Peiguo Liu

Transient Electrothermal Analysis of Multilevel Interconnects in the Presence of ESD Pulses Using the Nonlinear Time-Domain Finite-Element Method

Comprehensive electrothermal analysis of multilevel interconnects under electrostatic discharge (ESD) stress is carried out using the proposed nonlinear time-domain finite-element method (FEM). The technological, structural, and material parameters used in the analysis correspond to the advanced CMOS process of 90-, 65-, 45, and 32-nm nodes assessed by the International Technology Roadmap for Semiconductors. In order to enhance the computation efficiency and to reduce the memory cost, the preconditioned conjugated gradient technique combined with the element-by-element approximate factorization method is introduced to handle the sparse matrices formed by FEM. The nonlinear material parameters including the temperature-dependent electrical and thermal conductivities are treated rigorously. The transient temperature distributions, the maximum temperatures, and the temperature rise time of 3- and 4-level interconnect structures under the injection of ESD pulses with various waveforms are obtained and discussed.

Graphene based tunable fractal Hilbert curve array broadband radar absorbing screen for radar cross section reduction

This paper proposes a new type of graphene based tunable radar absorbing screen. The absorbing screen consists of Hilbert curve metal strip array and chemical vapour deposition (CVD) graphene sheet. The graphene based screen is not only tunable when the chemical potential of the graphene changes, but also has broadband effective absorption. The absorption bandwidth is from 8.9GHz to 18.1GHz, ie., relative bandwidth of more than 68%, at chemical potential of 0eV, which is significantly wider than that if the graphene sheet had not been employed. As the chemical potential varies from 0 to 0.4eV, the central frequency of the screen can be tuned from 13.5GHz to 19.0GHz. In the proposed structure, Hilbert curve metal strip array was designed to provide multiple narrow band resonances, whereas the graphene sheet directly underneath the metal strip array provides tunability and averagely required surface resistance so to significantly extend the screen operation bandwidth by providing broadband impedance matching and absorption. In addition, the thickness of the screen has been optimized to achieve nearly the minimum thickness limitation for a nonmagnetic absorber. The working principle of this absorbing screen is studied in details, and performance under various incident angles is presented. This work extends applications of graphene into tunable microwave radar cross section (RCS) reduction applications.

An Efficient Method to Reduce the Numerical Dispersion in the LOD-FDTD Method Based on the (2, 4) Stencil

A parameter-optimized (2, 4) stencil based locally-one-dimensional (LOD) finite-difference time-domain (FDTD) is presented with much reduced numerical dispersion errors. The method is first proved to be unconditionally stable. Then by using different optimization schemes, the method is optimized to satisfy different accuracy requirements, such as minimum dispersion errors in the axial directions, in the diagonal direction, and in the specified angles. Performances of the parameter-optimized LOD-FDTD with different time steps and frequencies are also studied. It is found that the parameter optimization can significantly reduce numerical dispersion errors, bringing them down to the level of the conventional FDTD but with the time step exceeding the CFL limit and without much additional computational cost. In addition, the optimized parameters are not sensitive to frequencies; in particular, the optimized parameters obtained at a higher frequency still present low numerical dispersion errors at a lower frequency.

A Novel Method of Energy Selective Surface for Adaptive HPM/EMP Protection

In this letter, a new method of energy selective surface (ESS) is presented for adaptive high-power microwave/electromagnetic pulse (HPM/EMP) protection, and a self-actuated ESS is designed with super-dense diode arrays. A prototype of size 35<formula formulatype=inline><tex Notation=TeX>

High-Order Interface Treatment Techniques for Modeling Curved Dielectric Objects

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Dual-Band Reconfigurable Terahertz Patch Antenna With Graphene-Stack-Based Backing Cavity

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A Novel Frequency Selective Structure With Quasi-Elliptic Bandpass Response

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A Novel Three-Dimensional Frequency Selective Structure

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Improved OAM-Based Radar Targets Detection Using Uniform Concentric Circular Arrays

Three modified conformal techniques combined with high-order finite-difference time-domain method (FDTD (2, 4)) are proposed to investigate the interaction of electromagnetic waves with three-dimensional (3-D) curved dielectric surfaces. These proposed conformal techniques utilize an effective average dielectric constant to modify the update equations in the FDTD (2, 4) scheme, which is derived by area, linear, and volume averages of different dielectric regions in twenty seven spatial discrete cells at most, respectively. Some numerical results are presented to show the accuracies of linear and area average techniques. Good agreements are obtained with those of the method of moments and other analytical ones, even with coarse meshes adopted for handling electrically large or complex geometries effectively. Further, using our proposed techniques, the RCS of some typical 3-D objects are predicted and studied in detail.

A Tunable Ultra-Broadband Ultrathin Terahertz Absorber Using Graphene Stacks

The concept of dual-band reconfigurable terahertz patch antenna using a graphene-stack-defined backing cavity is presented. The proposed antenna employs patch resonance based on backing cavity defined by interleaved graphene/Al2O3 stacks, which can be dynamically dual-resonance frequency-tuned on large range about 1 THz via electrostatic gating on the graphene stack. The performance is analyzed in terms of its directivity, sidelobe suppression, return loss, and bandwidth for different chemical potential. By applying different voltages on graphene stack, the direction of the antenna main beam can be steered with appreciable variation range.