Si-Ping Gao

Two-Dimensional Discontinuous Galerkin Time-Domain Method for Modeling of Arbitrarily Shaped Power-Ground Planes

This paper presents a two-dimensional discontinuous Galerkin time-domain (2-D DGTD) method for modeling arbitrarily shaped power-ground planes in high-speed electronics. The DGTD method has advantage over the finite-difference time-domain method in handling complex geometries, and allows high-order spatial discretization for improved accuracy. Its explicit time-stepping scheme also reduces computational cost compared to the implicit finite element time-domain method. The proposed method is validated against both measurement and commercial software to demonstrate its accuracy and efficiency.

Estimating Interference to Airborne Patch Antenna With Limited Information

In practice, the detailed geometry information of an off-the-shelf antenna is unavailable. To achieve the estimation of radio frequency interference to an airborne patch antenna with available information, this paper proposes to utilize an equivalent model of the patch antenna. The equivalent model is derived based on the patch antennas radiation pattern. It shows the same radiating and scattering performances as the original patch antenna. Since, no effective port or phase information is provided by the equivalent model, the reaction theorem was employed to calculate the interference without such information. Simulation and measurement results show that the proposed method can effectively estimate the interference to patch antennas with limited information. Furthermore, it avoids direct modeling of the complex structure of patch antennas and reuses the radiating fields of equivalent models which significantly reduces the computation time and memory cost.

A compact common-mode noise suppression filter for high speed differential signals using defected ground structure

A wideband and compact microstrip filter for common-mode electromagnetic (EM) noise suppression in high speed circuit well beyond GHz is presented in this paper. The noise reduction is realized by using specific etched slots in ground metallic plane as defected ground structure (DGS). The effect of the DGS on the characteristics of the investigated filter is examined. It is proved that the common-mode noise can be reduced by more than 15dB at center frequency of 8.4 GHz with a bandwidth from 5.4 GHz to 11.4 GHz. The differential signal is unaffected. The filter size is comparably small to the wavelength interested and the fractional bandwidth of the stop band is 71%. It is also proved the proposed approach is more efficient and effective for the EM noise reduction after comparison with other conventional filters. The proposed simple method for increasing microstrip line insertion loss for the sake of EM noise suppression can be used extensively in microwave filter design.

A linear model of transmission coefficients for placement of monopole antennas on electrically large cylindrical surfaces

Based on the ray analysis of monopole excitation, this work proposes a linear model of transmission coefficients against the logarithm of the distance between monopole antennas on electrically large cylindrical surfaces. The linear model is determined by using two sample data, and it is then used to predict the transmission coefficient between two monopole antennas. Given the desired level of transmission coefficient, the distance between monopole antennas can be calculated using the linear spatial model, which is useful for the placement of monopole antennas on electrically large cylindrical surfaces. Simulation results are presented to illustrate the effectiveness of the proposed linear model.

Common-mode filter using cavity-backed defected ground structure for multilayer PCB

A simple but effective common-mode noise suppression filter using cavity-backed defected ground structure (DGS) is proposed for the application of multilayer printed circuit board (PCB). This filter adds a substrate-filled metallic cavity beneath a conventional DGS. Due to the shielding effect of the cavity, the back-radiation of the DGS can be significantly reduced, while the filtering behavior of the DGS is retained in the resonant frequency band. The frequency responses and design parameters of the proposed filter are analyzed via full-wave simulation. An equivalent circuit model is also built based on the simulation result to understand the filtering behavior. It shows that an improved signal integrity (SI) is obtained with good EMI performance for a multilayer PCB.

Intense THz-coherent transition radiation from laser solid plasma interaction

We investigate intense broadband terahertz radiation generation based the interaction of high intensity ultrashort laser with solid plasma. THz pulse with electric field of hundreds of MV/cm are generated using laser with intensity of about 1018 W/cm2. Theoretical model, simulations agree well with experiments, and reveal that the THz radiation is coherent transition radiation by hot electrons produced in laser-plasma interaction. We have studied both planar and nanorod array targets, latter of which efficiently enhance the intensity and directionality of the THz source.

Effective modeling of multidirectional CFRP panels based on characterizing unidirectional samples for studying the lightning direct effect

The electrical conductivity of a carbon fiber reinforced plastic (CFRP) panel is highly anisotropic due to its varied fiber orientations. This paper presents an effective modeling method for studying the lightning direct effect on a multidirectional CFRP panel based on an electrical conductivity characterization of unidirectional samples. The characterization using 4-probe method is done with a simple measurement setup. The measured DC conductivity is validated by comparing the samples behavior in AC regime (lightning spectrum) obtained from measurement and simulation. It is subsequently used in the modeling of a 32-layer multidirectional CFRP panel excited by a lightning current. Simulation results show that the proposed method is able to effectively model multidirectional CFRP panels, which might be useful to studying the current-carrying capacity of CFRP panels under lightning strikes.

Evaluating airborne slotted waveguide antenna arrays using an equivalent model based on near-field samplings over slots

This paper proposes to evaluate the installed performance of a slotted waveguide (SWA) antenna array on large platforms using an equivalent model based on near-field samplings over slots. The tangential electric fields over the SWA slots were first sampled to obtain equivalent magnetic current sources. The equivalent sources were then put on a closed perfect electric conducting box, same profile of the SWA, to form the equivalent model. This equivalent model avoids direct modeling of the complex inner structure and the thickness of the SWA. The installed radiation of the SWA on a platform was calculated by adding the direction radiation from the equivalent sources and the scattered fields from the induced currents over the whole antenna-on-platform system, where the induced currents were obtained by the method of moments. The effectiveness and efficiency was demonstrated via numerical cases.

A discontinuous Galerkin Time-Domain method for modeling of power-ground planes with narrow slots and signal vias

This paper presents a Discontinuous Galerkin Time-Domain (DGTD) method for modeling of power-ground planes with narrow slots and signal vias in high-speed electronic packages or PCBs. Based on the surface equivalence theorem, the 2D Maxwells equations for power-ground planes solved by the 2D DGTD method are coupled with the telegraphers equations for slots solved by the 1D DGTD method. The proposed DGTD method is then integrated with via-circuit models to include the effects of signal vias. The accuracy and efficiency of the method are validated against full-wave commercial software. A speed-up of about 14 times against the commercial software is achieved.

Near-field scanning and its EMC applications

This paper first briefly surveys the near-field scanning for antenna measurements, then focuses on the near-field scanning for electromagnetic compatibility (EMC) applications. Key theories and practices are covered, and some latest development and open issues regarding the near-field scanning for EMC applications are finally presented.