A new detection algorithm based on constant false alarm rate (CFAR) algorithm, which is applicable to radar image with homogeneous background, is proposed in this paper. This algorithm firstly estimates the parameters of the probability model of background accurately. Then a conventional global CFAR is done using the results of estimation. In estimating the parameters of background, a novel iterative algorithm, which is self-adaptive, is given. The simulation results demonstrate that the performance of the proposed detection algorithm is very close to the theoretical optimum value, and better than CA-CFAR, GO-CFAR and SO-CFAR.

Compact and simple bandpass filter (BPF) structure using microstrip isosceles triangular patch resonator (ITPR) is proposed. The new filter design technique is based on two main ideas: Firstly, cutting the corners of the triangular structure, to make the filter size more compact. Secondly, etching slit in staircase form near the base of the triangle in order to improve the filter performances. The proposed filter was designed and fabricated on Taconic CER-10 substrate with a relative dielectric constant of 10 and a thickness of 0.64 mm using standard photolithography process. The final dimension of the proposed filter is measured at 5.7 mm×7.6 mm. Measured S-parameters showed that the filter achieves a 3-dB fractional bandwidth of 55% at center frequency of 10.36 GHz, with measured insertion loss of 2.08 dB and measured return loss better than 10 dB. The measured results are in good agreement with the simulated results.

We present an iterative inner-outer scheme for the efficient solution of large-scale electromagnetics problems involving perfectly-conducting objects formulated with surface integral equations. Problems are solved by employing the multilevel fast multipole algorithm (MLFMA) on parallel computer systems. In order to construct a robust preconditioner, we develop an approximate MLFMA (AMLFMA) by systematically increasing the efficiency of the ordinary MLFMA. Using a flexible outer solver, iterative MLFMA solutions are accelerated via an inner iterative solver, employing AMLFMA and serving as a preconditioner to the outer solver. The resulting implementation is tested on various electromagnetics problems involving both open and closed conductors. We show that the processing time decreases significantly using the proposed method, compared to the solutions obtained with conventional preconditioners in the literature.

An analytical model for the description of the electromagnetic waves propagation in a layered medium consisting of sectors having the locally spherical symmetric distributions of refractivity is introduced. Model presents analytical expressions for the phase path and refractive attenuation of electromagnetic waves. Influence of the inclined ionospheric layers is a cause of the ionospheric interference in the trans-ionospheric communication satellite-to-satellite or satellite-to-Earth links. It follows from the analytical model that the identification of the inclined ionospheric layers contributions and measurements of their location and parameters may be fulfilled by use of comparative analysis of the amplitude variations and the eikonal acceleration of the RO signals. Model is applied to analysis of the radio occultation (RO) signals propagating through the ionosphere and atmosphere. Model explains existence of the ionospheric contributions in the RO signals at the altitudes 30-90 km of the RO ray perigee as connected with influence of a tangent point in the ionosphere where the electron density gradient is perpendicular to the RO ray trajectory. By use of the CHAMP RO amplitude data a description of different types of the ionospheric contributions to the RO signals is introduced and compared with results of measurements obtained earlier in the communication link satellite-to-Earth at frequency 1.5415 GHz of MARSAT satellite.

An approach based on acoustics and its theoretical analogies to electromagnetism is used in the present research to study the detection of the acoustic wave energy radiated by the thermal random motion of material particles of the brain during activation or caused by pathology. Pressure and particle velocity are calculated in analytical mathematical forms for the case of human brain monitoring, which can be implemented by a prototype passive acoustic brain monitoring system (PABMOS). Representing theoretically the configuration of this approach, a sphere is used to model the human head and an internal point source in order to simulate potential pressure alterations due to intracranial abnormalities or local functional activations. Finally, numerical results concerning the particle velocity (pressure field distribution) at the surface of the head model, which can implicitly be measured by the suitable piezoelectric sensors of the system, for arbitrary positions of the internal source, are presented.

In this paper, we introduce a different approach of previously reported method to determine absorption and emission cross-sections (δ_a and δ_e), and dopant concentration in Erbium doped optical fibers (EDOFs) with low background loss (α). We call this new method as variant input single cutback method (VISCM). There is technical similarity between VISCM and conventional cutback method (CCM) for determination of cross-sections, but in former pump and signal powers are not used together. We numerically verify the effect of different parameters such as input power, background loss, and EDOF amplifier cutback length on the cross-sections using VISCM and CCM. We also present the simulation results of maximum gain and optimum length using obtained cross-sections by two methods. We show that the VISCM presents more accuracy than that of CCM in any conditions. In the presence of α, both CCM and VISCM give not actual but pseudo values for the δ_a and δ_e. Using pseudo parameters values obtained by VISCM for α < 10 dB/km, the error of maximum gain and optimum length of designed EDOF is shown negligible.

A novel multi-wavelength fiber optical parametric oscillator (MW-FOPO) with a ring cavity structure is proposed. In the ring cavity of the MW-FOPO, a Sagnac loop filter which is formed by a 3-dB optical coupler, a polarization controller and a segment of polarization maintained fiber is used as the comb filter, and a segment of highly nonlinear fiber is used as the gain medium. Multi-wavelength lasing of the MW-FOPO with a wavelength spacing of about 0.8nm is achieved and its power stability at room temperature is demonstrated by measuring peak power fluctuation within 42 minutes for 5 lasing wavelengths. The output spectrum of the MW-FOPO covers a large wavelength region from 1500nm to 1610 nm. A comparison of the output spectra between the MW-FOPO and the multi-wavelength Erbium-doped fiber laser is also presented.

In this paper, a new calculating method for the characteristic impedance (Z_c) of transmission lines with perturbation and periodic modified ground structure (MGS), such as defected ground structure (DGS), photonic bandgap (PBG), and substrate integrated artificial dielectric (SIAD), is discussed. The proposed method is based on simple transmission line theories and proper related equations. The previous method to find Z_c of transmission lines with MGS or perturbation produces the fluctuating Z_c value depending on frequency, while the proposed method results in a constant value without frequency-dependence. As examples, several microstrip lines with DGS, PBG, and SIAD structure are simulated and measured, and their Z_c values are calculated from S-parameters by the previous and proposed methods. It is shown that the Z_c obtained by the proposed method is much more reliable than that calculated by the previous method for all examples.

A complete study for the deployment of a wireless sensor network in a forest based on ZigBee is presented in this paper. First, due to the lack of propagation models for peer to peer networks in forests, propagation experiments were carried out to determine the propagation model. This model was then used for planning and deploying an actual wireless sensor network. The performance of the network was compared with the expected theoretical behavior to extract some conclusions that are presented in the paper. Finally, some general conclusions, as an estimation of the minimum number of routers necessary to cover a given area, are extracted from the experiments and presented in the paper.

This paper presents modeling of the complex permeability spectra, fabrication and a wide frequency range characterization of a toroidal LTCC ferrite sample. A commercial ferrite tape ESL 40012 is used, and standard LTCC (Low Temperature Co-fired Ceramic) processing has been applied to the sample fabrication. The characterization was performed using a short coaxial sample holder and a vector network analyzer in the frequency range from 300 kHz to 1 GHz, at different temperatures. Using the model of the complex permeability spectra dispersion parameters of ferrite LTCC material has been determined for various temperatures. Characteristics of test samples are compared with modeled results and commercially available toroid made of similar NiZn ferrite material.

The diffraction of a uniform unit-amplitude E-polarized plane wave is considered in the case of its normal incidence on a strip periodic metal grating placed on the anisotropic hyrotropic ferromagnetic half-space boundary. The Dirichlet boundary conditions on the grating strips, the medium interface conjugation conditions, the Meixner condition that the energy is finite in any confined volume and the radiation condition are applied, and the boundary value diffraction problem in terms of Maxwell's (Helmholtz) equations is equivalently reduced to the dual system of functional equations with exponential kernel. The system is shown to be the Riemann-Hilbert problem in analytic function theory with the conjugation coefficient differing, in general, from ``-1" and dependent on the incident wave frequency. An analytical regularization procedure based on the Riemann-Hilbert boundary value problem solution with the following use of the Plemelle-Sokhotsky formulas is suggested, resulting in the system of linear algebraic equations of the second kind with a compact operator. For vthese systems, the truncation technique possibility has been shown. Calculation algorithms and simulation packages in terms of C++ language have been developed. As a result, the reflection coefficient performance has been studied over sufficiently wide ranges of frequency and constitutive and geometrical parameters of the electrodynamical systems of interest. The frequency bands of the reflection coefficient resonant behavior have been established and examined. A numerical analytical model of these resonances has been proposed.

Applying a sparse constraint on the beam pattern has been suggested to suppress the sidelobe level of a minimum variance distortionless response (MVDR) beamformer. In this letter, we introduce a weighted sparse constraint in the beamformer design to provide a lower sidelobe level and deeper nulls for interference avoidance, as compared with a conventional MVDR beamformer. The proposed beamformer also shows improved robustness against the mismatch between the steering angle and the direction of arrival (DOA) of the desired signal, caused by imperfect estimation of DOA.

An ultra wideband (UWB) coplanar waveguide (CPW) fed rectangular monopole antenna, which is of band notched characteristic for Wireless Local Area Network (WLAN), Worldwide inter-operability for Microwave Access (WiMAX) and the C-band satellite communications, is proposed, fabricated and measured. In order to obtain the desired dual band rejections, a piece of pentagonal slotline and a pair of inverted L-shaped stubs are loaded on the CPW fed rectangular monopole antenna of enhanced impedance bandwidth. The antenna is printed on the FR4 substrate of 40 mm (width) × 41 mm (length) × 0.5 mm (thickness), and is optimized by ANSOFT HFSS. A prototype is fabricated according to the optimized parameters values, and the antenna characteristics are measured. The results show that the antenna is of UWB characteristic and exhibits band rejection of 3.2-4.25 GHz and 5.1-6.15 GHz, which covers WLAN, WiMAX, and C-band satellite communications.

This paper proposes a technique of the source location estimation with the modulated scattering technique (MST) for indoor wireless environments. The uniform circular scatterer array (UCSA) that consist of five optically modulated scatterers as array elements and a dipole antenna at the center of the UCSA is employed for estimating a source location from the impinging signal. In contrast with a conventional uniform circular array (UCA), the proposed method using the MST needs only one RF path. Also, the plane-wave assumption of the impinging signal is not necessary for an array signal processing because the proposed method is based on a phaseless measurement. Therefore, the proposed method can be applied in short-range LOS and NLOS environments that the plane-wave signal cannot be formed. A source location is estimated by using a simple estimation algorithm based on the power difference of the scattering signals modulated by two scatterers on the UCSA. The power difference is caused by different propagation losses between a source and each scatterer. The performance of the proposed method is demonstrated by measuring the angles of the incoming signals in the anechoic chamber and by comparing the estimated angles with the simulated results.

An efficient technique for the analysis of scattering by uniaxial anisotropic objects is presented. The technique is based on the method of higher order MoM of the surface integral equations. This higher order MoM solution uses the higher order hierarchical basis functions which are based on the modified Legendre polynomials. Numerical results are given to demonstrate that the higher order hierarchical basis functions are more accurate and efficient in the calculations of uniaxial anisotropic objects scattering problem than the low-order basis function.

Time-modulated antenna arrays attracted the attention of researchers for the synthesis of low/ultra-low side lobes in recent past. This article proposes a Multi-objective Optimization (MO) framework for the design of time-modulated linear antenna arrays with ultra low maximum Side Lobe Level (SLL), maximum Side Band Level (SBL) and main lobe Beam Width between the First Nulls (BWFN). In contrast to the conventional optimization-based methods that attempt to minimize a weighted sum of maximum SLL, SBL, and BWFN we treat these as three different objectives that are to be achieved simultaneously and use one of the best known Multi-Objective Evolutionary Algorithms (MOEAs) of current interest called MOEA/D-DE (Decomposition based MOEA with Differential Evolution operator) to determine the best compromise among these three objectives. Unlike the single-objective approaches, the MO approach provides greater flexibility in the design by yielding a set of equivalent final solutions from which the user can choose one that attains a suitable trade-off margin as per requirements. We compared time-modulated antenna structures with other linear array synthesis such as the excitation method and the phase-position synthesis method on the basis of the approximated Pareto Fronts (PFs) yielded by MOEA/D-DE and the best compromise solutions determined from the Pareto optimal set with a fuzzy membership-function based method. The final results obtained with MOEA/D-DE were also compared with the results achieved by three state-of-the-art single objective optimization algorithms. Our simulation studies on three significant instantiations of the design problem reflect the superiority of the MOEA-based design of time-modulated linear arrays.

A rigorous analytical procedure is developed that allows the exact evaluation of the complete integral representations for the time-harmonic electromagnetic (EM) field components generated by a vertical magnetic dipole (VMD) lying on the surface of a flat and homogeneous lossy half-space. Closed-form expressions for the radial distributions of the EM field components induced on the surface of the half-space are provided in terms of exponential functions and modified Bessel functions. Such expressions make it possible to overcome the limitations implied by the previously published quasi-static solutions, which are valid only in the low-frequency range. Numerical results are presented to show where the quasi-static approximations deviate from the exact solutions for a given homogeneous medium as frequency is changed. The computed amplitude and phase frequency spectra of the EM field components demonstrate that the quasi-static approach fails at frequencies higher than 1 MHz, and that, in particular, it leads to underestimating the EM field strength. Finally, it is also shown that at a frequency equal to or greater than 10 MHz excellent results in terms of accuracy may be obtained by using the high-frequency asymptotic forms of the exact solutions.

This paper presents a novel coplanar waveguide (CPW) dual passband filter using the split-modes of the loaded stub square loop resonators. With the CPW feeding line, two microstrip stub resonators built on the rear sides are used to suppress the first even resonance. The modes splitting characteristics of the proposed structure are analyzed. A dual passband filter covering center frequencies of 4.8 GHz and 6 GHz is fabricated to verify the validity of the methodology. Good agreement between simulated and measured results is demonstrated.

A racket-shaped slot ultra-wideband (UWB) antenna coupled with parasitic strips for band-notched application is proposed in this paper. By attaching a pair of parasitic rectangular strips on the bottom of the substrate, a band-notched characteristic is well realized. Adjusting the length, width of the two strips and the distance between them, a band-rejected filter characteristic at the WLAN operation in 5.15-5.825 GHz frequency band can be obtained. The fabricated antenna has a small size of 20×37.5 mm². Good agreement is achieved between the simulated and measured results, both of which show an ultra-wide impedance bandwidth from 3.1 to 10.6 GHz for VSWR less than 2 except the bandwidths of 5.15-5.825 GHz for WLAN.

In this paper the characteristic equations of the E^y_mn and E^x_mn modes of the dielectric rectangular waveguide have been derived using the mode matching technique. No assumptions have been taken in the derivations which have been straight forwardly done. Two ratios have been introduced in the characteristic equations and the new set of characteristic equations thus obtained are then plotted and graphical solutions are obtained for the propagation parameters assuming certain numerical values for the introduced ratios. The results have then been compared to those obtained by Marcatilli and Goell for rectangular dielectric waveguides. The comparisons depict a good agreement in the three methods at frequencies well above cut-off.