Gao Huo-tao

FDTD Analysis and Application of Sleeve Monopole Antenna

Based on the symmetry of the structure, a two-dimensional finite difference time domain (FDTD) method is used to analyze the sleeve monopole antenna on the infinite perfect conductor ground fed by a coaxial line. The fields in time domain are then turned into frequency domain through the discrete Fourier Transform to compute the surface current distribution and the input impedance of the sleeve monopole antenna. The gain or pattern of the monopole antenna is also computed, employing the combination of the image theory and the near-to-far transformation in frequency domain. All the computed results agree very well with the results of other methods and measured ones, verifying the application of the FDTD method to analyze the sleeve monopole antennas. The voltage standing wave ratio (VSWR) of the sleeve monopole antennas with different heights and radii of the sleeve are checked to study the influence of the sleeve, which indicates that the height and the radius of the sleeve are both important to the impedance bandwidth of the sleeve monopole antennas.

Estimation of Mutual Coupling Coefficient of the Array by Simulated Annealing Algorithm

We propose a method for estimating the mutual coupling coefficient among antennas in this paper which is based on the principle of signal subspace and the simulated annealing (SA) algorithm. The computer simulation has been conducted to illustrate the excellent performance of this method and to demonstrate that it is statistically efficient. The benefit of this new method is that calibration signals and unknown signals can be received simultaneously, during the course of calibration.

Estimation of mutual coupling coefficient by simulated annealing algorithm

In this paper, we propose a method for estimating the mutual coupling coefficient among antennas, which is based on the principle of signal subspace and the simulated annealing algorithm. The computer simulation have been conducted to illustrate the good performance of this method and to demonstrate that it is statistically efficient. The benefit of this new method is that calibration signals and unknown signals can be received simultaneously, during the course of calibration.

Scattering from Rough Surfaces Using the 'Shooting and Bouncing Rays' Technique

The “shooting and bouncing rays” (SBR) technique is used to analyze the electromagnetic scattering characters of ocean rough surfaces varying with time. Some numerical results are presented and compared with the method of moments, and some factors, such as the incident angle, polarization and frequency are investigated which influence on electromagnetic scattering characters of ocean rough surfaces.

Optimal design of broadband loaded receiving antenna for HFSWR using simulated annealing

One of the major challenges in using coast-based high frequency surface wave radar (HFSWR) is, for the purpose of the long-range detection of ships and aircraft as well as icebergs, or the remote sensing of the ocean environment using the coast-based HFSWR, how the size of transmitting and receiving antennas are reduced at lower end of the HF band. In this paper, according to the operating frequency bandwidth for a HFSWR, where both the gain and the voltage standing wave ratio (VSWR) of a receiving monopole can satisfy the requirement of engineering design, it mainly describes the process in which the loading circuit parameters, locations of the loads along the antenna, as well as matching network parameters are optimized by the simulated annealing algorithm (SAA) to achieve a VSWR less than 3 in the operating frequency bandwidth. Several examples antennas illustrate that the SAA is an effective method for designing HF broadband loaded antennas.

The relationship between mutual coefficient errors and the amplitude and phase errors of channels

In general, an accurate mutual coupling correlation is necessary for an array antenna to reach ideal sideiobe level. If the mutual coefficient matrix of an array antenna is perfectly known, one can completely compensate the effect of mutual coupling and realize the desired sidelobe level in theory. However, the mutual coefficient matrix obtained wherever by calculation on by measurement has a limited precision. In this paper, the requirements on the precision of matrix coefficient for compensation in low sidelobe array antenna are discussed. The relationship between mutual coefficient errors and the amplitude and phase errors of channels is derived.

The EM scattering from one-dimensionally lossy fractal surfaces

The EM scattering from rough surface has been investigated in the past years. Periodic and random models are often used in modeling the rough surface. Recently, the fractal geometry is rapidly improved. It provides a new way to model the rough surface whose characteristics are long-range order and short-range disorder. In this paper, A fractal function is used to model the rough surface. A scattering coefficient for calculating the angular distribution and the amount of energy in the spectrally scattering field to the fractal characteristics of the surfaces by finding their analytical expressions is derived by using the Kirchhoff solution. In the end, we calculate some scattering patterns.