D. G. Fang

Synthesis of nonuniformly spaced arrays using genetic algorithm

In many engineering situations, nonuniformly spaced arrays are necessary or useful due to feed network structures, actual system constraints and so on. Other than many conventional synthesis methods, the genetic algorithm (GA) can be used to synthesize such arrays to reach the requirement of the sidelobe level. The optimized variables in the nonuniformly spaced array are usually chosen as the element positions. In the application of digital beamforming antenna systems, the optimized variables may be chosen as element positions, amplitudes, phases or some combination of them, which provide more degrees of freedom to the synthesis of arrays than before. Simulation results show that this method is valuable.

Mutual coupling reduction between two conformal microstrip patch antennas

A novel structure to reduce the mutual coupling between two conformal microstrip patch antennas has been proposed in this paper. In this structure, a parasitic tape is added on each microstrip patch element. With this parasitic structure, a 19.8rib mutual coupling reduction between two conformal mierostrip patch antennas was obtained, while the antenna radiation patterns in both E-plane and H-plane remain unaffected. The field distributions of the mierostrip antenna were investigated. From the field distribution, it is seen that the mutual coupling is depressed by the parasitic structure. In addition to the good performance in the mutual coupling reduction, the proposed structure is easy to be fabricated and with low profile,

Study on the elimination of surface wave by metal fences

The microstrip antenna is a low-profile planar structure and is inexpensive compared with other types of antennas due to the ease of manufacture. However, patch-antenna designs have some limitations such as restricted bandwidth, low gain, and a decrease in radiation efficiency due to surface wave modes. Surface wave modes in microstrip substrates may cause the undesired energy losses and the reduction of the radiation efficiency of the patch antenna. A scheme to eliminate such modes by using metal fences is proposed. This structure can be easily realized by a metalated hole in manufacturing. It is observed that the patch antenna with this structure shows reduced levels of surface wave modes, thus improving the gain and the radiation pattern.

A Novel Wideband Aperture-Coupled Circularly Polarized Stacked Patch Antenna

This paper presents a novel wideband aperture-coupled circularly polarized stacked patch antenna. With the combination usage of the aperture-coupled feed, one stacked parasitic patch and one three-stub hybrid coupler, both the impedance bandwidth and the 3 dB axial ratio (AR) bandwidth have been improved considerably. The proposed antenna operating in the X band exhibits a simulated -10 dB return loss bandwidth of 37% and an AR<3 dB bandwidth of 40.3%. The maximum gain is 8.4 dBi

The application of closed-form mutual impedance formula in the analysis of the finite patch antenna array

Mutual coupling of the antenna element always degenerates the performance of array antennas. The analysis of this effect using a conventional method of moments leads to a huge number of basis functions and unknowns, respectively. The mutual impedance formula between patch antennas based on synthetic asymptote and variable separation is applied to take into account the parasitic element effects through an element by element method of mutual impedance correction. This method can successfully predict the performance of the finite array as well as greatly reduce the computer time and memory usage especially in the optimization of the finite array.

Some effective methods in computational electromagnetics

Some effective methods in computational electromagnetics other than those involved in commercial software are introduced. These methods include a space mapping technique, extra port method to involve parasitic influence, extrapolation and adaptive frequency sampling techniques, synthetic asymptote technique and artificial neural network technique. Their mechanisms, such as getting formulas or making use of the mapping between different levels, are not quite the same. They have the same goal, which is to make a good balance between accuracy and efficiency. The principle of each method is briefly addressed. Some research work done in the authors laboratory or in cooperation with others is introduced. Finally some future research work is suggested.

Entire domain based diakoptic method of lines

An entire domain method of lines (EDMoL) is proposed here to take both the advantages of entire domain basis model and method of lines (MoL), which can save computation time significantly. This method is an extension of the triangular basis diakoptic MoL. The formulas of EDMoL are given in detail. Numerical examples and some interesting results are also presented.

Design and Optimization of a Typical High-Speed Digital Transmission Channel

This paper optimizes the building blocks of a typical high speed digital transmission channel. It demonstrates how the physical parameters that generally considered to be jerkwater greatly affect the performance of high speed transmission at last. We give a few suggestions to increase simulation efficiency and especially to avoid the uncertainly of manufacturing

Microstrip Antenna Research at Millimeter Wave Technique Laboratory of NJUST

This paper gives an overview of the microstrip antenna research carried out at Millimeter Wave Technique Laboratory (MWTL) of Nanjing University of Science and Technology (NJUST). It describes the development on both the antenna elements and the arrays for different requirements such as high gain, low side lobe level, wide frequency bandwidth, equal beamwidth in both principal planes, wide angle coverage pattern, low cross polarization, pattern diversity array, circular polarization array and specific function array needed in monopulse radar. In addition to the structure, the design approaches and tools are briefly introduced. The performance of adaptive nulling under the presence of mutual coupling in digital beamforming microstrip antenna array is discussed as well

Simple formula of mutual impedance of patch antennas constructed from variable separation of the near field and radiation pattern of the far field

Knowledge of mutual coupling between antennas is of much importance for the design of practical antenna arrays of finite size. This paper constructs a formula for mutual impedance between patch antennas based on the physics of the static near field coupling and of the far field radiation couplings, i.e., the near and far asymptotes. The two asymptotes are then combined to form a synthetic asymptote [1], of separated variables of the center-to-center distance r and the azimuth angle ϕ. Only 12 coefficients are to be determined by matching with a full wave analysis with commercial software, such as IE3D. Our formula is complete with no restriction on the detailed structures of patch, feed and substrate.