Lecture 4: HFSS 3D Layout - · PDF fileLecture 4: HFSS 3D Layout Introduction to ANSYS HFSS . ... – Select the menu item Layout > Draw HFSS Air Box – Select the menu item View

Release 2015.0 April 15, 2015 1 © 2015 ANSYS, Inc.

2015.0 Release

Lecture 4: HFSS 3D Layout

Introduction to ANSYS HFSS


HFSS 3D Layout Workflow

Layout Stackup Circuit Elements

Excitations

HFSS Setup

Initial Mesh Adaptive

Mesh Solve

Frequency Sweep

Post Processing

HPC HPC

GUI

Solve HPC

Mesh

Solution Process

Design Setup


Example: PCB Layout

• PCB Layout Exercise • This example is intended to show you how to create, simulate, and analyze a section of PCI Express Gen 3 printed circuit board by

extracting S-parameters of the selected net SECONDARY3 utilizing ANSYS HFSS 3D Layout capabilities. This example covers the following topics:

– Creating a sub-design

– Creating Ports

– Analysis Setup

– Extracting S-parameters


HFSS 3D Layout Workflow

Import Layout Stackup Circuit Elements

Excitations

HFSS Setup

GUI

Solve HPC

Mesh

Design Setup

3rd Party Layout


• Importing a Layout • Note: In order to follow the steps outlined in this example, verify that the following applications are installed:

– ANSYS Electromagnetics Suite 2015

– ANSYS Alinks for EDA

– Cadence Allegro 16.x (optional)

– Download brd file from: http://www.intel.com/content/dam/www/public/us/en/documents/reference-guides/pci-express-gen-3-connector-high-speed-ceb-reference-design.zip

• Note: If you do not have access to Cadence Allegro, contact ANSYS Technical Support for an archive of the training examples layout.

• Launching ANSYS Electronics Desktop 2015.0 • To access ANSYS Electronics Desktop, click the Microsoft Start button, select Programs > ANSYS Electromagnetics > ANSYS

Electromagnetics Suite 16.0. Select ANSYS Electronics Desktop 2015

Getting Started

http://www.intel.com/content/dam/www/public/us/en/documents/reference-guides/pci-express-gen-3-connector-high-speed-ceb-reference-design.zip

























Import BRD File

• Import Cadence Layout (BRD) • Note: Skip to the next page if you do not have Cadence APD installed

• Select the menu item File > Import > Cadence APD/Allegro/SiP

– File name: pcie_gen3_fab3.brd

– Click the Open button

• Extract Import dialog box opens up

• Click the OK button

From the Extracta Import window, we can select only the Nets to imported and also setup the Port excitations by checking the box under Setup ports. For this exercise, we will go with the default settings


Import aedtz File

• Restore Archive (aedtz) • Note: Skip to the next page if you imported the Cadence APD brd file

• Select the menu item File > Restore Archive

– File name: pcie_gen3_fab3.aedtz

– Click the Open button

– Project File Restore Location Dialog

• Open project after restoring

• Click the Save button


HFSS 3D Layout Desktop

Property Window

Project Manager

Layout Editor

Message Manager Progress Window

Components Window

Nets Window

Layers Window

Menu bar Tool bar


Project Manager Window

• HFSS 3D Layout Desktop – Project Manager • Multiple Designs per Project

• Multiple Projects per Desktop

• Integrated Optimetrics Setup

Project

Design

Simulation Results

Design Setup

Optimetrics Setup •Parametric •Optimization •Sensitivity •Statistical

Project Manager Window


Changing the View

• Toolbar

• Layout Context Menu • Right-click in the Layout Editor and select View

Zoom In

Zoom Out

Zoom area

Fit All

Zoom Selected

Zoom previous

Pan

Rotate

Reset Orientation

Solid Default

Sketch

Display Modes


Changing the View (Continued)

• Layers Window • Controls the Stackup view. Select the menu item View > Layers

Fill/Unfill All

Show/Hide All

Shapes

Lines

Pads

Holes

Components

Stackup/Non-Stackup Layers

Click the radio button to make the layer active

Here TOP layer is the Active layer



• Nets Window • Controls Net Visibility. Select the menu item View > Nets

– Corresponding Nets will be displayed based on the selected category in Nets Classification

– Click on the Net and right-click to select one of the options (Show, Show (Hide All Other), Create Ports, etc...)

Nets Classification

Nets



• Components Window • Lists the Components present in the design. Select the menu item View > Components

– Click on the component and right-click to configure either Ports or Solder ball properties across the component.

List of Components Use the Components Window to select the component or a component class

and configure either Ports or Solder ball properties across the component



• Component Libraries Window • Select the menu item View > Component Libraries

– Built-in circuit components (active, passive, and distributed device models from transistors to tranmission lines) are included.

– External models can be imported.

In general for 3D layout designs, we can hide the Component Libraries window



• Shortcuts • Since changing the view is a frequently used operation, some useful shortcut keys exist. Press the appropriate keys and drag the

mouse with the left button pressed:

– Fit All: Ctrl + D

– Rotate: ALT + Drag or Click Center Mouse Button (click wheel) + Drag

• In addition, there are 9 pre-defined view angles that can be selected by holding the ALT key and double clicking on the locations shown on the next page.

– Pan: Shift + Drag

– Dynamic Zoom: ALT + Shift + Drag or Mouse Wheel

Predefined View Angles

Top

Bottom

Right Left


Edit Stackup

• View the Layer Stackup • Select the menu item Layout > Layers

– Click on the icon in the top row to toggle the visibility of all layers on. Click the Apply button

– Units: mil

– Select the row Name: BOTTOM

• Thickness: 1.9mil

• Material: From the pull-down, select COPPER

• Dielectric Fill: From the pull-down, select Air

– Select the row Name: UNNAMED_006

• Thickness: 3mil

• Material: From the pull-down, select Edit

– Select: Nelco N4000-13 SI (tm)

– Click the Apply and close button when you are finished

LAYER3 (1.4mil)

LAYER2 (1.4mil)

TOP (1.9mil)

BOTTOM (1.9mil)

Nelco 13 SI (3mil)

Nelco 13 SI (3mil)

Nelco 13 SI (49.4mil)

Stackup


Verify Material Properties (Continued)

• Verify Material Properties • Using the Project Manager, expand the project tree to display the Materials within the Definitions folder

– Double-click on the material: Air

• View/Edit Material Dialog

– Material Name: Air

– Relative Permittivity: 1.0006

– Relative Permeability: 1.0000004

– Click the OK button

– Double-click on the material: COPPER

• View/Edit Material Dialog

– Material Name: COPPER

– Relative Permittivity: 1

– Relative Permeability: 0.999991

– Conductivity: 59590000

– Dielectric Loss Tangent: 0

– Press the OK button

Stackup


Cutout Subdesign

• View All • Select the menu item View > Fit Drawing. Or press the CTRL+D key

• Create User Layer • The following steps will create a “user” layer that will be used to draw the cut-out region

• Select the menu item Layout > Layers

– Display: Non-stackup layers

– Using the mouse, click on the row for the layer Measures

– Press the button Insert Above to open the Add Layer Dialog

• Name: Region

• Type: User

• Press the OK button

– Press the Apply and Close button

• Set Active Layer • There are two easy ways to set the active drawing layer

1. From the toolbar, locate the toolbar for the Active Layer. From the pull-down, select the layer Region

2. From the Layers window, check the radio button for layer Region

Layout

View > Layers

Active Layer Layers Dialog


Cutout Subdesign

• Create a Rectangle for the cut-out • Select the menu item Draw > Primitive > Rectangle

– Using the coordinate entry at the bottom of the windows, enter the following:

• Units: mm

• X: 0, Press the Tab key

• Y: 35, Press the Enter Key

• Press Tab key twice

• Delta X: 105, Press the Tab Key

• Delta Y: 25

• Press the Enter Key

• Save the project • Select the menu item File > Save

Layout


Cutout Subdesign

• Cutout Subdesign • With the rectangle selected, select the menu item Layout > Cutout Subdesign

– Click on the column Include to select all nets for clipping

– Click on the column Clip at extents to select all nets.


• A new design will be added to the project.

Layout

Cutout design

Clip at extents controls what happens to nets that extend past the cut-out region


Add Connections for Connector Body

• Adding Connections for Connector Body • From the Components dialog window

– Expand IC, expand IC 700000-903, Click on U10 component and Right-click

• Click on Model ...

– Die Properties

• Type: Flip chip

• Orientation: Chip down

– Solder Ball Properties

• Shape: Cylinder

• Diameter: 1.2954mm

• Mid Diameter: 1.2954mm

• Height: 1.2954mm

• Material: solder


To create connections for the connector body, we have to add Solder balls. This is done by defining Solder Ball Properties to the component

Reference plane is automatically added


Add Connections for Connector Body

• Adding Connections for Connector Body • From the Components dialog window


• Click on Model ...

– Die Properties

• Type: Flip chip

• Orientation: Chip down

– Solder Ball Properties

• Shape: Cylinder

• Diameter: 1.2954mm

• Mid Diameter: 1.2954mm

• Height: 1.2954mm

• Material: solder


To create connections for the connector body, we have to add Solder balls. This is done by defining Solder Ball Properties to the component

Reference plane is automatically added


Create Ports

• Create Ports • From the Components dialog window


• Click on Create Ports on Component...

– Select the net: SECONDARY3

– Port Configuration

• Type: Port

– Click OK


Create Ports

• Create Ports • From the Components dialog window


• Click on Create Ports on Component...

– Select the net: SECONDARY3

– Port Configuration

• Type: Port

– Click OK


Define HFSS Extents

• HFSS Extents • Using HFSS Extents, we define the computation region for HFSS.

– Dielectric Horizontal padding and the dimensions of Airbox are defined. The values can be entered as absolute values (10mm) or as percentage of the maximum of either length or width of the dielectric-polygon

• Select the menu item HFSS 3D Layout > HFSS Extents

– Dielectric

• Horizontal Padding: 0

– Airbox

• Horizontal Padding: 0

• Vertical Padding: 0.025

• Sync:


• To visualize the HFSS extents:

– Select the menu item Layout > Draw HFSS Air Box

– Select the menu item View > Rotate to rotate

HFSS Air Box

Draw HFSS Air Box


Solution Setup

• Creating an HFSS Solution Setup • Select the menu item HFSS 3D Layout > Solution Setup > Add HFSS Solution Setup

– Click the General tab:

• Setup Name: HFSS Setup1

• Solution Frequency: 2.5 GHz

• Maximum Number of Passes: 20

• Maximum Delta S: 0.02

• Save fields


• The frequency sweep setup dialog will automatically appear

– Name: Sweep 1

– Use Q3D to solve DC point

– Sweep Type: Interpolating

– Specify frequency sweep

• Type: Linear Step

• Start: 0 GHz

• Stop: 2.5 GHz

• Step: 0.01 GHz

– Options

• Relative error: 0.5%

• Enforce causality (DC point required)

• Enforce passivity

– Press the OK button

Add HFSS Solution Setup Toolbar

Solve Setup


Analyze

• Save Project • Select the menu item File > Save

• Analyze • Select the menu item HFSS 3D Layout > Analyze

• Solution Data • Select the menu item HFSS 3D Layout > Results > Profile

– To view the Profile, Click the Profile Tab.

– To view the Convergence, Click the Convergence Tab

• Note: The default view is for convergence is Table. Select the Plot radio button to view a graphical representations of the convergence data.

– To view the Matrix Data, Click the Matrix Data Tab

• Press the Close button when you are finished viewing the Solution Data


HFSS Workflow


Mesh Solve

Frequency Sweep

Post Processing

HPC HPC

GUI

Solve HPC

Mesh

Solution Process

Design Setup

Import Layout Stackup Circuit Elements

Excitations

HFSS Setup


HFSS – Automated solution process

Adaptive Port Refinement

Solve

Quantify Mesh Accuracy

Mesh Refinement

Frequency Sweep Yes No

Max(|DS|)<goal?

Initial Mesh

Adaptive Mesh Creation

Geometry Initial Mesh Converged Mesh

Initial Mesh Refine Mesh Freq. Sweep

Meshing

Electrical Mesh Seeding/Lambda Refinement

Geometric Mesh Initial Mesh


About Frequency Sweeps

• HFSS – Frequency Sweep Types • Discrete – Solves using at every sweep frequency using the mesh created during the adaptive refinement process

– Matrix Data and Fields (Option) at every frequency in the sweep

• Interpolating – Adaptively fits discrete solve points to a polynomial using the mesh created during the adaptive refinement process

– Matrix Data at every frequency in the sweep

Solve Setup


NDE: Makes it easy to interactively view plots of S-Parameters. It simplifies viewing data sets for design with large port counts. NDE also supports passivity and causality tests, SPICE and state-space model creation, and can be used to compare multiple datasets.

Reports: Reports can be updated dynamically and they are stored with the project so the plots or tables are recalled when the project is reopened. Reports support user defined equations and advanced data markers.

Matrix Data: Simulation results are updated real-time during the solution process so this is the best place to monitor the progress of the adaptive mesh process. Users can also view the Profile and Convergence from the same dialog

S-Parameter Post-Processing

Matrix Data

Reports

Post Processing

Network Data Explorer (NDE)


Viewing Results

• Create Reports • Select the menu item HFSS 3D Layout > Results > Create Standard Report> Rectangular Plot

– Solution: HFSS Setup1: Sweep 1

– Domain: Sweep

• Quantity: Select (U10.1.SECONDARY3,*)

(Use CTRL key to select both the quanties)

• Function: dB

• Click New Report button

– Click Close button

Post Processing

Hold CTRL Key to select both the quantities)


View Results

• Explore results using Network Data Explorer • For terminal data with large port-count, Network Data Explorer provides an efficient and dynamic mechanism for investigating

results.

– In the Project tree, right-click on the Sweep 1 entry and select Results > Network Data Explorer

– Set Format dB

– Check Select all


SPICE Export

• Export results using Network Data Explorer • From ndExplorer

– Click the Broadband button

• File: Select a valid path and filename using the Browse button

• Full wave spice format: Select desired output

• Click the OK button to export


2015.0 Release

Lecture 4-1: HFSS 3D Layout Design Setup

Introduction to ANSYS HFSS


Project Manager

• Project Manager • The Project Manager window provides a tree view of the design setup and is logically ordered to group Boundaries, Excitations, and

Analysis setups. This section will provide the basics necessary to understand how to proceed to setup a design after the Layout exists. It will cover Materials, Excitations, Boundaries and Analysis setup.


HFSS 3D Layout Design Setup GUI

Solve HPC

Mesh

Layout

Material Properties

Verify Stackup Simulation

Nets

Define Cut-out Region

(Optional)

Define HFSS Extents

HFSS Analysis Setup

Define Excitations

Define RLC

Adaptive Mesh Frequency

Solver Settings

Frequency Sweep


Layout Import

• Cadence Layout Import • The following layout import options are available for Cadence

– Cadence APD/Allegro/SiP

• Directly imports BRD and MCM files

• Imports layouts using the Designer Links translators which are used to enable running HFSS inside of Cadence

• Automatic import of RLC components from layout database

• Support Net filtering and automatic port creation during import

• Uses Cadence Extracta which requires Cadence to be installed on the local machine

• Requires an Alinks for EDA license

– ANX

• Exported from Cadence

• Uses Designer Links translators to import a ready to simulate design from Cadence

• Does not require Cadence to be installed

– ANF

• Exported from Cadence

• Does not require Cadence to be installed

• Mentor Layout Import • All Mentor layouts should be imported using ODB++


Stackup

Material Properties

Verify Stackup


Stackup

• Stackup - Imported Layout • The most common workflow for HFSS 3D Layout is to import an existing manufacturing based layout from a supported EDA Layout

tool. As part of the import, the layer stackup will also be imported. It is important to verify the stackup settings prior to doing any additional simulation preparation.

• The following stackup items should be verified:

– Thickness (Use Stackup Editor)

– Material layer assignment (Use Stackup Editor)

– Material properties (Use Material Definitions in Project Manager)

• If you are repeatedly working on the same manufacturing process and it is not correctly defined from import, the stackup editor has an option to export a simulation stackup that can be imported and reused without any additional changes.

• Stackup - User Defined • The native HFSS 3D Layout editor can be used to create new designs or import layouts that don’t contain stackup definitions (GDSII).

In this case, use the stackup editor to add layers to the design. The default stackup editor mode is to create laminate stackups which are created by stacking dielectrics and signal layers one upon the other. Disabling the laminate mode allows additional flexibility to define elevations as well as thickness.

• If you are repeatedly working on the same manufacturing process, the stackup editor has an option to export a simulation stackup that can be imported and reused.


Accessing the Material Manager

• Material Manager • There are multiple ways to access the Material Manager

– Stackup Editor: Material is a property for each layer

– From Project Manager: A list of the material definitions used in a project

• Note: It is recommended that you verify the material properties for any imported material.

– From the Library Setup: To create and manage a user defined material database

• Select the menu item Tools > Edit Libraries > Materials...

Project Manager Stackup Editor


Types of Materials

• Material Types • Simple Materials

– Dielectrics: Fields exist and are solved for inside of the 3D Object

• Causal material definitions for Lossy Dielectrics

– Conductors: Fields are solved at the surface

Simple Material Definition


Selecting a Material Definition

• Selecting a Material Definition • Search by Name: Find existing material definition

• View/Edit Material: View or Edit the present material definition

• Add Material: Create your own custom material definition

• Clone Material: Modify an existing material. Only material definitions that are part of the project can be modified


Design Settings

• Design Settings • Select the menu item HFSS 3D Layout > Design Settings…

• Lossy Dielectrics (Enabled by Default)

– Automatically use causal materials: Layers with constant material permittivity greater than one and dielectric loss tangent greater than zero will be treated as frequency dependent. Their actual permittivity and conductivity will be determined by the Djordjevic-Sarkar algorithm.

– Recommended setting for:

• RF Applications: Disabled

– Note: The Djordjevic-Sarkar model assumes the material properties are defined at 1GHz. In many cases this will produce unexpected results for RF applications where the material properties are being defined at higher frequencies.

• SI Applications: Enabled

– Note: It is common practice to use the S-Parameters to generate SPICE models or to use them directly in transient circuit simulations. Since ensuring causality is critical for transient circuit simulations, frequency dependent materials should be used.


Excitations

Define Excitations


Excitations

• Excitations • Because of the automation afforded within HFSS 3D Layout, port setup is generally considered much easier than in HFSS. While

HFSS 3D Layout automates a considerable amount of the setup it is still prudent to define physical ports that are consistent with how the device will be used or characterized. Typically port creation in HFSS 3D Layout is as simple as selecting and edge or point.

• Port Types • Lumped Ports: Supports vertical or coax configurations

• Circuit Ports: Supports point to point connections

– Define Positive and Negative terminals + Layer Connection

• Wave Ports: For stripline and/or multi-coupled lines

• Port Boundary • Within HFSS 3D Layout, Lumped Ports can be toggled to PEC or RLC

boundary conditions. Vertical and Horizontal Lumped Ports can be defined as PEC and RLC. Coax Lumped Ports can only be toggled to PEC

• Solution Type: Driven Terminal • If you are comparing to HFSS, Driven Terminal is the default and only option in HFSS 3D Layout. This does not need to be set and

can’t be changed.


Embedded Components

• Embedded Components • RLC or N-Port S-Parameters can be directly embedded in an HFSS 3D Layout simulation

– Notes:

• This option is not supported in HFSS

• The RLC boundary is used in HFSS and HFSS 3D Layout Port Boundary uses a different approach

• Can be automatically imported from Cadence Layout

Right-click on Circuit Elements


Boundaries

Boundaries


Define HFSS Extents

• HFSS Extents • Using HFSS Extents, we define the computation region for HFSS.

– Dielectric Horizontal padding and the dimensions of Airbox are defined. The values can be entered as absolute values (10mm) or as percentage of the maximum of either length or width of the dielectric-polygon

• HFSS Extents can be defined in either of the two ways:

– Right-click on Boundaries in the Project Manager window and select HFSS Extents...

– Select the menu item HFSS 3D Layout > HFSS Extents...


Define HFSS Extents

• HFSS Extents • Select the menu item HFSS 3D Layout > HFSS Extents

– Define the Dielectric padding and Airbox padding

• To visualize the HFSS extents:

– Select the menu item Layout > Draw HFSS Air Box

– Select the menu item View > Rotate to rotate

Draw HFSS Air Box

HFSS Air Box


Solve Setup

Solve Setup


Analysis Setup

• Solution Setup controls HFSS Solution process. • Set the Solution Frequency

• Control the initial mesh

• Set the convergence criteria

• Control how the mesh is modified between passes

• Control the port’s solution and convergence criteria

• Select the basis function used to describe the fields

• Choose the matrix solver

Right-click on Analysis


HFSS 3D Layout Solution Process


Mesh Solve

Frequency Sweep

Post Processing

HPC HPC

GUI

Solve HPC

Mesh

Solution Process


HFSS Meshing

• Automatic Adaptive Meshing for HFSS Simulation • Geometrically conforming, tetrahedral mesh automatically generated and refined below a user defined electrical length.

• Iterative algorithm solves the fields of the model and intelligently refines the mesh until S-parameters converge below a user defined threshold, Max Delta S.

– User defines frequency or frequencies at which adaptive meshing is performed.

– After each solution, tetrahedral elements are “graded” for their accuracy to Maxwell's Equations.

– User defines percentage of “bad” tetrahedral elements to be refined after each pass (30% Default).

Vertex: Explicitly Solved

Edge: Explicitly Solved

Face: Interpolated

Geometrically conforming, tetrahedral mesh

Meshing


HFSS – Automated solution process

Adaptive Port Refinement

Solve

Quantify Mesh Accuracy

Mesh Refinement

Frequency Sweep Yes No

Max(|DS|)<goal?

Initial Mesh

Adaptive Mesh Creation

Geometry Initial Mesh Converged Mesh

Initial Mesh Refine Mesh Freq. Sweep

Meshing

Electrical Mesh Seeding/Lambda Refinement

Geometric Mesh Initial Mesh


Example: Adaptive Meshing

• Automatic Adaptive Meshing • Provides an Automatic, Accurate and Efficient solution

• Removes requirement for manual meshing expertise

• Meshing Algorithm • Meshing algorithm adaptively refines mesh throughout geometry

• Iteratively adds mesh elements in areas where a finer mesh is needed to accurately represent field behavior

– Resulting in an accurate and efficient mesh

Convergence vs. Adaptive Pass

Mesh at each adaptive pass

Meshing


Solution Frequency

• Solution Frequency : • The Solution frequency is used to create the adaptive mesh.

– Defines the spatial resolution of the mesh through the Lambda Refinement step

– Lambda Refinement is wavelength dependent.

• Determines the frequency used to evaluate the mesh’s convergence.

• Typically choose the highest frequency of interest or for resonant antennas, the resonant frequency

• Higher frequency mesh is valid at lower frequencies. • A mesh created at a higher frequency will be denser than a mesh at lower a

frequency because the wavelength is smaller.

• The denser mesh is likely to pickup the field variations associated with lower frequencies behaviors.

• Low frequency mesh is NOT valid at higher frequencies. • A mesh created at a lower frequency will be coarser than a mesh created at

a higher frequency because the wavelength is longer.

• The coarser mesh is less likely to pickup field variations associated with the higher frequencies


Convergence Criteria

• Adaptive mesh loop has two exit criteria: • Maximum Number of Passes (Time)

– Controls how many adaptive passes are allowed to be performed

– 15 is a reasonable initial value

• If value is too low, solution will complete before an accurate mesh is created by the adaptive solution process

• Solution will likely take fewer than 15 passes to converge and will stop when convergence criteria is met

• Convergence Per Pass (Accuracy)

– Indicates the solution’s sensitivity to mesh variations

– Relates to the accuracy of the solution

Refine Mesh (Single Frequency)

Full Volumetric Solution (S-Parameters/E-Fields)

Converged (∆S)

No

Adaptive Mesh Loop

Done Yes

Adaptive mesh loop will iterate and refine the mesh until the maximum Number of Passes or Maximum

Delta S is met

Convergence Plot


Converging on Maximum Delta S

• Summarizes the S-Parameter’s sensitivity • A single number for the entire S-Matrix

• Accounts for magnitude and phase variation for all S-parameters simultaneously.

• Default value of 0.02 is reasonable for most cases

• Reports the worst case violation

• DON’T over-specify • Setting the Maximum Delta S too small wastes computer resources and time.

• DON’T under-specify • Setting the Maximum Delta S too large jeopardizes accuracy.

1D NN SSMaxSMax


Setting the Maximum Delta S Criteria

• Maximum Delta S • Always set the Delta S with your error tolerance in mind.

• Consider the worst case scenarios when setting the Maximum Delta S

– A worst case magnitude error can be determined by assuming the S-parameter magnitude is the only source of error (phase is perfectly accurate) .

– Most likely actual solution is much closer since the error will be split between the magnitude and phase solve value of 0.98 could be between 0.99 and 0.97

1D NN SSMaxSMax

± 0.01

* plots assume asymptotic convergence

Linear Units dB Units

A solve value of S = 0.98

could be between 0.99

and 0.97 when using

|DS| = 0.01

Expected Range for |S| = 0.98 & Max(|DS|) = 0.01


FEM Solver Technology Overview

• Direct Solver (Default) • Default technique

• Solves matrix equation Ax=b

– Multi-frontal Sparse Matrix Solver to find the inverse of A

– Solves for all excitations(b) simultaneously

• Iterative Solver • Reduces RAM and can improve simulation speed

• Solves matrix equation MAx=Mb

– M is a preconditioner – For HFSS this is a lower order basis function solution

– Major computation is the matrix-vector multiplication: (MA)x

– Iterates for each excitation or simultaneously solve using HPC License

• Iterative Solver is more sensitive to mesh quality

– Reverts to Direct solver if it fails to converge

Solve

Check this box to enable Iterative Solver


FEM: Basis Order

• Hierarchical basis functions • Zero or First or Second order basis functions

• Higher-order elements have increased accuracy

• Convergence is a function of basis order

• Mixed Order (Default) • hp-FEM Method

– Refines element order(p) and element size(h)

• Automatically distributes element order based on element size

• Generates optimum combination of hierarchical basis functions (Zero and First and Second)

– Efficient use of computing resources

• Default for HFSS 3D Layout

Solve


Frequency Sweeps

• Discrete Frequency Sweep • Solves using adaptive mesh at every frequency

• Matrix Data and Fields at every frequency in sweep

• Interpolating Frequency Sweep • The calculation of wide-band S-parameters in HFSS is achieved using the Interpolating sweep. This method fits S-parameter data to

a rational polynomial transfer function using a minimum number of discrete finite element method (FEM) solutions.

• Matrix Data at every frequency in sweep

S11

(d

B)

11

11

...

...

pspsps

zszszsS

qqq

qqq

See: IEEE Trans. Microwave Theory Tech., Vol. 46, No. 9, Sept. 1998


• Interpolation Convergence • The Interpolating sweep type yields the poles and zeros of the transfer function. This information can be directly used in the

Laplace Element from which a Full-Wave SPICE™ model can be generated (HSPICE, Spectre RF, PSPICE).

– Enforce Passivity

– Enforce Causality

• DC Solve for Frequency Sweeps • Use Q3D to solve DC point

– Eliminates Extrapolation

– Doesn’t support Wave Ports

Frequency Sweeps Frequency

Sweep

Lecture 4: HFSS 3D Layout - · PDF fileLecture 4: HFSS 3D Layout Introduction to ANSYS HFSS . ... – Select the menu item Layout > Draw HFSS Air Box – Select the menu item View

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