A modified particle swarm optimization (PSO) algorithm applied to planar array synthesis considering complex weights and directive element patterns is presented in this paper. The modern heuristic classical PSO scheme with asynchronous updates of the swarm and a global topology has been modified by introducing tournament selection, one of the most effective selection strategies performing in genetic algorithms the equivalent role to natural selection, and elitism. The modified PSO proposed combines the abilities of the classical PSO to explore the search space and the pressure exerted by the selection operator to speed up convergence. Regarding the optimization problem, the synthesis of the feeds for rectangular planar arrays consisting of microstrip patches or subarrays of microstrip patches is considered. Results comparing the performance and limitations of classical and modified PSO-based schemes are included considering both test functions and planar array complex synthesis to best meet certain far-field radiation pattern restrictions given in terms of 3D-masks. Finally, representative synthesis results for sector antennas for worldwide interoperability for microwave access (WiMAX) applications are also included and discussed.

Studies of dual channel, polarisation agile, quad-ridge and octo-ridge feeds suggest that mode degeneracy in multi-ridge structures severely constricts operational bandwidths, for a large range of ridge dimensions. Mode characteristics in dual-ridge, quad-ridge and octo-ridge waveguide are examined in this paper, with a view to identifying both the nature of the degeneracy, and its implications for bandwidth. The results presented have been generated using a full-wave finite element electromagnetic field simulator.

In this paper, a novel multi-band EBG structure is presented. By making slots on Sievenpiper High Impedance Surface(HIS) to increase the inductance and capacitance, the resonant frequency of the EBG structure can be significantly reduced.Transmission line method is used to determine the band-gap of the EBG structure.The simulated and experimental results show that the novel EBG structure can provide multiple band-gap. This proposed EBG can be usefully applied to multiple frequency antennas and low profile antennas.

A bandpass filter (BPF) using CPW combined with microstrip is proposed. The target BPF is composed of two element filters built from combined CPW and microstrip structure. The design of element filter is based on the lumped elements approach with each circuit component built from a CPW or microstrip. In the circuit model, transmission zeros are created by the passband edges to enhance the signal selectivity. The element filter's characteristics are analyzed by the lumped L-C circuit model. Experiment is conducted, and a good agreement is observed between the measurement and simulation.

Wet antenna attenuation during rain events is examined through carrying out simulated rain experiments. These were conducted on the receiving antenna located at Penang, Malaysia. The findings from these experiments are used to estimate rain attenuation data for that path by adjusting the collected data for wet antenna attenuation. This was done for the 1-year period of March 2007 to February 2008 and includes average and worst month cumulative distribution functions. The results of the measurement indicated that the wet antenna effect is a significant attenuator, and should be included in a link budget. The measured attenuation values were 4 dB for the wet feed window and total reflector plus feed window attenuation value of 6.3 dB at 20.2 GHz, at a rain rate of 100 mm/h.

The paper presents the ionospheric effect on the power transmitted by satellite solar power station. Consequently, the Faraday rotation and losses due to ionospheric layer are calculated at 2.45 GHz frequency. It is observed that the fluctuation in the Faraday rotation in day time is found to be the maximum as compared to the night hours and. Loss due to depolarization is found to have the maximum value at noon hours for all the seasons (summer, winter and spring) however, the loss is the highest for summer season as compared to winter and spring season. This is logically correct because the ionization is the highest in summer in comparison to winter which gives rise to maximum electron content and maximum depolarization.

Ultra Wideband (UWB), an impulse carrier waveform, was applied at HF-VHF frequencies to utilize surface wave propagation. Due to the low duty cycle of the pulse, the energy requirements are significantly reduced. UWB involves the propagation of transient pulses rather than continuous waves which makes the system easier to implement, inexpensive and small. The use of surface wave propagation (instead of commercial SHF UWB) extends the communication range. The waveform, transmitter, receiver, modulation and channel characteristics of the novel system design will be presented.

The scattering of electromagnetic plane wave from an artificial object containing thin long perfectly conducting needles embedded in a homogeneous background material is characterized by parameters like positioning, orientations and lengths of needles. Firstly, models of random errors in positioning and orientation of perfectly conducting needles are proposed. Secondly, their effects upon ensemble averaged RCS is analyzed. It is investigated theoretically that increasing error in positioning and orientation of conducting needles reduces ensemble averaged RCS.

Inaccurate range estimates often restrict indoor positioning systems, resulting in a more remarkable drawback when using an already-deployed IEEE 802.11 network. This is the case of the time delay based location system that this paper deals with. The main causes of these inaccuracies are multipath and non-line-of-sight (NLOS) effects. These effects can be solved to a large degree by characterizing arrival times and range estimation errors. For this reason, this paper analyzes multipath and NLOS effects involved in the round-trip time (RTT) discrete measuring process, which is conducted before each range estimate. RTT observations obtained in this process for different real indoor environments provide useful statistical information that allows making the work extendable to other similar scenarios. Moreover, from this statistical information, the nodes in the network can estimate several parameters of the range estimates distribution while performing the location process. These are used to reduce the error caused by multipath components and to predict and correct the NLOS biases produced. In this way, the NLOS error is dynamically estimated and corrected, achieving better results than classical approaches based on static parameters.

Composites containing conducting inclusions are required in many engineering applications, especially, for the design of microwave shielding enclosures to ensure electromagnetic compatibility and electromagnetic immunity. Herein, multilayer shielding structures are studied, with both absorbing and reflecting composite layers. In this paper, fiber-filled composites are considered. For modeling absorbing composites with low concentration of conducting cylindrical inclusions (below the percolation threshold), the Maxwell Garnett theory is used. For reflecting layers, when concentration of inclusions is close to or above the percolation threshold, the McLachlan formulation is used. Frequency dependencies for an effective permittivity are approximated by the Debye curves using a curve-fitting procedure, in particular, a genetic algorithm.

A gas will breakdown in a high electric field and the mechanisms of this breakdown at DC and high frequency fields have been an object of study for the past century. This paper describes a method to induce breakdown in a uniform microwave field using a reentrant sub-quarter wave resonator. Slater's theorem is used to determine the magnitude of the threshold electric field at which breakdown occurs. The breakdown threshold is modeled using the effective electric field concept, showing that breakdown varies with pressure as E_bd=CP^m (1+(ω/ B·P)²)^1/2 where P is the pressure, B and C are fit parameters, and m was found experimentally to equal 1/2. This function exhibits a minimum at P_min=ω/B. Breakdown data from the literature for nitrogen at various microwave frequencies were found to exhibit breakdown minima at the pressure predicted by our own determination of B, further validating the model.

The excitation of metamaterial and non metamaterial, Electromagnetic (EM) modes and fields in an anisotropic, parallel plate waveguide (meeting Dirichlet and Neumann boundary conditions), is studied, using a modified coordinate transformation [3, 4] which reduces Maxwell's equations to the form of a Helmholtz wave equation satisfying Dirichlet and mixed-partial derivative boundary conditions. The EM modes and fields of the system are excited by a novel, slanted electric surface current excitation (Figs. 1 and 2) whose slant angle has been chosen to coincide with the surfaces of constant phase of the anisotropic modes which may propagate in the waveguide. Also presented, for comparison purposes, is the EM field excitation analysis of an isotropic parallel plate waveguide whose dimension, operating frequency, and source is identical to the anisotropic waveguide and whose material parameters are very close to those of the anisotropic waveguide. The analysis consists of several parts. Sections 1 and 2 of the paper describe the Helmholtz wave equation and boundary conditions that arise from use of the modified, coordinate transformation. In Section 3 the modal characteristic equation of the system is derived and in Section 4 this equation is solved to determine the propagating and complex (or non propagating) modes that may exist in the waveguide. For the anisotropic material parameters chosen in the paper, in Section 4, one of the propagating modes of the system was shown to be a metamaterial mode (also called a backward traveling wave, phase velocity and direction of real, positive power flow in opposite directions). An analysis in Section 4 was also presented from which the cutoff frequency of the waveguide could be determined. Sections 5-8 of the paper were concerned with using the complex Poynting theorem and an EM complex power reaction equation to study complex power and energy in the waveguide. The complex Poynting theorem and the reaction equation were also used to derive several power and reaction orthogonality relations that exist between the propagating (including non metamaterial and metamaterial modes) and complex modes of the systems. Using the orthogonality relations derived in Sections 5-8, in Section 9, an efficient matrix analysis based on the reaction equation of Section 8 from which the EM modes excited by a given slanted electric surface current (Section 5) could be determined is presented. The reaction-matrix analysis and the matching of EM boundary conditions near an electric surface current source were shown to be directly related. In Section 10, for comparison to the anisotropic waveguide study under consideration, a Green's function analysis was used to determine the EM fields that would be excited in an isotropic waveguide having EM characteristics similar to that of the anisotropic waveguide. In Section 11 wavenumber and modal orthogonality results were presented and in Section 12 the EM fields corresponding to a specific electric surface current example were calculated for both the anisotropic and isotropic waveguides. In Section 11, six tables of data for the anisotropic and isotropic cases giving numerical examples of the modal wavenumbers that were calculated for the propagating and complex modes of the system (Tables 1 and 2), numerical examples of the modal orthogonality relations that the waveguide modes satisfied (Tables 3 and 4), and numerical examples of the modal power that was transmitted by different propagating modes for anisotropic waveguide case (Table 5) and isotropic waveguide case (Table 6) were presented. In Section 12 for both the anisotropic and isotropic waveguides cases studied, plots of the EM fields near the surface current were shown to meet EM boundary conditions near the electric surface current and near the waveguide walls to a high degree of accuracy. The conservation of complex and reaction power as delivered by and radiated from the electric current source was observed to hold for both the anisotropic and isotropic waveguides studied to a high degree of accuracy.

The characteristics of a slot antenna on a perfectly conducting elliptic cylinder coated by nonconfocal chiral media are investigated. The structure is fed with a line source or plane wave. The analysis is carried out by expressing the fields in and around the cylinder in terms of Mathieu and modified Mathieu functions using the separation of variable and exact boundary value technique. The unknown aperture field is expressed in terms of Fourier series with unknown expansion coefficients. The expansion coefficients are found by applying the boundary conditions on different surfaces and employing the addition theorem and orthogonality properties of the Mathieu functions. For TM and TE cases some numerical results of the antenna gain for co- and cross-polarized waves are presented and discussed.

In finite element analysis, methods for the solution of sparse linear systems of equations usually start out with reordering the coefficient matrix to reduce its bandwidth or profile. The location of pseudo-peripheral nodes is an important factor in the bandwidth and profile reduction algorithm. This paper presents a heuristic parameter, called the "width-depth ratio" and denoted by κ. With such a parameter, suitable pseudo-peripheral nodes could be found; the distance between which could be much close to or even to be the diameter of a graph compared with Gibbs-Poole-Stockmeyer (GPS) algorithm. As the new parameter was implemented in GPS algorithm, a novel bandwidth and profile reduction algorithm is proposed. Simulation results show that with the proposed algorithm bandwidth and profile could be reduced by as great as 33.33% and 11.65%, respectively, compared with the outcomes in GPS algorithm, while the execution time of both algorithms is close. Empirical results show that the proposed algorithm is superior to GPS algorithm in reducing bandwidth or profile.

This paper presents novel approaches for dual-band bandpass filter design utilizing stepped impedance simplified cascaded quadruplet resonators (SI-SCQRs) with slot coupling. A pair of SI-SCQRs forms a cross coupled dual-band filtering path to provide high selectivity passband response, and a slot coupling structure provides SI-SCQRs with another filtering path for improving and controlling the performances of the dual-band filter such as insertion loss and bandwidth. Measured insertion losses are 0.26 dB and 1.2 dB and return losses are better than 16.3 dB and 15.2 dB at the first and second passband frequencies, respectively, with a mid-stopband attenuation around 30 dB.

This paper proposes an enhanced MoM scheme to integrate arbitrary N-port networks into geometry models. This scheme is based on the incorporation of network equations into the standard MoM scheme. The suggested scheme is validated by comparison of the characteristics of a linear amplifier with those obtained by PSPICE. A general application of the enhanced MoM scheme is to handle complicated antenna or EMC problems including various types of network devices. Its potential to handle antenna-amplifier systems, automotive or other EMC problems is outlined.

This paper presents an innovative Direct Radiating Array (DRA) architecture exploiting aperiodic tilings of the plane. In particular, a pinwheel tiling has been selected in order to fix positions of the different radiating sources, which are constituted by properly shaped elements. Such a choice allows to achieve a good aperture efficiency and very low pseudo-grating lobes while using only two different kinds of radiating elements. Preliminary results are shown and discussed with reference to both cases wherein the single tiles are not fully populated and wherein ad-hoc sub-array radiators are used. The very encouraging results achieved leave open the way for further interesting possibilities.

We propose and demonstrate a Multiwavelength Brillouin Bismuth/Erbium Fibre Laser (MBBEFL) with the ability to control the number of wavelength channels generated. A multi-wavelength comb output is obtained using a 7.7 km DCF as a non linear gain medium to generate Stokes wavelengths through the process of Stimulated Brillouin Scattering (SBS). The DCF is pumped by a Raman pump source at 400 mW to lower the dispersion loss and promote the generation of the Stokes wavelengths. A 49 cm long Bismuth based Erbium Doped Fibre (Bi-EDF) is used as an optical amplifier to provide the necessary gain for the Brillouin Pump and also act as the gain medium for the generated Stokes signal.

In this paper we present the results of ellipsometry on a grid of S-shape particles engraved on an epoxy substrate. We show the value of the ellipticity and the tilt angle of the principal axis of ellipsis of the transmitted wave as a function to the angle between the polarisation of the incident plane wave and the principal axis of the particles. The optical axes of the material are found, and the dependence of the absorption to the angle of polarisation is shown. Using a least squares method with the measurements, we calculate the dichroism and the birefringence of the material.

This paper presents a novel multi-objective optimization of printed microstrip-fed monopole antenna for ultra wideband (UWB) applications. Two objective functions are minimized in this design: return loss and transient distortion. Using this method, a set of optimum antennas are achieved instead of a single design. Optimization is performed to reduce distortion in different scenarios. When distortion reduction only in E-plane or in both of E- and H-planes is considered, the obtained set of applying this algorithm dominates reported UWB antennas. Therefore, the obtained result provides a set of proper designs for UWB systems with random physical orientationt.