Underground of HFSS

7/23/2019 Underground of HFSS

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2011 ANSYS, Inc. May 9, 20121

HFSS Hybrid Finite Element and Integral

Equation Solver for Large Scale ElectromagneticDesign and Simulation

Laila Salman, PhDTechnical Services Specialist

[email protected]


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2011 ANSYS, Inc. May 9, 20122

Overview of Simulation Trends and Technologies

ANSYS Simulation Technologies Overview

ANSYS Electromagnetic Simulation Techniques:

HFSS-FEM

HFSS-IENew in v12

Hybrid FE-BINew in v13

Hybrid IE-RegionsNew in v14

Physical OpticsNew in v14

High Performance ComputingHFSS with Domain Decomposition Method (DDM)New in v12

HFSS-IE with industry standard Message Passing Interface (MPI)New in v14

Examples

Agenda


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2011 ANSYS, Inc. May 9, 20123

Simulation Trends

Full System Simulations

Require simulation of more complicated and electrically large problems Efficient simulations

Types of problems to solve


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2011 ANSYS, Inc. May 9, 20124

Ansoft Simulation Technologies

Finite Element Method HFSS

Efficiently handles complex material and geometries

Volume based mesh and field solutions

Fields are explicitly solved throughout entire volume

Integral Equations HFSS-IE

Efficient solution technique for open radiation and scattering

Currents solved only on surface mesh

Efficiency is achieved when structure is primarily metal

Physical Opticsnew in v14 HFSS-IE

High frequency approximation

Ideal for electrically large, smooth objects

Currents are approximated in illuminated regions and set to zero

in shadow regions

1storder interactions


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2011 ANSYS, Inc. May 9, 20125

Hybrid Finite Element Integral Equations

Finite Element Method

HFSS Efficiently handles complex

material and geometries

Hybrid Finite Element - Integral Equations

FE-BINew in v13

IE-Regions New in v14

Hybrid method invoked inside of HFSS Design using

IE-Regions or FE-BI boundary conditions

Hybrid method takes advantage of features from

both methods to allow for more efficient simulations

FE-BI

IE-Regions

Integral Equations

HFSS-IE Efficient solution

technique for open

radiating and scattering

of metallic objects


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2011 ANSYS, Inc. May 9, 20126

High Frequency Technique: Physical Optics

Physical Optics

HFSS-IE Ideal for electrically large,

conducting and smooth

objects

High frequency asymptotic solver available inside of

HFSS-IE designs

Currents are approximated in illuminated regions and set tozero in shadow regions

First order interaction only, single bounce

Source excitation from HFSS Far Field Data-Link of incidentplane wave

Usage Applications include

Electrically large - RCS, Antenna Placement, ReflectorAnalysis

Quickly estimate performance of electrically large problems

Full wave solution is beyond computation resources


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Hybrid MethodsFE-BI

IE-Regions


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Finite Element Boundary IntegralMesh truncation of infinite free space into a

finite computational domain

Alternative to ABC or PML radiationboundary conditions

Hybrid solution of FEM and IE

IE solution on outer faces

FEM solution inside of volumeFE-BI Advantages

Arbitrary shaped boundary Conformal and discontinuous to minimize solution

volume

Reflection-less boundary condition High accuracy for radiating and scattering problems

No theoretical minimum distance fromradiator

Reduce simulation volume and simplify problem

setup

FEM Solution

in Volume

IE Solution

on Outer Surface

Fields at

outer surface

Iterate

Free space

FE-BI

Arbitrary shape


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Finite Element Boundary Integral:Boundary Condition Setup

Enabled with HFSS-IE license feature inside of

an HFSS Design

Setup is similar to ABC boundary condition

Enabled by selecting Model exterior as HFSS-IE domain

Radiation surface must enclose entiregeometry

1 infinite ground plane allowed

Direct vs. Iterative Matrix Solver

Direct Matrix Solver Preferred method with FE-BI

Quickest solution

Iterative solver Uses the least amount of RAM


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Finite Element Boundary Integral:Example Problem

FE-BIABC

FE-BISurface

FE-BI can be used to significantly

reduce required computerresources

Large volume of air inside ofradome can be removed from the

FEM solution domain Air volume would be required if using PML

or ABC

Two FE-BI surfaces will be applied Conformal to radome

Conformal to horn antenna (10 GHz)

10 GHz RAM (GB) Elapsed Time

ABC 15 70min

FE-BI 7 30min


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2011 ANSYS, Inc. May 9, 201211

IE-Regions New in v14

FE-BI

IE Region

In a hybrid FEM-IE solution, IE Regions allow

uniform regions of free space ordielectric to be removed from the FEMsolution

Metal objects can be solved directly withan IE solution applied to surface

Removes need for air box to surroundmetal objects

Dielectric regions can be replaced with anIE Region on the boundary of uniform

dielectric material

Solution inside of dielectric is solvedusing IE

Surface currenton metal block

FEM Only Solution

Hybrid FEM-IE Solution


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2011 ANSYS, Inc. May 9, 201212

IE-Regions:Boundary Condition Setup

IE-Regions can be applied to metal or

dielectric objects inside of an HFSSDesign

Metal Objects

Typically exterior to air box region withFE-BI outer radiation boundary or

Internal to dielectric IE Region Dielectric Objects

Must be interior to air box regionAssignment:

Select Object

HFSSIE RegionsAssign As IE Region

Air Volume truncated with FE-BI

radiation boundary condition

IE Solution Applied to Metal outside of

air box and dielectric inside of air box


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2011 ANSYS, Inc. May 9, 201213

IE-Regions:Example Problem

IE-Region Applied to RCS of Electricaly Large

Dielectric Sphere Hybrid FEM-IE solution of scattering from

dielectric sphere using IE-Regions

Uniform volume of dielectric removed byapplying IE-Region to surface of dielectric sphere

Radius = 900mm, r = 4, F = 1GHz

FEM Only Hybrid FEM-IE

1 GHz RAM (GB) Elapsed Time

FEM Only 33.4 222min

Hybrid FEM-IE using IERegions 3.2 35min

IE-Region

applied to

dielectric

Sphere

FEM Only

Hybrid FEB-IE Solution

10X Less 7X Faster


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2011 ANSYS, Inc. May 9, 201214

Hybrid Solution

With the addition of IE regions to HFSS v14, a fully hybridized solution of FEMand IE is capable of solving electrically large problems more efficiently

FEM and IE

FE-BI

Truncate an FEM solution space with any arbitrary surface using a boundary

integral

IE-Regions

When used along with FE-BI, conducting objects outside of FEM solution space can

be solved directly with IE, eliminating the need for conducting objects to be

enclosed in an air volume

Homogenous dielectric volumes can be removed from the FEM solution andreplaced with the equivalent IE solution in the region, useful when dielectric

regions are electrically large requiring large FEM solution volume


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2011 ANSYS, Inc. May 9, 201215

High Performance ComputingApplied to Hybrid MethodsHPC with HFSS using Domain Decomposition

HPC with HFSS-IE using MPINew in v14


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2011 ANSYS, Inc. May 9, 201216

High Performance Computing

Increase simulation capacity using High Performance Computing (HPC)

Domain Decomposition Method (DDM) for HFSS

HFSS only

HFSS using FE-BI and IE-RegionsNew in v14

Distributed Memory Parallel for HFSS-IENew in v14

Uses industry standard Message Passing Interface (MPI)

Perform HFSS-IE simulation by distributing solution across machines in a cluster ornetwork


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2011 ANSYS, Inc. May 9, 201217

High Performance Computing with HFSSusing DDM

HPC distributes mesh sub-domains, FEM and

discontinuous IE domains, to networked processors and memory

FEMDomain 1

FEM

Domain 2

FEM

Domain 3

FEM

Domain 4 IE Domain

Distributes mesh sub-domains

to network of processors FEM volume can be sub-

divided into multiple

domains

IE Domains that are

discontinuous will bedistributed to separate

nodes when they become

large

Significantly increases

simulation capacity Multi-processor nodes can be

utilized


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2011 ANSYS, Inc. May 9, 201218

High Performance Computing with HFSS-IEusing MPI

The HFSS-IE solver in HFSS v14 uses the industry standard Message Passing

Interface (MPI) and can perform solutions that distribute memory use across

machines in a cluster or network

Simulation capacity is only limited by available computer resources

Enables simulation of electrically large problems

HFSS-IE uses MPI to perform a solution distributed

across networked computers


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2011 ANSYS, Inc. May 9, 201219

New features in HFSS v14 enabling largescale electromagnetic design andsimulation

Hybrid FEM and IE Solution

FE-BI and IE-Regions

Requires HFSS and HFSS-IE license

Distributed Memory Hybrid HFSS and

HFSS-IE

For Hybrid HFSS and HFSS-IE

HFSS, HFSS-IE and HPC License

For HFSS-IE Only

HFSS-IE and HPC License

Physical Optics

Requires HFSS-IE license

HFSS v14 Licensing Configurations forElectrical Large Simulations

HFSS License

(FEM)HFSS-IE License

(IE/PO)

HPC License

DDM

Hybrid orData-linked

solutions


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2011 ANSYS, Inc. May 9, 201220

ExamplesFinite Element - Boundary Integral

IE-Region

Physical Optics

High Performance Computing


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2011 ANSYS, Inc. May 9, 201221

Array on Spacecraft Using FE-BI

7 Element Helix Antenna Array

integrated on satellite platform Dielectric solar panels and antenna

supports do not make this problem

ideal for HFSS-IE

Inclusion of solar panels create an

electrically large model

64wide at 3.5 GHz

Using ABC or PML boundary would

require an Airbox equal to 21k 3

FE-BI can reduce the required Airbox

to 1.2k 3

FE-BI applied to conformal Airbox ABC or PML would be applied

to much larger Airbox


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2011 ANSYS, Inc. May 9, 201222

Array on Spacecraft Using FE-BI: Results

Array platform integration simulatedwith conformal FE-BI

RAM requirements reduced by 10x

RAM reduction as a result of removingthe surrounding free space

Only possible using FE-BI

Boundary

Type

Airbox

Volume

Number of

Domains

Total RAM

(GB)

ABC 21k 3 34 210

FE-BI 1.2k 3 12 21

10X Less


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2011 ANSYS, Inc. May 9, 201223

Reflector Analysis Using IE-Regions

Multiple techniques have been developed to analyze reflector antennas using HFSS

Full HFSS Solution - Model entire solution space using only HFSS

High level of fidelity also requires most computer resources

Data Link SolutionsSource feed excitation modeled separately from reflector

Data link solutions only include 1 way coupling from source excitation to reflector

Hybrid Solutions

Efficient, high fidelity solution using hybrid FEM-IE techniques

Fidelity

ComputerResources

Data LinkIE Solutions

Full HFSS Solution

Hybrid Solutions

Data LinkPhysical Optics

Hybrid Solution uses FEM for feed and

IE applied to reflector

Full HFSS solution requires

large air box (~37k 3

)


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2011 ANSYS, Inc. May 9, 201224

Reflector Analysis Using IE-Regions: Setup

Analysis of electrically large reflector antennas may benefit from multi-step

design approach utilizing several simulation methodologies

Data Link

Full Wave Solutions

Hybrid Solutions

Data Link

Physical Optics

Feed Antenna

Design

HFSS to HFSS-IE or PO Data-link:

Source excitation solved in HFSS

Used as data linked excitation into a Physical

Optics or HFSS-IE simulationHybrid Solution - FE-BI and IE-Region

Full wave simulation performed using ahybrid solution in HFSS

IE-Region applied to reflector

FE-BI applied around feed


Data Link with HFSS

and Physical Optics

FEM solution with FE-BIIE solution on reflector


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2011 ANSYS, Inc. May 9, 201225

Reflector Analysis Using IE-Regions: Results

Full Wave SolutionHFSS to IE Data-Link

HFSS to PO Data-Link

IE solution on reflector

FEM Solution with FE-BI

Full wave solution possible using hybrid FEM-IE solution, enabled with FE-BI

and IE-Regions

Agreement between methods only show small difference in peak and

side lobe levels

Offset fed reflector

Backscatter and blockage not fully included in either data-linked

simulationeffects would be more significant for center fed reflector


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2011 ANSYS, Inc. May 9, 201226

Reflector Analysis Using IE-Regions: Results

Boundary Type Airbox Volume Total RAM (GB) Elapsed Time (hours)

Full HFSS solution (FEM Only, DDM) 37k 3 163.5 (1stpass) 2.7 (1stpass)

Full Wave Hybrid FEM-IE 8.6 3 (Feed Only) 5 0.5

HFSS to IE Data-Link NA 3.4 0.2

HFSS to PO Data-Link NA 0.4 1 minute

Hybrid FEM-IE HFSS to PO Data-LinkHFSS to IE Data-Link

>32X Less >10X Faster

H b id S l ti f A t Pl t A l i


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2011 ANSYS, Inc. May 9, 201227

Hybrid Solution for Antenna Placement AnalysisUsing IE-Regions

Antenna performance modeled with

placement in proximity to human head Cell phone platform and antenna with

complex material properties and

geometry are ideally modeled using FEM

solution

The uniform, high dielectric properties ofthe head are ideally modeled using IE

solution

Hybrid Solution

An internal dielectric IE Region can beapplied to head geometry to reduce

computational size and improve

efficiency

FEM solution is applied remainingvolume Human Head Material Properties:

r= 79,

= 0.47simems/m

1.8 GHz

Hybrid Solution for Antenna Placement Analysis


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2011 ANSYS, Inc. May 9, 201228

Hybrid Solution for Antenna Placement AnalysisUsing IE-Regions: Results

Cell Phone Only

FEM Only: Cell Phone + Head

Hybrid: Cell Phone + Head

FEM Only SolutionHybrid FEM-IE Solution

Solution Type Total RAM (GB) Elapsed Time

(hours)

FEM Only 6.2 1

Hybrid Solution 3 0.5

1.8 GHz 1.8 GHz

IE-Region Boundary

Condition Applied

2X Faster2X Less


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2011 ANSYS, Inc. May 9, 201229

Hybrid Solution for Antenna Placement AnalysisUsing IE-Regions

Antenna performance modeled with placement in proximity to human head inside vehicle

Cell phone platform and antenna with complex material properties and geometry are ideallymodeled using FEM solution

The uniform, high dielectric properties of the head are ideally modeled using IE solution

The car is ideally modeled using IE-Region

Hybrid Solution Setup

An internal dielectric IE-Region can be applied to head geometry to reduce computationalsize and improve efficiency

An exterior metallic IE-Region is applied to car model

FEM solution is applied remaining volume

IE solution on car body using IE-Regions

FEM solution around body and cell phone

IE solution applied to dielectric human

body using IE-Regions


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2011 ANSYS, Inc. May 9, 201230


(hours)

Hybrid FEM-IE

Solution

11 2.7

Hybrid Solution for Antenna Placement AnalysisUsing IE-Regions: Results

Full FEM Solution


(hours)

Full FEM

Solution

160 GB (DDM) 8


3X Faster15X Less


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2011 ANSYS, Inc. May 9, 201231

Solution @ High Freq. Total RAM (GB) Elapsed Time (sec)

Full Wave (HFSS-IE) 1.4 87

Physical Optics 0.1 14

Physical Optics (PO) for Electrically LargeSimulations

Physical Optics

Full Wave Solution

High frequency asymptotic

solver Scattering and antenna

placement of electrically

large objects

Incident Wave

Full Wave Solution Physical Optics Solution

RCS of PEC Sphere

Highlights capabilities andlimitation of physical optics

Creeping wave effects notaccounted for by PO

When electrical size ofsphere becomes large, full

wave solution converges

with physical optics

solution


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2011 ANSYS, Inc. May 9, 201232

Physical Optics for RCS of ElectricallyLarge Structures

0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00 180.00IWavePhi [deg]

-70.00

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

10.00

Y1

PECRCS_HH ANSOFT

Physical Optics

Full Wave Solution

Full Wave Solution Physical Optics

Good correlation between full wave

solution and physical optics

solution for RCS of electricallylarge cone-sphere

Creeping wave effects not accounted forin physical optics solution

Apparent as incident angles

approach tip and sphere side ofcone-sphere

Tip

Sphere

Shadow Region

Solution @ High

Freq.

Total RAM (GB) Elapsed Time

Full Wave (HFSS-IE) 6.6 2 hours

Physical Optics 4.8 16 minutes


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2011 ANSYS, Inc. May 9, 201233

International Space Station (ISS): AntennaPlacement and Blockage Simulations

110 meters

Multiple antenna and communication channels operating on and around the ISS are subjectto blockage due to the large structure

Physical Optics allows us to model important navigational and communications challenges

Degradation of communications due to adjusting solar panels on ISS

Blockage of GPS signals used by docking vehicles


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2011 ANSYS, Inc. May 9, 201234

Physical Optics for S-Band Communications on ISSAntenna Blockage

733

Solution @ 2GHz Total RAM (GB) Elapsed Time(min)

Physical Optics 47 57

Source

location


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2011 ANSYS, Inc. May 9, 201235

Distribute HFSS-IE Using MPI

Full wave solution using HFSS-IE of electrically large structures

RCS of fighter aircraft at 5GHz

250

175


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2011 ANSYS, Inc. May 9, 201236

Distributed HFSS-IE Solution: Fighter Aircraft

Full wave solutionScattering of fighter aircraft at

5GHz

Large scale simulation possible

by using compute cluster of

10 networked machines

Solution only possibly using

distributed computing

resources

Distributed HFSS-IE Solution Resources

Average Memory 32 GB

Total Memory (10 nodes) 325 GB

Total Time 33.5 Hours

Scattering

Physical Optics Solution

Full Wave HFSS-IE Solution


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Full HFSS Solution

Hybrid HFSS

(FE-BI/IE-RegionNew in v14 )

HFSS-IE with

HPC/MPINew in v14

ModelMaterialComplexity

Summary

ModelElectr

icSize

Data Link

IE Solutions

DataLink

PhysicalOpticsNew in v14

Fidelity

Underground of HFSS

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