigenmodes. The problem is simplified by assuming that the lattice dimensions are smaller than a half wavelength and invoking the nearest neighbor approximation. In this manner, we find the structure supports three modes: an ordinary mode and two extraordinary modes. In the long-wavelength limit, the ordinary mode propagates with the same wave number as that predicted using the classic Clausius-Mossotti relations, while, for most cases, the two extraordinary modes are confined to thin surface transition layers near the boundaries of the slab. A systematic method is presented to find the scattering from the slab, and the results are confirmed by full wave simulation using Ansoft HFSS.

In recent years, Wireless Sensor Networks (WSNs) have transitioned from being objects of academic research interest to a technology that is frequently being employed in real-life applications and rapidly being commercialized. The performance of a WSN is largely affected by high quality deployment and precise localization of sensor nodes. This article deliberates autonomous deployment of sensor nodes from an Unmanned Aerial Vehicle (UAV). This kind of deployment has importance in emergency applications, such as disaster monitoring and battlefield surveillance. The goal is to deploy the nodes only in the terrains of interest, which are distinguished by segmentation of the images captured by a camera on board the UAV. In this article we propose an improved variant of a very powerful real parameter optimizer, called Differential Evolution (DE) for image segmentation and for distributed localization of the deployed nodes. Image segmentation for autonomous deployment and distributed localization are designed as multidimensional optimization problems and are solved by the proposed algorithm. Performance of the proposed algorithm is compared with other prominent adaptive DE-variants like SaDE and JADE as well as a powerful variant of the Particle Swarm optimization (PSO) algorithm, called CLPSO. Simulation results indicate that the proposed algorithm performs image segmentation faster than both types of algorithm for optimal thresholds. Moreover in case of localization it gives more accurate results than the compared algorithms. So by using the proposed variant of Differential Evolution improvement has been achieved both in the case of speed and accuracy.

A broadband antenna integrated with the system ground plane of the Portable Media Player (PMP) device for digital television (DTV) signal reception is proposed. The antenna comprises of a quarter-wavelength monopole and a gaps-coupled open loop antenna that can generate two adjacent resonant modes to form a wide operation band. Result shows a wide bandwidth of 464-856 MHz to cover the DTV signal reception in 470-806 MHz band. Details of the proposed antenna designs and experimental results of the construct prototypes are presented.

In this paper, a tri-band metamaterial-inspired monopole antenna is proposed for multi-band wireless applications. A metamaterial consisting of three dual-band modified S-shaped resonators (MSRs) is directly connected to a regular monopole element, which can not only support the two WiFi bands but also bring the resonant frequency of monopole element down to the WiMAX band while the length of the antenna is maintained unchanged. The simulated and measured results verify our design for the wireless applications.

Arbitrarily polarized plane-wave diffraction equations for semiinfinite periodic rectangular grooves (RG) in a perfectly conducting plane are approximately proposed. To obtain diffraction equations for semi-infinite periodic RG, we utilize an overlapping T-block method as proposed for the analyses of finite and infinite numbers of RG, and the subtraction technique with infinite periodic solutions. The proposed semi-infinite solutions are then applied to finite periodic RG with very large number of diffracting elements. For verification of our approach, we performed numerical computations for finite periodic RG and compared our solutions based on semi-infinite equations with previously published analytic solutions, thus obtaining favorable agreement and proving computational efficiency.

The paper presents an analytical investigation of a tapered core optical fiber of which the outermost section is loaded with radially anisotropic liquid crystal. The analyses are dealt with transverse modes supported in the fiber structure followed by the relative distribution of power in the different fiber sections. Preliminary dispersion characteristics of the guide are also illustrated. The results demonstrate that the TE modes transport very large amount of power in the outermost liquid crystal region --- the criteria much useful for fiber optic sensing and field coupling devices.

The electromagnetic losses and shielding efficiency of shields for a buried three phase high voltage cable are studied for several shielding configurations. The shields are U-shaped gutters covered with plates, and the power cables are positioned either in trefoil or in flat configuration. The shielding efficiency and the losses are compared for shields with the same geometry but several shielding materials: aluminium, and two ferromagnetic steel grades. The numerical models are validated with experimental results. From the experiments, it is observed that the average reducing factor of the flux density is about 7 with the flat cable configuration while the average reducing factor of the flux density is about 5 with the trefoil cable configuration. But the power losses in the DX52 shield for trefoil configuration is about 40% lower compared to the flat configuration. In case of trefoil configuration, the losses are 12.41 W/m per meter length in the shield for a current of 750 A. Next to the shield material and the cable configuration, the paper investigates the influence of several parameters on both the shielding efficiency and the losses: the size of the shield, the current amplitude in the cable and the thickness of the shield.

In this paper, microstrip line resonators with loaded elements are proposed and studied to design microstrip diplexer. To demonstrate the design ideas, the equivalent circuits of the proposed resonators are built and studied. It is found that the different loads on different positions of the proposed half-wavelength resonator make the resonator have different features, which will easily control the characteristic of the diplexers. And here, resistor, open stub, and shorted stub are used as loaded elements. It is found the resistor loaded on the center of the microstrip line resonator can extremely reduce the unloaded quality factor of even-mode resonant frequency, which can be used to suppress the harmonics of the diplexer. The loaded open stub not only can reduce the size of the diplexer, but also can control the frequency ratio between the fundamental frequency and second harmonic of a resonator, which can increases the frequency ratio between the two passbands of the diplexer. As for the loaded shorted stub, it can enlarge the size of the diplexer. To demonstrate the design ideas, three diplexers are presented. The comparisons between the loaded and unloaded diplexers are given. The experimental results agree well to the theoretical predictions and simulations.

A specialized type of traveling-wave field-effect transistor (TWFET), the gate and drain lines of which contain series capacitors, series inductors, shunt capacitors, and shunt inductors, is considered to provide a platform to manage unattenuated dispersion-free envelope pulses. Because of the nonlinearity caused by the gate-source Schottky capacitance, the dispersive distortion is well compensated. Moreover, the FET gain can cancel the wave attenuation caused by electrode losses. This paper discusses the design criteria of a TWFET using the nonlinear Schrodinger equation obtained by perturbation. Several numerical calculations follow to validate it.

A delay nonlinear differential equation is proposed to investigate the condition of the microwave chaotic behavior existing between the antenna and the front-end protection circuit of a receiver such as the radar front-end limiter circuit. This investigation concerns the case of intentional or unintentional signals applied to the antenna outside of its bandwidth. Bifurcation diagrams show that the chaotic behavior appears for antenna impedance up to 10 Ω and for amplitudes greater than 1.2 V. Electrical simulation results agree well with theoretical ones.

Recently, substrate integrated waveguide (SIW) technology attracts more and more attentions in the development of millimeter-wave integrated beamforming network (BFN) depending on its inherent advantages. However, the SIW-based BFN usually has a relative large circuit size. To overcome this weakness, we propose a novel multi-folded SIW Butler matrix at the center frequency of 60 GHz. Such a structure can reduce the circuit area more than 75% compared with the conventional single-layer version. Two different full-wave simulation tools are employed to validate our design. This folded BFN offers a number of benefits, such as highly compact configuration, low couplings between adjacent paths, and wide operation bandwidth. For convenient use, the SIW ports can be converted to the microstrip line ports arranged in order through a special broad-band two-layer transition network. Such a miniaturized SIW Butler matrix presents an excellent candidate in the development of compact intelligent millimeter-wave communication system.

We present a rigorous full wave calculation of the optical force on a dielectric cylindrical particle of an arbitrary size under the illumination of one dimensional (1D) Airy beam. The radiation force is written in terms of the cylindrical partial wave expansion coefficients of the non-paraxial 1D Airy beams. Our simulation results demonstrate that an Airy beam can accelerate the microparticles along its parabolic trajectory, while transverse to which the particles are trapped at the center of its main lobe, corroborating the possibility of the long distance particle transport by means of an Airy beam.

Millimeter waves can be used to detect concealed objects because they can penetrate clothing. Therefore, millimeter wave imaging draws increasing attention in security applications for the detection of objects under clothing. In such applications, it is critical to estimate the distances from objects concealed in open spaces. In this paper, we develop a segmentation-based stereo-matching method based on passive millimeter wave imaging to estimate the longitudinal distance from a concealed object. In this method, the concealed object area is segmented and extracted by a k-means algorithm with splitting initialization, which provides an iterative solution for unsupervised learning. The distance from a concealed object is estimated on the basis of discrepancy between corresponding centers of the segmented objects in the image pair. The conventional stereo-matching equation is modied according to the scanning properties of the passive millimeter wave imaging system. We experimentally demonstrate that the proposed method can accurately estimate distances from concealed objects.

In this paper we describe the realization of a low cost radiometer which can be used to detect and show the microwave electromagnetic field emitted from human body. The system uses components available in the consumer market: low cost LNB (Low Noise Block: low noise pre-amplifier, mixer and post-amplifiers) and a parabolic antenna for satellite TV. The base line stability problems of the system are removed using a detector in linear region and a digital integrator for correction of the base line. The PC resident software triggers an educational video on the origins of electromagnetic radiation when a person, entering in the antenna beam, is detected; in addition to this, it is possible to show an infrared image taken by a camera.

This article proposes a novel 4-sector cylindrical-rectangular microstrip array with high-gain operation and multi-beam radiation for IEEE 802.11j MIMO WLAN system. With the use of 1 x 2 array, the impedance bandwidth for the operating band of 5 GHz can reach about 2.5% (125 MHz), which is enough for IEEE 802.11j specifications. Peak antenna gains across the operating band are close to 11.0 dBi with the gain variations of 0.3 dBi.

Reflection from a perfect electric conductor (PEC) plane of infinite dimensions embedded in a second order nonlinear medium is studied. The reflected wave has two parts, one due to linear behavior, the other due to nonlinear behavior of the medium. The expressions of the reflection coefficients for parallel and perpendicular polarization cases are obtained. The reduction of reflection coefficient to a linear medium case is also reported. Dependence of the said coefficients on incident electric field intensity and the angle of incidence is also plotted.

New methods are presented for increasing the bandwidth of wire antennas using impedance loading. This paper extends the seminal Wu-King theory of the internal impedance profile that produces travellingwave only current modes on a center-fed dipole antenna. It also presents a numerical optimization methodology based on Central Force Optimization, a new deterministic multidimensional search and optimization metaheuristic useful for problems in applied electromagnetics. A CFOoptimized loaded monopole antenna is described in detail and compared to the same structure loaded with a fractional Wu-King profile. The CFO monopole generally performs better than other designs using either the full or fractional Wu-King profiles or the extended Wu-King profiles. The methods described in this paper should be useful in any wire antenna design that utilizes impedance loading to increase bandwidth.