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Contents

1. IntroductionIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-

2. Using GEOSTAR for COSMOSHFS 3DElectromagnetics in GEOSTAR . . . . . . . . . . . . . . . . . . . . . . . 2-

COSMOSHFS 2D and COSMOSCAVITY . . . . . . . . . . . . 2-1

Modeling Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Creating Geometry in GEOSTAR: . . . . . . . . . . . . . . . . . . . 2-2

Exporting Geometry from Other Solid Modeling Systems . 2-2

Exporting SolidWorks Models to GEOSTAR . . . . . . . . . . 2-3

Getting Your Model to GEOSTAR . . . . . . . . . . . . . . . . . . . 2-4

What to Do in GEOSTAR . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5List Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Dimensions of the Model . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Viewing Your Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-

Define Material Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Defining Material Sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Picking a Material from the COSMOSM Material Library 2-8

Activating a Material Set . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Meshing the Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

Element Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

Changing Element Size . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

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Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

Important Points to Remember . . . . . . . . . . . . . . . . . . . . 2-14

About Selection Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

Running Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

Visualizing the Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21

S-parameter Versus Frequency . . . . . . . . . . . . . . . . . . . . 2-21

3. Detailed ExampleIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

What is GEOSTAR? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Step 1: Importing the Geometry to GEOSTAR . . . . . . . . . . . 3-3

Step 2: Assigning Materials . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Step 3: Meshing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

Sep 4: Assigning Boundary Conditions . . . . . . . . . . . . . . . . . 3-8

Step 5: Performing Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 3-15

Step 6: Visualizing Results . . . . . . . . . . . . . . . . . . . . . . . . . 3-17

4. Magic Tee Junction

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Step 1: Importing the Geometry to GEOSTAR . . . . . . . . . . . 4-2

Step 2: Assigning Materials . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

Step 3 Meshing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Sep 4: Assigning Boundary Conditions . . . . . . . . . . . . . . . . . 4-7

About Selection Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

Step 5: Performing Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 4-13Step 6: Visualizing Results . . . . . . . . . . . . . . . . . . . . . . . . . 4-15

A. Material Constants . . . . . . . . . . . . . . . . . . . . . . A-1Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .I-1

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1. Introduction

Introduction

For years the finite element method (FEM) has been the key design and simulation

tool for engineers working in a wide range of disciplines. Due to its flexibility in

implementation, the finite element method has attracted so many people to work on

a wide spectrum of problems such as structural, fluid, and thermal problems. Those

working in the area of high frequency electromagnetics (from radio frequencies,

RF, to optics) have, on the other hand, relied more on analytical approaches, when

ever possible, empirical and semi-empirical models, or simple solution techniqueswith limited accuracy and range of applicability. Several numerical difficulties

associated with the nature of the high frequency electromagnetic fields and their

representation in a discretized space have slowed the introduction of the FEM

as a reliable tool in RF, microwave, millimeter-wave, and optical designs.

In 1995, Integrated Microwave Technologies Inc. and Structural Research and

Analysis Corporation developed HFESAP (High Frequency Electromagnetic

Simulation and Analysis Package), an FEM package for the analysis and design of

passive microwave and digital circuits with accuracy, speed, efficiency and ease ofuse. The package included two-dimensional, axisymmetric and three-dimensional

modules for the analysis of waveguides and transmission lines as well as axisym-

metric and 3D resonant structures. HFESAP, now called COSMOSHFS 2D and

COSMOSCAVITY, is complemented by COSMOSFS 3D to provide a full

wave solution for high frequency electromagnetic problems.

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COSMOSHFS 3D is a program that simulates arbitrary three-dimensional passive

structures, including scattering parameters, port propagation parameters and

animated full-wave field solutions

Based on the Finite Element Method, COSMOSHFS 3D uses tangential vector

basis functions along with options to use iterative or direct solvers. COSMOS

HFS 3D is available as part of Structural Researchs COSMOSM finite element

analysis system which comes with a standard pre- and postprocessor, calledGEOSTAR, that is used for all analysis types provided by SRAC. While you may

build your geometry directly in GEOSTAR, you may use your favorite solid model

ing package to build the geometry and then import it to GEOSTAR. GEOSTAR

supports almost all popular CAD systems (refer to the next chapter for a list).

Most of the practical problems to be solved by COSMOSHFS 3D has more

than one material. GEOSTAR accepts assemblies from several CAD systems

where each component of the assembly can be exported to GEOSTAR as a part

which may be assigned a different material. COSMOSWorks, a program fullyintegrated with SolidWorks, is particularly powerful for this kind of problems

since it provides a very friendly environment to export SolidWorks assemblies

directly to GEOSTAR where you assign the desired materials, mesh the assembly,

specify boundary conditions, run the analysis, and visualize the results. Refer to the

COSMOSM Getting Started manual for details.

In addition to the S-parameter field solver, COSMOSHFS 3D offers you an

optional access to a full-wave resonant cavity field solver that directly determines

the resonant frequencies and corresponding modal fields of arbitrary three-dimensional structures. You can then perform subsequent S-parameter analysis at

and around the resonant frequencies for a complete characterization of the

structure. You may also export the calculated S-parameters to external files in

various circuit simulator formats including Compact, Citifile, and Touchstone.

COSMOSHFS 3D application areas include radio frequencies, microwave,

millimeter-wave, wireless, passive waveguide components, MHMIC, MMIC,

microstrip, stripline, launchers, coupling structures, connectors, transitions,

discontinuities, spiral inductors, interdigitated capacitors, filters, hybrids and vias.

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2. Using GEOSTAR

Electromagnetics in GEOSTAR

GEOSTAR is the standard pre- and postprocessor of all analysis modules of

the COSMOSM finite element system. In addition to electromagnetics, the

COSMOSM system includes modules to perform stress analysis, fatigue analysis,

thermal analysis, and fluid flow analysis.

The COSMOSHFS Suite includes COSMOSHFS 2D and COSMOSCAVITY

(High Frequency Simulator and Cavity Solvers, previously called HFESAP) andCOSMOSHFS 3D.

COSMOSHFS 2D and COSMOSCAVITY

COSMOSHFS 2D is a finite element-based package for the analysis and design of

2D and axisymmetric passive mircrowave and digital circuits. COSMOSHFS 2D

is an integrated program that combines quasi-static, frequency-dependent and time

domain analyses. It invokes one or more sub-modules to analyze transmission-lineor waveguide structures and simulate their time domain response under specified

excitation and termination conditions.

COSMOSCAVITY is a general frequency domain program for the analysis of

resonant structures. Its applications include the analysis and design of cavities,

dielectric resonators, frequency meters, connectors, cavity filters, and oscillators. I

for COSMOSHFS 3D

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solves the vector wave equation for the resonant frequency and the corresponding

modal field distributions.

This chapter will show you how to use GEOSTAR to use COSMOSHFS 3D to

model and calculate S-parameters only. Separate manuals are available for

COSMOSHFS 2D and COSMOSCAVITY.

Modeling Geometry

There are two ways to model your geometry:

1. Create your geometry directly in GEOSTAR.

2. Create your geometry in your favorite solid

modeling package and then export it to GEOSTAR.

Creating Geometry in GEOSTAR

You may use GEOSTAR to create 3D geometries. The

geometric entities in GEOSTAR include: keypoints,

curves, surfaces, contours, regions, polyhedra, volumes,

and parts. COSMOSHFS 3D requires the creation of

parts or volumes which are the only two entities that you may mesh to createtetrahedral elements with nodes. To learn how to create geometry in GEOSTAR,

refer to COSMOSM Users Guide, Command Reference, and on-line help.

Exporting Geometry from Other Solid Modeling Systems

Modern CAD systems provide parametric, feature-based solid modeling

environment which simplifies geometric modeling and modification. For this

reason, many users prefer to create their geometry in their favorite CAD system andthen import it to GEOSTAR.

GEOSTAR supports the following solid modeling CAD systems:

SolidWorks,

Pro/Engineer and PT/Modeler (Parametric Technologies Corp.),

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Solid/Edge (Intergraph),

MicroStation Modeler (Bentley Systems),

Helix Design Systems (MICROCADAM)

Eureka (Cad.Lab),

CADDS5 (ComputerVision),

I-DEAS (SDRC), and

Other generic CAD systems.

Integrated analysis packages are available for SolidWorks, Solid/Edge

(Intergraph), MicroStation Modeler, Pro/ENGINEER and PT/Modeler, Helix

Modeling, AutoCAD, and Eureka.

After creating your geometry in the favorite CAD system, you will be able to

generate a COSMOS GEO file or an IGES file that you may import to GEOSTAR

Exporting SolidWorks Models to GEOSTAR

SRAC has developed a fully-integrated interface with Solid/Works. The

interface is currently 100% fully integrated for stress, frequency, buckling, and

thermal analyses. When COSMOSWorks is installed, an FEM menu appears in

SolidWorks.

Although the interface is not fully

integrated for use with electro-

magnetic analysis, it is still very

useful since it lets you import

SolidWorks geometry in both part

and assembly modes to GEOSTAR.

To export SolidWorks geometry:

1. Build your part or assembly as

usual.

2. Verify the units used in your

model by choosing Tools,

Options, clicking the Grid/Units

tab, and checking the Length Unit field.

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3. Choose FEM > Preferences.

4. Click the Export tab.

5. In the Cosmos Setting, clickGeometry Only.

6. From the Unit drop-down menu, choose the unit system used in SolidWorks.

If you choose a unit that is different from that used in SolidWorks, COSMOS

Works will do the conversion from the unit in SolidWorks to the unit specified

in the Preferences, Export dialog box.

7. If you like to launch GEOSTAR automatically after exporting a model, check

the Launch GEOSTAR box.

8. Click OK.

9. From the FEM menu, choose Export. The Save As dialog box opens.

10. From the Save as type drop-down menu, choose COSMOS Files (*.geo). This is

the file that you will load into GEOSTAR using the File, Load command (in

GEOSTAR). The File will be loaded automatically if the Launch GEOSTAR

option is activated in the Preferences, Export dialog box.

Getting Your Model to GEOSTAR

If you have generated a GEO file, you need to import it to

GEOSTAR through the File > Loadcommand.

IGES files are imported to GEOSTAR through the Control >

CAD_System > Read CAD Inputcommand. This command will

open a dialog box in which you may specify the source CAD

system. You may choose the type of the file from the CAD

System menu shown in the figure.

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You may not modify or change geometry that you have imported from a CAD

system. Such geometries must be used as is. If you need to make a change, go

back to your CAD system, make the change, and export the new geometry to

GEOSTAR. The only operations that you may use are: Identify, List, and Plot

What to Do in GEOSTAR

GEOSTAR is large program that supports many types of analyses including

structural, thermal, fluid flow, and electromagnetics. The remainder of this chapter

will emphasize the commands related to COSMOSHFS 3D.

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List Parts

If you exported SolidWorks geometry in the part mode, you will have only one par

in GEOSTAR. If you exported an assembly, you will have a number of parts that is

equal to the number of components in your assembly.

To list parts:

1. From the Geometry menu, choose Parts.

2. Choose List. The PARTLIST dialog box opens.

3. Click OK. The parts are listed.

Dimensions of the Model

Once your model has been imported into GEOSTAR,it is important to verify that it has the proper

dimensions. Use the Control, Measure command to

measure the length of a curve in the model. If the

length does not match your expectations, go back to

your CAD system, set the length units properly, and

try again.

Viewing Your Model

Use buttons in the Geo

Panel and commands in

the Viewing menu to get a

good view of your model

by rotating, zoomin in, etc.

Use the on-line help if you

need more information.

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Define Material Properties

Material properties are defined through the Propsets menu. In

general, several attributes are needed to completely define a

finite element in GEOSTAR. These include the element group

type, real constant set, and the material property set. For

COSMOSHFS 3D, the only attribute needed is the material

property set.

Defining Material Sets

GEOSTAR provides flexible ways to define material properties.

You may define properties on-line or you may select materials

from a material library. The COSMOSM Material Library for

electromagnetics is included in a text file called usermat.lib

which may be edited to define new materials or properties as desired. The filePickmat.lib contains the COSMOSM Material Library for other modules. It is

important to remember that whenever you mesh a part, it will assume the properties

of the active material set. Material set number 1 is active by default. In cases where

you have multiple materials, the recommended procedure is to activate (or define)

the proper material property set before meshing the desired part(s). If there is only

one material set, you may define it at any time before running the analysis (before

or after meshing).

If you ran an analysis and you just need to study the effect of changing the material,just redefine the material set and run the analysis again.

The material properties that are used in COSMOSHFS 3D are:

PERMIT_R: Real part of relative permittivity.

PERMIT_I: Imaginary part of relative permittivity.

MPERMIT_R: Real part of relative permeability.

MPERMIT_R: Imaginary part of relative permeability.

ECON: Electrical conductivity.

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Picking a Material from the COSMOSM Material Library

To pick a material from the library:

GROSTAR comes with a fairly extensive library of microwave materials for

printed circuits, coaxial cables, and semiconductors. This library is separated from

the regular COSMOSM Material Library for convenience.

1. To choose a material from this library, select User Material Library, from the

Propsets menu, the USER_MAT dialog box opens.

2. In the Material Property set field, enter the label of the material set. Thedefault is the last material number you have defined + 1.

3. From the Material Name drop-down menu, choose the desired material to be

assigned to this set.

4. The Unit label is not used for COSMOSHFS 3D.

5. Click OK. The material set you just defined becomes active.

To list material property sets:

1. From the Propsets menu, choose List Material Props. The MPLIST dialog

box opens.

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2. Click OK. Material sets and properties are listed. The Temp/BH-Cr field is not

used by COSMOSHFS. The labelA indicates that the set is active which means

that elements generated at this time will be associated with this material.

To make a material lossless:

1. Pick a material from the User Library as described above.

2. From the Propsets menu, choose User Material Library. The USER_MAT

dialog box opens.

3. In the Material Set Number field, make sure to enter the material set number

you want to make lossless (do not accept the default).

4. From the Material Name drop-down menu, choose LOSSLESS.

5. List the material as shown above to verify that PERMIT_I is set to zero (it wilnot be listed). Other properties remain unchanged.

Activating a Material Set

The last defined material set becomes active by default. You may define a material

set, mesh the associated part(s), define another set, mesh its associated parts and so

on, or you may define all material property sets at once and then activate the

desired set and mesh the associated part(s).

To activate a material set:

1. From the Control menu, choose

Activate > Set Entity. The ACTSET

dialog box opens

2. From the Set Label drop-down menu,

choose MP: Material Property.

3. ClickContinue. Another dialog box opens.

4. In the Material Set Number field, enter the desired set number.

5. ClickOK. The specified material set number becomes active.

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Meshing the Model

Because the analysis results depend on the quality of the models mesh, before

meshing, it is important to specify a reasonable element size. The element size

should be small enough to accurately predict the S-parameters matrix for the

highest frequency of interest.

Element Size

Calculate the element size based on the highest frequency of interest. It helps to list

default element size suggested by GEOSTAR. It is suggested to use the smaller of

the two numbers.

Typically, an average of 10 elements per wavelength, corresponding the highest

frequency of interest in the parts material should be kept. Occasionally, additional

mesh control may be required on regions and/or surface to locally to increase or

decrease the mesh density in and around areas of high field concentration and rapid

field variation.

A polyhedron is the air-tight surface area of a 3D object. A part is made up of

one or more polyhedra. Multiple polyhedra in a part represent cavities com-

pletely enclosed by the outer polyhedron. If you are importing geometry from

a CAD system, polyhedra and parts are automatically created.

To list polyhedra, choose Geometry, Polyhedra, List. Listing polyhedra is importan

because:

1. It lists the element size suggested by GEOSTAR to generate a reasonably fine

mesh, and

2. It lists the regions forming the part. This is particularly useful when you have

multiple parts since it helps identify the common regions. For example, we may

conclude from the list below that regions 2 and 14 are common to polyhedra 1

and 2.

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The suggested size is used by default but may

be easily changed as will be shown in the next

section.

Changing Element Size

To change the element size:

1. From the Meshing menu, choose Mesh Density.

2. Choose Mesh Density. The PHDENSITY dialog box opens.

3. Specify the desired polyhedra. It is recommended to use the same element size

for all polyhedra unless it is required to minimize the number of elements due to

machine resources.

4. Set the desired Element Size.

5. Specify Tolerance. Using a tolerance larger than the default helps speed and

some times in avoiding meshing problems.

6. ClickOK.

The Mesh Density menu lets you specify different element sizes for different

regions, contours, and even curves. It is suggested to use these features only if

you have to like in the case where you have large as well as very small fea-tures in your model. Small features that are not important in your model

should be suppressed in the CAD system. If you use different dimensions for

different polyhedra, make sure that their common regions have the same den

sity. This can be insured through the Meshing, Mesh Density menu.

To mesh the model:

1. Define a material set or activate an existing material set.

2. From the Meshing menu, choose Auto_Mesh, Parts. The MA_PART dialog

box opens.

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3. Pick the beginning part or type its able in the Beginning part field.

4. Pick the ending part or type its label in the Ending part field.

5. In the Increment field, key in the increment between parts in the pattern

6. From the Element Order drop-down menu, choose 0:Low. High order

elements are not used in COSMOSHFS 3D, so make sure to choose the Low

order.

7. ClickOK. Meshing of the specified parts starts. Each element will have a

tetrahedral shape defined by 4 nodes. The elements will be associated with the

active material set.

8. Repeat steps 1 through 7 as many times as needed to mesh all other parts.

To display the elements in different colors based on material:

1. From the Meshing menu, choose

Elements> Activate Elem. Color.

TheACTECLR dialog box opens.

2. From the Color flag drop-down

menu, choose 1: Yes.

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3. From the Set label drop-down menu, select MP: Material Property.

4. Accept theDefault colors flag set to 1:On.

5. ClickOK.


Elements > Plot. The EPLOT

dialog box opens.

7. Accept the default entries, and ClickOK. The elements are redisplayed in

different colors based on their material.

Boundary Conditions

For COSMOSHFS 3D, only three types of boundary conditions can be used:

GC: Grounded Conductor

This boundary condition should be used on metallic surfaces. It imposes a

perfect electrical conductor boundary condition by setting the tangential

component of the field to 0.

PMC: Perfect Magnetic Conductor

This boundary condition should be used for symmetric surfaces where the

magnetic field is purely normal to surface, i.e., this boundary condition forces the

tangential component of the magnetic field to be 0.

PORT: Port

Define access ports to the structure. Use this boundary condition to define the

ports of your model. Ports should be numbered sequentially starting at 1.

To apply boundary conditions:

1. From the LoadsBC menu, choose E-Magnetic, HiFreq_B.C, Define ByRegions. The CBRG dialog box opens.

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2. Point to the desired region and click the left button of the mouse. A regions

highlights.

3. If the highlighted region is correct, click the left button again to accept. If some

other region is highlighted, click the right button to reject.

If the desired region is not highlighted, keep rejecting until the proper region

highlights and then accept by clicking the left button.

4. From the Boundary Conditions Type drop-down menu, choose GC: Grounded

Conductor, PORT: Port, or PMC: Perfect Magnet Conductor.

5. Click Continue.

6. Continue to specify input based on the selected boundary condition.

Important Points to Remember

Boundary conditions should be only applied to parts that have been meshed. Al

boundary conditions applied to boundaries of parts that have not been meshed

will be ignored.

All boundary conditions are applied from the LoadsBC menu.

The only types accepted by COSMOSHFS 3D are GC: Grounded Conductor,

PORT: Port, and PMC: Perfect Magnet Conductor.

If you need to apply a boundary condition to too many regions, it may be more

efficient to create a selection list and then apply the boundary condition to all

the entities at once.

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Ports must be labeled sequentially starting at 1.

Detailed steps to apply perfect magnetic conductor condition:

1. From the LoadsBC menu, choose E-Magnetic, HiFreq_B.C, Define By

Regions. The CBRG dialog box opens.

2.Pick the Beginning region.

3. From the Boundary Condition Type

drop-down menu, choose PMC:

Perfect Mag. Conductor.

4. Click Continue.

5. Pick the ending region.

6. In the Increment field, enter the increment between regions in the pattern. If two

regions are used, use the difference between the two labels.

7. Click OK. The PMC condition will be displayed at the specified regions.

8. You may repeat the steps above as many times as needed.

It may be more efficient to create a selection list and then apply the PMC to

all regions. In this case use 1 for the beginning region, type RGMAX for theending region, and 1 for the increment.

Detailed steps to apply ground conductor condition:

1. From the LoadsBC menu, choose E-Magnetic, HiFreq_B.C, Define By


2. Pick the Beginning region.

3. From the Boundary Condition Type

drop-down menu, choose GC: Ground

Conductor.

4. Click Continue.

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5. In the Conductor Number field, enter the

ground conductor number. Start from 1.

6. In the Relative Permeability Value field,

enter the relative permeability value.

7. Pick the ending region.

8. In the Increment field, enter the increment between regions in the pattern. If tworegions are used, use the difference between the two labels.

9. Click OK. The GC condition will be displayed at the specified regions.

10. You may repeat the steps above as many times as needed.

About Selection Lists

Selection lists are filters that can be applied to a group of entities in GEOSTAR.

When a selection list is active for a given entity, GEOSTAR will only recognize the

members of that entity that are in the selection list. For example if you like to apply

an identical boundary condition to many regions, you may have to repeat the

corresponding command several times. To simplify

this process, you may create a selection list that

contains all such regions and then apply the boundary

conditions to all regions which results in applying the

condition to regions in the active selection list.

Operations related to selection lists are available in

the Control, Select and Unselect menus. Several

ways are available to create, modify, initialize, and

complement selection lists. Up to 10 selection lists

may be defined for each entity (like regions). It

should be noted that selection lists work for

postprocessing also. For example, if you generate a

nodal field plot while a selection list is active for nodes, then the field will be

plotted for the selected nodes only. Similarly if you plot or list all nodes, only nodes

in the selection list will be plotted.

Set operations are also available for selection lists. For example you can define a

new selection lists that is the union or the intersection of two existing selection lists

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The status of selection lists may be

conveniently viewed and controlled by the

STATUS3 Table accessed by clicking the

Status3 button in the Geo Panel or from

Control, Select, Status Table 3.

Use the online help to get information on

the various operations for the selection

lists.

Running Analysis

Before running the analysis, it is

important to set your analysis and

output options.

To set analysis options:

1. From the Analysis menu,

choose HiFreq_Emagnetic >

Analysis Option. The

A_HFRQEMdialog box opens.

2. From theAnalysis option

drop-down menu, choose

SPARAMETER.

3. In the Units field verify that

the proper unit is selected.

This flag is the only way the

program knows about the units

used in your geometry. Even if

you imported your geometry

from COSMOSWorks or other

CAD systems, to GEOSTAR they are just numbers. Make sure to specify the

proper unit that corresponds to your model. Use the Control, Measure menu to

verify the dimensions of your model.

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4. From the Analysis menu, choose

HiFreq_EMagnetic > S-parameters

> Set Options. TheA_HFRQEM

dialog box opens.

5. In theNumber of ports field, enter the

number of ports you have defined in

your model.

You must enter the exact number of ports you have defined. Ports must have

been numbered sequentially starting from 1.

6. In the Starting frequency (GHz) field, enter the lowest frequency of interest.

7. In theEnding frequency (GHz)field, enter

the highest frequency of interest.

Remember that you should have used thisnumber to specify the element size.

8. In the Frequency increment (GHz) field,

enter the desired number.

9. In the Impedance Multiplier field, enter the

impedance multiplication factor.

If a GC or PMC boundary condition is used as a symmetry boundary condi-tion, this field must be set to 2 or 0.5 so that the impedance computed by the

simulator corresponds to the impedance of the entire structure and not the half

model.

10. In the field matrix solution method, choose direct or iterative.

The direct method performs a matrix factorization and requires more memory

while the interactive method uses less memory, i.e., can be used for very large

problems, but may be slower.

11. If the Renormalized Smatrix flag field, indicate whether or not the simulator

should compute the renormalized scattering matrix. This is needed in order to

be able to output the scattering parameters in various circuit simulator formats

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12. ClickContinue.A dialog for setting more solution parameters is displayed.

13. The number of modes to be considered and the de-embedding length should be

specified for each port.

14. For each port, specify the additional solution parameters. The number of modes

to be considered and the de-embedding length should be specified for each por

Depending on the solution parameters chosen, the amount of data output by

the simulator may be very large. To control the amount of disk space used, the

output options give you some control over what the simulator writes out.

To set output options (optional):

1. From the Analysis menu, choose HiFreq_EMagnetic > S-parameters > Set

Output. TheHF_SPAROUTdialog box opens.

2. From the Circuit Simulator Flag

drop-down menu, select the

desired format. The available

formats are Citifile, Compact,

and Touchstone.Note that the

dominant mode S-parameters

only are output to these files.

3. From the Output Option drop-down menu select None, Nodal, Elemental, orboth Nodal and Elemental. This controls which field quantities are to be written

by the simulator. Note that only the solution based on dominant mode excitation

at each port is written.

4. ClickOK.

To run the analysis:

1. From the Analysis menu, choose RunAnalysis. GEOSTAR will start preparinginformation needed by COSMOSHFS.

Preparing data is currently slow. It will be improved in future releases.

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Visualizing the Results

After finishing the analysis, you are ready to visualize the results. COSMOSHFS

3D generates results for port propagation characteristics as well as various

scattering parameters matrices and impedance and admittance matrices. These

results may be viewed by listing them in a text format or alternatively by plotting

them versus frequency.

To list the S-parameters matrix:

1. From the Results menu, choose List, HF Emag Result. TheHF_RESULT

window opens, showing the Port Propagation Parameters and the Generalized

S-Matrix at each frequency. If additional calculations were requested, i.e.,

renomalization or de-embedding, they are also displayed in this window.

The generalized S-parameters have four indices, i, n, j, and m. The entry Sin

jm corresponds to the ratio of the wave associated with mode n at port i

when port j is excited with mode m.

S-parameter Versus Frequency

Multiple S-parameters may be displayed on the same plot by assigning each one of

them to a separate graph. Selected graphs can subsequently be plotted.

Only S-parameters for the dominant mode at each port can be plotted.

To activate Sij graph:

1. From the Display menu, choose XY-Plots > Activate Post Proc. The

ACTXYPLOTdialog box appears.

2. In the Graph Number field, enter 1

for the first graph or the appropriate

number for the other graphs.

3. In the Row Number, enter i, the

desired row index of the desired

matrix.

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4. In the Column Number field, enter j, the desired column index of the desired

matrix. by entering i in step 3 and j in step 4 we have chosen to plot the ij entry

of the matrix to be selected in step 5.

5. From the Y Variable drop-down menu, choose the proper matrix and format of

the plot. For example MatrixS Mag, will select the magnitude of Sij.

6. ClickContinue.

7. From the Graph Color drop-down menu, choose the color you want for the

graph line.

8. From the Graph Line Style drop-down menu, choose Solid.

9. From the Graph Symbol Sign drop-down menu, select Circle.

10. Set the Graph ID field to the desired label, for example Mag (Sij).

11. ClickOK.

12. You may repeat the steps above to activate more graphs by changing the graph

number in step2, and the i and j values in steps 3 and 4.

To generate the XY plot:

1. From the Display menu, choose XY Plots, Plot Curves,. The XYPLOT dialogbox opens with a list of all available graphs.

2. From the Plot Graph drop-down menu,

you may choose which curves you

want to graph. 1: Yes for example,

indicates that you want to generate the

first curve.

3. Press OK. The graph is displayed in the active window.

In addition to the scattering parameters, you may also view field distribution in the

model for a given frequency and a given port excited by its dominant mode. The

real and imaginary parts of the electric field, magnetic field and current densities

may be plotted.

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To plot the electrical field intensity:

1. From the Results menu, choose Plot > Electromagnetic. The ACTMAGdialog

box opens.

2. In the Frequency Number(frequency step) field, enter the desired frequency

step (step 1 is the lowest requested frequency).

3. In the Port Numberfield, enter the desired port number. This means that the

solution to be used is the one where the specified port is excited with itsdominant mode.

4. From theEntity Flag drop-down menu, choose Node.

5. From the Componentdrop-down menu, choose ER_R: Resultant Electrical

Field Intensity (Real part).

6. ClickContour Plot, Vector Plot, Iso Plot, or Section Plot. Another dialog box

will open based on the type of plot you select.

7. Set desired values and clickOK. The default element number is the highest

element label available in the database. The variableELMAXmay be entered

instead of writing a number. Similarly RGMAX and NDMAX refer to the

highest region and node labels in the database.

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3. Detailed Example

Introduction

This simple tutorial will guide you step-by-step through your first COSMOS

HFS 3D analysis.

This tutorial assumes that you have used Microsoft Windows before and

know how to run programs, resize windows, and manipulate parts within

COSMOSM GEOSTAR.

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What is GEOSTAR?

GEOSTAR is the basic pre- and postprocesser of COSMOSM products. You may

create your geometry in GEOSTAR or import it from your favorite CAD system.

Steps to Perform Electromagnetic Analysis

The following steps describe the general procedure for performing electromagnetic

analysis:

To perform electromagnetic analysis:

Create your geometry in GEOSTAR or use your favorite CAD system.

If you are not using GEOSTAR to create your geometry, generate a COSMOS

file or an IGES file from your CAD system,

Mesh your model,

Assign material from a library or specify the desired material properties,

Specify ports and other loads and boundary conditions,

Set your options for the electromagnetic analysis,

Run the analysis, and

Visualize the results in graphical and tabulated formats.

COSMOSHFS 3-D provides coupling with thermal analysis, so you may

continue to perform thermal analysis and visualize the results. Results of

your electromagnetic analysis will still be available after running thermalanalysis.

In this example, you will learn how to:

1. Import the geometry to GEOSTAR through a GEO file.

The GEO file for this example was created in COSMOSWorks which is a

fully integrated interface with SolidWorks for structural and thermal

analyses.

2. Define element attributes,

3. Mesh the model,

4. Assign ports and apply other boundary conditions,

5. Set your analysis options,

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6. Run electromagnetic analysis, and

7. List the S-parameters, generate the S-parameters versus frequency plots, and

visualize electric and magnetic fields.

Step 1: Importing the Geometry to GEOSTAR

To start a new problem in GEOSTAR:

1. Start GEOSTAR. GEOSTAR starts and the Open Problem Files dialog box

opens.

2. In theLook in field,

browse to the directory

which you want to use forthe new problem.

3. In the File name field,

enter the name you like to

give to the new problem.

4. ClickOpen. GEOSTAR

sets the new problem. All

related database files will

be created in the specified folder.

To import the geometry file:

1. From the File menu, select Load. The

File dialog box opens.

2. Click the Find... button and browse to

the vprobs\HFS folder under your

COSMOSM directory.

3. Choose the COAX.GEO file and clickOpen.

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4. ClickOK. The file will be imported. The message window will echo the

progress of loading the file. The geometry will be constructed on the screen.

Reconstructing the model should take a few seconds for this model.

Step 2: Assigning Materials

To define material properties, you may select a material from a

library, or you define material properties directly.

There are two material libraries available for use with

COSMOSM. The COSMOSM Material Library and the

InfoDex Material Library. The COSMOSM Material

Library is available by default. The InfoDex Material

Library is more extensive and may be optionally acquired. You may also edit the COSMOSM Material Library to add

more materials and electromagnetic properties as desired.

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To define material property set number 1:

1. From the PropSets menu, select Material Property. The Mprop dialog box

opens.

2. In the message Material Property Set field, verify that 1 is entered.

3. From the Material Property Name drop down menu, choose PERMIT_R.

4. ClickContinue.

5. In the Property Value field, enter 1.0 (for air).

6. ClickOK. The first MPROP dialog box opens again to let you define more

properties.

7. ClickCancel to exit the dialog box.

It is recommended to list and examine material property sets before

continuing with rest of the steps.

To List material property sets:

1. To list material property set 1,

choose List Material Props

from PropSets. TheMPLIST

dialog box opens.

2. ClickOK to accept default

numbers for beginning,

ending, and the increment to list material set number 1. Each row lists a material

property. NUXY is defined by default as 0.3 for structural models and is not

used for electromagnetic analyses.

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The letter A indicates that Material Set (Label) 1 is active. Any mesh

generated at this point will assume the active material set.

Step 3: Meshing

Once the geometry and material specifications were determined, the model is ready

to be meshed. You may want to list the default element size and change it if you

like.

To list the default element size selected by the program:

1. From the Geometry menu, choose

Polyhedra > List. The PHLIST dialog

box opens.

2. ClickOK. The element size is listed as

shown.

The default element size is 2.7711 (mm). All regions making up the

polyhedron are listed. You may make it smaller for finer mesh or larger for a

coarser mesh. The element size and tolerance list here will be used unless

changed as shown next.

To change the default element size:

1. From the Meshing menu, choose Meshing Density > Polyhedron Elem Size.

The PHDENSITYdialog box opens.

2. In the Beginning Polyhedron field, key in 1. There is only one polyhedron in

this model.

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3. In the Ending Polyhedron field, key in 1.

4. In the Increment field, key in 1.

5. In the Average elements size field, key in

0.5.

6. In the Tolerance field, key in 0.001.

7. ClickOK.

To Mesh the Model:

1. From the Meshing menu, select Auto-Mesh > Parts. TheMA_PARTdialog box

opens.

2. In the Beginning Part field, verifythat 1 is entered. There is only one

part in this model.

3. In the Ending Part field, verify that

1 is entered.

4. In the Increment field, verify that 1

is entered.

5. In the Hierarchy check flag field,

verify that No is active.

6. In the Element Order Flag filed,

verify that Low order is selected.

High order mesh is not used

in COSMOSHFS 3D.

7. In the Number of Smoothing

Iterations field, verify that 4 is

entered.

8. ClickOK. GEOSTAR starts building the mesh. After few seconds, the mesh

will be generated. You will see the nodes as shown.

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To view the mesh:

1. From the Meshing menu, choose Elements

> Plot. TheEPLOTdialog box opens.

2. In the Beginning Element field, enter 1.

3. In the Ending Element field, use the

default number given in the dialog

box. This is the highest element

number in the model.


is keyed in.

5. ClickOK. The elements are plotted

as shown.

Sep 4: Assigning Boundary Conditions

The purpose of this stage is to assign boundary conditions to the model.

Metallic surfaces are assigned Grounded Conductor condition,

The plane of symmetry is assigned Perfect Mag. Conductor conditions, and

Ports are assigned the Port conditions.

To plot regions:

1. From the Geo Panel window, click the CLS

button to clear the screen.

You may also enter CLS in the Message

window. You will be prompted to set acolor. See the STATUS1 table for color

code. 16 is white.


Regions > Editing > Plot. The RGPLOT

dialog box opens.

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3. In the Beginning Region field verify that 1 is keyed in.

4. In the Ending Region field, enter the maximum number of regions in the mode

(default). In this model there are 10 regions.

5. In the Increment field, verify that 1 is keyed in.

6. ClickOK. The regions will be plotted on the screen.

To define ports:

Three ports will be defined for this

structure as shown.

1. From the LoadsBC menu, choose

E_Magnetic > Hi-freq_B-C >

Define by Regions. The CBRGdialog box opens.

2. Point to region 6 and click the left

button of the mouse. Region 6

highlights and 6 appears in the

Beginning Region field.

3. Click once more to accept. If a

wrong region highlights, rejectusing the right button until region 6

highlights and then click the left

button to accept.

4. In the Boundary condition type drop down field, choose Port.


6. In the Port Number field, enter 1.

7. In the Ending Region field, input a large

number, accept the default number 6.


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To assign Ground Conductor condition to all other regions:

Ground Conductor condition will applied to the rest of the regions in the structure.

Namely regions 3, 4, 9, and 10. You may continue the procedure above to apply

ground conductor condition to regions 3 and 4 with an increment of 1 in one step

and similarly repeat for regions 9 and 10. We will use the selection list utility

instead.

The utility is particularly useful when

many regions are to be assigned an

identical condition. The regions (or

other entities) are chosen in a selection

set and then the condition is applied to

all regions while the proper selection

list is active. All regions mean all

selected regions in this case. This

procedure lets you apply the conditionin one shot to all regions in the selection

set. Alternatively, you may repeat the

command to apply the condition. There

are many ways to select and unselect

entities to selection lists.

To create a selection list:

1. From the Control menu, chooseSelect > by Picking. The SELPIC

dialog box opens.

2. From the Entity name for Selection

Set 1 drop down menu, choose

RG:Region.

3. ClickContinue. The SELPICdialog

box opens.

4. Using the left mouse button click on

one of the curved regions, the region

will highlight. If the program

highlights the desired region, click

the left mouse button again to

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7. In the Conductivity value field is set to 5.8e+007 value by default.

8. In the Relative permeability value field, verify that 1 is keyed in.

9. In the Ending Region field, key in

RGMAX. This forces the system

to assign the given BC to all the

regions in the active selection list.

RGMAX is a variable that refers

to the highest region number in the

database.

10. In the Increment field, verify that

1 is keyed in.

11. ClickOK. The boundary condition is applied as shown.

To deactivate selection set number 1:

1. Click the Status3 button in the Geo Panel window. The Status Table 3 dialog

box opens.

Notice that Selection Set number 1 is active and that Region (RG) selection

is on.

2. Click on ON twice to turn off the selection set.

3. ClickSave. The selection set may be activated at any time later.

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4. To get help for the STATUS3 (Status of Selection Lists), click the Help icon.

Step 5: Performing Analysis

In this stage, we setup the solver and output options.

To setup analysis options:


HiFreq_Emagnetic > Analysis Option. The

A_HFRQEMdialog box opens.

2. From the Analysis option drop down field, choose SPARAMETER.

3. In the Units field verify that the 0:mm option is chosen.

4. ClickOK.



HiFreq_EMagnetic > SParameters >

Set Options. TheHF_SPARSOLN

dialog box opens.

2. In the Number of ports field, enter 3.

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3. In the Starting frequency (GHz) field, enter 1.

4. In the Ending frequency (GHz) field, enter 10.

5. In the Frequency increment (GHz) field, input 0.5

6. In the Impedance multiplier field, input 0.5.

7. You can keep the other entries as given by the default values.

8. ClickContinue.


10. In the Number of Modes field, enter 1.

11. In the De-embedding Length field, enter 0.

12. Repeat steps 8 to 10 for port 2 and 3 as

shown.

13. ClickOK.

For the number of ports you should enter the total number of ports in the mod

el. Also remember that ports must be numbered sequentially starting from 1.


1. From the Analysis menu, choose Hi-

Freq_EMagnetic > SParameters >

Output Options. TheHF_SPAROUT

dialog box opens.

2. From the Circuit Simulator drop-down menu, choose Citifile, Compac,

Touchstone, or None.

3. From the Output Option drop-down menu, select Nodal.

4. ClickOK.

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To run analysis:

1. From the Analysis menu, choose HiFreq_EMagnetic > Run Analysis.

Analysis starts.

2. After analysis is completed. Click the OK

button in the Solution Complete window.

Step 6: Visualizing Results

Once the analysis is completed, you may visualize results in both graphical and

tabular formats as shown below.

To list the S-Matrix:

1. From the Results menu, choose List > HF Emag Result. TheHF_RESULT


S-Matrix at each requested frequency.

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9. In the Ending Element field, keep the default number given by the program.

That is the highest element label in the model.

10. In the Increment field, verify that 1 is keyed on.

11. ClickOK. The results are displayed in the main window.

To generate a vector plot for the electric field:

1. Repeat steps 1 through 5 in the procedure above.

2. Click the Vector Plot button. The

MAGPLOTdialog box opens.

3. In the Line flag drop-down menu, choose

2: Vector.

4. In the Beginning Node field, input 1.

5. In the Ending Node field, choose the default number. The default number is the

highest node number in the model.

6. In the Increment field, verify that 1 is active.

7. In the Vector scale factor field, verify that 1 is keyed in.

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8. ClickOK. The mesh and the vector plot are displayed.

To generate a section plot of the electric field:

1. Again repeat steps 1-5 as described above.

2. Click the Section Plot button. The

SECPLOTdialog box opens.

3. From the Orientation of section

planes drop-down menu, choose

0: X.

4. ClickContinue.

5. In the Number of section planes field, enter 10.

6. From the Section plan positions drop-down menu, choose 0: Defaults.

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7. ClickContinue. The field on the symmetrical planes is displayed.

To generate a graph of an S-Parameter Versus Frequency:

First we will activate and setup options for the first graph.

To activate the S11 element graph and setup options:

1. From the DISPLAY menu, choose XY_Plots > Activate Post Proc. The

ACTXYPLOTdialog box appears.

2. In the Graph number field, enter 1.

3. In the Row number, enter 1.

4. In the Column number field, enter also 1.

By entering 1 in steps 2 and 3 we have

chosen to plot the S11 element of the S-

Matrix.

5. From the Y variable drop-down menu, choose MatrixS_Mag, to display the

magnitude of S11.

6. ClickContinue. A dialog box opens for plotting options.

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4. Magic Tee Junction

Introduction

The Magic Tee, also called the Hybrid Tee junction, has important properties which

make it suitable for microwave bridges, discriminators and many other applica-

tions. In this example, we will analyze the Hybrid Tee junction shown below:

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Magic TeeJunction

The letter A indicates that Material Set (Label) 1 is active. Any elements

that you generate will assume the active material set.

Step 3: Meshing

Once the geometry and material specifications were determined, the model is readyto be meshed. You may want to list the default element size and change it if you

like.

To list the default element size selected by the program:



box opens.

2. ClickOK. The element size is listed asshown.

The default element size is 1 (mm). All regions making up the polyhedron

are listed. You may make it smaller for finer mesh or larger for a coarsermesh. The element size and tolerance list here will be used unless changed

as shown next.

To change the default element size:

1. From the Meshing menu, choose Meshing Density > Polyhedron Elem Size.

The PHDENSITYdialog box opens.

2. In the Beginning Polyhedron field, key in

1 (or point to the model and click leftbutton). There is only one polyhedron in

this model.

3. In the Ending Polyhedron field, key in 1

(or point to the model and click left

button).

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5. In the Average elements size field, key in 12.

The selected element size of 12 mm satisfies the requirement that the element

size may not exceed 1/10 of the wave length of the operating signal.

6. In the Tolerance field, key in 0.01.

7. ClickOK.

To verify the new mesh density setting:



box opens.

2. ClickOK.

To Mesh the Model:

1. From the Meshing menu, select Auto-Mesh > Parts. TheMA_PARTdialog

box opens.

2. In the Beginning Part field, verify

that 1 is entered. There is only one

part in this model.

3. In the Ending Part field, verify that 1

is entered.

4. In the Increment field, verify that 1 is

entered.

5. In the Hierarchy check flag field, verify that No is active.

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6. In the Element Order Flag filed, verify that

Low order is selected.

High order mesh is not used in

COSMOSHFS 3D.

7. In the Number of Smoothing Iterations

field, verify that 4 is entered.

8. ClickOK. GEOSTAR starts building themesh. In few seconds, the mesh will be

generated. You will see the nodes as shown.

To view the mesh:


Elements > Plot. TheEPLOTdialog box

opens.

2. In the Beginning Element field, enter 1.

3. In the Ending Element field, use the default

number given in the dialog box. This is the

highest element number in the model.

4. In the Increment field, verify that 1 is keyed

in.

5. ClickOK. The elements are plotted asshown.

Sep 4: Assigning Boundary Conditions

The purpose of this stage is to assign boundary conditions to the model. Metallic surfaces are assigned Grounded Conductor condition, and each of

the 4 ports is assigned the Port condition.

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To plot regions:

1. From the Geo Panel window, click the CLS button to clear the screen.

You may also enter CLS in the Message window. You will be prompted to

set a color. See the STATUS1 table for color code. 16 is white.

2. From the Geometry menu, choose Regions > Editing > Plot. The RGPLOT

dialog box opens.

3. In the Beginning Region field verify that 1 is keyed in.

4. In the Ending Region field, enter the maximum number of regions in the mode

(default). In this model there are 18 regions.


6. ClickOK. The regions will be plotted on the screen.

To define ports:

Four ports will be defined for this structure as shown.

1. From the LoadsBC menu, choose

E_Magnetic > Hi-freq_B-C >

Define by Regions. The CBRGdialog box opens.

2. Point to region 9 and click the left button of the mouse. Region 9 highlights and

9 appears in the Beginning Region field.

Port 1

Port 2Port 3

Port 4

Region 9

Region 7

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3. Click once more to accept. If a wrong region highlights, reject using the right

button until region 9 highlights and then click the left button to accept.

4. In the boundary condition type drop down field,

choose Port.



7. In the Ending Region field, accept the default region number (9).


9. ClickOK. Port 1 is defined as shown.

10. Repeat the steps above to define port 2

(Region 7) and port 3 (Region 18). Do not

forget to type in the proper port number in

the Port Number field of the CBRG dialog

box.

11. Port 4 must be defined using the 3 regions

which make it up. You can repeat the steps

for each of the 3 regions as shown above, or

you may define the port in 2 steps by

applying the condition to 2 of the regions

using the proper beginning, ending and then

defining it for the third region.

Region 1

Region 2

Region 12

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For example, you may use 1, 2, 1, or 1, 12, 11, etc. for the beginning region

ending region, and increment. Note that selecting 12, 1, and 11 for the

beginning region, ending region, and increment will also apply the condition

to regions 1 and 12.

If you define Port 4 in 2 or 3 steps, make sure to enter 4 for the port number

each time.

Instead, you may use selection lists to apply boundary conditions to many

entities in one step. This will be demonstrated in the next step.

To assign Ground Conductor condition to all other regions:

Ground Conductor condition will be applied to all regions except the ones we used

to define the ports. You may continue the procedure above to apply ground

conductor condition to all these regions. Instead we will use the selection list

utility.

About Selection Lists

Selection lists are very useful during pre- and

post-processing. A selection list acts like a filter.

When a selection list is active for an entity,

GEOSTAR will only recognize the members of

this entity that are on the selection list. Up to 10

selection lists may be created for each entity.There are several convenient ways to select and

unselect entities including specifying labels,

picking using the pointing device, specifying a

window, using reference (selecting members of

entity associated with another) entity, specifying a

window in 3D space, and selecting elements

based on their attributes.

Refer to the Control,Select, and Unselect menus for details). In this example, we

will create a selection list for regions by unselecting the regions that we used for

ports. We will then apply the ground conductor condition to all regions which will

be interpreted by GEOSTAR as the regions on the selection list.

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To create a selection list:

1. From the Control menu, choose Unselect > by Picking. The UNSELPIC

dialog box opens.

2. From the Entity name for Selection Set 1 drop down menu, choose RG:

Region.

3. ClickContinue. The UNSELPIC

dialog box opens.

4. Using the left mouse button click on region 9 (port 1), the region will highlight

If the program highlights the desired region, click the left mouse button again to

accept. Otherwise click the right button to reject until the proper region

highlights and then accept by clicking the left button.

5. Keep selecting regions used to define

the ports (regions 9, 7, 18, 1, 2, and

12) as shown in the figure.

6. ClickOK. Selection list number 1

is created and activated. Now

GEOSTAR filters out the specified

region from the list of regions that

it recognizes.

7. Click the CLS button to clear the

screen.


Regions > Editing > Plot. The

RGPLOTdialog appears.

9. Press OK. Only the regions which

belong to the active set are plotted.

While a selection list is active,

GEOSTAR will only see the members

of the entity that are in the selection

list.

To assign Ground Conductor boundary condition:

1. From the LoadsBC menu, choose E_Magnetic > Hi-freq_B-C > Define by


2. ClickContinue.

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3. In the Beginning Region field,

verify that 1 is keyed in.

4. In the Boundary condition type drop

down field, choose Grounded

Conductor.

5. ClickContinue.

6. In the Conductor Number field,

key in 1. In the Conductivity value

field, verify that 5.8e+007 is keyed

in.

7. In the Relative permeability value field, verify that 1 is keyed in.

8. In the Ending Region field, key in RGMAX. This instructs GEOSTAR to

assign the given BC to all the regions in the active selection list. RGMAX is a

variable that refers to the highestregion number in the database.


is keyed in.

10. ClickOK. The boundary condition

is applied as shown.

To deactivate selection set number 1:

1. Click the STATUS3 button in the Geo

Panel window. The Status Table 3

dialog box opens.

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To run analysis:

5. From the Analysis menu, choose HiFreq_EMagnetic > Run Analysis. The

analysis starts.

6. After analysis is completed. ClickOK

in the Solution Complete window.

Step 6: Visualizing Results

Once the analysis is completed, you may visualize results in both graphical and

tabular formats as shown below.

To list the S-Matrix:

1. From the Results menu, choose List > HF Emag Result. TheHF_RESULT


S-Matrix at each requested frequency.

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To plot resultant electric field intensity produced by exciting a port at 2.0 GHz

1. First we create four windows for the four plots. To do so, choose Create from

the Windows menu. Repeat this process for three times. To tile the windows,

choose Tile from the Windows menu.

2. Activate the first window

simply by clicking in it.

3. From the Results menu,

choose Plot > Electro-

magnetic. TheACTMAG

dialog box opens.

4. In the Frequency number field, enter 5 (corresponds to a frequency of2 GHz)

5. In the Port number field, enter 1.

6. In the Entity flag drop down field, choose Node.

7. From the Component drop down field, choose ER_R: Resultant Electrical

Field Intensity (Real).

8. ClickContour Plot button. TheMAGPLOT

dialog box opens.

9. From the Line flag drop-down menu,

choose 0: Fill.

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10. In the Beginning Element field, enter 1. In the Ending Element field, keep

the default number given by the program. That is the highest element label in

the model.

11. In the Increment field, accept 1.

12. ClickOK. The plot are in generated in the active window

13. Repeat steps 2 through 11 for the other three windows to produce the plots

corresponding to ports 2, 3, and 4. Make sure that you enter the proper portnumber in step 5 each time.

It is instructive to notice the electric field distribution inside the T-junction.

For example, when Port 4 is excited with 2 GHz field, a standing wave is cre

ated at Port 4 waveguide due to the reflection of the applied field at the junc-

tion. You may also notice the equi-amplitude fields at Ports 1 and 2

waveguides and, most importantly, the zero-field at Port 3 waveguide.

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For the section plot generated for Port 4, it is more informative to change the

orientation of the section planes to be parallel to the Z-axis. This would need

to change only the Orientation of section planes field in the SECPLOTdia-

log box to Z-axis option.

To generate X-Y plots for the magnitude and phase of the first element in the

scattering matrix versus frequency:

To plot magnitude versus frequency

1. From the Display menu choose XY_Plots > Activate post-Proc. The

ACTXYPOSTdialog box opens.


3. In the Row number field, enter 1.

4. In the Column number field, enter 1.

5. From the Y variable drop-down menu choose MatrixS_Mag option. ThenclickContinue.

6. TheACTXYPOSTdialog box opens. Accept the default values and clickOK.

7. To display the plot, choose XY_Plots > Plot Curves from the Display menu.

The plot is generated.

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To plot phase versus frequency:

1. From the Display menu choose XY_Plots > Activate Post-Proc. The

ACTXYPOSTdialog box opens.


3. In the Row number field, enter 1.

4. In the Column number field, enter 1.

5. From the Y variable drop-down menu choose MartixS_Phase option and click

Continue.

6. TheACTXYPOSTdialog box opens. Accept the default values and clickOK.

7. To display the plot, choose XY_Plots > Plot Curves from the Display menu.

The plot is generated.

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A. Material Constants

Table A.1 Dielectric\Constant and Conductivity of Some Materials (at 25C)

MaterialRelative Permitivity (r) Conductivity ()

x107 mhos/mr r

Alumina 10.70 0.0001 10-16

Gallium Arsenide (GaAs) 12.90 - depends on doping

Germanium (Ge) 16.00 - depends on doping

Glass (plate) 6.00 0.0300 10-13

Mica 6.00 0.2000 10-15

Oil (mineral) 2.20 0.0004 10-14

Paper (impregnated) 3.00 0.1000 -

Paraffin 2.10 0.0004 ~10-15

Plexiglass 3.40 - -

Polyfoam ~1.05 - -

Polystyrene 2.70 0.0002 10-16

Polyvinyl chloride (PVC) 2.70 - -

Porcelain 5.00 0.0040 -

PVC (expanded) ~1.10 - -

Rubber (neoprene) 5.00 0.0200 10-13

Quartz 5.00 0.0010 10-17

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