Junjie Mao

Study about the radiation characteristics of bow-tie antennas with discrete resistor-loaded

The ground penetrating radar (GPR) system is an effective tool for nondestructively sensing subsurface environment. One of the most critical hardware components for the performance of the GPR system is the antenna, and the bow-tie antenna is one of common antennas used in the system. The conventional bow-tie antennas with perfect electrical conductors (PEC) panels have variable characteristics that depend on operating environment. In this paper, a bow-tie antenna with exponential discrete resistor-loaded is present. Radiated waveforms, input impedances, and footprints of resistor-loaded bow-tie antenna are investigated through the finite difference time domain (FDTD) method. The results show that the antenna with exponential discrete resistor-loaded can terminate the reflections at the end of antennas, and it is considerably less sensitive to their environment than the conventional bow-tie antenna with PEC panels.

Research on mobile communication radio propagation characteristic based on 3DPE

In this paper, a macrocell radio propagation model for mobile communication is established based on three-dimensional parabolic equation (3DPE). The loss characteristics of radio propagation around buildings are calculated by using this 3DPE model when buildings distributing differently on flat ground or irregular terrain. The results are compared with the physical optics (PO) method and three-dimensional Ray tracing method. The compare shows the 3DPE model is accurate and valid. So it provides an excellent propagation prediction model for mobile communication.

Adaptive dynamic meta particle swarm optimization algorithm and application in 3D power pattern synthesis for conformal arrays

The adaptive dynamic Meta particle swarm optimization (ADMPSO) algorithm is proposed to apply in power patterns synthesis for conformal arrays. To begin, the dominated subgroup and nondominated subgroup are defined on the basis of traditional Meta particle swarm. Meanwhile, the adaptive dynamic modulating for multiple-subgroup is realized by introducing the downsizing of nondominated subgroup, and the expansion of dominated subgroup, which improves both the convergence speed and exploration ability significantly. Finally, based on the target fitness function built for power pattern synthesis in arbitrary arrays, ADMPSO algorithm has been used in synthesizing three dimensional (3D) power patterns for conical array, with all polarization fields considered.

Multidomain pseudo spectral time-domain modeling of waveguide structure

In this paper, the design of excitation source is discussed when the characteristic of the waveguide is analyzed using multidomain pseudospectral time-domain (MPSTD). The S parameters of a typical 3D waveguide bend are calculated using MPSTD. The numerical results are compared with the FDTD, and which confirm accuracy and efficiency of the MPSTD. This paper presents a scheme to analyze the waveguide structure accurately, which extends application field of the MPSTD.

An automatic load-balanced parallel multilevel fast multipole method for large scale electromagnetic scattering problem

A parallel multilevel fast multipole method for computing the large scale electromagnetic scattering problem is proposed and implemented in this paper. In recent years, multilevel fast multipole method (MLFMA) has been widely used for analyzing electromagnetic scattering problem of electric large object. In order to extend the range of problem that can be solved using this algorithm, we implement a parallel fast multipole method which can run on the distributed memory computer system. This parallel algorithm is based on the message-passing interface (MPI). A compressed octree based parallel domain subdivision algorithm is used for efficiently avoiding the load balance problem between different CPUs which is caused by the irregular object shape. The parallel efficiency of this algorithm is demonstrated by different computing examples. We have solved electromagnetic scattering problem of many practicality military targets with more than 5,000,000 unknowns using our parallel multilevel fast multipole code on Drawing 4000A Super-Computer at Shanghai Super-Computing Center.

Field strength prediction behind a lossy dielectric block by using the 3D parabolic equation model

In this paper, a 3D parabolic equation wave propagation model based on split-step Fourier (SSF) transform for field strength prediction behind a lossy dielectric block, which just like an actual building in urban mobile communication system is presented. Field decomposed odd part and even part used to dealing with ground boundary condition is proposed here. And Fourier transform adding forward difference (FT-TD) approach, which used to dealing with the block vertical surface boundary condition is also brought forward. Comparing the result with the published literature, the validity of these methods is testified.

A method to accelerate the MOT arithmetic in TD-MOM EFIE

A method was presented to accelerate the MOT arithmetic using method of moment in time domain EFIE. Using a time window in the MOT method, to eliminate the iterative calculation which has no contribution to the present time step, in this way, accelerate effect was obtained.