In this paper, a modified Bayesian Optimization Algorithm (BOA), named M-BOA, is proposed to introduce a suitable mutation scheme for the traditional procedure in order to speed up the convergence of the algorithm and to avoid it to be trapped in local minima or to stagnate in suboptimal solutions. The proposed algorithm has been applied both to a specific mathematical test function and to sparse linear antenna arrays design, showing outperforming capabilities not only with respect to the standard BOA, but also with respect to other assessed global optimization methods.
The complex dispersion characteristics of the surface wave modes of plasma column loaded closed cylindrical waveguides have been investigated. The numerical results for partially or fully plasma loaded waveguides have been obtained from the Method of Moment(MOM), the exact dispersion equation and the quasistatic dispersion equation. A numerical technique based on the solution of the MoM has been proposed in order to obtain the complex propagation constant from the exact solution. The surface wave modes obtained from these methods have been presented comparatively in the figures. Thus, the insufficiency of the quasistatic approximation to obtain the complex surface wave modes has been shown. Additionally, the study involves a comprehensive literature review including physical descriptions and/or behavior in different physical media of surface wave modes and complex wave modes.
Doherty type Power Amplifier (DPA) design is one of the most practical efficiency enhancement methods that provide moderate linearity. Asymmetrical device usage and employment of bias adaptation are among the most commonly used Doherty architectures in recent applications. In this paper, the efficiency performances of bias adapted DPA and asymmetrical DPA are compared based on the new efficiency expression that is derived in terms of the conduction angle. The efficiency of bias adapted DPA is analyzed in terms of conduction angle of the peaking device; various bias waveforms are proposed and their effects on enhanced efficiency performance are demonstrated. This paper also facilitates an approach to determine the required relative periphery of the peaking amplifier in order to have a fully load modulated asymmetrical DPA. Both DPA structures are designed and implemented at the output power of 50 dBm with nearly 60% drain efficiencies in 6 dB load modulation region. The measurements verify the better efficiency characteristics of the bias adapted DPA and asymmetric DPA in comparison to the conventional DPA. For the first time in the literature, as a fair comparison, the performances of asymmetrical DPA and bias adapted DPA are compared on the same platform and their advantages as well as drawbacks are demonstrated using measurement results.
Non-line-of-sight (NLoS) maritime mobile radio channel in 5 GHz band is experimentally investigated in this paper through wideband channel soundings. During the measurements, the transmitter was installed onboard a speed boat, while the receiver was placed on the roof top of a building on shore. Different types of cargo ships anchored off the east coast of Singapore were examined as obstructions for the NLoS propagations. Besides power delay profile (PDP), stand-off distance is introduced in this work to analyze the NLoS propagations associated with three different types of cargo ships. The measured PDPs and stand-off distances are found to be comparable qualitatively with the simulated results using 3-D ray tracing. The reported information is found to be useful for military applications such as unmanned surface vehicles (USVs) in maritime environments or surveillance.
In this paper, a stage wise realization of compact Bluetooth - UWB dual-band diversity antenna with WiMAX and WLAN band-notch characteristics is presented. The proposed structure consists of two co-planar semicircular dual band-notch monopole antennas, mounted with planar spiral. Individual antenna configuration provides an impedance bandwidth (VSWR < 2) for dual-band i.e. both Bluetooth and UWB bands. For dual band-notch characteristic, two sets of spirals are capacitively coupled with the feed line of antenna. This configuration provides band-notch (VSWR > 2) for WiMAX i.e. (3.3-3.6 GHz) and WLAN (5.13-5.85 GHz) bands. For enhancing reception capabilities of the proposed structure, twin coplanar antennas are used to fulfill diversity requirements. However, due to coplanar and close proximity to each other, there is high possibility of mutual coupling between coplanar antenna elements. To address the mutual coupling between elements, cross-strip variable-sized frequency selective structures are used. Antenna diversity of the proposed structure is validated by measuring radiation pattern characteristic and envelop co-relation factor (ECC). A good agreement between measured and simulated responses ensures that the proposed diversity antenna can be used for interference free Bluetooth/UWB dual-band applications.
Polarization reconfigurable patch antennas which can switch polarization states among vertical and horizontal linear polarization (LP), left- and right-hand circular polarization (CP) is demonstrated in this paper. The original orthogonal linear polarized antenna is a square patch fed by two ports at the adjacent edges. CP operations can be activated by introducing perturbations at the opposite corners of the patch. If a diode is loaded on every perturbed corner, the antenna polarization states can be alternated by controlling the bias voltage of two PIN diodes. Perturbation elements can be cut on the patch or on the ground. Two antenna prototypes are suggested, simulated, and verified by experiments. These polarization reconfigurable antennas have good antenna performances of low reflection coefficient, axial ratio, and cross-polarization (X-pol), and high isolation between two LP operations. They have concise structure with only two PIN diodes being required. The two reconfigurable antennas are low cost and can be integrated easily in wireless communication systems.
Evolutionary Search Algorithms (EA) have been intensively used in solving numerical optimization problems. Since design of antenna arrays is a numerical optimization problem, EAs have been intensively used in solving antenna arrays design problems. Although EAs are widely used in antenna array design problems, a performance comparison study of the intensively used EAs for circular antenna array design problem has been scarcely studied. In this paper, 3 different circular antenna array design problems have been solved by using 15 different evolutionary search algorithms (i.e., ABC, ACS, BSA, CK, CLPSO, CMAES, DE, E2-DSA, EPSDE, GSA, JADE, JDE, PSO, SADE, S-DSA). The objective function designed for solution of the relevant circular antenna array design problems ensures minimization of side lobe levels, acquisition of maximum directivity, and null control of the non-uniform, planar circular antenna array. Obtained statistical analysis results show that S-DSA solves the relevant circular antenna array design problems statistically better than the other evolutionary algorithms used in this paper.
Gaussian beams techniques are high-frequency asymptotic methods that can be used to model the propagation/interaction of fields in a variety of problems. In this article, an expansion is proposed to express the scattering of magnetic/electric currents from a curved interface in terms of a new kind of elementary beams, the conformal Gaussian beams. The expansion characteristics rely on the physical properties of the configuration, which leads to represent the scattering with a small number of conformal Gaussian beams. An analytical formulation for the conformal Gaussian beams is developed, which expression is derived from an asymptotic evaluation of the radiation integrals valid at great distance from the interface. An example is presented to show that this analytical formulation is in good agreement with the reference result. Numerical tests are led on the expansion in order to show that the scattering can be represented with accuracy by adding the contribution of conformal Gaussian beams.
In this paper test study on low-cost civil engineering construction material is presented. In fact, in several civil constructions the strategy is to build up to first "fence" to EMI that limits interferences while using only in some limited areas high-cost ad hoc shielding material. The materials used in this study are tested at the Universita di Napoli Parthenope, formerly Istituto Universitario Navale (IUN) Reverberating Chamber (RC) according to a nested approach. Tests are made in the frequency range from 2 to 18 GHz and show that low-cost materials are able to achieve about 16 dB of shielding effectiveness (SE) in contrast to ad hoc materials that show about 50 dB in SE.
In this paper, band pass filters based on the microstrip configuration and utilizing coupled defected ground structures are presented. The 50 Ω microstrip line has a gap discontinuity in the middle and characterized by stepped impedance resonators on either half. The four fractal geometries tested for defected ground are the first and second iterations of the modified Moore curve, the closed staircase curve and a dual concentric closed staircase curve. The filters have a compact size and planar geometry. The modified Moore first iteration has a measured pass band from 2.27 GHz to 11.86 GHz, whereas the second iteration has a measured pass band from 1.85 GHz to 6.71 GHz. The measured pass band of the closed staircase is from 2.38 GHz to 7.21 GHz. The dual-concentric closed-staircase DGS filter offers a dual-band response with the measured pass band being from 2.41 GHz to 5.01 GHz and from 5.81 GHz to 8.35 GHz. All the filters are intended for UWB applications. A parametric study for the controlling parameters is also presented.
A great deal of researches have so far been conducted on the analysis of eccentricity in induction machines. However, they mostly consider radial non-uniformity and neglect nonuniformity in the axial direction, but in practice, the axial non-uniformity due to rotor misalignment faults is quite common. This paper presents a modified model of a three-phase squirrel cage induction machine under different rotor misalignment conditions. For this purpose, general expressions for air gap and mean radius of induction machine, considering axial non-uniformity, have been developed. The proposed model is able to calculate the time varying inductances versus rotor angle for three-phase squirrel cage induction machines under general rotor misalignment, including static, dynamic and mixed rotor misalignment in the frame of a single program. Simulation results were verified by the experimental ones.
Based on technical analysis and budget link experimentation, the main purpose here is to show improvement of HF half loop antennas in terms of signal-to-noise ratio (SNR) and stealthy for a combat ship. A special designed HF antenna brings a high quality communication over 1000 NM. A suitable integration of a HF half loop antenna at ship corners contributes to the ship stealthy. This paper shows the antenna performance and the benefit of the completely body integrated HF half loop antenna regarding whip antennas. The corresponding SNR is 15 to 20 dB better than for a conventional antenna.
A highly sensitive, passive relative humidity (RH) sensor using polyvinyl-alcohol (PVA) dielectric film is presented. For the first time, PVA is investigated in microwave RF sensing devices for low cost, high resolution and accurate chipless RH sensor realization. Comparative study with traditional humidity sensing Kapton polymer is presented to validate superior performance of PVA film. Results are presented for two different passive high Q resonators to validate sensing performance in wide applications. Moreover, a new sensing parameter is described to investigate sensitivity measurement through resonance frequency and Q factor variation. The RH sensor has the potential to be integrated with mm and μm-wave high frequency passive RFID for ubiquitous sensing.
The study of this paper focuses on the power angle spectrum (PAS) of the satellite communication downlink in rain environment at millimeter-wave bands. The two-dimension angle distribution expression of the incoherent intensity of the ground receiving antenna in rain is deduced in detail. The coherent intensity is discussed according to the first-order multiple scattering approximation theory. The calculation model of PAS is given based on the coherent intensity and the incoherent intensity angle distribution. Based on the Marshall-Palmer raindrop size distribution, the rain-induced attenuation coefficient γ = ρ<σt>, as well as the average scattering amplitude function of rain area, is calculated and discussed by Mie method; the two-dimension and the one-dimension PASs are simulated and analyzed at different incident angles for different rain rates, frequencies and polarizations. The PAS model and the simulation results given in this paper are important for the quantitative evaluation of the impacts of rain environment on MMW MIMO channel characteristics.
A new SAR radiometric terrain correction method was proposed to reduce the terrain effects in sloped regions. Based on this method, a procedure for polarimetric SAR terrain effect reduction was proposed, including geometric correction, shadow detection, radiometric terrain correction, and polarization orientation angle shift compensation. Experiments using RADARSAT-2 polarimetric SAR data of the Three Gorges Area, China demonstrated the effectiveness of the proposed radiometric terrain correction method. Both visual and quantitative analyses showed that after the proposed radiometric terrain correction method was applied, the contrast between different slopes that caused by local incidence angle differences, foreshortening, and layover was significantly reduced. The difference of backscattering intensity on slopes facing the radar sensor and facing away from the sensor was reduced from 12.5 dB before radiometric correction to 1.3 dB. The overall accuracy of land use / land cover classification was improved by 11.2 percent using the terrain corrected polarimetric SAR data.
In this paper, a nontrivial local oscillator uncorrelated phase noise analysis is proposed for frequency synthesizer of a passive millimeter-wave Synthetic Aperture Interferometric Radiometer (SAIR) imager BHU-2D designed for concealed weapon detections on human bodies with high imaging rates. The frequency synthesizer provides local oscillator signals for both millimeter-wave front-ends and intermediate frequency I/Q demodulators for the receivers. The influence of local oscillator uncorrelated phase noise in different offset frequency ranges on the visibility phase errors have been systematically investigated, and the corresponding system level visibility specifications are drawn. The integrated RMS phase error has been applied to set uncorrelated phase noise requirements in the most critical offset frequency range for visibility error control. The synthesizer design is given, and measurement results have proved that the visibility phase error requirement is achieved by the PN analysis method proposed with system-level visibility error tests performed. To conclude, the phase noise effects on SAIR visibility phase errors are investigated by theory, and are properly limited by the PN requirement analysis method to ensure that the system-level visibility phase error specification is satisfied.
Interferometric devices have drawn great interest in all-optical signal processing for their high-speed photonic activity. Quantum-dot semiconductor optical amplifier (QD-SOA)-based gate has added a new momentum in this field to perform all-optical logic and algebraic operations. In this paper, for the first time, a new scheme for all-optical full adder using fife QD-SOA based Mach-Zehnder interferometers is theoretically investigated and demonstrated. The proposed scheme is driven by three input data streams; two operands and a bit carried in from the next less significant stage. The proposed scheme consists of two XOR, two AND, and one OR gate. The impact of the peak data power as well as of the QD-SOAs current density, maximum modal gain, and QD-SOAs length on the ER and Q-factor of the switching outcome are explored and assessed by means of numerical simulation. The operation of the system is demonstrated with 160 Gbit/s.
Diamond dipole antennas with textile Artificial Magnetic Conductor (AMC) sheet-like waveguide were designed to investigate the possibility of improving transmission between antennas. Fleece fabric is used as the substrate of the textile AMC while SHIELDIT fabric is used as the conductive patches and ground plane. The AMC surface is designed to resonate at 2.45 GHz with the goal to enhance the transmission between antennas. A small textile AMC waveguide sheet as well as an AMC waveguide jacket were fabricated. The S-parameters performance of the two antennas with textile AMC sheet was investigated in a free space environment and near to human body setting. The effect of different antennas' orientations was also considered. Measurements were conducted thoroughly to validate the simulated findings. Compared to free space environment, S21 transmission between two dipoles is improved up to maximum -10 dB when having textile AMC waveguide sheet beneath them. For both off-body and on-body placements, significant transmission enhancement has been observed with the introduction of the AMC sheet-like waveguide. Directive radiation patterns with high gain have also been achieved with the proposed AMC waveguide jacket.
Multifractal correlation, which studies the spatial correlation characteristics of two points with different singularity indexes, is a generalization of multifractal single point statistic. This paper introduces multifractal correlation theory into the characteristic analysis of aircraft echoes from low-resolution surveillance radars, and discusses the application of multifractal correlation characteristics in target classification. Firstly, on basis of introducing multifractal correlation theory, the multifractal correlation characteristics of aircraft echoes from surveillance radars are analyzed in detail by means of the multifractal correlation analysis. Secondly, on basis of the foregoing analysis, several characteristic parameters of the echo multifractal correlation spectrum are defined, and the support vector machine (SVM) based on the defined characteristic parameters is taken as the classifier to classify different types of aircraft targets. Finally, real recorded aircraft echo data are adopted to do the classification experiments, and the experimental results validate the proposed method.
A 1.3 m piecewise reflectarray demonstrator has been designed, manufactured and tested, that radiates a contoured beam coverage over North America. A very good agreement is obtained between the theoretical and measured radiation patterns. Many innovative techniques and processes were developed in order to meet the challenging specifications of a space telecommunication antenna.