Simulation Advances for RF, Microwave and Antenna Applications · •Hybrid Solving introduced in...

© 2011 ANSYS, Inc. September 26, 2011

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Simulation Advances for RF, Microwave and Antenna Applications


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• Advanced Integrated Solver Technologies

– Finite Arrays with Domain Decomposition

– Hybrid solving: FEBI, IE Regions

• Physical Optics Solver in HFSS-IE

• Transient Finite Elements in HFSS

• New layout interface for HFSS: Solver on Demand in Designer

• Usability Enhancement

– Radiated fields…..

– Network installation improvements

– 3D modeler improvements

• CAD Integration in Workbench

– Improved Multiphysics flow

Overview


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Advanced Solvers: Finite Arrays with DDM


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Finite Arrays with Domain Decomposition

Efficient solution for repeating geometries (array) with domain decomposition technique (DDM)


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A Review: Domain Decomposition

Distributed memory parallel solver technique

Distributes mesh sub-domains to network of processors

Significantly increases simulation capacity

Highly scalable to large numbers of processors

Automatic generation of domains by mesh partitioning

• User friendly • Load balance

Hybrid iterative & direct solver • Multi-frontal direct solver for each sub-

domain • Sub-domains exchange information

iteratively via Robin’s transmission conditions (RTC)

Distributes mesh sub-domains

to networked processors and memory


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Finite Arrays Solve large finite array designs

Efficient setup and solution

Define unit cell and array dimensions • Efficient geometry creation and

representation

Efficient Domain Decomposition solution

• Leverages repeating nature of array geometries

• Only mesh unit cell • Virtually repeat mesh throughout

array

Post-process full S-parameter • Couplings included • Edge effects included

3D field visualization

Far field patterns for full array

Memory efficient

Enabled with the HFSS HPC

product


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Finite Arrays by Domain Decomposition

• Each element in array treated as solution domain

• One compute engine can solve multiple elements/domains in series

Distributes element sub-domains



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Example: Skewed Waveguide Array

• 16X16 (256 elements and excitations)

• Skewed Rectangular Waveguide (WR90) Array

– 1.3M Matrix Size

• Using 8 cores

– 3 hrs. solution time

– 0.4GB Memory total

• Using 16 cores

– 2 hrs. solution time

– 0.8GB Memory total

• Additional Cores

– Faster solution time

– More memory.

Unit cell shown with wireframe

view of virtual array


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Skewed Waveguide Array

• Patterns from 8X8 Array – Dashed is

idealized infinite array analysis

– Solid from finite array analysis

• Two simulations use identical mesh

• Note edge effects due to finite array size


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Running Finite Array

Use Master/Slave unit cell design to adapt the mesh

• Called “Unit Cell for Adaptive Meshing” in image

Copy/Paste Design • Called “8X8 Array” in image

Create a single pass setup in finite array design

On “Advanced” tab use “Setup Link” to link mesh from unit cell design

Doing adaptive meshing in finite array design will be time consuming and not as efficient


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Efficient: 8X8 Array Patch Array

Direct solver with 12 cores • 5:05:14

• 60.8 GB RAM

Finite Array DDM with 12 cores

• 00:44:53

• 1.8 GB

6.8X faster

33.8X less memory


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HPC: Faster with additional cores

Linux cluster • 16X Dell PowerEdge R610

– Dual six-core Xeon X5760, 8GB per core

Same 8X8 array of probe feed patch antennas

3M+ matrix size, 64 excitations

Study performed using 101, 51 ,26, 11, 6 and 3 engines.*

• 101 simulation time = 17 min., 20X faster than direct solver

• *Three engines used as baseline

1

2

3

4

5

6

7

0 50 100 150

speed factor

speed factor

Number of cores


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Hybrid Solving: Finite Element-Boundary Integral


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• Antenna Placement Study: UHF Antenna on Apache UH64 airframe

– Finite Elements with DDM

– Boundary Integral (3D Method of Moments)

– Hybrid Finite Element-Boundary Integral (FE-BI)

Finite Element-Boundary Integral Solving Larger Problems with Rigor


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Hybrid Solving: Finite Element- Boundary Integral

Apache helicopter

• UHF antenna placement study @ 900 MHz

Solution volume

• 1,250 m3

• 33,750 λ3

Solution Specs

• 72 engines

• Matrix size = 47M

• 6 adaptive passes

• 300 GB RAM

• 5 hr 30 min

Finite Elements with DDM


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Apache helicopter

• UHF antenna placement study @ 900 MHz

Solution surface

• 173 m2

• 1557 λ2

Solution Specs

• 12 core MP

• 680k unknowns


• 83 GB RAM

• 5 hr 28 min

Boundary Integral, 3D MoM with HFSS-IE


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Apache helicopter • UHF antenna placement study @

900 MHz

FEM solution volume • 69 m3

• 1863 λ3

IE solution surface • 236 m2

• 2124 λ2

Solution Specs • 12 cores total using DDM with

MP

• Matrix Size = 2.9M


• 21 GB RAM

• 1 hr 3 min

Hybrid Finite Element – Boundary Integral

Compared to 72 core FEM solution

14X less memory, 5.5 times faster


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Hybrid Finite Element-Integral Equation Method

Finite Elements vs. Integral Equations

• Integral Equation Based Method

– HFSS-IE

– Efficient solution technique for open radiation and scattering

– Surface only mesh and current solution

Airbox not needed

to model free

space radiation

Airbox required

to model free

space radiation

• Finite Element Based Method

– HFSS

– Efficient handle complex material and geometries

– Volume based mesh and field solutions

This Finite Element-Boundary Integral hybrid method leverages the

advantages of both methods to achieve the most accurate and robust

solution for radiating and scattering problems

Conformal radiation

volume with Integral

Equations


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Summary of FEBI performance

Type Time, Ratio Memory, Ratio

FEM + DDM 5hr 30min, 1 300GB, 1

IE 5hr 28min, 1 83GB, 3.6

FEBI 1hr 3min, 5.5 21 GB, 14.3


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HFSS Hybrid Solving

• Hybrid Solving introduced in HFSS 13 with FEBI

– A highly accurate solution for open boundary problems

• Accurate: Solves directly for equivalent surface currents on absorbing boundary conditions

• Efficient: Conformal ABC to reduce FEM solution domain

– Also provides possibility of physically separate FEM volumes


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Example: Missile Launch


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FE-BI and Distributed Solving

HPC distributes mesh sub-domains, FEM and IE domains,


FEM

Domain 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 Domain is distributed to second node in machine list

• Significantly increases simulation capacity

• Multi-processor nodes can be utilized


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Hybrid Solving: IE Regions


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FEBI and Physically Separate “Domains”

1meter

10λ 1meter

20λ

1meter

30λ

Frequency Memory Required

3 GHz 2GB


6 GHz 10GB


9GHz 30GB

Reflector with multiple FE-BI domains • Conducting reflector and feed horn each surrounded

by air with FEBI applied to surface of air volumes

– Provides integral equation “link” between FEM domains

• But 3D MoM solution from integral equations could be applied directly to conducting surface only


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HFSS Hybrid Solving – IE Regions

• Parallelized

– IE regions solved in parallel.

– Analogous to FEM domains

• Rigorous

– Multiple reflection

• Automated


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IE Dielectric Regions

• Solve “large homogeneous blocks of dielectric” with a “boundary condition”

– Replace enclosed arbitrary dielectrics

– Solve with multiple open or enclosed IE regions

– Conducting IE regions may be inside dielectric IE regions

FEM

Conducting IE

Enclosed IE

Ground Penetrating Radar Antenna Air Surface Soil Mine

Different solution domains may be solved in parallel with DDM


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HFSS IE Regions - Example


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Physical Optics


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HFSS-IE PO

Asymptotic solver for extremely large problems

• In HFSS-IE • Solves electrically huge problems • Currents are approximated in

illuminated regions – Set to zero in shadow regions

• No ray tracing or multiple “bounces”

Target applications: • Large reflector antennas • RCS of large objects such as satellites

Option in solution setup for HFSS-IE.

Sourced by incident wave excitations • Plane waves or linked HFSS designs as a

source


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Physical Optics (PO)

Currents approximated as

J ≈ 2nxHinc

• Handles object scattering

using asymptotically

derived currents.

• There is an edge effect

but it does not yield the

true diffracted fields.

Source

Recieve

Scatterer


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PO Solver in HFSS-IE 14

• PO assumes the fields on all illuminated surface are the incident

fields

• Effects of the scatterers are included by assuming the incident fields

are scattered at each point on the body as if it were reflected from

an infinite tangent plane at that point; J~2(n x Hinc ) for PEC.

• For non-illuminated surfaces the J are set to zero.

Where: JPO = 2(n x Hinc )

PE

C


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PO Examples

Notice the shadowing of the gun barrel

on the tank and the tank on the ground.


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HFSS-IE PO - Example

Offset reflector 50 λ0 in

diameter fed by a horn

HFSS far field link

Simulated with 8 cores

IE: 48.3min and 11.9GB

PO: 23S and 286MB

Note > 120x speedup


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HFSS Transient


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Transient problems


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Aircraft: Pulsed RCS


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HFSS Transient

Introduced in HFSS 13.0

Discontinuous Galerkin Time Domain (DGTD)

• Finite element solution

– Retains accuracy and reliability of adapted unstructured-mesh

• Supports higher order basis functions

– Efficient for geometries with a wide range of geometric detail

• Local time stepping

– Based on element size, order and material property mesh elements may advance in time with different time steps


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HFSS Transient: New in R14

Transient Network Analysis

• Separate Frequency and Time domain “Edit Source“ settings

• Specify delay of TDR to synchronize rise times

• Handling of partial S due to passive ports

Transient

• Scaling and delay of individual sources

General

• Support for general frequency dependent materials


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Solver on Demand


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Designer RF with HFSS - Solver on Demand

HFSS - Solver on Demand • Intuitive PCB design entry for HFSS

• Chips, packages, channels, modules, …

• Designer layouts simulated with HFSS

– Automated boundary and port setups

– Finite dielectrics and ground supported

• Wave and Lumped Gap Port

– Single ended and Differential

– Vertical and Horizontal

– Coaxial, CPW and Grounded CPW


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Design Description

• Balanced Amplifier

• MMIC amplifiers in parallel

Power = 30dBm

P1dB = 11dBm

F=10GHz

Gain = 22dB


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Usability Enhancements


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General Enhancements • Save Radiated field data only

– Reduced the amount of stored data

• Import list for Edit Sources – Can include parametric variables

• Network Installation for clusters

– Improved reliability on Linux • Non-graphical solves without product-links • Solves are independent of Mainwin registry

– Installations on Windows • Non-graphical solves without product-links

• New Registry Configurations

– Installation: Lowest precedence – Defaults applicable to all users

– Machine: • Defaults applicable to all users on a machine.

– User : • Machine independent user specific default

– User and machine: Highest precedence • Defaults specific to user + machine

~10X

Reduction


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3D Modeler Enhancements

View customization.

• 64-bit user interface

• Post process larger simulations

• Z-stretch

• Speed Improvements

• Faster geometry loading

• Improved solid modeler speed.

• Improvements for selecting complex objects.


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CAD Integration on WB Improvements

• CAD integration in ANSYS Workbench provides direct link to 3rd party CAD tools

• Such as ProEngineer, Catia, SpaceClaim

• Added support for parametric analysis and distributed solving of CAD parameter


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Ansoft to ANSYS Geometry Transfer • Geometry and material assignment transfer from Ansoft to ANSYS • Consume geometry from multiple upstream CAD sources – Source can be any of CAD, DesignModeler or Ansoft products – Further geometry edits are possible in ANSYS Design Modeler

• Creates User Defined Model (UDM) for each geometry input.


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Conclusions • Advanced Integrated Solver Technologies

• Physical Optics Solver in HFSS-IE

• New Layout interface for HFSS: Solver on Demand in Designer

• Usability Enhancement

• Improved Multiphysics flow

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Simulation Advances for RF, Microwave and Antenna Applications · •Hybrid Solving introduced in...

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