Investigation of Patch Antennas Based on Embedded Multiple PBG Structure

In this paper, the characteristics of a small antenna using an H-shaped microstrip patch are studied. Significant reduction of antenna size can be realized when the H-shaped patch is used instead of the conventional rectangular microstrip patch antenna. The theoretical analysis is carried out based on the finite-difference time- domain (FDTD) method. The FDTD programs are developed and validated by available measurement results. The effects of various antenna parameters on the resonant frequency and radiation patterns are shown. Several design curves are presented, which are useful for practical antenna design. The electric current distributions on the patch and those on the ground plane are described, together with the results illustrating the electric field distributions under the patch. This antenna is suitable for applications where small size and broad beamwidth are required.

In the present work, the analysis and design of a line fed two-layers coupled rectangular patch antenna is presented. The return loss, the input impedance, and the radiation pattern of the proposed structure are determined using the finite difference time-domain (FDTD) method. The effect of changing the air gap layer thickness between the two layers of that antenna is studied. The results obtained by the FDTD method are found to be in good agreement with the published data. Also it is found that as the air gap layer thickness is increased the 10-dB return loss bandwidth is decreased while the 3-dB beamwidth of that antenna is increased.

The characteristics of a dual-frequency compact antenna, which uses a rectangular microstrip patch with a shorting pin, are studied. Compared with the conventional rectangular patch antenna, this antenna can achieve both a significant reduction of antenna size and a dual-frequency operation with a single feed. A detailed parameter study is performed. The theoretical analysis is based on the finite-difference time-domain (FDTD) method. The FDTD codes are developed and validated by measurement results. One antenna has been designed and fabricated, and the comparisons between the measured results and the calculated results are provided. The effects of several antenna parameters on two resonant frequencies, frequency ratio, and radiation pattern characteristics of the antenna have been analyzed and compared. The results of the return loss are also presented. It is shown that various frequency ratios (2.82-4.23) can be obtained by varying the design parameters of this antenna. Several design curves are also presented.

Various methods are available at the disposal for computing the solution of electromagnetic problems expeditiously. Electromagnetic scattering problems can be classified into two broader categories named as surface and volume problems. These problems can be solved using differential and integral equations. Differential equations based techniques use Finite Element Method (FEM) and Finite Difference Time Domain (FDTD) methods and major integral formulation based technique is Method of Moment (MOM). Any set of linear equations for a given system can be solved using direct or iterative methods. Direct solvers confront many computational complexities and use large amount of memory while iterative solvers reduce computational complexities and use less amount of memory. In this research work some integral equations based solver schemes such ass Finite Element Method (FEM), Finite Difference Time Domain Method (FDTD) and Method of Moments (MOM) for surface and volume scatters are discussed and results are compared. The comparison is with respect to complexity and memory requirements for different solution schemes.

New version of FDTD with GFM program in Schwarzschild space–time

The finite difference time domain (FDTD) method has been proposed and used for sound field simulation. To reproduce actual sound wave propagation in sound field simulations, it is necessary to apply the radiation characteristics. With the FDTD method, radiation characteristics can be applied by setting sound pressure in a dense grid arrangement. However, conventional techniques for capturing radiation characteristics use a sparse array of microphones and are considered insufficient for the FDTD simulation. Furthermore, the technique required to apply captured acoustic signals in a dense grid arrangement with the FDTD method has not been considered. In this paper, we propose a novel hardware and software system that captures the radiation characteristics for a dense grid arrangement and applies them to the FDTD method, while controlling the sound wave propagation with the non-propagation region. The proposed system produces the average differences from measured values of sound pressure, propagation time, center frequency, and log-spectral distortion of 1.8 dB, 0.04 ms, 700 Hz, and 3.5 dB, respectively, which is more accurate than the conventional techniques. The result shows that this system is useful for improving the accuracy of sound wave propagation reproduction with the sound field simulation.

Design of a rectangular patch antenna with a photonic crystal substrate

A small size patch antenna with high gain and high front-to-back (F/B) ratio has been newly developed. The antenna consists of two elements, that is, RF exiting element arranging on the front side and parasitic one on the back. The latter is terminated by the reactance. The antenna is as small as 80times80times8 mm in size and shows the gain and F/B ratio of 6 dBi and 15 dB at 950 MHz band, respectively. The obtained results are about 2 dB and 10 dB higher in gain and F/B ratio, respectively as compared with the conventional patch antenna. The size dependence of the performance has been investigated for antenna design by the simulation. The result shows that decreasing the element width with sacrificing the increase of thickness is found to be effective for minimizing the antenna volume.

A Ka-band MMIC active microstrip antenna is presented. The whole device consists of a GaAs microwave diode, a coplanar waveguide with an inductive slotted patch resonator, which acts simultaneously as a radio-active coupling aperture of a rectangular microstrip antenna and a microstrip rectangular patch antenna. The impedance characteristics of the antenna has been analyzed by using a direct three dimensional finite-difference time-domain (FDTD) method. The numerical results for the impedance of the antenna is shown to agree with the measurements.

We present a novel high-gain patch antenna utilizing composite right-left handed (CRLH) structure and dendritic cell metamaterials. The proposed CRLH antenna, composed of modified Sievenpiper mushroom unit-cells, is based on the positive first-order resonance mode for high gain. In addition, the dendritic cell metamaterials are used to surround the proposed antenna to further increase the antenna directivity and gain due to suppressing the surface waves. The experimental results show that the gain and the directivity of the proposed antenna with CRLH and dendritic cells can be improved by 3.88 dB and 8.82, respectively, in comparison with a conventional patch antenna. Moreover, a 10-dB bandwidth with 9.55% is achieved. The measured results are in good agreement with the simulated ones.

We have applied the finite difference time domain (FDTD) method with the supersymmetric quantum mechanics (SUSY-QM) procedure to determine excited energies of one dimensional quantum systems. The theoretical basis of FDTD, SUSY-QM, a numerical algorithm and an illustrative example for a particle in a one dimensional square-well potential were given in this paper. It was shown that the numerical results were in excellent agreement with theoretical results. Numerical errors produced by the SUSY-QM procedure was due to errors in estimations of superpotentials and supersymmetric partner potentials.

R wave is short for Rayleigh wave. R wave,on which the effect of gravity is generally inevitable,has received considerably extensive attention and been widely used in many fields,such as geological exploration,nondestructive test,etc. The effects of gravity on R wave velocity for elastic parameters were further analyzed based on available R wave velocity function,and the applicable range of the approximate one was given as well. Wave propagation through quasi-half-space isotropic linear elastic medium with gravity,under the excitation of differentiated Gaussian pulse( DGP) was studied by finite difference time domain( FDTD) method with staggered grid discretization,and extended boundary conditions were introduced.Velocity values obtained were closer to the theoretical ones. Meanwhile,the influence of gravity on time domain,frequency domain response was discussed. By analyzing the theoretical and numerical results,it is necessary to take the effect of gravity into account in simulation for more accurate prediction.

A finite difference time domain (FDTD) method in combination with the perfectly matched layer (PML) is used for dispersive media. The FDTD method is derived using the convolution relationship between the current density J and the electric field E. The high accuracy of the FDTD method is confirmed by computing the reflection and transmission coefficients for a one dimensional nonmagnetized plasma slab.

Patch antennas are widely applied in modern wireless communication systems. However, conventional patch antennas have the disadvantage of narrow bandwidth and are not suitable for Ku-band satellite broadcast reception. Many researchers have proposed various techniques to enhance the bandwidth of probe-fed patch antennas, e.g., employing thick substrate [1], adding parasitic patches either in the same layer (coplanar) [2]-[3] or in another layer (stacked) [4], and using capacitor-loaded patches [5]. With the first technique, the substrate thickness increases and induces the excitation of surface waves [6]. Apart from reducing the radiation efficiency, these surface waves diffract at the substrate edges and deteriorate the radiation patterns. The presence of coplanar and stacked geometry has the disadvantage of increasing the area and thickness of the antenna, respectively. Additional capacitors cause antenna gain reduction because of the ohmic loss of the loading chip resistor.

The numerical dispersion is one of the main factors to affect the accuracy of the finite-difference time-domain (FDTD) method. It can be easy to be taken for granted that a smaller time step leads to smaller simulation errors. This paper reveals that smaller time steps do not always make more accurate results in FDTD simulations. We analytically investigated how time steps affect the numerical dispersion of two FDTD methods: the leapfrog FDTD(2,2) method and the FDTD(2,4) method. The investigations in this paper show that in the FDTD(2,2) method, a larger time step limited by the Courant-Friedrichs-Lewy (CFL) condition is more helpful to reduce the numerical dispersion error. However, in the FDTD(2,4) method, as the time step grows, the numerical dispersion error decreases at the beginning and then increases. Several numerical examples are carried out to verify our analysis.