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1. © H. Heck 2008 Section 5.4 1 Module 5: Advanced Transmission LinesTopic 4: Frequency Domain Analysis OGI ECE564
Howard Heck
2. © H. Heck 2008 Section 5.4 2 Where Are We? Introduction
Transmission Line Basics
Analysis Tools
Metrics & Methodology
Advanced Transmission Lines
Losses
Intersymbol Interference
Crosstalk
Frequency Domain Analysis
2 Port Networks & S-Parameters
Multi-Gb/s Signaling
Special Topics
3. © H. Heck 2008 Section 5.4 3 Contents Motivation
Wave Equation Revisited
Frequency Dependence
Reflection Coefficient and Impedance
Input Impedance
Examples
Summary
References
4. © H. Heck 2008 Section 5.4 4 Motivation At high frequencies, losses become significant. This makes time domain analysis difficult, as the properties are frequency dependent.
Skin effect, dielectric loss & dispersion
We need to develop the means to understand those effects.
Example: How would we measure R, L, G, C for a PCB trace?
Frequency domain analysis allows discrete characterization of a linear network at each frequency.
Characterization at a single frequency is much easier
Frequency Analysis has advantages:
Ease and accuracy of measurement at high frequencies
Simplified mathematics
Allows separation of electrical phenomena (loss, resonance … etc).
5. © H. Heck 2008 Section 5.4 5 Key Concepts The input impedance & the input reflection coefficient of a transmission line is dependent on:
Termination and characteristic impedance
Delay
Frequency
S-Parameters are used to extract electrical parameters.
Transmission line parameters (R,L,C,G, TD and Zo)
Vias, connectors, socket … equivalent circuits
Periodic behavior of S-parameters can be used to gain intuition of signal integrity problems.
We’ll study S-parameters in section 5.5.
6. © H. Heck 2008 Section 5.4 6 Derive the lossy wave equation
Add a sinusoidal stimulus
7. © H. Heck 2008 Section 5.4 7 Wave Equation Revisited Goal: derive the frequency dependent impedance and reflection coefficients. Method: Starting with the RLGC equivalent circuit, we derive the differential equations.