Pingshan Wang

Cornell University, Ithaca, New York, United States

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Publications (6)7.29 Total impact

  • Pingshan Wang · E.C.-C. Kan
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    ABSTRACT: On-chip high-speed interconnects with underlayer orthogonal metal grids, including grid-backed lines (GBLs) and grid-backed coplanar waveguides (GBCPWs), are characterized through s-parameter measurements. For GBL test structures, the presence of underlayer metal grids reduces dispersion by a factor of 4 while the local speed of light decreases by a factor of 2 in comparison to those of conventional microstrip lines. The dispersion reduction comes from suppressing higher order modes; the local speed of light reduction comes from a longer current return path. These characteristics are beneficial for compact CMOS analog circuit designs. Losses caused by substrate and conductor lines are restrained by shielding the substrate and by involving weaker electric fields. Resonance at a frequency characterized by that of a patch antenna was observed and needs to be considered in high-speed circuit designs. The grids have weaker effects in the case of CPWs, where the side ground plate effects are significant. A signal transmission example shows that dispersion and frequency-dependent losses are important in determining the signal rise edge. Semi-empirical distributed resistance-inductance-capacitance-conductance (RLCG) equivalent circuit models are constructed for the interconnects below the resonant frequencies.
    No preview · Article · Sep 2004 · IEEE Transactions on Advanced Packaging
  • Pingshan Wang · Weiping Ni · Norman C. Tien · Edwin C. Kan
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    ABSTRACT: We report a ferromagnetic thin film characterization method and the measured microwave permeability of patterned permalloy films. The method incorporates ferromagnetic materials with transmission lines and extracts RLCG equivalent circuit elements from scattering parameters. The frequency-dependent effective permeability is then obtained from the incremental R and L caused by the ferromagnetic material. The measured high-frequency losses of thin permalloy ( Ni <sub>80</sub> Fe <sub>20</sub>) films between 1 and 20 GHz show that geometry design restrains ferromagnetic resonance and eddy-current effects effectively. Above ∼22 GHz, mode conversion occurs in the test structures. Other broadband structures are necessary for further extractions. © 2004 American Institute of Physics.
    No preview · Article · Jul 2004 · Journal of Applied Physics
  • Pingshan Wang · Gen Pei · E.C.-C. Kan
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    ABSTRACT: Pulsed wave interconnect is proposed for global interconnect applications. Signals are represented by localized wave-packets that propagate along the interconnect lines at the local speed of light to trigger the receivers. Energy consumption is reduced through charging up only part of the interconnect lines and using the voltage doubling property of the receiver gate capacitances. In a 0.18-/spl mu/m CMOS technology case study, SPICE simulations show that pulsed wave interconnect can save up to 50% of energy and /spl sim/30% of chip area in comparison with the repeater insertion method. A proposed signal splitting structure provides reasonable isolations between different receivers. Measured S-parameters of 3.8-mm interconnect lines fabricated through CMOS foundry showed that the distortion and attenuation of a pico second signal are much less serious than the theoretical predictions. Pulsed wave interconnect also enables time division application of a single line to boost its bit rate capacity. The use of nonlinear transmission lines (NLTL) is also proposed to overcome pulse broadening and attenuation caused by dispersion and frequency-dependent losses. Pulsed waves on an NLTL may be generated, transmitted, split and detected with components realizable in bulk and SOI CMOS technologies. Tapered NLTL can be used for pulse compression. NLTL edge sharpening abilities may be applicable for signal rise time control.
    No preview · Article · Jun 2004 · IEEE Transactions on Very Large Scale Integration (VLSI) Systems
  • Pingshan Wang · Norman C. Tien · E.C.-C. Kan
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    ABSTRACT: The mutual inductance and self-inductance of global interconnects are important but difficult to extract and model in deep submicrometer very large scale integration (VLSI) designs. The absence of effective mutual magnetic field shielding limits the maximum unbuffered interconnect line length. In this paper, we propose and demonstrate that permalloy-loaded transmission lines can be used for high-speed interconnect applications to overcome these limitations. Permalloy films were incorporated into planar transmission lines using a CMOS-compatible process. The line characteristics show that eddy-current effects are the limiting factors for the high-frequency permalloy applications when ferromagnetic resonance are restrained through geometry design. Patterning permalloy films effectively extends their application to above 20 GHz. The line characteristic impedances are about ∼90 Ω. Under 50 mA dc current biases, the line parameters did not change much. Moreover, the patterned permalloy reduces the magnetic field coupling between two adjacent transmission lines by about 10 dB in our design. The demonstrated operation frequency range, current carrying capability and magnetic field shielding properties indicate that the permalloy loaded lines are suitable for high-speed interconnect applications in CMOS technologies.
    No preview · Article · Feb 2004 · IEEE Transactions on Electron Devices
  • Pingshan Wang · E.C. Kan
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    ABSTRACT: High-speed interconnect lines with underlayer orthogonal metal grids show significant decreases in dispersions and signal transmission velocities below ∼10 GHz. Strong resonance occurs at higher frequencies, which can be accurately predicated by the rectangular patch antenna theory.
    No preview · Conference Paper · Nov 2003
  • Pingshan Wang · V.S. Kaper · S.J. Richard · E.C. Kan
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    ABSTRACT: A transient analysis method for nonlinear microwave circuit analysis is described in this paper. S-parameter microwave circuit theory and measurement-based small-signal scattering parameters of nonlinear devices are used directly to construct the large signal response of the circuits. This consistent modeling and analysis approach retains all the frequency-dependence information of the measured small-signal parameters. The method is applied to predict the large signal performance of a discrete AlGaN/GaN high electron mobility transistor (HEMT), biased in the common source amplifier mode. Reasonable agreement between the simulated and measured results is obtained. This method does not have limitations on the number of input carrier frequencies or the total number of frequencies. It is expected to be a useful and efficient tool in waveform engineering applications.
    No preview · Conference Paper · Jul 2003