Compared with the worst-case optimization-based approach, the probability-constrained approach is a more flexible one to robust adaptive beamforming. In this paper, a precise relationship between the two approaches is built in the case of Gaussian steering vector mismatch, which shows that the probability-constrained beamformer design can be interpreted in terms of the worst-case beamformer design. Numerical simulations demonstrate that the precise version of the probability-constrained beamformer is more robust to the steering vector mismatch than the other popular robust adaptive beamformers.

On the base of the binary search algorithm of backtracking, an enhanced binary anti-collision search algorithm for radio frequency identification (RFID) system is presented in this paper. With the method of transferring the collision bit in place of the ID of the tag, the proposed algorithm can improve identification efficiency significantly. Mathematical simulation result shows that compared with the binary search algorithm, dynamic binary search algorithm and the binary search algorithm of backtracking, the proposed algorithm outperforms the three algorithms previous when handling multiple RFID tags simultaneously.

A fast and accurate near-field-far-field transformation technique with helicoidal scanning is proposed in this paper. It is tailored for elongated antennas, since a prolate ellipsoid instead of a sphere is considered as surface enclosing the antenna under test. Such an ellipsoidal modelling allows one to consider measurement cylinders with a diameter smaller than the antenna height, thus reducing the error related to the truncation of the scanning surface. Moreover, it is quite general, containing the spherical modelling as particular case, and allows a significant reduction of the number of the required nearfield data when dealing with elongated antennas. Numerical tests are reported for demonstrating the accuracy of the far-field reconstruction process and its stability with respect to random errors affecting the data.

Wireless channel identification and equalization is one of the most challenging tasks because broadcast channels are often subject to frequency selective, time varying fading and there are several bandwidth limitations. Furthermore, each receiver channel has vastly different types of channel characteristics and signals to noise ratio. Here in this paper we consider channel equalization and estimation problem from trans-receiver perspective, specifically we try to estimate blind equalization schemes particularly using constant modulus Algorithm (CMA). We try to estimate a linear channel model driven by a QAM source and adapt a FSE (T/2) using CMA. It has been shown CMA-FSE successfully reduces the cluster variance so that transfer to a decision directed mode is possible and simultaneously error is reduced.

active phased array antenna has been developed that is capable of wide scanning angle with small deviation in antenna gain using printed dipole antennas with parasitic element, which may have the capability of adjusting the influence of mutual coupling in the array element pattern. The design of the parasitic element is examined and the effect of its shape on pattern characteristics is confirmed. Beam scanning angles of 58 degrees in the φ= 0^。 plane were obtained for each array antenna pattern.

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.

The problem of electromagnetic scattering by 3D dielectric bodies is formulated in terms of a weak-form volume integral equation. Applying Galerkin's method with rooftop functions as basis and testing functions,the integral equation can be usually solved by Krylov-subspace fast Fourier transform (FFT) iterative methods. In this paper,the generalized minimum residual (GMRES)-FFT method is used to solve this integral equation,and several adaptive acceleration techniques are proposed to improve the convergence rate of the GMRES-FFT method. On several electromagnetic scattering problems,the performance of these adaptively accelerated GMRESFFT methods are thoroughly analyzed and compared.

The scattering characteristic of paraxial gaussian beam from two dimensional dielectric rough surfaces is studied in this paper. The modification of the Kirchhoff approximation theory for rough surface scattering by an incident gaussian beam instead of a plane wave are developed based on conventional Kirchhoff scattering theory and plane wave spectrum expansion method. The coherent and incoherent scattered intensity and cross section of two dimensional dielectric rough surfaces is derived in detail. As a application, under incidence wave length λ = 1.06 μm, we calculate the coherent and incoherent scattered intensity and cross section of Gaussian beam scattering from plating aluminium dielectric rough surfaces change with the scattering zenith angles in different rough surface correlation length, rough surface height root mean square and other conditions. In the same scattering conditions, we compare the coherent and incoherent scattered section between the gaussian beam and plane wave to prove that our methods and programming cods is correct. The numerical results are shown that the incident gaussian beam size is much larger compared with the surface height correlation length, the normalized scattering cross section is the same as for an incident plane wave. The ratio between the beam size and the surface height correlation length play an important role in the scattering characteristic of the gaussian beam from two dimensional dielectric rough surfaces. The ratio is bigger, the coherent and scattered intensity and section is more remarkable and on the contrary the incoherent scattered intensity and section is relatively smaller.

The paper describes the propagation of a thin laser beam which passes through a hot turbulent jet, perpendicularly to the flow direction, using geometrical optics approximation. From the modelling of the random propagation direction of the laser beam along its whole path, the diffusion coefficient of the turbulent jet is determined by means of a shape optimization technique in which a genetic algorithm is used. The results obtained from the GA are then improved by the Golden Section method.

A full wave spectral domain method of moment along with reciprocity theorem analysis of finite phased array of aperture coupled circular microstrip patch antennas is presented. Both the electric surface currents on the patches and the equivalent magnetic current on the apertures are considered. Results of reflection coefficient magnitude, active input impedance, active element gain, efficiency and pattern are provided for different array size and element separations. By optimizing the parameters of the array, a better scan performance can be achieved. Furthermore, a comparison is made between array of rectangular and circular patches, with equal patch surface area, and it is shown that the array of circular patches provide a better scan performance than the array of rectangular patches.

In this paper, the channel estimation in multi-band OFDM (MB-OFDM) ultra-wideband (UWB) based multiple- antenna transmission systems is studied. For multiple antennas, each preamble designed by the Zadoff-Chu sequence satisfies the orthogonal property in the time domain. Therefore, the proposed preambles can improve the system performance and be applied to MB-OFDM specification in the case of more than two transmit antennas.

A closed form analytic solution is introduced for arbitrary Coupled Nonuniform Transmission Lines (CNTLs). First, the differential equations of CNTLs are written as a suitable matrix differential equation. Then, the matrix differential equation is solved to obtain the chain parameter matrix of CNTLs. Afterward, the voltage and current of lines are obtained at any point using the chain parameter matrix. The validation of the introduced solution is studied, finally.

A new miniature ultra-wideband exponential tapered slot antenna with gratings, which is fed by a 180 degree microstrip phase shifter network, has been introduced in this paper. The switch characteristic and the reflecting loss of the phase shifter is also analyzed. Some subminiature rectangular gratings are etched at the front and back end, as a result of which, the inner band characteristic is improved and the frequency band of the antenna is extended to more than 3 : 1 (S₁₁ < −10 dB). The radiation pattern has good direction property in the entire bandwidth and favorable symmetrical endfire radiation characteristic as well as more than 10 dB gain in the central frequency band.

Uniqueness of the initial-boundary value problems for a Tellegen media is studied. Initial-boundary value problems for a Tellegen Medium are summarized for the sake completeness; the conservation of energy for such a medium is reviewed. Sufficient conditions are given for the positive definiteness of the energy stored in a Tellegen media due to the fields. It is shown that the if the energy stored in a Tellegen medium is positive definite, then an initialboundary value problem for a Tellegen media has only one solution, if it exists.

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.

Based on theoretical calculations, the field intensity resulting from a transmitter of medium wave (waves propagation) enjoys a significant increase in the paths where ground conductivity increase and in special environmental conditions even if far away from the transmitter. This phenomenon distinguishes coverage areas of a transmitter from common procedures of determining coverage. This article examines and observes the above-mention issue and its results.

Radiation characteristics of shipborne antennas above lossy half-space are studied using the multilevel fast multipole algorithm (MLFMA). The near terms in the MLFMA are evaluated by using the rigorous half-space dyadic Green's function, computed via the method of complex images. The far MLFMA interactions employ an approximate dyadic Green's function via a direct-radiation term plus a single real image, with the image amplitude characterized by the polarization-dependent Fresnel reflection coefficient. Finally, radiation patterns of an ultra-shortwave antenna mounted on a realistic 3-D ship over seawater are presented and compared with a rigorous method-ofmoments (MoM) solution.

In this paper a novel approach based on Asymptotic Iteration Method (AIM) is presented to solve analytically the light propagation through one-dimensional inhomogeneous slab waveguide. Practically implemented optical slab waveguides based on traditional techniques are usually inhomogeneous and numerical methods are used to obtain guided wave characteristics. In this work, we develop analytical method for modal analysis includes Eigen modes (electric and magnetic fields distribution) and Eigen values (guided wave vector) using AIM. The developed method is applied to some especial examples.

The calculation method for radar cross-section (RCS) of reflector antenna placed under cone-shape dielectric radome has been proposed. The method based on the integral representations for a desired scattering field with using Lorenz lemma. These integral equations considered electromagnetic interaction between an antenna screen and a radome. The analysis of RCS calculation results for model antenna system with a conic dielectric radome has been carried out.

Based on the step-frequency RCS measurement system, high performance absorbers and low scattering supports, employing two log-periodic dipole antennas to carry out the quasi-monostatic measurement and many DSP techniques to reduce the error, the indoor accurate RCS measurement can be completed on UHF band. Experimental results show that the valid data waved less than 1 dB can be obtained over 70% of whole band.