Gölge Ögücü

A New Spatial Interpolation Algorithm to Reduce the Matrix Fill Time in the Method of Moments Analysis of Planar Microstrip Structures

A new spatial interpolation scheme is proposed to reduce the matrix fill time in the method of moments implementation of planar microstrip structures. The approach is based on the division of the distance between the basis and the testing functions into three, namely near, intermediate and far regions. The matrix entries in the near region are computed directly. The entries corresponding to both intermediate and far regions are evaluated in two steps: (1) choosing an adequate number of sampling points in these regions and computing the associated entries directly and (2) interpolating the remaining entries by using cubic spline or bicubic spline algorithms. To demonstrate the efficiency and accuracy, the technique is applied to a planar microstrip low-pass filter and a microstrip-line fed patch antenna problems. It is shown that the interpolation scheme can result in significant savings with high accuracy.

An interpolation algorithm to reduce the reduced matrix generation time in CBFM

This paper presents an interpolation scheme to reduce the computation time needed to generate the reduced matrix in the Characteristic Basis Function Method (CBFM). The first step in this approach is to identify the observation points and calculate the electric fields at those points that are produced by the induced currents represented by the macro-basis functions called the Characteristic Basis Functions (CBFs). Next, we interpolate the above field values to obtain the same at other points on the structure. Finally, the reduced matrix is formed by testing the electric field with the CBFs. Numerical results are presented to show the accuracy and computational efficiency of the method.

Hybrid Use of AWE With Spatial Matrix Interpolation in the Analysis of Printed Structures

In the asymptotic waveform evaluation (AWE) method, most of the CPU time is spent in the generation of the method of moment (MoM) matrix and its derivatives. In this letter, the hybrid use of the AWE method with the spatial interpolation of the MoM matrix is introduced to reduce the matrix generation time. The numerical results demonstrate the efficiency and the accuracy of the proposed technique.

Closed-Form Green's Functions for Finite Grounded Dielectric Substrate

The approximate closed-form Greens functions of the vector and scalar potentials in the spatial domain are derived for a horizontal electric dipole placed over a finite grounded dielectric medium. The effects of the discontinuity at the edges are considered by including the surface wave reflections from the edges, which are obtained as a function of the incident angle by using the edge admittance concept. The closed-form expressions of the reflection coefficients are then derived by means of the generalized pencil of functions method. The resulting Greens functions are the sum of the contributions of discrete complex images, the incident, and the reflected surface wave contributions.

Effect of 2100 MHz mobile phone radiation on healing of mandibular fractures: an experimental study in rabbits

ABSTRACT Fractures in the maxillofacial region are among the most frequent incidences in patients exposed to trauma. The aim of this study was to evaluate the effect of 2100 MHz electromagnetic radiation on the healing of mandibular fractures in rabbits. The study was carried out on 12 mature male New Zealand rabbits. After producing a left mandibular osteotomy, the fracture was repaired by using a plate screw. The rabbits were divided into two groups – control and experimental. The experimental group was exposed for 3 h daily to a 2100 MHz radiofrequency (RF) for 28 d. Biomechanical, histopathological and radiological tests were performed during the healing of the mandibular bone. According to the biomechanical tests, the energy absorption capacity, toughness and maximum strength of the mandibular bone were increased compared to the control group (6.84 vs. 2.57, 0.135 vs. 0.041 and 22.21 vs. 10.32, respectively). No significant differences between the two groups were found during the radiological assessment. However, the histopathological examination revealed that the fracture healing score was higher in the experimental group when compared to the control group (8.0 vs. 2.75, respectively). In conclusion, the results of this study showed that a 2100 MHz RF radiation positively affected fracture healing.

An algorithm for fast frequency sweep of planar microwave circuits

This paper presents an efficient approach for computing the response of microstrip circuits over a range of frequencies. Computational efficiency is achieved by first constructing the solutions for the current distributions by using the Characteristic Basis Function Method (CBFM) at a few frequency points within the desired band, and then re-using them as independent macro-basis functions at other frequencies within the desired range. Numerical results for a microstrip array, derived by using the direct and CBFM approaches, are included to illustrate the accuracy of the proposed approach.

A new update algorithm in FDTD implementation of anisotropic PML as an absorbing boundary condition

After the introduction of the perfectly matched layer (PML), alternative PML techniques were presented based on the concept of complex coordinate scaling, and uniaxial anisotropic media used as PML. In this paper, an anisotropic PML is used for mesh truncation of the FDTD computational domain. To update the field components, magnetic flux densities are used as dummy variables at intermediate steps, while in Gedney (1996) electric flux densities were used. By our scheme, the number of variables in the FDTD grid in the corner layers is reduced, yielding less CPU time and memory requirement. To compare the two methods, a 2D TE problem is studied. The graphs of error due to reflection from an anisotropic PML are presented.

Array Failure Diagnosis Using Nonconvex Compressed Sensing

The array diagnosis technique based on nonconvex compressed sensing approach is introduced for a uniform linear array. In this sense, lp minimization problem with p <; 1 is proposed for array diagnosis problem and it is solved using a weighted least squares approach. The proposed approach locates the faulty elements using less far-field measurements compared to the standard l1 minimization.

Analysis of printed structures on truncated dielectric slab and finite ground plane

An approximate Greens function for a finite grounded dielectric slab is obtained by using the edge-admittance concept. This Greens function is used in the method of moment solution of the mixed potential integral equation derived for printed structures.