This paper describes the design of a three-dimensional (3D) finite-difference time-domain (FDTD) simulation software for printed circuit board (PCB) modeling. The flow, the dynamics and important algorithms of the FDTD simulation engine will be shown. The software is developed using ob ject-oriented programming (OOP) approach, to enable code reuse and ease of upgrade in future. The paper begins by looking at how a 3D PCB structure is created using cubes, and proceed to show the inclusion of various lumped components such as resistors, capacitor, inductor and active semiconductor components into the model. The architecture of the FDTD simulation program is then carefully explained. Finally a few sample simulation examples using the software will be illustrated at the end of the paper.
In 2002, the MASAR (Malaysian Airborne Synthetic Aperture Radar) pro ject was initiated at Multimedia University (MMU), in collaboration with the Malaysian Centre for Remote Sensing (MACRES). The main ob jective of this pro ject is to construct an instrument for earth resource monitoring in Malaysia. The proposed SAR system is a C-band, single polarization, linear FM radar. This paper outlines the ma jor design issues and considerations for MASAR. In particular, the design and construction of the microwave system, microstrip antenna, and a high-speed data recording system are described. The SAR processing algorithm which incorporates motion compensation capability for high resolution image generation is also outlined.
Laplace's equation is solved analytically for lossy shielded coupled microstrip transmission lines. The solution is represented in fourier series expression and is being used to determine the capacitance and conductance matrices of the structure. The method is examined using some examples and then some results are obtained.
This paper studies solitons and its perturbations that is governed by the generalized nonlinear Schrödinger's equation with non-Kerr law nonlinearity. The quasi-stationarity is applied to the non-Kerr law case and an approximate solution is obtained. A few special cases of the non-Kerr law nonlinearity are considered, as examples, with the nonlinear damping type perturbation.
The finite difference time domain (FDTD) method is used to analyze a practical ground penetrating radar (GPR) antenna system operating above lossy and dispersive grounds. The antenna is of the resistor-loaded bow-tie type and the analysis is made for two known soil types, namely Puerto Rico and San Antonio clay loams. The soil is modeled by a two term Debye model with a static conductivity and it is matched to the mentioned soils by using curve fitting. The FDTD scheme is implemented by the auxiliary differential equation (ADE) method together with the uniaxial perfectly matched layer (UPML) absorbing boundary conditions (ABC). In order to model a real GPR environment, ground surface roughness and soil inhomogeneities are also included. The effect of soil properties on the GPR response and antenna input impedance is presented. Thus the ability to detect buried metal and plastic pipes is investigated.
An efficient algorithm combining the fast multipole method (FMM) and the characteristic basis function method (CBFM) for analysis of scattering from microstrip antennas over a wide band is introduced in this paper. In the hybrid algorithm, the characteristic basis function method is used to construct the currents on microstrip antennas by using characteristic basis functions (CBFs) which are constructed from the solution vectors at several samples using the singular value decomposition (SVD), thus obviating the need to repeatedly compute using a computational electromagnetic code and repeatedly solve a large method of moments matrix system at each point within the wide band of interest. The fast multipole method is used to obtain the solution vectors at these samples and speed up the matrix-vector product in the characteristic basis function method (CBFM). The resultant hybrid algorithm (FMM-CBFM) eliminates the need to generate and store the usual square impedance matrix and repeatedly use an iterative solver at each point and thus leads to a significant reduction in memory requirement and computational cost. Numerical examples are given to illustrate the accuracy and robustness of this method.
In this paper, analytical formulas have been derived for the electromagnetic field generated by a horizontal electric dipole inside high lossy half-space coated with a dielectric layer. This problem is corresponding to the electromagnetic field generated by a horizontal antenna in a submarine under an ice layer, or the measurement of the conductivity of the oceanic lithosphere with a horizontal antenna as the source, and a layer of sediment on the sea floor. These formulas obtained for the electromagnetic field can be employed to calculated the total field including the lateral-wave term and the trapped-surface-wave term. Because the wave number of the trapped-surface-wave term is different from that of the lateral-wave term, the interference appears in the total field. Additionally, this paper has presented the approximative formulas for a thin dielectric layer, which can be used for the communication in low frequencies region.
A new scheme for high-speed electro-optical conversions with potential application to data communication is investigated. As the core of investigation, a ring model utilizing relativistic electrons is introduced and the operating characteristics such as coupled wavelengths, gain and power are derived for a circular type of interaction. Advantages are addressed and practical challenges associated with the realization of this conceptual scheme are discussed in light of advances in fundamentally similar relativistic free electron lasing schemes.
The variational principle is employed to study chirped solitons that propagate through optical fibers and is governed by the dispersion-managed nonlinear Schrödinger's equation. Here, in this paper, the polarization-preserving fibers, birefringent fibers as well as multiple channels have been considered. The study is extended to obtain the adiabatic evolution of soliton parameters in presence of perturbation terms for such fibers. Both Gaussian and super-Gaussian solitons have been considered.
This paper presents a novel approach for the efficient solution of large-scale periodic microstrip antenna arrays using the newly introduced characteristic basis functions (CBFs) in conjunction with the method of moments (MoM) based on the conventional RWG basis functions. The CBFs are special types of high-level basis functions by incorporating the physics of the problem, defined over domains that encompass a relatively large number of conventional subdomain basis functions. The advantages of applying the CBF method (CBFM) are illustrated by several representative examples, and the computation time as well as the memory requirements are compared to those of conventional direct computation. It is demonstrated that the use of CBFs can result in significant savings in computation time and memory requirements, with little or no compromise in the accuracy of the solution.
Classical assesssment of the received power by a radar leads to a decorrelation of many relevant phenomena (i.e. propagation, backscattering), which may introduce modelling errors notably in the presence of large target with respect to the wavelength. To overcome this limitation, a new hybrid approach is proposed. It combines a method of propagation calculation (the parabolic wave equation) with a method of scattering calculation (the EFIE solved by a method of moment approach) and an application of the reciprocity principle (the power coupling factor). Each method constituting the hybrid approach is described; the example of a large cargo is chosen and its apparent RCS is evaluated above the sea at low frequency. The results are discussed, studying the influence of the different parts of the boat on the apparent RCS.
Lack of knowledge prevents us from exactly calculating the behavior of electromagnetic fields. We study two extremes in this respect: scattering against randomly distributed particles (no idea of the position or orientation of the scatterers), and random errors in antenna technology (small deviations from what we think are the proper parameters). Random variables are used to model our lack of knowledge, and far field expressions are studied. Using the concept of characteristic functions from probability theory, results for arbitrary probability distributions are obtained. We explain an anomaly in the forward scattering direction in single scattering theory, present simple formulas for the directivity, side lobe level, and beam efficiency for a general array antenna with random errors, and a simple formula for the scattering coefficient from a general frequency selective structure with random errors.
In this paper a novel method of generation of ultra-low resonance in a microstrip disk resonator is presented. The disk resonator is loaded with series L-C circuit across a selective location in the disk via a thin shorting pin. It is shown that in loaded disk resonator, the lowest resonance observed is in VHF range whereas the unloaded disk had a fundamental resonance at 1.76 GHz. This resonance is slightly offset from the series resonant frequency of L-C circuit. and it depends on the disk radius as well. Using IE3D, a commercial MoM solver, the said structure is simulated. The experimental results agree well with the simulated results. A closed form expression for computing the resonant frequency is given.
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