Particle Swarm Optimization algorithm (PSO) is a popular stochastic searching optimization algorithm to solve complicated optimization problems. The approach of retrieving duct parameters from the sea-surface reflected radar clutter is also known as Refractivity From Clutter (RFC) technique. RFC technique provides the near-real-time duct parameters to evaluate the radio system performance, without adding any hardware. Basic principles of PSO and its applications and RFC technique are introduced. Evaporation duct is retrieved based on RFC technique using PSO. The performance of PSO is validated using experiment data launched at East China Sea, and compared with those of genetic algorithm (GA) and ant colony algorithm (ACA). The results indicate that PSO has the advantages of faster convergence and higher retrieval precision than the other two methods.

A novel microstrip fed ultra-wideband (UWB) antenna with different band rejection techniques is presented in this paper. The antenna consists of a maple-leaf shaped radiator fed by a microstrip line with a finite ground plane on the other side of the substrate. The size of the UWB antenna is 30.5 × 35.5 mm² which is only about 0.3 × 0.35 λ² at 3 GHz. The calculated impedance bandwidth of the proposed antenna ranges from 3 GHz to 14 GHz with relatively stable radiation patterns. Two different techniques have been implemented to achieve band-notch characteristic in the 5.0-6.0 GHz WLAN frequency band. The first one uses an H-shaped slot cut away from the radiating patch while the other one uses two rectangular slits in the ground plane creating defected ground structure (DGS).

The effects of the fibroglandular tissue distribution of the breast on data-independent microwave imaging algorithms are investigated in this paper. A data-independent beamformer is a beamformer whose weights do not depend on the array data and are chosen, based on a channel model, to compensate for path-dependent attenuation and phase effects. The effectiveness and robustness of data-independent UWB beamforming algorithms relies upon two specific characteristics of breast tissue at microwave frequencies: firstly, that there exists a significant dielectric contrast between cancerous tissue and normal healthy breast tissue; secondly, that the propagation, attenuation and phase characteristics of normal tissue allow for constructive addition of the UWB returns using the Confocal Microwave Imaging (CMI) technique. However, two recent studies by Lazebnik et al. have highlighted a significant dielectric contrast between normal adipose and fibroglandular tissue within the breast. These results suggest a much more difficult imaging scenario where clutter due to fibroglandular tissue is a significant concern and that constructive addition of backscattered signals is potentially much more problematic than previously assumed. In this paper, three existing data-independent beamformers are tested on several different breast models, examining the effect of different fibroglandular tissue distribution on the performance of the data-independent imaging algorithms.

A 3D full-wave approach, based on the Foldy-Lax multiple scattering equations, is successfully extended to model massively-coupled multiple vias using differential signaling and shared antipad in high speed vertical interconnects. For the first time, this method has been used and tested on via-pair with shared antipad in multilayered structure. The magnetic frill current source on the port is calculated by using the finite difference method. Banded matrix iterative method is applied to accelerate the finite difference calculation. Numerical example of 15 signal via-pairs and 20 ground shielding vias in 6-layer board demonstrates that this approach is able to model the via-pair with shared antipad and to include all the coupling effects among multiple vias. The electrical performances of different signal driving schemes are provided and discussed. The coupling crosstalk on various via-pairs is compared. The improvement of signal integrity is shown by using differential signaling and shared antipad for via-pair in multilayered structure. The results are compared with HFSS and SIwave in accuracy and CPU. The CPU using Foldy-Lax approach is three orders of magnitude faster than using HFSS, and two orders of magnitude faster than using SIwave. The accuracy of Foldy-Lax is within 2% difference from HFSS up to 20 GHz, and outperforms SIwave in accuracy.

A three-dimensional scattering field Transmission Line Modeling (TLM) algorithm is established to obtain bistatic radar cross sections of frequency dispersive gyromagnetic objects. Starting from the 1D TLM modeling of gyrotropic materials, a scattering field TLM algorithm is derived for 3D calculations. For verification, the bistatic radar cross section results for several gyromagnetic structures are compared with the single frequency computations, where the permittivity and permeability tensors are made of complex constants at a given frequency.

This paper presents a new hybrid finite-difference frequency domain --- mode-matching method (FDFD-MM) for the analysis of electromagnetic wave scattering from configuration of metallic or dielectric cylindrical posts with arbitrary cross-section. In our approach each scatterer is treated as an effective circular cylinder represented by impedance matrix defined in its local coordinate system. In order to obtain the scattering parameters of arbitrary configuration of objects in global coordinate system an analytical iterative scattering procedure (ISP) is applied. This work is an extension of our previously published results, where our consideration were limited to two dimensional (2D) problems with TM excitation. In this paper we extended our analysis to two-and-a-half dimensional (2.5D) problems. The accuracy of the proposed method is presented and discussed. To verify our approach some numerical examples are presented. The obtained results are compared with the results published in literature and the ones obtained from own measurements and commercial software.

This paper presents an analysis about resonance on coupled systems when excited by square waves, generated through experiments using planar and ring coils. Because of the phenomenon described by its transfer function, a sum of responses appear when the square wave frequency increases, which causes a resonance response with high voltage, in several cases, greater than common turn ratio of the transformer. With parallel capacitances inserted on output, the resonance frequency reduction and change of gain is observed. Due to this effect, explanation of how output of Tesla transformer presents high voltage which is shown, and strategies to reach the maximal value on output are proposed.

In this work, a probe fed microstrip antenna design for the implementation of two dimensional arrays with individually fed radiating elements is presented. The performance of the antenna element, both isolated and in a 4×4 fixed array topology, is analysed using ADS and HFSS simulation software. Prototypes of the antenna element and of the array are manufactured and measured for the experimental validation of the design.

Microwave tomography deserves attention in biomedical imaging, owing to its potential capability of providing a morphological and functional assessment of the inspected tissues. However, such a goal requires the not trivial task of solving a non linear inverse scattering problem. In this paper, the factors affecting the complexity of the inverse problem are exploited to trace guidelines aimed at setting the matching fluid, the frequency range and the number of probes in such a way that the dielectric parameters of female breast tissues can be reliably retrieved. Examples, concerning 2D realistic numerical phantoms obtained by NMR images, are given to asses a osteriori the effectiveness of the proposed guidelines.

In this paper, a new technique is proposed for field effect transistor (FET) small-signal modelling using neural networks. This technique is based on the combination of the Mel frequency cepstral coefficients (MFCCs) and discrete sine transform (DST) of the inputs to a neural network. The input data sets to traditional neural systems for FET small-signal modelling are the scattering parameters and corresponding frequencies in a certain band, and the outputs are the circuit elements. In the proposed approach, these data are considered as forming random signals. The MFCCs of the random signals are used to generate a small number of features characterizing the signals. In addition, other MFCCs vectors are calculated from the DST of the random signals and appended to the MFCCs vectors calculated from the signals. The new feature vectors are used to train the neural networks. The objective of using these new vectors is to characterize the random input sequences with much more features to be robust against measurement errors. There are two benefits for this approach: a reduction in the number of neural networks inputs and hence a faster convergence of the neural training algorithm and robustness against measurement errors in the testing phase. Experimental results show that the proposed technique is less sensitive to measurement errors than using the actual measured scattering parameters.

In this paper, we propose a novel genetic algorithm (GA) called immunity GA (IGA) for array pattern synthesis with interference suppression using digital amplitude only control. The IGA is based on crossover evolution where the crossover operator is a variant of the known GA operator. A new formulation of the array factor transform for a specific number of elements N is expressed by a discrete cosine transform (DCT) with pre-computed DCT matrix. Evaluating thousands of candidate solutions generated by the IGA using the precomputed DCT matrix will result in a high speed computation. This high performance allows us to find a good approximation of the absolute minimum SLL of synthesized arrays with digital amplitude control. Simulation results show the effectiveness of this new algorithm for pattern synthesis with low SLL and null steering.

A sensing device comprising of a parabolic reflective surface and a bi-conical metal structure is proposed to focus terahertz energy on sample material in the sensing zone to create a strong interaction between terahertz signals and the sample under test. The signal enhancement by the sensing device is confirmed by modeling and simulation results. The proposed sensor is applied to investigate the polarization dependency of a split ring resonator (SRR), and spectral signatures of the SRR under different incident wave polarizations are obtained.

A compact ultra-wideband (UWB) planar monopole antenna is proposed. Multiple trapezoids and a semicircle are connected to form the patch of the monopole. The compact antenna not only has low return loss, but also has omni-directional radiation pattern over the ultra-wide bandwidth. Both the simulated and measured results are given and they are in reasonable agreement. The group delay, which is an indication of linearity between two proposed antennas, is also good. Parametric analysis on the patch shape has been performed to give some helpful design information.

This paper presents a microwave imaging method for malignant tumors using flanged parallel-plate waveguide probes, based on detecting the significant difference in complex permittivity that exists between the tumor and its surrounding tissues. The presence of a tumor is identified from a frequency scan of the resonant scattering parameters. The tumor location can be estimated using S₂₁ obtained at various positions of the region of concern, e.g. human organ, biological tissues, etc., while another probe transmits at the position yielding maximum resonating response of S₁₁, with triangulation technique. A tumor can also be distinguished from clutter items. With specific reference to the detection of breast cancer, simulation studies are presented to verify the performance of this probe and the proposed detection technique.

It is known that with restrictions on the type of the constitutive equations, Maxwell's equations in non-uniform media can sometimes be reduced to two 2nd order differential equations for 2 scalar quantities only. These results have previously been obtained in two quite different ways, either by a "scalarization of the sources", where the relevant scalar quantities are essentially vector potential components, and the derivation was limited to isotropic media, or alternatively by using the "scalar Hertz potentials", and this method has been applied to more general media. In this paper it is shown that both methods are equivalent for gyrotropic media. We show that the scalarization can be obtained by a combination of transformations between electric and magnetic sources and gauge transformations. It is shown that the method based on the vector potential, which previously used a non-traditional definition of the vector potentials, can also be obtained using the traditional definition provided a proper gauge condition is applied and this method is then extended from isotropic to gyrotropic media. It is shown that the 2 basic scalar Hertz potentials occurring in the second method are invariant under the source scalarization transformations of the first method and therefore are the natural potentials for obtaining scalarization. Finally it is shown that both methods are also equivalent with a much older third method based on Hertz vectors.

A novel Competitive Algorithm of Simulating Natural Tree Growth is presented in this paper. It searches from a simple status to complex ones and is characterized by quick convergence. The algorithm has been used to design a novel tree-shaped antenna which has an appreciably larger gain of 2\,dBi more than traditional dipole antenna with a reflector of the same size. A prototype antenna has been fabricated and tested. A good agreement between the calculated and measured results verifies the feasibility of the algorithm.

An open-ended waveguide probe has been adapted for complex permittivity determination and hence mechanical property inspection of cement-based materials. The probe uses amplitude-only reflection measurements at different frequencies for this goal, which is suitable for industrial based applications when cost and ease of use are important considerations. We have derived expressions by taking into account of the wavematerial interaction. The reference plane for measurements is set inside the waveguide to measure solely the reflected signal of the dominant mode. It is shown that the measurement results are in good agreement with the theory.

In this paper, we study metamaterial-based transparent shells, which are invisible to electromagnetic waves and fields. More general topics, including material loss, material discretization and far field distribution etc. are covered in order to facilitate possible realization. We design and analyze the transparent shells using optical transformation. Unlike the widely-studied cloaking devices which make the objects inside invisible, the transparent shells physically cover and shield the devices inside without sacrifice of their electrical performance since they are transparent to incoming electromagnetic waves. Due to the simple constitutive parameters, these transparent structures could be realized using artificial metamaterials in a wide frequency band, which may have wide applications in civil and military areas.

In this paper, a method to broaden the beamwidths of a crossed dipole antenna is proposed. By introducing four parasitic strips around the crossed dipole antenna, the beamwidths of the crossed dipole antenna in the vertical plane are broadened effectively, making the patterns uniform over a wide frequency band. An L-band prototype, operating in the frequency range from 1.1 GHz to 1.6 GHz, is fabricated and tested. The simulated and measured results show that the beamwidths at lower frequencies are broadened and uniform radiation patterns over the whole operating frequency band are obtained, making the crossed dipole suitable for wideband marine GPS (Global Positioning System) applications.

A simple, closed-form expression for the time-domain reflection coefficient for a pulsed TE10-mode wave incident on a dielectric material discontinuity in a rectangular waveguide is presented. This formula may be used to represent the transient field reflected or transmitted by a dielectric-filled waveguide section, which is useful in material characterization routines. An exponential function approximation to the reflection coefficient is presented, and the formula is validated both numerically and experimentally.