Appendix 6-5: HFSS 3D Solve Port Mesh on Coax Port Center Conductor Meshing 10 © 2015 ANSYS, Inc....

Release 2015.0 April 16, 2015 1 © 2015 ANSYS, Inc.

2015.0 Release

Appendix 6-5: HFSS 3D Solve

Introduction to ANSYS HFSS


HFSS Solution Process

Initial Mesh Adaptive

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


Initial Mesh Overview

• Ansoft TAU Mesh • Strict or Tolerant

– Effective on imported geometries

– Automatic healing and repair

• Ansoft Classic Mesh • Default for HFSS 3D Layout

Initial Mesh Settings

Meshing


Electrical Mesh: Seeding/Lambda Refinement

• Seeding (Optional) • Seeding is a advanced capability inside HFSS which allows the user to influence the initial mesh

• Can be used for several different reasons

– Reducing number of adaptive passes needed to solve project (time savings)

– Focus additional mesh in critical areas

• Lambda refinement • Ensures that first adaptive mesh is refined to a fraction of a wavelength

– Electrical size depends on solver basis order (Zero: 0.1λ, First: 0.3333λ, Second: 0.67λ, Mixed: 0.67λ)

Geometric Mesh (Initial)

Electrical Mesh (Lambda Refinement)

Meshing



• Port Solution • Performs 2D FEM Eigenmode solution of port

• Adaptive process used to properly determine excitation characteristic impedance and propagation constant

– Adaptive port process is only done as part of the initial mesh creation process

• Mesh on the port lines up with the mesh in the 3D volume

Initial Port Mesh on Coax Port

Refined Port Mesh on Coax Port

Center Conductor

Meshing


Dependent Solve Setup

• Initial mesh options • Allows user to specify another simulation's mesh as starting mesh

• Both simulations must be geometrically identical

• Common uses • Changing material properties without re-meshing

• Defining multiple solution frequencies for meshing

Meshing


Example: Dependent Solve Setup

• Multiple Solution Frequencies

950MHz

1800MHz

Excitation

Short

950MHz 1800MHz

Each frequency band excites a different part of the antenna. Meshing at a single frequency will not

guarantee accuracy.

Setup 1: 1800MHz

Dependent Mesh Setup: 950MHz

Sweep

Meshing


Dependent Solve Setup Solution Process


Solve (1800MHz)


Mesh Refinement

1800MHz Mesh Yes

Max(|DS|)<goal?


Electrical Mesh Seeding/Lambda Refinement

Geometric Mesh Initial Mesh

No

Solve (950MHz)


Mesh Refinement

Frequency Sweep Yes

Max(|DS|)<goal?


No

Meshing


Dependent Solve Setup (Continued)

• Multiple Frequency Bands • From the Project Manager, right-click on base setup (1800MHz)

– From the context menu, select Add Dependent Solve Setup

• The linked setup will automatically be added

• Open the Dependent Setup and change the adaptive mesh frequency, name, convergence criteria, etc.

• Note: The dependent mesh setup can be created manually from the Advanced tab in the Solution Setup Dialog.

– This can be used to link to designs that are not in the same project.

– When manually creating dependent mesh setups, it is recommended that you disable lambda refinement in the dependent solve setup (This is done automatically by the Add Dependent Solve Setup). Failure to do this with mixed order of basis function setup will override the element order information which will yield erroneous results.

Meshing


Curvilinear Elements

• Curvilinear Elements • Most accurate solution to fields on curved structures

• Mesh adapted about curved or true surfaces

• Element matrices computed using the curved boundaries

• Default: Disabled

Rectilinear mesh element Curvilinear mesh element

Red – HFSS

Blue – Analytic Curve

10 cm radius PEC sphere solved from 0.040 - 2 GHz

Meshing



Solution Process

Initial Mesh Adaptive

Mesh Solve Frequency

Sweep

HPC HPC

Solve


HFSS – Advanced Simulation Technology

Finite Element Method • Efficiently handles

complex material and geometries

Integral Equations (IE) • Efficient solution

technique for open radiating and scattering of metallic objects

Physical Optics(PO) • Ideal for electrically large,

conducting and smooth objects

FEM Transient • Ideal for fields that

change versus space and time; scattering locations

Solve


HFSS: Finite Elements (FEM)

• HFSS: Technology • A 3D volumetric Field solver

– Finite Element solver technology

– Visualize fields in the solutions volume

– Extract S-Parameters or Full-Wave SPICE models

• HFSS: Applications • Antenna placement, Radar cross section (RCS), and S-Parameters

• Signal Integrity

• On-chip component design

• Filters, EMI/EMC, Waveguide, Connectors

• HFSS: Advantage • Automated results with accuracy

– Effective utilization of automated adaptive meshing technique

• Ensures accuracy

– Employs advanced matrix solver technology for larger simulation

– Advanced material handling for complex designs

• HFSS: User Interface • 3D Parametric Modeling Editor

– ANSYS Workbench integration for CAD integration and Multi-Physics simulation

• 3D Parametric Layout Editor

Solve


HFSS: Planar EM (2.5D Method of Moments)

• Planar EM: Technology • A 2.5D Full-wave solver for layered medium

– Method of Moments solver

– Visualize currents

– Extract S-Parameters or Full-Wave SPICE models

• Planar EM: Applications • Arbitrary planar geometry with vias

• Planar Antennas, periodic EBG/FSS/Arrays

• On-chip Spiral Inductors

• Planar Filters

• Planar EM: Advantage • Automated results with accuracy

– Effective utilization of automated adaptive meshing technique


– Employs advanced matrix solver technology for larger simulation

– Advanced treatment of skin depth effects and 3D traces

• Planar EM: User Interface • Parametric Layout Editor

Solve


HFSS-Transient

• HFSS-Transient: Technology • Finite Element Transient Solver

– Hybrid Implicit/Explicit transient solver coupled with local time stepping

– Unstructured finite element tetrahedral mesh

• HFSS-Transient: Applications • Pulsed Ground Penetrating Radar (GPR), Electrostatic discharge (ESD), Time Domain Reflectometry (TDR), Transient field

visualization, Scattering Centers (RCS)

• HFSS-Transient: Advantage • Unstructured finite element tetrahedral mesh

– Conforms to physical geometry

– Incorporates HFSS Frequency Domain Adaptive Meshing

• Hybrid FEM Transient Solver

– Based on Discontinuous Galerkin Time Domain (DGTD)

– Mixed Order Basis functions

– Local Time Stepping - Based on element size and basis order

• HFSS-Transient: User Interface • Implemented as a Solution type in the HFSS design

– Shares same modeler interface and similar analysis setup

– Minimal user training required for existing users of HFSS

• New in HFSS 2015: Implicit Finite Element Time Domain Solver – Fast time domain analysis for low frequency applications such as ESD and lightning strike

Solve

TDR

RCS

GPR


HFSS-IE (Integral Equation Solver)

• HFSS-IE: Technology • An Integral Equation solver technology in the HFSS desktop

– A 3D Method of Moments (MoM) Integral Equation technique

– Uses equivalence principle to solve only on surfaces

• HFSS-IE: Applications • Efficient solution technique for large, open, radiating or scattering analyses

– Antenna placement, Radar cross section (RCS), and S-Parameters

• HFSS-IE: Advantage • Automated results with accuracy

– Effective utilization of automated adaptive meshing technique from HFSS


– Employs Adaptive Cross Approximation (ACA) technique for larger simulation

• Automated matrix based solution for larger problems

• Utilization of results from HFSS as a linked source

– Link can include effects of backwards scattering to the source geometry

• HFSS-IE: User Interface • Implemented as a design type in the HFSS desktop


– Minimal user training required for existing users of HFSS

• New in HFSS 2015: MLFMM fast solver for HFSS-IE • Improved speed and more efficient memory for very large scale simulations

SdrrGrJkk

jrES

)()()( 2

0

0

Solve


HFSS-IE: Physical Optics Solver

• Physical Optics: Technology • Currents are approximated in illuminated regions and set to zero in shadow regions

• First order interaction only (Single bounce)

• Source excitation from HFSS Far and Near Field Data-Link as incident plane wave

• Physical Optics: Applications • Efficient solution technique for large, open, radiating or scattering analyses

– Antenna placement, Radar cross section (RCS), and S-Parameters

• Physical Optics: Advantage • Quickly estimates performance of electrically large problems

• Ideal for electrically large, conducting and smooth objects

• Utilization of results from HFSS as a linked source

• Physical Optics: User Interface • Implemented as part of an HFSS-IE design type in the HFSS desktop


– Minimal user training required for existing users of HFSS/HFSS-IE

Solve


HFSS Hybrid Technology

• Hybrid Radiation Boundary • Finite Element Boundary Integral (FE-BI)

• Truncate an FEM Volume with any arbitrary surface using integral equations

• Hybrid IE-Regions • Two-way coupling between Finite Element Volumes with FE-BI radiation boundaries to a 3D Method of Moments region.

• Free Space Coupled

– Conducting objects outside of FEM solution space can be solved directly with 3D MoM, eliminating the need for conducting objects to be enclosed in an air volume

– Homogenous dielectric volumes can be removed from the FEM solution and replaced with the equivalent 3D MoM solution in the region, useful when dielectric regions are electrically large requiring large FEM solution volume

• Free Space + Current Coupled

– In addition to Free Space coupling, IE-Regions can touch the FE-BI boundary.

– Metallic structures can connect across domains allowing electric current to flow from metallic objects in the FEM Volume to touching metallic objects in 3D MoM region

Solve


Hybrid Radiation Boundary

• Radiation Technologies: • Absorbing Boundary Condition (ABC) – First Order Approximation to Free Space

• Perfectly Matched Layer (PML) – Anisotropic Absorber

• Finite Element – Boundary Integral (FE-BI) – Hybrid FEM+IE for Radiation

• FE-BI Advantages • Arbitrary shaped boundary

– Conformal and discontinuous

– Minimize FEM solution volume

• Reflectionless boundary condition

– High accuracy for radiating and scattering problems

• No theoretical minimum distance from radiator

– Reduce simulation volume and simplify problem setup

• Boundary Coupling

– Disjoint FEM volumes couple via FE-BI boundaries

• Setup is similar to ABC boundary condition

– Enabled by checking “Model exterior as HFSS-IE domain”

Solve


HFSS Example: FE-BI

• FE-BI significantly reduces required computer resources • Large air volume inside of radome is removed from the FEM solution

– Air volume is required if using PML or ABC

• Two FEM-IE domains are applied

– Conformal to radome

– Conformal to horn antenna (26 GHz)

HFSS with PML

26 GHz RAM Elapsed Time

PML 259G (DDM) 840min

FE-BI 64G 205min

19143 λ³

FE-BI: 4.1x speedup factor and 75% less RAM

HFSS with FE-BI

FEM-IE Surface

2860 λ³

Radome Horn Antenna

Solve


Hybrid IE-Regions: Free Space Coupled

• HFSS with IE-Regions: Free Space Coupled • Metal objects can be solved directly with an IE solution applied to surface

– Removes the need for air box to surround metal objects

• Homogeneous dielectric objects can be replaced with IE-Region

– Dielectric is solved using IE to surface

IE-Regions (6.2G RAM)

❶Dielectric

IE-Region

Metal

Dielectric

εr = 4

FEM Solution (20G RAM)

IE-Regions reduces RAM by ~70%

❷Metallic

IE-Region

Solve


HFSS Hybrid IE-Regions with Current Coupling

81% Less RAM: IE-Region vs. FEM

140G RAM

44G RAM

Black - FEM Red – Hybrid IE-Regions

FEM with ABC

231G RAM

22463 λ³

199 λ³

Hybrid IE-Region 44G RAM

❶FE-BI

❷IE-Region

50 λ

Continuous Current across

FEM and IE-Region

Solve


HFSS Solvers and Solver Options

Methods

HPC

Finite Element Integral Equation

Eigenmode Transient

Techniques

Direct

Iterative

Direct

Iterative

Hybrid Explicit/Implicit

DDM

Distributed

Multi-Threaded

Distributed

Multi-Threaded

Distributed

Multi-Threaded

Solve


FEM Solver Technology Overview

• Direct • 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 • 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

– Benefits from TAU Initial Mesh

– Reverts to Direct solver if it fails to converge

• Use of Solver Domains • See High Performance Computing (HPC)

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

• Fast Frequency Sweep • Uses an Adaptive Lanczos-Padé Sweep (ALPS)- based solver to extrapolate the field solution across the requested frequency range

from the center frequency field solution

• The time and memory required for a Fast sweep may be significantly greater than the time and memory required for a single frequency solution.

• Matrix Data and Fields 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


S11 (

dB

)

Adaptive Frequency

Example: Discrete Frequency Sweep

• Example: Discrete Sweep • 5 cm microstrip transmission line

• Each frequency point requested in a discrete sweep is explicitly solved using the mesh created in the adaptive solution process

Solved Frequency

Point

Frequency Sweep


S11 (

dB

)

Adaptive Frequency

S11 (

dB

) S

11 (

dB

) S

11 (

dB

) S

11 (

dB

) S

11 (

dB

) S

11 (

dB

) S

11 (

dB

) S

11 (

dB

) S

11 (

dB

) S

11 (

dB

) S

11 (

dB

) S

11 (

dB

)

DONE!

Example: Interpolating Frequency Sweep

• Example: Interpolating Sweep • 5 cm microstrip transmission line

Frequency Sweep

Solved Frequency

Point


HFSS Frequency Sweeps

• Interpolation Convergence • The interpolating sweep 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

Frequency Sweep


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Appendix 6-5: HFSS 3D Solve Port Mesh on Coax Port Center Conductor Meshing 10 © 2015 ANSYS, Inc....

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