This paper reviews recent progress and future directions of signal integrity design for high-speed digital circuits, focusing on four areas: signal propagation on transmission lines, discontinuity modeling and characterization, measurement techniques, and link-path design and analysis.

Signal Integrity Design for High-Speed Digital Circuits: Progress and Directions

A method is described for the determination of the effective electromagnetic parameters of a metamaterial based only on external measurements or simulations, taking boundary effects at the interfaces between a conventional material and metamaterial into account. Plane-wave reflection and transmission coefficients at the interfaces are regarded as additional unknowns to be determined, rather than explicitly dependent on the material parameters. Our technique is thus analogous to the line-reflect-line (LRL) calibration method in microwave measurements. The refractive index can be determined from S-parameters for two samples of different thickness. The effective wave impedance requires the additional assumption that generalized sheet transition conditions (GSTCs) account for the boundary effects. Expressions for the bulk permittivity and permeability then follow easily. Our method is validated by comparison with the results using the Nicolson-Ross-Weir (NRW) for determining properties of an ordinary material measured in a coaxial line. Utilizing S-parameters obtained from 3-D full wave simulations, we test the method on magnetodielectric metamaterials. We compare the results from our method and the conventional one that does not consider boundary effects. Moreover, it is shown that results from our method are consistent under changes in reference plane location, whereas the results from other methods are not.

Boundary Effects on the Determination of Metamaterial Parameters From Normal Incidence Reflection and Transmission Measurements

This paper addresses the difficulties involved in extracting efficient and accurate frequency-dependent per-unit-length RLGC parameters for lossy multi-conductor transmission lines using S-parameter models. One major difficulty involved with the conventional equations for the extraction of RLGC parameters is the discontinuity caused by the hyperbolic functions. This limits the extraction technique to specific lengths, frequencies, and number of lines in the model. In this paper, we propose to perform the extraction by using modified equations obtained by combining the transmission matrices of two similar lines with different lengths. Numerical examples demonstrate the robustness of the proposed method.

On addressing the practical issues in the extraction of RLGC parameters for lossy multiconductor transmission lines using S-parameter models

Electromagnetic wave transmittances of eight-harness-stain fabric glass fiber reinforced polyimide matrix composite with ≈11 mm thickness were measured in a terahertz (THz) frequency range using a terahertz time-domain spectroscopy (THz-TDS) system The transmittance value is nearly zero at a frequency of 10 THz The real part of the complex dielectric constant is 387 in the frequency range from 02 to 10 THz, and it is almost frequency independent Conversely, the imaginary part of the dielectric constant linearly increases with increase of the frequency from 012 (02 THz) to 033 (10 THz) The dielectric properties of the eight-harness-stain fabric glass fiber reinforced polyimide matrix composite were also estimated from those of the E-glass fabric and matrix using a series model for the dielectric constant and the dielectric loss tangent

Dielectric properties of eight-harness-stain fabric glass fiber reinforced polyimide matrix composite in the THz frequency range

An analytical methodology for characterizing electrical transitions associated with transmission line-based microwave channels is presented in this paper. The methodology is formulated using ABCD matrixes obtained from S-parameters measured to two lines with different length and terminated with the transition under investigation. This allows to determine the two-port network parameters of the transition in a simple and direct way. Excellent results are obtained when characterizing coplanar waveguide-to-microstrip and coaxial-to-microstrip transitions. Moreover, the methodology was also successfully applied to obtain the network parameters of packages fabricated on printed circuit board technology.

Characterization of Electrical Transitions Using Transmission Line Measurements

We have developed an accurate method for measuring the complex propagation constant and characteristic impedance of transmission lines embedded in multilayer printed circuit boards. It is based on mathematical error-removal schemes using two different length transmission lines and an advanced via-hole structure that minimizes coupling. Consequently, associated errors, due to discontinuities and interference can be effectively eliminated, and the frequency dependencies of the transmission line parameters can be clarified in wide frequency bandwidths. We verified the validity of this method in frequency ranges up to at least 18 GHz, by comparing the determined values with the theory derived from transverse electromagnetic (TEM) approximations.

T. Kushta

Papers

An accurate experimental method for characterizing transmission lines embedded in multilayer printed circuit boards