Once you’ve included these values in the line’s impedance, you can calculate the equivalent parameters in the RLCG( f) model as functions of frequency, and you can calculate losses on the line as a function of frequency. Modeling dispersion on a transmission line requires accounting for the dielectric properties of the substrate and bringing them into a model for the line’s characteristics impedance. This explains why different materials absorb and transmit different colors of light. In addition to the real part of the refractive index, the imaginary part of the dielectric function is also a function of the wave’s frequency.
This physical property refers to the fact that the real part of a material’s dielectric function, and thus the speed of an electromagnetic wave, is a function of the wave’s frequency. What is Transmission Line Dispersion?ĭispersion is a fundamental property of the interaction between real materials and the electromagnetic field. Let’s look at how transmission line dispersion plays a role in determining the characteristic impedance spectrum and how it is related to losses on a transmission line. This is important at very high frequencies and at fast edge rates, such as in SerDes channels. Any transmission line model needs to account for dispersion and losses seen by signals on the line. Doing this properly requires construction of the correct model for a PCB transmission line.
#TRANSMISSION LINE GEOMETRY HOW TO#
If you understand how to properly model signal behavior on a transmission line, you can ensure signals reach their destination with minimal distortion. If you understand how dispersion and losses are related on a transmission line, and how they are related to the line’s geometry, you can minimize signal distortion on an interconnect. This signal behavior is intimately related to dielectric and conductive losses on a transmission line. Transmission line dispersion is a critical aspect of signal behavior.
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