Abstract-The coplanar waveguide (CPW)-to-coplanar stripline (CPS) transition is analyzed theoretically and experimentally in this paper. To characterize this transition in the lower frequency band, a simple equivalent-circuit model that consists of uniform and nonuniform transmission lines is established. The elements of this model can all be obtained by the closed-form formulas; hence, this model is suitable for computer-aided-design application. This model is then applied to design and analyze the CPW-to-CPS transitions with various structure parameters. In the higher frequency band, the partially prizm-gridded finite-difference time-domain (FDTD) method is employed to take into account the bond-wire effect as well as the surface-wave leakage and space-wave radiation associated with the transition. In this study, results based on equivalent-circuit model, FDTD simulation, and measurement are compared. Good agreement among these results supports the usefulness of the proposed equivalent-circuit model and also validates the FDTD method. By using the equivalent-circuit model to optimize the transition configuration, the CPW-to-CPS transition with broad bandwidth and low insertion loss may be achieved.
This paper proposes a new flipchip structure which uses resonanting dual bumps to achieve best transition. By simply changing the distance between the two bumps, we can control the band of minimum reflection in the desired frequency band. The bandwidth over which the return loss is smaller than -20dB is 20-30%. The corresponding insertion loss in this band is less than -1.5dB. All results presented below are simulated with the FDTD method combined with PML.
A partially prism-gridded FDTD analysis is presented to deal with layered structures with curved boundary in transverse directions. It is applied to calculate the scattering paxameters of vias in multilayer packaging. The good agreement of the results with those by other methods verifies the accuracy of this analysis.
A partially tetrahedral-gridded FDTD method has recently been proposed to solve the time-domain electromagnetic scattering of two or threedimensional arbitrarily shaped dielectric objects [1], [2]. It successfully employs the conventional FDTD method for most of the regular region but introduces (.he tetrahedral edgebaaed finite element scheme to model the region near the arbitrarily curved surfaces. Numerical results of early time simulation validate that the method has the advantages of accuracy, flexibility, stability, and computational effiriency. For the analyses of electromagnetic problems of high Q systems, transient response over a very long duration is necessary. It is found that the simulation may suffer from late-time instability and spurious dc modes. This paper is focused on treating the two drawbacks of the hybrid method.
A. Temporal Filtering Technique for Late Time instabilityThe strategy employed here is to derive a low pass filter to suppress the computational error which is of higher frcquencies, while keeping the low frequency components nearly unchanged. The filter corresponds to an IIR system defined by
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