The analytical formulae based on the generalized reflection and transmission coefficient matrices for cylindrically stratified media are used to simulate the borehole effect on multicomponent induction logging responses in various ratios of mud conductivity and formation conductivity and to investigate the tool's eccentricity effect on the responses of coplanar coils and coaxial coils. The simulated data show that the borehole effect and the tool's eccentricity effect on the response of coplanar coils is greater than that on the response of coaxial coils in most cases. Then we give an algorithm for the correction of borehole effect on multicomponent induction logging responses, and the algorithm is based on the above-mentioned formulae to build forward model and regularized Newton method. Finally we correct borehole effect on the apparent conductivity responses of two different models with the algorithm, and the results demonstrate the effectiveness of the algorithm.

As wireless communication applications require more and more bandwidth, the demand for wideband antennas increases as well. One of the most applicable frequency bands is X-band (8-12 GHz). X-band frequencies are used in satellite communications. Radar applications, terrestrial communications and networking, motion detection and etc. Fractal passive Microstrip antennas are simple and novel structures that attract much attraction recently. In this paper, new Microstrip sierpinski modified and fractalized antenna using multilayer structure for achieving wideband behavior in X-band which in 7-10.6 GHz portion overlaps UWB working range. Using fractal defection in patch, multi higher order modes are inspired for coupling a much wider bandwidth. Roggers TMM3 (ε_r = 3.38) is used in this antenna as substrate. Working range for this antenna is from 7.7 GHz to 16.7 GHz (BW = 9 GHz). This antenna has simple structure, small size and 4 resonance frequencies. This fabricated and tested antenna is designed by Ansoft Designer software.

A novel design with low parasitic effect for eliminating the simultaneous switching noise (SSN) in high-speed circuits is proposed by using the aperiodic high-impedance surface (A-HIS) structure. The A-HIS configuration is proposed in this work, revealing suppression of the SSN from 1.1∼1.85 GHz. It is shown that the HIS structure with aperiodic design, the SSN will be effectively suppressed. The undesired resonances of the proposed A-HIS structure are less than that of the conventional structure below 1 GHz. Less undesired peaks will ensure the electromagnetic interference (EMI) and signal integrity (SI). The measured results show very well compared with the conventional periodical HIS structures. The suppression results of the proposed A-HIS structure is checked by both measurement and simulation results. By using this proposed method, the simplicity of the structure is easier to fabricate as well as to route signal lines with a perfect power/ground planes. In addition, the proposed designs provide excellent SSN suppression and good signal integrity (SI) as the conventional structure.

This paper presents an image reconstruction approach based on the time-domain and steady state genetic algorithm (SSGA) for a 2-D perfectly conducting cylinder buried in a half-space. The computational method combines the finite difference time domain (FDTD) method and the steady state genetic algorithms (SSGA) to determine the shape and location of the subsurface scatterer with arbitrary cross section. The subgirdding technique is implemented in the FDTD code for modeling the shape of the cylinder more closely. In order to describe an unknown 2-D cylinder with arbitrary cross section more effectively, the shape function is expanded by closed cubic-spline function instead of frequently used trigonometric series. The inverse problem is reformulatedin to an optimization problem and the global searching scheme SSGA with closedcubic-spline is then employed to search the parameter space. Numerical results show that the shadowing effect for the inverse problem in a half space results in poor image reconstruction on the backside of the cylinder. We propose the two-step strategy to overcome the shadowing effect. It is found that goodimaging quality could be attainedbasedon the proposed strategy.

We have studied the problem of diffraction of an electromagnetic spherical wave by a perfectly conducting finite strip in a homogeneous bi-isotropic medium and obtained some improved results. The problem was solved by using the Wiener-Hopf technique and Fourier transform. The scattered field in the far zone was determined by the method of steepest descent. The significance of the present analysis was that it recovered the results when a strip was widened into a half plane.

Circularly-polarized arrays of cavity backed slot (CBS) antennas are proposed for X-band satellite-earth communications. Two configurations of such circularly polarized arrays are investigated: cross-shaped and square-shaped arrays. Both configurations can produce right-hand circular polarization (RHCP) as well as lefthand circular polarization (LHCP) by proper setting of excitation phase for each element in the array. The finite-difference timedomain (FDTD) method is used to analyze the characteristics of the proposed arrays including the input impedance, S-parameters, radiation pattern, gain and axial ratio. The results show that the proposed array configurations seem very promising and useful for geostationary satellite applications.

We present a novel outdoor-indoor radio wave propagation model. It predicts the electric field envelope Cumulative Distribution Function (CDF) in a room placed near a radio communication emitter. The experimental CDF obtained from the simulation, fits the experimental CDF obtained from a measurement campaign carried out over 19200 sampling points inside the room. The maximum deviation found between these CDFs is less than 1%. Kolmogorov-Smirnov test is employed to analyze the goodness of fit. P-values around 99% are reached. A comparison is made with other classical methods reported in the literature as ray-tracing (RT) and a hybrid method employing finite-difference time-domain (FDTD) together with RT. The proposed model significantly improves the results achieved in those previous investigations. Although we study the problem in three dimensions, the repetitive nature of the algorithm allows us to parallelize the computation process speeding the calculations.

A narrowband trisection substrate-integrated waveguide elliptic filter with coplanar waveguide (CPW) input and output ports is proposed and demonstrated for X-band applications. The filter is formed by incorporating metallized vias in a substrate (RT/Duroid) to create cross-coupled waveguide resonators. The result is an attenuation pole of finite frequency on the high side of the passband, therefore exhibiting asymmetric frequency response. The fabricated trisection filter with a centre frequency of 10.05 GHz exhibits an insertion loss of 3.16 dB for 3% bandwidth and a return loss of -20 dB. The rejection is larger than 15 dB at 10.37 GHz.

In this paper we study on the one hand under delayedacknowledgement (Dly-ACK) mechanisms the option of using ACK Request to improve system robustness, and on the other hand the incorporation of effective retransmission schemes such as hybrid automatic repeat request (HARQ) to improve system throughput for an IEEE 802.15.3 compliant system. An expression of throughput is derived in terms of system parameters and channel conditions. A constrained optimization problem for system throughput is formulated. It is then solved numerically due to the high degree of nonlinearity in the payload size. Our results indicate that under poor channel conditions, the optimal throughput under HARQ scheme is significantly higher than that with ARQ, and larger payload size is proposed to further improve the performance.

A basis function with the traveling wave phase factor, called as the phase extracted (PE) basis functions in this paper, has been applied for efficient solution of scattering from 3 dimensional (3- D) electrically large objects. In this paper, a rigorous derivation is given as a physical insight of this basis function. Defined on large patches and containing propagating wave phase dependence, this kind of bases exhibits very strong directivity, leading to a highly sparsed impedance matrix. Based on such observation, a matrix sparsification technique and an impedance prediction technique have been developed in this paper. The total memory requirement and computational time could be reduced significantly with methods proposed in this paper. The basic requirements of basis functions, i.e., current continuity and absence of charge accumulation are demonstrated, and the excellent behavior of PE basis functions in wideband applications has been summarized briefly. Several numerical examples have been given to show its good accuracy and high efficiency in solving scattering from electrically large complex objects.

To apply the power-law to random mixing composites, the power parameter α is defined as the mean depolarization factor along the external field. The formula of α is derived from the effective medium theory and beta function distribution assumption to study the geometrical influence of scatterers. According to the simulation, we prove that α = 1/3 is fit to the composites of randomly distributed spherical dielectric scatterers, whereas α = 1/2 to the flake-like or cylindrical shaped scatterers. This law can be applied to both dilute and dense condition describing the effective permittivity of random mixing composites and extended to aligned cases, which are meaningful to practical applications.

In this paper, we investigate nonuniformly spaced linear arrays (NUSLA) rigorously. Several important problems in NUSLA design are solved with the combination of the Genetic Algorithm and Conjugate Gradient method (GA-CG). The pattern synthesis for the specified beamwidth and minimum achievable sidelobe level (SLL) are performed and for the first time, the graphs which show the relation between the beamwidth, sidelobe level and number of elements for NUSLA are derived. Also, the NUSLA's pattern for the specified directivity and sidelobe level is synthesized. The graphs showing the behavior of NUSLA relative to the increase of its length for a fixed number of elements are derived. These graphs showthe relations between the directivity and sidelobe level of NUSLA with its length. As a practical design, an array of parallel dipoles is designed for specified beamwidth/sidelobe level or specified directivity/sidelobe level. Furthermore, a novel Neural Network based model for the NUSLA is presented for the rapid and accurate computation of Sparameters. The computed S-parameters are used for the computation of coupling among elements. Then the GA-CG method can adjust these values in the synthesis process to achieve desired pattern and bearable coupling among elements.

This paper presents a new design of a compact patch antenna based on the slot matching concept. Switches are integrated with the previously inserted slots into the patch antenna to enhance the performance. The newly designed antenna is a multi-wideband antenna. It is able to achieve a return loss less than -9.54 dB and VSWR≤2 in more than four frequency bands in the range from 2 to 5GHz

This paper proposes the application of the Wiener filter in an adaptive manner in speech enhancement. The proposed adaptive Wiener filter depends on the adaptation of the filter transfer function from sample to sample based on the speech signal statistics (mean and variance). The adaptive Wiener filter is implemented in time domain rather than in frequency domain to accommodate for the varying nature of the speech signal. The proposed method is compared to the traditional Wiener filter and the spectral subtraction methods and the results reveal its superiority.

A new iterative technique based on the T-matrix approach is proposed for the electromagnetic scattering by dielectric cylinders, in particular cylinders with large aspect ratios. For such cases the conventional T-matrix approach fails. We use hypothetic surfaces to divide a cylinder into a cluster of N identical sub-cylinder, for each the T matrix can be directly calculated. Since any two neighboring subcylinder are touching via the division interface, the conventional multiscatterer equation method is not directly applicable. The coupling among sub-cylinder and boundary conditions at the interfaces are taken care of in our approach. The validity of the proposed method is demonstrated through agreement between theoretical predictions and numerical simulations as well as measurements for scattering from dielectric circular cylinders with finite length. The results clearly demonstrate that the new iterative technique can extend regular T-matrix approach to solve cylindrical cases with large aspect ratio.

In the planning and design of microwave communication links, the structure of the radio refractive index in the lower part of the atmospheric boundary layer is very important. In this work, measurements of atmospheric pressure, temperature and relative humidity were made in Akure (7.15^oN, 5.12^oE), South Western Nigeria. Wireless weather stations (Integrated Sensor Suite, ISS) were positioned at five different height levels beginning from the ground surface and at intervals of 50m from the ground to a height of 200m (0, 50, 100, 150 and 200 m) on a 220m Nigeria Television Authority TV tower at Iju in Akure North Local Government area of Ondo State. The measurement of the atmospheric variables was made every 30 minutes everyday. The study utilized the data for the first year of measurement (January-December 2007) to compute the radio refractivity and its refractivity gradient in Akure. From these parameters, the vertical distributions of radio refractivity are then determined. The results obtained show that the propagation conditions have varying degree of occurrence with sub-refractive conditions observed to be prevalent between January-July while Super-refraction and Ducting were observed mostly between August-December.

A new numerical method is presented for the design and optimization of linear arrays of nonuniformly spaced longitudinal slots on the broad wall of rectangular waveguides, based on the Method of Least Squares (MLS). Elliott's design theory for travelling-wave-fed slot arrays is extended to nonuniformly spaced slots. As a common approach in MLS, an error function is formulated according to the design goals (namely the input impedance matching and pattern synthesis) and then minimized with respect to the design parameters (namely slot lengths, offsets, spacings and excitations). Having the slot parameters, one can design a linear slot array which accounts for the desired input impedance matching and array pattern. This approach has the advantage of combining the ``nonuniform pattern synthesis'', which includes the external mutual coupling and element pattern of slots, with ``impedance matching'' and ``calculation of the array parameters''. This procedure increases the design speed as well as synthesizing any desired pattern. The MLS design results and those obtained by HFSS simulation software are in good agreement and verify the accuracy of the proposed method.

This paper presents the calculations of transmission line loss factor by extracting from the Q-factor measurement of the quarterwavelength open stub resonators over the designed frequency and other resonant frequencies. A comparison of the loss factor of the design frequency with other resonant frequencies of each of the stub's quarter-wave resonances is provided in this paper. The radiation and discontinuity losses are undesirably included in the unloaded Q-factor measurement andit shows that the unloadedQ-factor is not repeatable at different designed frequency. The implementation of the loss factor measurement by quarter-wavelength open stub resonators is becoming more andmore important to be consideredwith the increase of using the electronic circuits operating at high frequencies.

The measurement of the field radiated from an antenna placed above a finite ground plane experiences the effects of the field scattered by the edges of the ground plane. A new numerical method to remove these effects from measured data is presented here. It resorts to the image theorem and can be used for both near-field and far-field measurements. A simple and effective algorithm has been developed to apply that method to fields described by means of spherical wave expansion. A numerical validation shows the effectiveness of the method.

This paper reports on an experimental investigation of modes propagating along a conductor-backed slotline: the dominant mode, and the surface leaky mode. The measurement and the numerical experiments performed in the CST Microwave Studio verify theoretical findings of modes obtained by the method of moments applied in the spectral domain. The dispersion characteristic of the dominant mode on the conductor-backed slotline is determined by substituting this line by a flat slotted waveguide.