Sonnet Lite Seminar

2/9/2010

Sonnet 12 & Sonnet Lite

Shawn Carpenter

Sonnet Software, Inc.

100 Elwood Davis Road

North Syracuse, NY 13212

315-453-3096

http://www.sonnetsoftware.com

2/9/2010 © 2010 Sonnet Software, Inc www.sonnetsoftware.com

Course Outline Introduction to Sonnet & EM Analysis

– Choice of Solver Techniques

– Method of Moments & Meshing

– Ports & Sonnet box

Example 1 - Simple Microstrip Low-Pass Filter

– Intro to creating Sonnet Projects, analysis and viewing results

Example 2 - Zero-Length Through Line (ZLT)

– Understanding port calibration and de-embedding

– Evaluating EM analysis accuracy

– Testing dynamic range of an EM simulator

Example 3 - Variations on the Microstrip Low-Pass Filter

– Using Parameters to automate geometry modification

– Automated geometry sweeps and EM-based optimization

Example 4 – Spiral Inductor

– Create an inductor and isolate it in the box by shifting reference planes.

– Palette of geometries to generate the inductor shape.

– Simulate the inductor and measure the effective inductance.

Example 5 - SMD-based Low-Pass Filter on PCB

– Creating and evaluating planar spiral inductors

– Using Sonnet Components to include SMDs in your EM simulations


Sonnet LitePlus Certificate


2D cross sectional solvers are common for transmission line impedance calculators for various stack-ups. Picture a vertical cross section of substrate.

Sonnet is a Full-Wave 3D Planar EM solver.

Numerically solves Maxwell’s equations based on the EM Field Theory rather than on the classical lumped element circuit theory.

Full 3D EM handles fully arbitrary 3D shapes.

2D Analysis 2.5D Analysis 3D Planar Analysis

3D Arbitrary Analysis

EM Analysis Approaches

Surface Meshing

AnalysisVolume Meshing

Analysis


Volume Meshing (Full 3D EM)– Full 3D EM Meshes the Entire Volume of the simulation

problem.

– Best for 3-D arbitrary structures.

– Sonnet sells and supports CST Microwave Studio® (MWS) 3D

EM simulator in North America.

– MWS can perform Time Domain simulations using the

Hexahedral (rectangular) mesh.

– MWS can also perform Frequency Domain simulations using

the Tetrahedral (triangular) mesh.


Surface Meshing (3D Planar EM)– MoM only meshes metals. MoM Does not mesh

dielectrics

– Sonnet planar MoM meshes with 2D elements on the surface of metals.

– Shielded environment– Sonnet planar MoM uses a shielded formulation. – Sonnet defines a simulation problem in a

conducting box. – Sonnet uses a background grid for a spatial FFT.

Top down

view of CPW

junction

showing the

current

density

Rectangular

mesh

subsections

visible


– Sonnet’s simulator technique performs

electromagnetic analysis for arbitrary 3D planar (e.g.,

microstrip, coplanar, stripline, etc.) geometries,

maintaining full accuracy at all frequencies.

– em, the simulator, is “full-wave” in that it takes into

account all possible coupling mechanisms.

– The analysis inherently includes dispersion, stray

coupling, discontinuities, surface waves, moding,

metallization loss, dielectric loss and radiation loss.

– Since em uses a surface meshing technique, i.e. it

meshes only the surface of the circuit metallization,

em can analyze predominately planar circuits much

faster than volume meshing techniques.

Sonnet


Sonnet EM Analysis

Sonnet calculates all the coupling between all of the

currents including currents on different metal layers

and vias.

Sonnet captures and calculates coupling that is not

included in closed-form circuit-level modeling. Coupling


Sonnet Problems in a Box

The sides of the box are

perfectly conducting grounds;

boundary values for Green’s

functions used in the

simulation. This gives the

technology very high accuracy.

The top and bottom of the box

can be changed to 377 ohms.

Dielectrics are uniformly thick

layers.

Sonnet defines a simulation problem inside of a

perfectly conducting box.

…hence the description ―shielded‖ planar MoM for Sonnet


Sonnet Operates on Geometry

Sonnet em

simulation takes

circuit layout

geometry as its

input.

Schematic Capture

(e.g. Cadence® Virtuoso®,

Agilent ADS,

AWR® Microwave Office®)

Circuit

Simulation

LayoutEM Simulation

Sonnet can also get

substrate and

frequency

information from

frameworks.


Sonnet Outputs

em

S,Y,Z parameters(Touchstone, Compact, CSV formats)

Far-Field Antenna Patterns

SPICE model extraction(SPICE, Hspice) pi, and broadband “BBSPICE”

Current Density information(JXY file) for Sonnet post-processors

Outputs from Sonnet’s simulation engine

―em‖ include:


1+-

Sonnet Box-wall Ports

The box wall provides perfect ground reference

Sonnet box wall ports are infinitesimally inserted between the transmission line and the perfectly conducting box wall.

top down view

The lab bench analogy to a Sonnet port is a voltage source inserted in a finite gap between the transmission line and the box wall.


Sonnet Box and Cell Size

160

10

Circuit -> Box in xgeom

top down view


Sonnet Box Dielectric Stack Up

Circuit -> Dielectric Layers

10

1003D view

Defining the

dielectric layer

stack up in

xgeom


10 mils of er = 3

100 mils of er = 1

air

First Sonnet lab example - microstrip

filter using default box and cell size.

1 cell wide and entire

length/width of box

4 cells above and 4

cells below

Top down view in xgeomentire box is 16 cells by 16 cells

We’ll analyze

this structure

from 0.1 to 40

GHz.

Hands-0n Lab: Example 1

Microstrip Filter


Start Sonnet

Turn on your PC and do a ―Start => Programs =>

Sonnet 12.52 => Sonnet‖ sequence.

The Sonnet Task Bar will appear on your display.

We are going to make a model.

The

Sonnet

Task

Bar


Start Model

Click on ―Edit Project‖ in the Task

Bar and select ―New Geometry‖.

The Project Editor Window (xgeom)

will open.


Edit Dielectric Stack-Up

Do a ―Circuit => Dielectric

Layers‖ sequence to open

Dielectric Layers window.

Top of Project Editor


Set Layers for Microstrip

Select lower layer and

click on ―Edit‖.

Define the substrate

dielectric: 10 units (mil)

thick of epsilon 3.

Select upper layer (air)

and change thickness to

100.

You do not need to

rename the layers but

can if you wish.


Use Toolbox for Microstrip Line

Highlight ―Adds a rectangle‖ in the Toolbox

and make a rectangle 1 square high running

from left to right in the Project Editor. The

rectangle should end at the box walls. Place

the rectangle in the middle of the box; top to

bottom.


Make Side Arms

Repeat the process, making a second rectangle as side arm (stub).

Side arm goes 4 squares above to 4 squares below the through line.


Add Ports to Ends of Through

Select ―Add Port‖ in Toolbox.

Click on end of through to add

a port.

Repeat for other end of

through.


Set Up Analysis

Do an ―Analysis => Setup‖ sequence and

define range of simulation: 0.1 to 40 (GHz).



Save Model and Run

em in the Project

Editor runs the

simulation; also

found in Task Bar



Watch Results Appear


View Response

Click on ―View Response‖ to

see plots of the S-parameters.


Plot the Results You Wish

The response viewer emgraph will open and you will see S11 in dB.

To see other results, do a right click on the ―Curve Group‖ and ―Edit Curve Group‖ to select results.

Add S21 to the plot.


S11 & S21

We made

a low pass

filter!


Starter Filter Lab Extra Credit

Make the cell size smaller, 2.5

mils square rather than 10 mils

square.

Resimulate and see if the

increased resolution and

accuracy changes the results.

How did the change affect

simulation time?

The box settings dialog box can

be found by going to ―Circuit =>

Box‖ in the xgeom project editor.


Method of Moments Both shielded and

unshielded work as follows:

Divide surface of metal into

N subsections.

Calculate coupling between

subsections.

This coupling fills an NxN

matrix.

Invert matrix for current

distribution and S-

parameters.


Sonnet Cells & SubsectionsCells make up the background spatial FFT grid. This FFT is used

to rapidly give a high quality Green’s function for the coupling.

Subsections are what Sonnet uses for simulation.

1 cell Subsection

same as 1 cellSubsection made

of multiple cells


Cells and Subsections

Sonnet sets up a uniform grid of cells

in the workspace. These are the

smallest pieces of metal which will be

analyzed.

The cells are combined into

subsections. The subsections are

graded in size and shape depending

upon what is nearby.

The model size and simulation time

grows as the number of subsections

increases.

cell

subsection


Sonnet Captures Edge Currents

Sonnet accurately captures the physical edge current on

transmission lines. These currents affect the loss in the

transmission line.

Regions

of high

edge

current


Other Features in Sonnet

• Conformal Mesh – for curved transmission lines

• Thick Metal Modeling – using multiple sheets

• Integration with AWR, ADS, and Cadence

Virtuoso

• Co-calibrated ports – calibrated internal ports

• SMD – circuit elements in Sonnet layout

• Remote EM Analysis Job Queuing

• Cluster Computing – with or without LSF

• Multithreading up to 8 cores with high

performance solver


De-embedding Find this entry on de-embedding in the Sonnet User’s Guide

Chapter 7

De-embedding

Each port in a circuit analyzed by em introduces a

discontinuity into the analysis results. In addition, any

transmission lines that might be present introduce phase

shift, and possibly, impedance mismatch and loss.

Depending upon the nature of your analysis, this may or

may not be desirable. De-embedding is the process by

which the port discontinuity and transmission line effects

are removed from the analysis results.


De-embedding in T & M

Device

Under

Test

(DUT) cable

A hardware device under test is connected to the cables/probes of a

vector network analyzer (VNA).

The reference plane of the VNA measurement is shifted to the DUT in

order to deembedded the cables/probes removing their effects from

the measurement.

To VNA

cableTo VNA


Deembedding Designs in em

Port

Metal

Box

Walls

Sonnet

Design

(DUT)Transmission Line

A Sonnet design may be isolated from the side walls of the

box by using deembedded transmission lines.

Sonnet does not require the use of deembedded

transmission lines. Some designs can touch the box walls

directly.

Sonnet perfectly deembeds box wall ports with or without a

deembedded transmission line.

Port

Transmission

Line


No Shifted Reference PlanesIf we wish to include the

feedline effects in the results

the branchline coupler

simulation does not need to

include shifted reference

planes.

Sonnet calibrates out the

effects of capacitive coupling

between the Sonnet box wall

and the transmission lines

going to ports; the port

discontinuity.

Whether or not to use shifted reference planes to de-embed

transmission lines depends more upon how close the rest of

the design can be to the Sonnet box.


Shifted Reference PlanesAdding the length of transmission line and shifting the reference

plane moves the body of the branchline coupler further away from

the box walls horizontally without changing the electrical length of

the coupler leg.

This distance is longer than in the example

without shifted reference planes.


Exercise 2 – Zero Length Thru

1. The theoretical results for a zero length through-line can be exactly

defined, no matter what the line type:

a) |S11| and |S22| = 0

b) |S21| and |S12| = 1

c) Ang(S21) and Ang(S12) = 0

2. This simulation measures the accuracy of the em calculation and the de-

embedding algorithm.

3. It determines the noise floor of the simulation. If the response you’re

looking for is not well above this level, the results could be in question.

For example, if the noise floor is about –45 dB you can’t expect to get

reliable results for a filter that needs a 50 dB of rejection.

De-embed from both ports to effect zero length. Why?


ZLT Simulation Plan Define the working environment

– Box 500 x 160 mils with cells 10 x 5 mils

– Box lossless top and bottom metal

– Symmetry

– Default units of mils and GHz

Define the geometries

– Dielectric layer 50 mils of er = 10.2 loss tan 0.002

– Air dielectric layer of 500 mils above substrate

– Metal for polygons copper: conductivity 5.8 e7, thickness = 1.34, CR = 0

– Rectangle of width “w” (20w50) on layer 0 running from x = 0 to x= 500 centered on symmetry line.

– Ports at both ends with reference planes shifted into the middle so as to touch.

Define the type of analysis to be done

– Analyze from 1 to 10 GHz in one GHz steps

– Linear frequency sweep

Simulate and analyze


Start Sonnet: Sonnet Task Bar

After starting Sonnet,

the Task Bar will open.

You can start a new

project by Selecting

―Edit Project‖ or merely

clicking on ―Project‖.

Then you may start a

new geometry or netlist

or select an existing

project.

Start a new Geometry.

1

2

3}


Starting a Design

This blank Project Editor window with a Quick Start Guide and

Toolbox opens if you select New Geometry to begin a project.

Quick Start Guide: A very

good help in starting a new

model by importing a CAD

file or drawing in Sonnet.

Project Editor

Toolbox

Read Sonnet Suites Getting Started Manual!


Quick Start Guide

If you chose to Draw manually in Sonnet

and click on Next in the opening Quick

Start Guide, this window will open.

If you chose to import

a dxf, GDSII, or Gerber

file type, this

alternative window will

open.

Both windows walk

you through the steps

needed to get a model

running.

Some steps are

optional because

Sonnet has default

settings.


Defining the Circuit

Basic parameters of the circuit are defined from the Circuit button on the Project Editor.


Box Parameters

Click on Circuit

Chose Box

This is an important

window: you set the

mesh size, the work

space (Box Size), add

symmetry if possible,

and pick the metal for

the top and bottom of

the box.


Magnetic Symmetry ―Mirror‖

Checking ―Symmetry‖

places a ―mirror‖

across the Sonnet

box; right to left. The

top half of the box is

the only portion

simulated. It is

mirrored across the

dotted line with the

same sign to the

electric field. This will

reduce the time and memory by 75% BUT

be certain the

excitation has the

symmetry set by this

magnetic wall.

Set the box as shown above.


Material Libraries

If you follow the instruction in the QSG to Specify dielectric layers or

Specify metal types, a window will open in which you can define the

materials or select from a Library. Sonnet has set-up Global

Libraries and you can Specify your own.


Lossy Metal

Do a ―Circuits =>

Metal Types.‖ The

window to right will

pop up. To define

lossy metal, ―Add‖ a

metal type.

After you have

added all the metals

you want, select one

to be the default

―Metal for New

Polygons‖.


Metal Editor

The Metal Editor will

open if you ―Add‖ a

metal type and you

can define the metal.

You can select a metal

from a library but you

still need to edit the

thickness. We want

1oz Cu, 1.34 mil thick.

The thickness

specified affects loss

calculation. Sonnet

models metal layers

as infinitely thin.

Add Copper to the

metal types.


Dielectric Layers

Click on Circuit

Chose

Dielectric

Layers

Add, Edit, or

Delete layers

Location in dielectric

stack of metallization

layer(s)


Dielectric Editor

After you chose a particular dielectric layer and select ―Edit‖, the

window to the right opens and you define the dielectric

properties and thickness of the layer. Edit the lower dielectric

layer as shown above. Edit the top to be 500 mil of epsilon 1.


Adding a Metal Polygon

metallization

layer

The Toolbox is your friend.

Can be used to input metal shapes,

ports, vias, etc.

This icon adds rectangles: click &

draw

Add a metal

rectangle

centered on

the symmetry

line and

running from

the left to the

right box wall.


Ports

Move to the metallization

layer where you want the

port.

Use the Toolbox and click on

the Add Port icon.

Click on the polygon edge

where you want the port.

In Sonnet Lite you can use

internal ports as well as the

standard box wall ports.


Move the Reference Planes

Modeling a Discontinuity Internal Port Placement

The reference planes for ports can be shifted from the edges of the workspace.

―Circuit Ref. Planes/Cal. Length‖ brings up a window where the location of

the planes may be defined.

Move (Fixed) the reference planes from the left and right so they touch.

If lost click on ―Help‖


Hints from ―Help‖

If you get confused about features of Sonnet (such as

reference planes), the on-line Help and the User’s Guide can

be of great help.


Setup an em Simulation

Click on Analysis.

Chose Set Up.

Select the type of

Analysis Control

you wish to use.

Save File.

Setup the analysis to

be a Linear

Frequency Sweep

from 1 to 10 GHz

using 1 GHz steps.


Analysis Monitor: Response

Click on em in the Task

Bar or in the Project

Editor to start simulation

Select Project

Simulation starts

View Response or View

Current from here or from

Task Bar.

Response Data begins to

appear as the solver runs.


Analysis Monitor: Timing Info

Timing Info

contains

simulation times

and memory

requirements.


Response Viewer

Other curves

can be added

to the plot by a

right click on

the Curve

Group.


ZLT Results

Leave DB[S11] on

the left axis and

add ANG[S21] to

the right.

Both results

should be VERY

close to 0.

This shows that

Sonnet has a low

noise floor for

deembedding

and shifting

reference planes.

Try this with

other simulators.


View Current

If the ―Compute

Current Density‖ box

had been checked in

the set up (see above),

you can see the

currents.

Setup for current

density and analyze

from 1 to 10 GHz

using 1 GHz steps.


ZLT Current

metal layer frequency


What have we learned?

To build a model in Sonnet:

1. Define your working environment first. This

includes box size, metal types, and dielectric

layers.

2. Use the Toolbox to put metal shapes on the

proper layers and to add vias and ports.

3. Set up the analysis type proper for your

model: ABS, parameter sweep, etc.

4. Check yourself (and your software)

occasionally by doing a simple model for

which you know the results.


Exercise 3 LP Filter (more detail)

•Parameterization

•Parameter Sweeps and Optimization


Open the ―Starter‖ ModelWe will take the

model first built in

this training class

and parameterize it

to change the

geometry.


Initial Box Settings

If you wish to keep the original model, save it to a new file name.

Do a ―Circuit => Box‖ sequence to open the Box Settings. Lock

the Box Size and change the number of cells per side from 16 to

64. Then turn on symmetry. If your through line was not split in

half by the dotted symmetry line, select all your geometry and

slide it up or down to center it in the box.


Model with Symmetry On


Anchored Parameter: Stub Width

Notice that you can add a

dimension label (Tools => Add

Dimension) as well as a parameter.

Parameters are used to set

the distance between two

points. You can also

include other points which

will move with one of the

control points or the other.

We want to parameterize the

width of the stubs. To do

this we will use an anchored

parameter. We want to fix

(anchor) one edge and

move the other.


Setting First Control Point

For anchored parameters, the first control point does not move. After

selecting to add an anchored parameter, click on the first (fixed)

control point. We chose one of the points on the stub. Note that a

prompt shows at the bottom left of the Project Editor, helping you

decide what to do next.

Prompt at bottom of Project Editor

Select the

anchor point


Second Control Point and

Additional Points

Click on the second control

point (reference point), on the

other side of the stub. Again,

there is a prompt.

You now add any additional

points you want to move

when the second control

point moves. We want to

move the other corner

(bottom edge) of the stub.

You can click on the point or

window it. You again have a

prompt. After selecting the

other point, press ―Enter‖ on

the keyboard.


Labeling the Parameter

After pressing Enter, a window will pop up

and you can input a name for the

parameter. A parameter call out will appear

on your geometry and you can position it

with your mouse. Doing a left click will fix

the call out in place.


Adding a Symmetric

Parameter: Stub Line Length

We want to keep the filter

centered top/bottom as

we change the stub

length.

To do this we add a

symmetric parameter to

adjust the length.


First Control Point and

Additional Points

For symmetric parameters, both

control points move and you may wish

to have additional points move directly

with them.

After selecting to add a symmetric

parameter, click on the first control

point. Then select the additional

―points to be adjusted‖.

Press ―Enter‖ on the keyboard, letting

the software know you are done with the

first group and moving on to the

second.

First control

pointOther point to

be adjusted


Second Control Point and

Additional Points

Select the second control point

and the additional points

following the prompts at the

bottom of the Project Editor.

Press ―Enter‖ and the window

will pop up where you can input

the name of the parameter. The

call out will appear on your

geometry and you can move it

to a good location.

Second

control point

Other point to

be adjusted


Circuit Variable ListAfter setting a few parameters, you can do a ―Circuit

=> Variable List‖ sequence to open a table of the

variables for the model.

The values from the table can be manually changed

to see the redesign of the model, and to check the

setup of the parameters.


Parameterized Model

Make the model and

analyze from 0.1 to

40 GHz using ABS.


Filter Response With Initial,

Arbitrary Parameters


Parameter Sweep

Do an ―Analysis => Setup‖ and change the analysis Control to a

parameter sweep. In ―Parameter Sweep Entry‖ window select an ABS

sweep from 0.1 to 40. Select ―ws‖ to sweep between 10 and 40 mils.


Setup for Sweep of Stub Width

Analyze from 0.1 to

40 GHz using ABS

and sweeping the

stub width. This

took 7 seconds on a

2.6GHz Core 2 Duo

CPU laptop

With Sonnet Lite, you

can sweep one

parameter at a time

With LitePlus you

optimize one

parameter at a time


Viewing Sweep Response

After the simulation has

finished, view the

response. Edit the

curve group and “Select

Combinations” to see

results for different

parameters. “Select All”

the parameters and plot

S11 on the left axis and

S21 on the right.


Sweep Results

If you position the

cursor over a data

point, the values

for that point will be

shown



To help build geometries in Sonnet:

1. Build the correct topology in an “easy” form first.

Then parameterize the model and adjust the

parameters to give the correct geometry.

2. Parameterize your models out from one point to

avoid circular definitions.

3. Use both anchored and symmetry parameters to

get the correct “growth” of your models.

4. First adjust your parameters using engineering

knowledge then use parameter sweeps and

optimization to find the final design.


Sonnet Lab 4: Spiral Inductor

• We’ll create an inductor and

isolate it in the box by shifting

reference planes.

• We’ll start with the palette of

geometries to generate the

inductor shape.

• We’ll simulate the inductor and

measure the inductance.


Lab 4 Specifications Summary Define the working environment

– Top dielectric 150 mils of air er=1 no loss

– Second dielectric 3 mils of air

– Bottom dielectric 10 mils of Rogers RO4232 from global library

– Box 300 x 300 mils with cells 2 x 2 mils

– Box free space top and lossless bottom

– Default units of mils and GHz

– Create a metal type ½ oz. copper 0.68 mils thick and sigma = 5.8 e7.

Synthesize the inductor

– 3.5 turns

– 4 mil width and 4 mil gap

– 1st and 2nd turn lengths both 58 mils

– Air bridge above

– Shift reference planes from the box wall out to the inductor

Define the type of analysis to be done

– Analyze from .1 to 4 GHz using ABS

– Put a fixed frequency point at 1 GHz

Simulate and analyze


―Design‖ the Inductor

• We want a filter from a linear simulation program using inductors

and capacitors. The capacitors will be SMD; ―ideal‖ components.

The inductors will be microstrip coils.

• First we will ―design‖ the inductor.

• Start a Sonnet model using the default units (mil) and set the

dielectric layers as shown here: 10mil of RO4232, 3mil air, and

150mil air.

• The added middle air layer is for an air bridge on the inductors.


Add Lossy MetalDo a Circuit => Metal

types to bring up the

table of metals for the

model.

Click on ―Add‖ to add a metal

type.

In the metal editor window

click ―Select metal from

library.‖


Select Copper from Library

• In the metal library select Copper and click on ―OK‖ to move

Copper into the metal editor.

• In the metal editor set the thickness to 0.68 mils.

• Then click on OK to add the metal types for the model.


Use ½ oz. Cu

• After ½ oz. Cu, 0.68 thick, is in the metal types set it as

the metal for new polygons.

• Leave CR=0.


Specify Sonnet Box• We will use lines and

spaces for the

inductors which are

4mil wide. To get good

accuracy with low

memory requirements

we set the Sonnet box

to have 2mil cells.

• The box should be

300x300mil in size to

hold the final filter.

• Take the ―lid‖ off the

box by setting the Top

Metal to Free Space.


Build a Rectangular Spiral

Move to level 1 in the stack up for the coil metal. Then use the

Toolbox to build a rectangular spiral. Make a 3.5 turn spiral with 4mil

conductors and spacing. Set the starting sides to 60mil and 58 as

shown. These dimensions were chosen to give us an inductor near

the design value. Use an air bridge above the spiral. The tool will add

vias and a short line on the level above the coil.


Spiral and Feed Lines

Put the spiral in the middle of the Sonnet box. Add 4mil

wide lines (2 cells) to the spiral. These run to the side

box walls.

Feed line Vias and air bridge

Feed line


Add Ports to Feed Lines

Use the Add Port tool (circled icon) to add ports (circled) on the

feed lines at the box walls.


Shift the Reference Planes • Save the model as ―coil‖

• This model is used to

calculate the inductance of

the spiral.

• To accurately obtain the

inductance of the spiral we

need to shift the reference

planes for the ports into the

spiral, removing the effects

of the box wall and feed

lines.


Link Reference Plane to Coil• In the window setting the reference plane, link both the left

and right to a polygon using your mouse.

• Select the edges of the spiral as the locations.


Analysis Setup

• The low pass filter is

designed with a band edge

of 1 GHz.

• We used a Frequency Sweep

Combination to force a point

at 1 GHz.

• Set up the analysis to cover

0.1 to 4 GHz with ABS. This

will check out-of-band

response.

• Save the model and

simulate.


Single Spiral Response


Coil Effective Inductance• View the response,

S11, and add an

equation (Inductance

1) to the right axis.

(Right click – add

equation curve)

• Place the cursor on

the inductance near 1

GHz to read an L of

9.91nH; at 1.0GHz.

This is close to the

desired 9.8nH

• Above 4GHz, the coil

is capacitive. It has

gone past the self

resonance frequency.


Sonnet Components for Surface

Mount and Internal Devices in EM

Simulation


Surface Mount Devices and

Simulation Surface Mount Devices (SMDs) are

very popular in compact high frequency designs.

They can be discrete components (L, R, C, transistors, SAW devices, etc.) or more complex multi-pin packages.

The SMD-to-board interface is electrically important; most high frequency simulators do not account for this.

Pads and SMD terminals represent RF discontinuities that can be significant.


Sonnet has a very basic linear frequency circuit simulation capability included.

Sonnet linear simulation is used in the components feature and in the netlist projects feature.

Sonnet Has Linear Simulation

Sonnet can mix linear circuit simulation with EM simulation. Hierarchically, the EM structure is one circuit element.

green metal

Sonnet EM

simulation

capacitors

circuit

simulation


Sonnet Components

EM analysis can

included surface

mount devices—either

ideal or with vendor-

supplied S-parameter

models in Sonnet

Components. Only

ideal components in

Sonnet Lite.

Components may be

left as ―Ports only‖ so

that SMD models may

be attached in another

RF circuit simulator.

4-Port Amplifier model

embedded in EM simulation

(linear)

2-Port surface mount

resistors, capacitors,

inductors embedded in

EM simulation


Internal Components

Sonnet Components can represent Surface Mount Devices, elements buried in a dielectric stackup or ideal lumped elements

Combines both EM and netlist simulation

Component model automatically included by Sonnet netlist, or in your favorite framework (ADS, MWO, Cadence, etc.)

S-parameter SMD models (such as provided by SMD vendors) may be used

Provides an accurate way to account for parasitics associated with surface mount pads and device terminal discontinuities

Utilizes Sonnet’s General Local Ground (GLG) technology with automatic Co-Calibrated™ (CC) Ports – New in Sonnet Suites Release 11


The Connection Matters

SMD Package

Contact Terminals

SMD Package

Current Density under the

package shows discontinuities

around contact pads. Sonnet

characterizes and includes

these discontinuities in your

analysis

RF discontinuities

under package

parts must be

accurately

included.

The SMD contact

terminal width is

important to the

size of the

discontinuity.


Class Example: SMD Low-Pass

Filter (LPF)

• Sonnet Lite allows circuits with 3

ideal components.

• We will build this LPF in Sonnet

using microstrip coils and ideal

capacitors.

• This will be implemented on 10-mil

Rogers RO4403 with ½-oz copper.

Initial lumped element design

of a Chebyshev LPF from

AWR Microwave Office Filter

Synthesis Wizard.


Start the Filter Build

• The initial simulation

of the spiral was to

find the proper

inductance.

• Now we use this coil

to make the designed

LPF.

• Discard the feed

lines and ports.

• Select all of the coil,

slide it to the left and

use Copy and Paste

to make a duplicate.

Copy and paste tools

original

copy


Modify (flip) the Coil Copy


Position the Copied Spiral

Select all of the copied & flipped spiral and position it

with the air bridges in line and the vias 20mil, 10 cells,

apart. Add a rectangle to connect the spirals.

vias

Connecting trace


Add 24mil Wide Feed Lines

Position the coil pair near the center of the box and add 24mil wide

feed lines. These will be near 50 ohms on 10mil RO4403.


Add Pads for SMD

• Add two 20x12 mil pads for

the SMD capacitor between

the coils.

• The pads should be 24mil

apart.


Add Pads for Outer SMDs

Copy the pair

of pads

between the

coils and add

them to the

input and

output sides

of the filter.

Add box wall

ports at the

ends of the

feeds.


Adding an Ideal SMD Component

Do a ―Tools => Add Component => Ideal‖

sequence and add a 5.4pF capacitor. Assume the

terminals for the capacitor are 12 mil wide. The

―Assistant‖ should help answer questions.


Creating an Ideal SMD

Ideal Components are 2-terminal devices (R, L, C)

The connection width can be the entire line width, one cell (Sonnet grid), or a user-defined width

This should be sized for the SMD terminal contact width, if known

Physical size of the package may be specified, but is only important for visualization


Add Cap Between Pads at Input Side

of Circuit

Check to be certain you are on metallization layer 1. Then move

the cursor to the edge of the top pad at the input, left figure

above. Notice the blue triangle at the center of the edge. Click

there and then move the cursor down to the edge of the bottom

pad, right view. Notice the X in the center of that edge. Click

there to place the cap between the pads.


Component Assistant

A Component Assistant automatically opens during this process with helpful reference information and setup tips.

Component Assistant is Context Sensitive for any item on the Component menus—just click.


Add Physical Size

If you desire for visualization, a physical size can now be added to

the component. Do a right click on the component and chose

Component Properties. Then select the physical size you want.


Copy & Paste First Cap

• Using the standard

Windows tools,

select the first

capacitor, copy and

paste it.

• Slide the copy into

place between the

second pair of

output pads.

• Be certain to align

the component

properly on the pad

edges.


Add Third CapacitorPaste another copy of the

cap between the center

pair of pads. Right click on

this component and

change it to 8.1pF.


Add Vias to Ground• Use the Toolbox to add

Edge Vias to the

outside side of the SMD

pads.

• Select the via icon and

then the outer edge of a

pad.

• Note the yellow icon

with a downward arrow

head and a ground

symbol. This indicates

that the via you add will

go down to ground.

• Add grounding edge

vias to all three

capacitors.

Edge via down

Via rectangle up


The Connection Matters

SMD Package

Contact TerminalsSMD Package

Current Density under the

package shows discontinuities

around contact pads. Sonnet

characterizes and includes

these discontinuities in your

analysis

RF discontinuities

under package

parts must be

accurately included.

The SMD contact

terminal width is

important to the size

of the discontinuity.


Set Up Simulation

Do an Analysis => Setup

sequence to open the analysis

parameter window. In the

Analysis Control box use the

default ABS setting and set

the range to 0.1 to 5 GHz.

Then save the model and

simulate.


Oops: Error

Using Sonnet Lite the

simulation will fail

immediately due to an error.


Error: Too Much Memory for Lite


Adjust Speed/Memory

Go to the Speed/Memory window from the Analysis Setup. Move

the slider to the middle position, Coarse mesh with Edge Meshing.

This will reduce the memory but hopefully not lower accuracy too

much.


Click on em to Start Simulation

The ABS sweep

should require 7

simulations, each

needed about 4

seconds.


Response Data for Design

• Now the simulation needs

only 13 MB and runs on

Sonnet Lite.

• On a 2.6GHz Core 2 dual

CPU laptop it takes 4 sec.

per frequency.

• ABS needs 7 samples to

converge for broadband

results.


Sonnet LPF S-Parameters

• Note the null near 2.76

GHz.

• If one of the spirals is

flipped vertically to

reverse the sense of

current flow, the null

disappears.

• The null comes from

coupling which you see

only with an em

simulation.

flipped vertically


Current View

Click on View

Current to bring up

emvu. Select a

metallization layer

and frequency.

Notice current flow

on the pads, around

the contacts for the

components.

metallization

layer

frequency


3D Current View

The current view was changed to 3D; top left.

The swirling of current up vias and around on the

pads can be easily be seen.


More Refined LPF Meshing

The model was run in

Sonnet Pro with the

high accuracy setting

in Speed/Accuracy

and with 1mil cells.

It required 137 MB,

10x the Sonnet Lite

model.

The results however

are nearly identical.

They overlap in this

figure.



1. Ideal Components make it very easy to run initial prototype simulations that include all EM effects of the interconnects and vias.

2. Vendor models (Data File Components) can be added for realistic circuit modeling.

3. Ports-Only Components let you build EM models for full layout and leave connection ports where you can add your devices in a circuit simulation framework.

4. Current Density can show the effects of the Components.

5. Sonnet Components put EM simulation to the front-end of high frequency circuit design.

Documents

Sonnet Lite Seminar