ppt-313 qucs a getting started guide -...

www.beTheSignal.comCompany Confidential 1

PPTPPT--313 QUCS a Getting Started Guide313 QUCS a Getting Started Guide

Eric BogatinEric Bogatin

Signal Integrity EvangelistSignal Integrity Evangelist

Teledyne LeCroyTeledyne LeCroy

www.beTheSignal.comwww.beTheSignal.com

Jan 2014

Copes can be downloaded from www.beTheSignal.com (PPT-313)

www.beTheSignal.com 2

Outline

� Simulation: a blessing and a curse

� Practice Safe Simulation: Rule #9

� Getting started with QUCS

� Five examples:

� Signals in the time and frequency domain

� A TDR

� Reflections, terminations and topologies

� An impedance analyzer

� A VNA


Types of Numerical Simulation Tools

Signal Analysis: (predicting signal

waveforms based on numerical

analysis): excel, Matlab,

MathCAD, SI Studio;.

Circuit Simulation: (SPICE:

simulating voltage and currents

based on circuit elements)

Electromagnetic Simulation (modeling: converting

geometry and materials into electrical models): HFSS,

CST, Momentum, Simbeor, Sigrity, ;.

1 2 3 4 5 6 7 8 90 10

-30

-20

-10

-40

0

freq, GHz

Diffe

rential R

esp

onse,

dB

Input geometry and materialsSolve Maxwell’s equations,

output fields, currentsOutput S-parameters, model

parameters


The Power of Simulation

� Explore design space with virtual prototypes

� Convert physical design into electrical models

� Explore performance of electrical models

� Answer “;it depends” questions

� maximum data rate a channel will support

� selecting optimize capacitor values

� Faster time to an optimized design

� Learn Signal Integrity by doing it


QUCS: Quite Universal Circuit Simulator

� A SPICE like circuit simulator

� It is NOT a modeling tool

� You have to supply the circuit models and

parameter values

� If you can draw the circuit (schematic) QUCS will

predict the voltages and currents in time or

frequency

� The perfect introduction to simulations


Why Commercial Simulators

� QUCS is “open source” (free)

� “Free” comes at a price

� What you can pay up for:

� more features, capability, models, elements,

� ease of use

� support

� automation, scripting

� faster time to correct answer

� If QUCS is adequate for your application, you can’t beat free.


Learning Modes

� Read it

� Hear it

� Write it

� Teach it

� Do it

� Measure real prototype

� Simulate virtual prototype

Signal and Power

Integrity-

Simplified


The Danger of Simulation

Just because there are a lot of digits or it goes

to high frequency, doesn't mean it’s an accurate

prediction of the real world


Practice Safe Simulation


Download Instructions

� Open source: http://qucs.sourceforge.net/

� www.beTheSignal.com: under PPT-313

and ECEN 5224

� courtesy copy of the software

� installation instructions

� some manuals

� five examples projects


Installation Process

� Open downloaded zip folder

� Review readme file

� Install QUCS

� Move the _prj folder to the .QUCS directory

� Re-start QUCS

� Good to go


Example #1: Spectrum of Signals

� Orientation

� zoom navigation

� parameters (press return to lock in values)

� simulation

� displays

� Rise time and Spectrum


Example #2: a TDR

V_reflected = V_TDR_10psec – V_incident

V_incident = 1 v


Example #3: Terminations and Reflections


Example #4: Impedance Analyzer

V(f) = I(f) x Z(f)


Example #5: A Network Analyzer (and S-parameter viewer)


Next Steps

� Download QUCS

� Download the 5 example projects

� Now you try it;

ppt-313 qucs a getting started guide -...

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