1 Day 3, Session 3: Intro to Transmission Lines Star-Hspice Basic Training 2000 Introduction to Transmission Lines l Overview q What is a transmission line? q Who benefits from using transmission line analysis? q Key circuits for digital systems analysis l The components q Ideal transmission lines q Lossy elements Types of lossy elements Syntax Physical levels Electrical levels Geophysical microstrips RCLG microstrip equivalent circuit
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Day 3, Session 3: Intro to Transmission LinesStar-Hspice Basic Training 2000
Introduction to Transmission Lines
l Overview
q What is a transmission line?
q Who benefits from using transmission line analysis?
q Key circuits for digital systems analysis
l The components
q Ideal transmission lines
q Lossy elements
� Types of lossy elements
� Syntax
� Physical levels
� Electrical levels
� Geophysical microstrips
� RCLG microstrip equivalent circuit
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Day 3, Session 3: Intro to Transmission LinesStar-Hspice Basic Training 2000
Transmission Lines
l What is a transmission line ?
q A transmission line is a device intended to deliver an output signal at a distancefrom the point of signal input.
q Any conductive pathway can show transmission line effects at high enoughfrequencies and/or long enough lengths.
q Examples include:
� Microstrips
� Coaxial cables
� Ribbon cables
� IC package interconnect
� PC board traces
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Day 3, Session 3: Intro to Transmission LinesStar-Hspice Basic Training 2000
Transmission Lines
l Who benefits from using transmission line analysis ?
q System designers
q IC designers
� High-speed digital
� High-frequency analog
� Interconnect
q PC board designers
q Anyone concerned about cross-talk and signal integrity
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Day 3, Session 3: Intro to Transmission LinesStar-Hspice Basic Training 2000
l Ground references are treated like the signal line
l Can be coupled ( 5 lines max.)
l Automatic lumping, including resistive loss, mutual coupling
N lumps
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Day 3, Session 3: Intro to Transmission LinesStar-Hspice Basic Training 2000
Lossy Transmission Lines: U-Element
l Syntax for U model
q .model Umodel_name U level=3 plev=x elev=x keyname=val
l Transmission lines are ALL level 3, and there are combinations of physical levels andelectrical levels. The number of conductors in the element is determined by the model(NL=val).
l Have a reference point if analysis is critical (field solver)
l There are three electrical levels:
q elev=1 Geophysical (geometry based calculation of RCLK)
METAL|DIELECTRIC Material type: METAL or DIELECTRIC
ER Dielectric constant (relative permittivity)
UR Relative permeability
CONDUCTIVITY Static field conductivity of conductor or lossy dielectric (S/m)
LOSSTANGENT Alternating field loss tangent of dielectric (tan �)
q The Star-Hspice field solver assigns the following default values for metal: CONDUCTIVITY = -1 (perfectconductor), ER = 1, UR = 1. PEC is a predefined metal name with the default values and cannot beredefined.
q The Star-Hspice field solver assigns the following default values for dielectrics: CONDUCTIVITY = 0(lossless dielectric) , LOSSTANGENT = 0 (lossless dielectric), ER = 1, UR = 1 . AIR is a predefineddielectric name with default values and cannot be redefined.
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Day 3, Session 3: Intro to Transmission LinesStar-Hspice Basic Training 2000
BACKGROUND Background dielectric material name. By default, AIR is assumed for the background.
thickness Layer thickness
q Layers are listed from bottom to top.
q Metal layers (ground planes) are located only at the bottom, top, or both top and bottom.
q Layers are stacked in y-direction, and the bottom of a layer stack is at y=0.
q All conductors must be located above y=0.
q Background material must be dielectric.
q Free space without ground: . LAYERSTACK mystack
q Free space with a (bottom) ground plane: .LAYERSTACK halfSpace PEC 0.1mm
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Day 3, Session 3: Intro to Transmission LinesStar-Hspice Basic Training 2000
PETL: Defining Shapes
.SHAPE sname Shape_Descriptor
sname Shape name.
Shape_Descriptor See the following subsections.
l Rectangles
RECTANGLE WIDTH=val HEIGHT=val <NW=val> <NH=val>
WIDTH Width of rectangle (length in x-direction).
HEIGHT Height of rectangle (length in y-direction).
NW Number of segments for the width discretization.
NH Number of segments for the height discretization.
q Normally, it is not necessary to set the values of NW and NH since they are automatically setby the solver depending on the accuracy mode.
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Day 3, Session 3: Intro to Transmission LinesStar-Hspice Basic Training 2000
PETL: Defining Shapes (cont.)
CIRCLE RADIUS=val <N=val>
RADIUS Radius of the circle.N Number of segments for discretization.
STRIP WIDTH=val <N=val>
WIDTH Width of strip (length in x-direction).N Number of segments for discretization.
POLYGON VERTEX=(x1 y1 x2 y2 ...) <N=(n1,n2,...)>
VERTEX (x, y) coordinates of vertices. Listed either in clockwise or counter-clockwise direction.
N Number of segments for each edges. If only one value is specified, then this value is used for all edges. The first value of N, n1, corresponds to the number of segments for the edge from (x1 y1) to (x2 y2).
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Day 3, Session 3: Intro to Transmission LinesStar-Hspice Basic Training 2000