topics: ansoft hfss — 3d boundary manager...

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source types:

s.

Ansoft HFSS — 3D Boundary Managerics:

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rceste Portsped Gap Sourcessiderations Whenfining Portsdent Waveage and Current Sourcesnetic Bias

SourcesWhen you select Source, you may choose from the following

• Port• Incident wave• Voltage drop• Current• Magnetic bias

Note: These sources are available only for driven solution

ell Online Help System 265 Copyright © 1996-2002 Ansoft Corporation

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ground is a perfect E bound-re typically placed on this to the external world.

to a semi-infinitely long erties as the port. In solving is excited by the natural he 2D field solutions gener-

s for the 3D problem. The at each port.

idually. Each mode incident excited by a signal of one is generated, port 2 is set to

a lumped gap source. ort. The S-parameters can ted. Lumped gap sources


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PortBy default, the interface between all 3D objects and the backary through which no energy may enter or exit. Wave ports ainterface to provide a window that couples the model device

Ansoft HFSS assumes that each port you define is connectedwaveguide that has the same cross-section and material propfor the S-parameters, the software assumes that the structurefield patterns (modes) associated with these cross-sections. Tated for each port serve as boundary conditions at those portfinal field solution computed must match the 2D field pattern

Ansoft HFSS generates a solution by exciting each port indivon a port contains one watt of time-averaged power. Port 1 iswatt, and the other ports are set to zero watts. After a solutionone watt, and the other ports to zero watts and so forth.

Within the 3D model, an internal port can be represented by Lumped gap sources compute S-parameters directly at the pbe renormalized and the Y-matrix and Z-matrix can be compuhave a user-defined characteristic impedance.


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use the following procedure

ource type.

not use an embedded

ode associated with the an one mode to analyze

inals pull-down menu.

. When you select one, a

e. o compute voltage data

Multiplier field.

ctor. The maximum num-


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rceste Portsefining Terminalsped Gap Sourcessiderations Whenfining Portsdent Waveage and Current Sourcesnetic Bias

Wave PortsA wave port is a traditional transmission line port. In general, to define a wave port.

> To create a wave port:1. For the selected surface or 2D object, select Port as the s2. Select Wave Port from the Type pull-down menu.3. Enter a name for the port or accept the default name. Do

blank in the port name. 4. By default, the system assumes that only the dominant m

port’s cross-section is present at a port. To specify more that the port:a. Select View Modes from the View Modes/View Termb. Enter a value in the Num field.c. Choose Enter. Each mode is listed in the Modes list.

5. To set an impedance or calibration line on a port mode:a. Select a port mode from the Modes list. b. Select Use Impedance Line or Use Calibration Line

Y appears under Imped or Calib in the Modes list.c. Define the location of the impedance or calibration lin

6. Optionally, define terminals for the wave port if you wish tfor the port that can be used for circuit analysis.

7. Select Polarize E Field to polarize the E-field on the port.8. Enter the impedance multiplier for the model in the Imped9. Choose Assign.

Note: For terminal solutions, specify one mode per conduber of modes on any port is 25.


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s, a terminal-based descrip- the traditional mode-based

be created on the ports to rminal voltage lines:

e line must be created for

ce or “ground” conductor to

For example, the setup on

not independent.

box one time regardless

inals pull-down menu. the Terminals list.

in the Terminal Name hich they appear in the

must have a voltage line

pears under Defined in

ual to the number of a lumped gap source one port, they are


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rceste Portsefining Terminalsped Gap Sourcessiderations Whenfining Portsdent Waveage and Current Sourcesnetic Bias

Defining TerminalsFor projects containing multi-conductor transmission line porttion in terms of voltages and currents may be more useful thanS-matrix. To facilitate such a description, terminal lines must define port voltages. Use the following guidelines to set up te

• Solve for all present TEM modes. One terminal voltageach port mode in the device.

• In general, draw a single terminal line from the refereneach port-plane conductor.

• Be consistent with the setup of terminal voltage lines. port 1 should usually be the same as that on port 2.

• Voltage loops are not permitted because voltages are > To define terminals:

1. Select the Define Terminals check box. Select this checkof the number of ports.

2. Select View Terminals from the View Modes/View TermNew fields appear in the window. Each terminal is listed in

3. Select a terminal from the Terminals list.4. Enter a name for the terminal or accept the default name

field. The names of the terminals will affect the order in wlist.

5. Set a terminal voltage line on the terminal. Each terminal defined. To set a terminal voltage line:a. Select a port terminal from the Terminals list. b. Define the location of the terminal voltage line. A Y ap

the Terminals list.6. Choose Assign.

Terminals are now specified for the port.

Note: The number of terminals on a wave port must be eqmodes set for the port. The number of terminals on should be one. Note that if terminals are defined fordefined for all ports in the model.


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t can be located internally ources compute S-parame-ed and the Y-matrix and Z-

edge of the trace to the gap source). The default

t with the metal. Use lumped ces for strip lines and other

ance must be non-negative.s are defined.

conducting cap required ort-circuiting the source.


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rces

e Portsped Gap Sources

efining Terminal Voltage, pedance, and Calibra-

on Linesrminal Voltage Linespedance Lines

alibration Lineseed for Polarizationpedance Multipliers

siderations Whenfining Portsent Wavege and Current Sourcesnetic Bias

Lumped Gap SourcesLumped gap sources are similar to traditional wave ports, buand have a complex user-defined impedance. Lumped gap sters directly at the port. The S-parameters can be renormalizmatrix can be computed.

A lumped gap source can be defined as a rectangle from theground (a lumped gap source) or as a traditional port (a waveboundary is perfect H on all edges that do not come in contacgap sources for microstrip structures and use wave gap sourwaveguide structures.

For lumped gap sources, the following restrictions apply:

• The complex impedance must be non-zero and the resist• Only one port mode is allowed, or one terminal if terminal• An impedance line and a calibration line must be defined.

Note: When a gap source is used as an internal port, the for a traditional port must be removed to prevent sh


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p source.

ource type.nu.not use an embedded

ap source:he Resistance field.e in the Reactance field.

. When you select one, a

e. Multiplier field.

he boundaries list. If termi-ge line for each single termi-

r a lumped gap source on the lumped gap f a wave impedance; it is the modal voltage V and on. (The magnitude of e, you would get an iden- impedance for a lumped the same complex

the magnitude of the for a passive device.


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rceste Portsped Gap Sources

efining Terminal Volt-ge, Impedance, and Cal-

bration Lineserminal Voltage Lines

pedance Linesalibration Lineseed for Polarizationpedance Multipliers

siderations Whenfining Portsdent Waveage and Current Sourcesnetic Bias

In general, use the following procedure to define a lumped ga

> To create a lumped gap source:1. For the selected surface or 2D object, select Port as the s2. Select Lumped Gap Source from the Type pull-down me3. Enter a name for the port or accept the default name. Do

blank in the port name.4. Do the following to define the complex impedance of the g

a. Enter the resistance or real part of the impedance in tb. Enter the reactance or imaginary part of the impedanc

5. To set an impedance or calibration line on the port mode:a. Select the port mode from the Modes list. b. Select Use Impedance Line or Use Calibration Line

Y under Imped or Calib appears in the Modes list.c. Define the location of the impedance or calibration lin

6. Enter the impedance multiplier for the model in the Imped7. Choose Assign.

The port is assigned to the selected surface and appears in tnals are defined, you will also need to define a terminal voltanal.

Note: The user-defined complex impedance Zs defined foserves as the reference impedance of the S-matrix source. The impedance Zs has the characteristics oused to determine the strength of a source, such asmodal current I, through complex power normalizatithe complex power is normalized to 1.) In either castical S-matrix by solving a problem using a complexgap source or renormalizing an existing solution to impedance.

When the reference impedance is a complex value,S-matrix is not always less than or equal to 1, even


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ion Lines

.

and Z fields or select the pt these coordinates for hen you choose Enter,

and Z fields.tart point. When you point to the end point. . If necessary, choose currently entered in the

the start point above. vector coordinates in the specifies the direction r values for the x, y, and

reflect the length of the inate fields with nonzero ary, choose Reset Start

peration.

the view window. An arrow ltage, I for impedance, or C in which the line points,

he start point and end point.

oint. Thus, if your start 0,0) as the vector coordi-per left corner) would be


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rces

e Portsped Gap Sources

efining Terminal Volt-ge, Impedance, and alibration Linesrminal Voltage Linespedance Lines


siderations Whenfining Portsent Wavege and Current Sourcesnetic Bias

Defining Terminal Voltage, Impedance, and Calibrat> To define a terminal voltage, impedance, or calibration line:

1. Choose Set from the Edit Line menu for the selected line2. Define the line in one of the following two ways:

• Specify its endpoints:a. Enter the coordinates for the start point in the X, Y,

new point using the mouse. Choose Enter to accethe start point or Cancel to cancel the operation. Wfields for entering a vector appear below the X, Y,

b. Specify the end point in the same manner as the sspecify the end point, a line is drawn from the startThis allows you to view the line before accepting itReset Start to set the start point to the coordinatesX, Y, and Z fields.

• Specify a point and a vector:a. Specify the point in the same manner you specify b. Specify the vector using the mouse or entering the

X, Y, and Z fields under Enter vector. The vector from the point you specified earlier. When you entez coordinates, the Vector length field changes to vector (and the line). You may change all the coordvalues by specifying a new vector length. If necessto reset the start point.

3. Choose Enter to accept the line or Cancel to cancel the o

Terminal voltage, impedance, and calibration lines appear in indicates the direction of the line and a letter (T for terminal vofor calibration) specifies the line type. To reverse the directionchoose Edit Line/Swap Points to swap the coordinates for tThe line’s direction will be reversed.

Note: Vector coordinates are entered relative to the start ppoint has coordinates of (0,10,0) and you enter (0,2nates, the absolute coordinates (displayed in the up(0,30,0).


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oints, choose Edit Line/it Line/Copy Impedance (if

ndaries. In general, draw a nductor to each port-plane a single line segment. In terminal voltage line through t draw more than one termi-ort-plane conductor, nor

ect conductor.

nated with “+” and “-” sym- is established by an arrow base of the arrow is synony-


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efining Terminal Volt-ge, Impedance, and alibration Lines

erminal Voltage Linespedance Lines



To copy a previously defined impedance or calibration line’s pCopy Calibration (if you’ve defined an impedance line) or Edyou’ve defined a calibration line).

Terminal Voltage LinesTerminal voltage lines are used to define voltages on port bousingle terminal voltage line from the reference or “ground” coconductor. Each terminal voltage line is currently restricted tocertain geometries, this restriction may force you to draw the a second conductor. This is permissible; however, you cannonal voltage line connecting a given reference conductor and pdraw a terminal voltage line with its entire length along a perf

In circuit analysis, the polarity reference for a voltage is desigbols. The voltage polarity reference on a terminal voltage linewhere the head of the arrow is synonymous with “+” and the mous with “-”.


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zed S-matrices that have is often desirable to com-uch as 50 ohms.

odal S-matrix, the system ort. There are several ways v and Zvi methods —

nce calculation using power e computed over the area of ause V is computed by inte-

the solution to a Zpv or Zvi ce line.

s expected to be at a maxi-e center of the microstrip, rectangular waveguide,

eparate set of impedance s from mode to mode.


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pedance LinesComputing Character-istic Impedance

Defining the Imped-ance Line

Impedance Lines and Modes



Impedance LinesThe S-matrices initially calculated by the system are generalibeen normalized to the impedances of each port. However, itpute S-matrices that are normalized to specific impedances s

To convert a generalized modal S-matrix to a renormalized mfirst needs to compute the characteristic impedance at each pto compute characteristic impedance. Two methods — the Zprequire an impedance line.

Computing Characteristic ImpedanceAnsoft HFSS will always calculate Zpi impedance, the impedaand current, which are well-defined for a port because they arthe port. Zpv and Zvi are not calculated by default. This is becgrating along a user-defined impedance line. To renormalize characteristic impedance, you must have defined an impedan

Defining the Impedance LineIn general, select two points at which the voltage differential imum. For example, on a microstrip port, place one point in thand the other directly underneath it on the ground plane. In aplace the two points in the center of the long sides.

Impedance Lines and ModesIf you are analyzing more than one mode at a port, define a slines for each mode. The orientation of the electric field differ


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ort, the direction of the field st two directions. In the fig-he left or to the right. Either . To specify a direction, you y defining a calibration line.

e in terms of a physical con- the waveguide carrying the expected. But if the “up” ide, the incoming signal will ble to define which way is meters can be shifted from

ative to other ports having boratory measurements (in nnecting two ports

excitation signal and a ports-only solution is


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Calibration LinesWhen Ansoft HFSS computes the excitation field pattern at a pat ωt=0 is arbitrary: The field can always point in one of at leaure shown below, the mode 1 field at ωt=0 can either point to tdirection is correct — unless a preferred direction is specifiedmust calibrate the port relative to some reference orientation b

In the case of rectangular waveguides, visualize the differencnection. If the “up” side of a port is aligned with the “up” side ofexcitation signal, the signal at the port is in phase with what isside of the port is connected to the “down” side of the wavegube out of phase with the expected signal. Likewise, it is desira“up” at all ports on a structure; otherwise, the resulting S-parathe expected orientation.

Calibrate a port to define a preferred direction at each port relidentical or similar cross-sections. In this way, the results of lawhich the setup is calibrated by removing the structure and cotogether) can be duplicated.

Note: Because calibration lines determine the phase of thetraveling wave, they are ignored by the system whenrequested.


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only is the “positive” and eld is aligned is also arbi-

f the dominant mode can be no preferred direction.

f you select Polarize E

ction of the E-field at ωt=0 referred direction, define a alibration line must lie in the

guidelines. Otherwise,

veguides. a single conductor

mmetry boundary. symmetry boundary


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Need for PolarizationIn some cases, such as when a port is square or circular, not“negative” direction in question — the line with which the E-fitrary.

For example, in the case of a square waveguide, the E-field oaligned with either the horizontal or vertical direction. There isHowever, the system aligns the field with the calibration line iField.

Circular waveguides also require a polarized E-field. The direcan point in any direction. To align the simulated field with a pcalibration line and select Polarize E Field. In this case, the cmiddle of the port — that is, in the symmetry plane.

Warning: When polarizing the E-fields, observe the following the results may not be as expected.• Polarize the E-field only on square or circular wa• Make sure the port on the waveguide only feeds

(the waveguide wall). • Do not polarize the E-fields if you are using a sy

The polarization is automatically enforced by thecondition.


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nces will not be for the full

multiplier:

Such models have one-half f the full structure, resulting ure..5. Such models have the

l structure, resulting in

t E boundaries, adjust pedance multiplier for a ce you would be multiplying


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Impedance MultipliersIf you have defined a symmetry plane, the computed impedastructure.

Generally, use one of the following values for the impedance

• If the structure has a perfect E plane of symmetry, use 2. of the voltage differential and one-half of the power flow oin impedances that are one-half of those for the full struct

• If the structure has a perfect H plane of symmetry, enter 0same voltage differential but half the power flow of the fulimpedances that are twice those for the full structure.

• If the structure has a combination of perfect H and perfecaccordingly. For example, you do not have to enter an imstructure with both a perfect E and perfect H boundary sinby 2 and 0.5.


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orts.

as the background or e ports.

a port unless one of the .t unless one of the objects is

sed to perfect conductors.

ed. For example, if a geo-d, that curved surface can-

rts, do not arrange the port on a ferrite material, sepa-to the relative permittivity of

the following error message

ial materialname on


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rceste Portsped Gap Sourcessiderations When fining Portsort Locationsorts are Planarerrite Materials and orts

nisotropic Materials and ortsultiple Modesorts on Microstripsength of Uniform Cross-ection

dent Waveage and Current Sourcesnetic Bias

Considerations When Defining PortsThis section highlights things to keep in mind when defining p

Port LocationsOnly surfaces that are exposed to non-existent objects (suchobjects defined as perfect conductors) can be defined as wav

• Do not define a surface that cuts through an object to be objects is assigned the material characteristics of a metal

• Do not define the interface of two internal objects as a porassigned the material characteristics of a metal.

• Surfaces defined as lumped gap sources cannot be expo

Ports are PlanarA port must lie in a single plane. Ports that bend are not allowmetric model has a curved surface exposed to the backgrounnot be defined as a port.

Ferrite Materials and PortsWhen designing a problem containing ferrite materials and poso that it touches the ferrite material. If you must place a portrate the two with a dielectric with a relative permittivity equal the ferrite.

If your problem contains a port that touches a ferrite material,appears:

Can not solve portname with ferrite materthe port.


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that

ary condition (finite ort. Although a radiation se because it is generally

a radiation boundary can be R_ABC_ON_PORT is set.rmal to the port.

ll propagating modes in the ropagating modes may be model so that such modes

f Uniform Cross-Section, re information.

S-parameters. For example, ructure, the final result is a

nuation constant, α, that determine which modes ultiple modes and gener- solution). Then, inspect ciated with each mode.


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rceste Portsped Gap Sourcessiderations When Defin- Portsort Locationsorts are Planarerrite Materials and Portsnisotropic Materials nd Portsultiple Modesorts on Microstripsength of Uniform Cross-ection


Anisotropic Materials and PortsAn anisotropic material can be in contact with a port provided

• there is no loss on the port, i.e., a lossy material or boundconductivity or impedance) cannot be in contact with the pboundary is lossy, it can be in contact with a port in this canot modeled as lossy where it touches the port. Note that modeled as lossy if the environment variable ZERO_ORDE

• one principal axis of the anisotropic material is aligned noMultiple Modes

The number of modes should be set high enough to include aport cross-section over the frequency range of interest. Non-pexcluded only if the port plane is far enough away from the 3Dhave negligible effects. See the proceeding section, Length oand the Technical Notes section on mode propagation for mo

Each additional mode at a port results in an additional set of if you are analyzing two modes at each port in a three-port st6x6 S-matrix.

Note: Non-propagating modes are those that have an atteis greater than their phase constant, β. One way to need to be modeled is to set up the problem with mate a solution with no adaptive passes (a ports-onlythe complex propagation constant, , assoγ α jβ+=


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rostrips, define the ports to ip. Ansoft HFSS then wn the microstrip inside a

en defined as ports. Each icrostrip to the conductive

2


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rces

e Portsped Gap Sourcessiderations When Defin- Portsort Locationsorts are Planarerrite Materials and Portsnisotropic Materials and ortsultiple Modesorts on Microstripsngth of Uniform Cross-ectionent Wavege and Current Sourcesnetic Bias

Ports on MicrostripsWhen assigning ports to geometric models that represent micinclude the dielectric below the strip and the air above the strassumes that the port is being excited by a wave traveling dopackage with conductive walls.

In the following figure, the shaded faces in the model have beport’s cross-section extends through the air surrounding the mshield surrounding the entire problem.

Port 1

Port


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at each port. For example, ause it does not contain a on the right includes a rectly.

h to allow non-propagating ort will prevent the simu-

one-eighth of the dominant because it is an evanescent ger than one-eighth of a igher order mode in the sim-

des to die out because the bination of the modes you igher order modes to be n near the discontinuity is a e length of uniform cross-ected waves to die out, then e dominant mode, resulting

rt for reflected modes to ot be what you expected —

suming that the wave d length of the uniform ttenuation constant, α.

n


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rces

e Portsped Gap Sourcessiderations When Defin- Portsort Locationsorts are Planarerrite Materials and Portsnisotropic Materials and ortsultiple Modesorts on Microstripsength of Uniform ross-Sectionent Wavege and Current Sourcesnetic Bias

Length of Uniform Cross-SectionThe geometry must include a length of uniform cross-sectionthe waveguide on the left below is not modeled correctly beclength of uniform cross-section at either port. The waveguidelength of uniform cross-section at each port; it is modeled cor

The length of the uniform cross-section should be long enougmodes to die out. Otherwise, the boundary conditions at the plated solution from matching the actual solution.

For example, if a non-propagating mode takes approximatelymode’s wavelength to die out — either because of losses or mode — then you should make the uniform cross-section lonwavelength. Otherwise, you must include the effects of that hulation.

You must make the port long enough for non-propagating mosystem forces the field pattern at each port to be a linear comrequest. For example, if discontinuities in a structure cause hreflected back toward a port face, then the actual field solutiolinear combination of all relevant modes. If the port length, thsection leading to the port face, is not long enough for the reflthe energy in those modes will affect the apparent energy in thin erroneous results. In cases where port lengths are too shodecay, a field solution involving only the dominant mode will n

Note: Reflected waves attenuate as a function of , aspropagates in the z direction. Therefore, the requirecross-section depends on the value of the mode’s a

No cross-sectionat ports

Uniform cross-sectioat ports

e αz–


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most dominant mode.

ne direction and is uniform n. The angle at which the idence. The equation that

tion vector k and the E-field tes. If you are specifying the e may be defined. If you are incident waves present.

he plane wave magnitude is .

rce type.eld polarization vectors:

ystem. X, Y, and Z fields

the X, Y, and Z fields. o define a plane wave s the coordinates for k.

5 k r⋅ ωt+( )cos


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rceste Portsped Gap Sourcessiderations When Defin- Portsort Locationsorts are Planarerrite Materials and Portsnisotropic Materials and ortsultiple Modesorts on Microstripsength of Uniform ross-Section


that is, it will not be for a structure being excited with only the

Incident WaveAn incident wave (plane wave) is a wave that propagates in oin those directions perpendicular to its direction of propagatioincident wave impacts the device is known as the angle of incthe solver uses to calculate the incident wave is

where

• Einc is the incident wave.• E0 is the E-field polarization vector.• is the free space wave number. It is equal to .• is the propagation vector. It is a unit vector.• r is the position vector and is equal to .

When defining the incident wave, you may enter the propagapolarization vector E0 in either cartesian or spherical coordinaincident wave in cartesian coordinates, only one incident wavusing spherical coordinates, you must specify the number of

Plane-wave sources are specified in a peak sense. That is, if t5 V/m, then the plane wave incident field magnitude is

> To set up an incident wave:1. For the selected surface, select Incident wave as the sou2. Do one of the following to define the propagation and E-fi

• To define the vectors using Cartesian coordinates:a. Select Cartesian (the default) as your coordinate s

appear for the k and E0 vectors.b. Enter the x-, y-, and z-components for k vector in

The k vector must be a unit vector. For example, ttravelling in the positive z direction, enter (0,0,1) a

Einc E0ejk0– k r⋅( )=

k0 ω µ0ε0k

xx yy zz+ +

E t( ) =


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Z fields. The magnitude

i, Theta, and Eo vector

ints. Because θ is swept t each grid point an in. The number of y multiplying the number

Theta fields.ting the vectors.

ist.

e propagation vector k are entered in spherical ogonal.

.

. Keep in mind that the number of increments. For 0° into 10° increments, nts. Each point is equidis-t being the Start point and ch point selected in the φ the range of θ points. of φ.


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c. Enter the coordinates for E0 vector in the X, Y, andof the E0 vector cannot be zero.

• To define the vectors using Spherical coordinates:a. Select Spherical as the coordinate system. The Ph

fields appear. b. Under Phi, enter the following:

c. Under Theta, enter values for Start, Stop, and Pothrough each φ point, a spherical grid is created. Aincident wave is present traveling towards the origincident waves and grid points can be calculated bof φ points by the θ points.

d. Enter the φ and θ components of E0 in the Phi and3. Choose Refresh Arrow(s) to redraw the arrows represen4. Choose Assign.

The incident wave is defined and appears in the boundaries l

Note: When entering k and E0 in cartesian coordinates, thmust be orthogonal to E0. However, when k and E0coordinates they are automatically specified as orth

Start The point where the rotation of φ beginsStop The point where the rotation of φ ends.Points The number of points on the sweep of φ

number of points is not the same as the example, to divide a sweep from 0° to 18you would enter 19 points for 18 incremetant from the next point with the first pointhe last point being the Stop point. At eadirection, the system will sweep throughUse the View button to view the values


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fine the electric and mag-otential or current flow on e. That is, if a voltage gap

ce behaves as v(t) = 5cosωt.

ltage and direction of the E-d structure is very small be assumed across the ctric field across the gap on

gnitude and direction of the when the feed structure is t on the surface is assumed

onstruct a problem with-an generate a field solu-ommands dealing with or replaced with new


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rces

e Portsped Gap Sourcessiderations Whenfining Portsent Wave

age and Current urcesltage Drop

urrentreating a Voltage or Cur-ent Sourcenetic Bias

Voltage and Current SourcesVoltage and current sources (or gap sources) allow you to denetic field strength on a boundary by specifying the electric pthat surface. Circuit gap sources are specified in a peak senssource magnitude is 5 volts, then the time domain circuit sourThis is also true for a current gap source.

Voltage DropThe voltage source boundary condition lets you specify the vofield on a surface. This type of boundary is used when the feecompared to the wavelength and a constant electric field mayfeed points. In this case, Ansoft HFSS assigns a constant elewhich you specified the voltage.

CurrentThe current source boundary condition lets you define the macurrent flow through a surface. This type of boundary is usedvery small compared to the wavelength and the electric currento be constant across the feed points.

Note: Because voltage and current sources allow you to cout ports (and thereby without S-parameters), you ction without calculating S-parameters. As a result, cports and S-parameters will be removed, disabled, commands.


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as the source type. Value field.efine the vector in one of

and Z fields or select the pt these coordinates for hen you choose Enter,

and Z fields.tart point. When you point to the end point. it. If necessary, choose currently entered in the

on:the start point above. g the vector coordinates ector specifies the you enter values for the hanges to reflect the all the coordinate fields gth. If necessary,

vector. When you have the direction and a letter

urface and appears in

tor, remember that the us, if your start point has vector coordinates, the

ould be (0,30,0).


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rces

e Portsped Gap Sourcessiderations Whenfining Portsent Wave

age and Current urcesoltage Dropurrentreating a Voltage or urrent Sourcenetic Bias

Creating a Voltage or Current Source> To set up a voltage or current source:

1. For the selected surface, select Voltage drop or Current2. Enter the value of the source — in volts or amps — in the3. Choose Set Vector to select the direction of the source. D

the following two ways:• To define the vector by specifying its end points:

a. Enter the coordinates for the start point in the X, Y,new point using the mouse. Choose Enter to accethe start point or Cancel to cancel the operation. Wfields for entering a vector appear below the X, Y,

b. Specify the end point in the same manner as the sspecify the end point, a line is drawn from the startThis allows you to view the vector before acceptingReset Start to set the start point to the coordinatesX, Y, and Z fields.

• To define the vector by specifying a point and a directia. Specify the point in the same manner you specify b. Specify the direction using the mouse or by enterin

in the X, Y, and Z fields under Enter vector. The vdirection from the point you specified earlier. Whenx-, y-, and z-coordinates, the Vector length field clength of the vector (and the line). You may changewith nonzero values by specifying a new vector lenchoose Reset Start to reset the start point.

4. Choose Enter to accept the vector or Cancel to cancel thefinished, a line appears on the model. An arrow indicates (v or i) indicates the type of source.

5. Choose Assign. The source is assigned to the selected s

Note: When you enter coordinate values under Enter vecvector coordinates are relative to the start point. Thcoordinates of (0,10,0) and you enter (0,20,0) as theabsolute coordinates (displayed in the upper left) w


the boundaries list.

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net internal field that biases rrite producing a nonzero be uniform, the tensor coor-obal coordinate system. coordinate system rotations stem is calculated on a tet-by the field directions calcu-

n the positive z direction of ystem is assumed to be is the same as the model’s

bility tensor must be rotated ate system. This is accom-

ce type.

ld.o the xyz-coordinate

ordinate system is obtained

the X Angle field)

ees (from the Y Angle

from the Z Angle field)


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rces

e Portsped Gap Sourcessiderations Whenfining Portsent Wavege and Current Sourcesnetic BiasniformInternal Bias

on-Uniform

Magnetic BiasWhen you create a ferrite material, you must also define the the ferrite. The bias field aligns the magnetic dipoles in the femagnetic moment. When the applied bias field is assumed todinate system is user specified through a rotation from the glWhen the applied bias field is non-uniform, the user-specifiedare not allowed. The permeability tensor’s local coordinate syrahedron by tetrahedron basis, with the direction determined lated in the static solution.

UniformThe applied DC bias that causes ferrite saturation is always ithe tensor coordinate system. Initially the tensor coordinate saligned with the fixed coordinate system — the tensor’s z-axisz-axis. To model other directions of applied bias, the permeaso that its z-axis lies in another direction on the fixed coordinplished by specifying the rotation angles about the axes.

> To specify a uniform applied bias field:1. For the selected object, select Magnetic bias as the sour2. Select Uniform as the applied bias field type.3. Enter the internal bias of the ferrite in the Internal Bias fie4. Enter the rotation of the permeability tensor with respect t

system in the X, Y, and Z fields.5. Choose Assign.

The angles should be defined in such a way that the tensor coin the following manner:

1. Rotating the tensor coordinate system by α degrees (fromaround the fixed x-axis.

2. Rotating the resulting tensor coordinate system by β degrfield) around the new y-axis.

3. Rotating the new tensor coordinate system by γ degrees (around the new z-axis.


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panel, the permeability ten-l, the tensor is rotated β the tensor is rotated γ or has the coordinate sys-

ould rotate the tensor coordi-d coordinate system. To do n, and 0 for the Z Rotation.

the applied bias field. The cing a nonzero magnetic he demagnetization field h can be much smaller than e ferrite after accounting for to be uniform in magnitude but are amperes/meters in

s field, the non-uniform mag-rrite’s permeability tensor is tic field causes the tensor to n field components perpen- achieve in practice. Even if e material will have non-uni-

y’

x’

x’’

γ

y’’

z’’


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e Portsped Gap Sourcessiderations Whenfining Portsent Wavege and Current Sourcesnetic BiasniformInternal Bias

on-Uniform

This concept is illustrated in the following graphic. In the first sor is rotated α degrees about the x-axis. In the second panedegrees about the y'-axis (the new y-axis). In the third panel,degrees about the z''-axis (the new z-axis). The resulting tenstem (x''y''z'') relative to the fixed coordinate system.

As an example, to model the DC bias in the x direction you wnate system such that its z-axis lay along the x-axis of the fixethis you would enter 0 for the X Rotation, 90 for the Y Rotatio

Internal BiasThis is the DC magnetic field within the ferrite that results fromapplied field aligns the magnetic dipoles in the material produmoment — commonly known as the demagnetization field. Topposes the applied bias and results in an internal field, whicthe applied field. The internal bias field is the net field within ththe demagnetization field. The internal bias field is assumed and direction. The units of magnetic bias field are selectable,the MKS system.

Non-UniformTo accurately model a ferrite in an applied static magnetic bianetic bias fields must also be calculated. In Ansoft HFSS, a fea direct result of an applied static magnetic bias field. The staassume an hermitian form, with cross coupling terms betweedicular to the bias. However, a uniform bias field is difficult tothe bias field is nearly uniform, a non-ellipsoidal shaped ferrit

z

y

y’

α

z’

x y’

x

z’

z’’

β

x’1. 2. 3.


form demagnetization with resulting non-uniform fields in the ferrite.

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rate a solution for non-uni-y be imported into Ansoft

ce type.

in the Magnetostatic nsion.

elds within ferrites:for the Maxwell 3D Field

.he Ansoft HFSS model only need to import the

imulator model.n parameters for the ion.the Ansoft HFSS project. uses the Maxwell 3D c project name field as tion.

purchased the Maxwell imulator documentation tatic fields.

imports the solution infor-is. The position of every lution will not be accu-

rtual objects, but do not


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rceste Portsped Gap Sourcessiderations Whenfining Portsdent Waveage and Current Sourcesnetic Biasniformon-Uniform

Use the magnetostatic solver provided in Maxwell 3D to geneform magnetostatic fields. Once a solution is generated it maHFSS.

> To specify a non-uniform applied bias field:1. For the selected object, select Magnetic bias as the sour2. Select Non-uniform as the applied bias field type.3. Enter the name of the Maxwell 3D Field Simulator project

project name field. You do not need to enter the .pjt exte4. Choose Assign.

> To generate a solution for non-uniform static magnetic bias fi1. Start the Maxwell Control Panel and create a new project

Simulator with the Projects command. 2. Create and open a new Ansoft HFSS project.3. Draw and save the geometry for the Ansoft HFSS problem4. Open the Maxwell 3D Field Simulator project and import t

— the .sld file in the Ansoft HFSS project’s directory. Youobjects that correspond to the magnetic materials.

5. Add any magnetic bias circuitry to the Maxwell 3D Field S6. Set up the materials, boundary conditions, and the solutio

Maxwell 3D Field Simulator problem and generate a solut7. Exit the Maxwell 3D Field Simulator project and return to 8. Set up and solve the Ansoft HFSS problem. Ansoft HFSS

Field Simulator project you specified in the Magnetostatithe source of the non-uniform magnetostatic field informa

Note: To specify the non-uniform bias field you must have3D Field Simulator. Refer to the Maxwell 3D Field Sfor instructions on solving for non-uniform magnetos

Warning: You must import the geometry. When Ansoft HFSS mation it does so on a tetrahedra by tetrahedra basobject must correspond exactly; if it does not, the sorate. You may delete unnecessary objects or add vichange the position of any existing objects.


topics: ansoft hfss — 3d boundary manager...

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