Phased array antennas are a viable solution to a number of problems related to radio communications applications. In this work, the multi-objective stochastic MOPSO algorithm is used to optimize the spatial configuration of a symmetric phased linear array. The defined optimization goals were the suppression of the radiation pattern sidelobes at a specified maximum scan angle as well as the minimization of the induced voltages correlation at the receiver frontend in order to maximize diversity performance. Non-linear constraints were enforced on the solution set, related to the multi-antenna system aperture efficiency and related to the mismatching when the array is scanned. The obtained optimized configurations for an array composed of 16 dipoles resulted in reducing the sidelobes up to 2.5 dB, when scanned 60° away from broadside, compared to a linear array with elements spaced λ/2 apart. Furthermore, the optimized dipole arrays were characterized by a maximum element correlation of 0.12 to 0.43. The performance of obtained configurations was shown to be tolerant to feed phase variations that appear in realistic implementations. The arrays were analyzed employing the Method of Moments (MoM).

The symmetric and asymmetric double Langmuir probe systems with their necessary driving circuits are developed for characterization of low pressure inductively coupled nitrogen plasma, generated and sustained with 13.56 MHz RF source and an automatic impedance matching network. First of all the plasma parameters such as ion saturation current, electron temperature and electron number density are determined with symmetric double probe system at different input RF powers, filling gas pressures and radial distance from the plasma chamber wall. Then the electron temperature and electron energy probability function are determined with asymmetric double probe system at the centre of the discharge plasma chamber by changing the filling gas pressure and input RF power. It is observed that the electron temperature and electron number density increase with the increase in input RF power and radial distance but decreases with the increase in filling gas pressure. The electron energy probability function determined with asymmetric probe system evidently deviates from the Maxwellian, particularly at low filling gas pressures.

The presence of desired signal in the training data for sample covariance matrix calculation is known to lead to a substantial performance degradation, especially when the desired signal is the dominant signal in the training data. Together with the uncertainty in the look direction, most of the adaptive beamforming solutions are unable to approach the optimal performance. In this paper, we propose an evolutionary algorithm (EA) based robust adaptive beamforming that is able to achieve near optimal performance. The essence of the idea is to shape the array beam response such that it has maximum response in the desired signal's angular range and minimum response in the interferences' angular range. In addition, the approach introduces null-response constraints deduced from the array observation to achieve better interference cancelation performance. As a whole, the proposed optimization is solvable using an improved variant of the differential evolution (DE) algorithm. Numerical simulations are also presented to demonstrate the efficacy of the proposed algorithm.

This paper presents a numerical study of the thermal effects induced by a commercial RFID antenna in vials filled with blood plasma. The antenna is located under a conveyor belt which transports cardboard boxes bearing test tubes or pooling bottles. Part of the energy used to read the RFID tags penetrates into the vials and heats the plasma. Our aim is to assess if the RFID technology can alter the quality of the blood plasma by increasing excessively its temperature. To do so, we first compute the specific absorption rate inside the vials with the finite element method. Then, assuming that no heat dissipation process is present, we estimate the number of continuous reading cycles required to increase the plasma temperature 0.1°C in the worst-case scenario. Finally, we compare this number with the number of reading cycles required to obtain all the data from the tags under normal usage conditions.

An over-mode metal rectangular waveguide is widely used in the generation, propagation, coupling, and transition of microwaves. When applied as the beam-wave interaction circuit of some high power microwave devices, a rectangular waveguide is expected to operate at a single electromagnetic mode. To do that, unwanted modes resulted from spurious oscillations should be suppressed. In this paper, a method of selective suppression of electromagnetic modes in rectangular waveguides by loading distributed losses in some special position of waveguide inner wall is presented. By using the method, the unwanted modes can be attenuated much larger relative to the operating mode. The presented method can be used to improve the stability of rectangular waveguide beam-wave interaction circuit.

In this paper, we investigate the exploitation of the polarimetric diversity signal properties in a bistatic polarimetric MIMO radar to improve the performance of joint estimation of direction of arrival (DOA) and direction of departure (DOD) of targets using Combined ESPRIT-RootMUSIC technique. Numerical simulations are carried out to illustrate the performance of the proposed approach.

In recent years, metamaterials have been the subject of research interest for many investigators worldwide. However, most of reported metamaterial microstructures are obtained based on human intuition, experience or large numbers of simulation experiments which were time-consuming, ineffective or expensive. In this paper, we propose a novel negative index metamaterial microstructure design methodology that uses a FDTD solver optimized by genetic algorithm (GA) technique in order to achieve a simultaneously negative permeability and permittivity. Firstly, an novel genetic algorithm optimization model for wide frequency band of negative refraction was proposed. Then the effectiveness of the new technique was demonstrated by a microstructure design example that was optimized by GA. By using numerical simulations techniques and S-parameter retrieval method, we found that the GA-designed optimal solution can exhibit a wide LH frequency band with simultaneously negative values of effective permittivity and permeability. Therefore, the design methodology presented in this paper is a very convenient and efficient way to pursue a novel metamaterial microstructure of left-handed materials with desired electromagnetic characteristics.

This paper presents the performance of an Adaptive transmit beamspace beamformer (ATBBF) in a dynamic channel for Multiple input single output (MISO) per user wireless system. ATBBF consists of a of several transmit beamformers on the Transmit antenna array (TAA). The antenna weights of each Transmit beamformer (TB) are held constant while input to a TB is weighted by an adaptive beamspace weight. An algorithm that updates beamspace weights of all transmit beamformers of an ATBBF at the base station is described. It updates on the basis of a single feedback from the mobile. The feedback consists of one bit that indicates which of the two normalized perturbed beamspace weights that were time multiplexed onto the pilot signal from the base station delivered more power to the mobile. This algorithm is named Beamspace gradient sign feedback algorithm (BGSF) as its feedback mechanism is similar to that of Gradient sign feedback (GSF) algorithm that updates antenna weights of a TB. Performance metric of ATBBF is derived and analyzed in a dynamic channel undergoing Rayleigh fading. Performance comparison between an ATBBF with BGSF algorithm and a TB with GSF is made in terms of convergence and tracking of various slow and fast fading channels by simulations. Both full dimension (FD) and Reduced dimension (RD) ATBBF are considered. Comparisons show that FD ATBBF gives equivalent performance to that of TB and outperforms RD ATBBF.

Extinction and backscattering from thin curved fibers of finite conductivity are computed by solving the Pocklington integro-differential equation using the Moment Method with point matching scheme. For simplicity of interpretation these computations were performed at long wavelengths, in the Drude domain. The effect of the degree of curvature on the cross sections is examined for high and low fiber conductivities, and for two incident geometries: normal and parallel to the plane of the curved fiber. The computations show a narrowing and decreasing cross sections with increased fiber curvature for both low and high conductivities. The normal geometry produces larger cross sections than the parallel case.

A method for modeling and designing of coupled resonators photonic crystal (PC) filters for wavelength division multiplexing (WDM) systems is presented. This proposed method is based on coupling coefficients of intercoupled resonators and the external quality factors of the input and output resonators based on the circuit approach. A general formulation for extracting the two types of parameters from the physical structure of the PC filters is given. At last, we redesign a third-order Chebyshev filter which has a center frequency of 193.55 THz, a flat bandwidth of 50GHz, and ripples of 0.1 dB in the pass-band. The filter's structure derived from the proposed method is more compact.

A novel approach to moving target detection is proposed for dual-channel SAR system. This approach is on the basis of eigen-decomposition of the sample covariance matrix and examines the statistic of the second eigenvalue and the Along-Track Interferometric (ATI) phase for ground moving target indication. Based on this statistic, a new Constant False Alarm Rate (CFAR) detector can be designed to solve the problem of GMTI. To detect slow moving targets more accurately, the second eigenvalue and the ATI phase pre-thresholds are implemented before a CFAR detector. Experimental results on measured SAR data are presented to demonstrate that this novel detector has wider range of detection velocity and lower false alarm probability.

This paper proposes a rigorous theory of the H-plane four-port (cruciform) waveguide junction with a conducting diaphragm and a dielectric layer in the main (input) waveguide arm. This theory is based on the mode matching method in conjunction with Fourier transform technique and including the edge conditions in vicinity of the diaphragm edges. The numerical analysis of the cruciform waveguide junction is done, and optimal parameters of inclusions are predicted based on the minima of voltage standing wave ratio (VSWR) in the main arm.

The dispersion relation of piecewise linear recursive convolution finite difference time domain (PLRC-FDTD) method for space-varying plasma is analyzed using a novel equivalent method. The equivalent dispersion and dissipation errors have been taken into account. The efficiency of the novel equivalent method is substantiated by computing the test and reference transmitted electric field. The comparison of the test and reference solutions validates that the equivalent method is an efficient method to analyze the dispersion relation of PLRC-FDTD method used for space-varying plasma.

A method for measuring the sensitivity of a capacitive proximity sensor and an application using the sensor as a proximity detector in mobile phone antennas is presented. 2D sensor data plots were physically more exact for tuning sensor placement. 3D sensor data plots were suitable for sensor intensity comparison, highlighting sensor differences in multiple sensor applications and effects in sensor`s output due to shadowing mechanical objects. The antenna proximity sensor was measured and optimised with sensitivity measurements. In a PIFA application the antenna load could be detected from both sides and from above the antenna on a scale o 4.03•10^-14 F to 4.33•10^-14 F. The cases present all possible positions of holding a phone used in either the ``calling'' or ``browsing'' mode. The method and the application emphasise the physical sensitivity and electrical fields of the sensor. The characteristics can be further improved by using other sensor types, sensor data fusion and advanced imitation of multisensory spatial interaction by humans and animals.

To deal with pattern synthesis of antenna arrays, a chaotic particle swarm optimization (CPSO) is presented to avoid the premature convergence. By fusing with the ergodic and stochastic chaos, the novel algorithm explores the global optimum with the comprehensive learning strategy. The chaotic searching region can be adjusted adaptively. To evaluate the performance of CPSO, several representative benchmark functions are minimized using various optimization algorithms. Numerical results demonstrate that the proposed approach improves the performance of the algorithm significantly, in terms of both the convergence speed and exploration ability. Moreover, CPSO was applied to array synthesis examples, including the equally spaced linear array, unequally spaced linear array and conformal array, compared with other optimization methods. Experimental results show its high performance in the pattern synthesis with low side lobe, multi-nulls and shaped beam.

Due to the ill-posed nature of nonlinear inverse problems of borehole geophysics, a parameterization approach is necessary when the available measurement data are limited and measurements are only carried out from sparse transmitter-receiver positions (limited data diversity). A potential remedy is the joint inversion of multi-physics measurements. A parametric inversion approach has desirable attributes for multi-physics measurements with different resolutions. It provides a flexible framework to put the sensitivities of multi-physics multi-resolution measurements on equal footing. In addition, the number of unknown model parameters to be inverted is rendered tractable with parameterization. Consequently, a Gauss-Newton based inversion algorithm taking advantage of the Hessian information can be advantageously employed over inversion approaches that rely only on gradient information. We describe a new dual-physics parametric joint-inversion algorithm to estimate near-borehole fluid permeability and porosity distributions of rock formations from fluid-flow and electromagnetic measurements. In order to accommodate the cases in which the measurements are redundant or lack sensitivity with respect to certain model parameters causing nonuniqueness of the inverted solution, the objective functional to be minimized is regularized with a penalty term. One of the central aspects of this approach is the determination of the regularization parameter. The latter must be chosen in such a way that the relative importance of the misfit between measured and predicted data and the penalty term are effectively balanced over the course of minimization. We propose a new method of adaptively choosing the regularization parameter within a Gauss-Newton method based joint-inversion algorithm using a multiplicative regularization strategy. The multiplicative regularization method is tested against additive regularization in joint-inversion problems involving wireline formation tester transient pressure and induction-frequency electromagnetic logging measurements. The multiplicative regularization method delivers improved convergence rates over additive regularization for all investigated problems. Inversions of relatively more noise-contaminated measurements benefit more from multiplicative regularization.

In present work, a microstrip Sierpinski modified and fractalized antenna using multilayer structure to achieve dual band behavior for WLAN applications has been proposed. Due to the space-filling properties of fractal geometry, the proposed antenna is smaller in size than the conventional Euclidean-type. An equilateral triangular patch antenna with Sierpinski Gasket fractal shape has been designed and studied. An electromagnetic coupled stacked structure of two different patches operating at two frequencies (2.4 GHz Bluetooth and 5.8 GHz Wireless LAN) has been designed for dual band WLAN applications.

MVDR beamformer is one of the well-known adaptive beamforming techniques that offers the ability to resolve signals that are separated by a fraction of an antenna beamwidth. In an ideal scenario, the MVDR beamformer can not only minimize the array output power but also maintain a distortionless mainlobe response toward the desired signal. Unfortunately, the MVDR beamformer may have unacceptably low nulling level, which may lead to signicant performance degradation in the case of unexpected interfering signals. A new robust MVDR beamforming is presented to control the nulling level of adaptive antenna array. In this proposed approach, the beamforming optimization problem is formulated as a multi-parametric quadratic programming (mp-QP) problem such that the optimal weight vector can be easily obtained by real-valued computation. The presented method can guarantee that the nulling level are strictly below the prescribed threshold. Simulation results are presented to verify the efficiency of the proposed method.

This paper presents the development of a standard surface mountable ceramic ball grid array (CBGA) package with an integrated patch antenna in low temperature cofired ceramic (LTCC) technology for emerging single-chip 60-GHz radios. It addresses the challenges of low-loss wire bonding interconnections required between the chip and the antenna as well as the package to allow efficient utilization of available space for miniaturization. The compact package of size 12.5×8×1.265 mm³ achieves good electrical performance. For instance, the package part exhibits insertion loss <0.08 dB, return loss >22 dB, and attenuation rate <0.2 dB/cm below 5 GHz; while the antenna part demonstrates 8-GHz impedance bandwidth and 8±2 dBi peak realized gain at 60 GHz. Simulated and measured results are compared. They agree reasonably well, indicating the feasibility of designing and manufacturing the integrated antenna package in LTCC for millimeter-wave applications.

The fields inside a rectangular waveguide with an internal coating of chiral nihility metamaterial are determined. These fields are then fractionalized utilizing the fractional curl operator to find the fields for the intermediate geometries which are also termed as the fractional order geometries. It is noted that no electric field exists inside the chiral nihility coating backed by perfect electric conductor (PEC) surface. The fractional order geometries are related through the principle of duality. The behavior of the fields with respect to the fractional parameter, α is analyzed.