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• Compute the radiated fields in the near-field and far-field • Display the calculated data for the near field and far field.• Save the radiated fields. • Load previously calculated radiated fields.• Clear the computed radiated field solutions.

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near-field or far-field region. near field and far field.

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Compute Computes the radiated fields in theDisplay Data Displays the calculated data for theSave Fields Saves the computed fields.Load Fields Loads previously saved computed fClear Deletes the solution computed for t

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r the radiation surface are e. This space is typically egion. The near-field region d E(x,y,z) external to the

(1)

tial to the surface.l to the surface.l to the surface.

points on the surface.

nction can be approximated

normal∇ G⟩ ) sd

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Radiated FieldsWhen calculating radiation fields, the values of the fields oveused to compute the fields in the space surrounding the devicsplit into two regions — the near-field region and the far-field ris the region closest to the source. In general, the electric fielregion bounded by a closed surface may be written as

where

• s represents the radiation surfaces.• j is the imaginary unit, .• ω is the angular frequency, 2πf.• µ0 is the relative permeability of the free space.• Htan is the component of the magnetic field that is tangen• Enormal is the component of the electric field that is norma• Etan is the component of the electric field that is tangentia• G is the free space Green’s function, given by

where • k0 is the free space wave number, .• r and represent, respectively, field points and source

In the far field where r>>r' (and usually r>>λ0), the Green’s fuas

E x y z, ,( ) jωµ0Htan⟨ ⟩G Etan ∇ G×⟨ ⟩ E⟨+ +(s∫=

1–

G ejk0 r r'––

r r'–-----------------------------=

ω µ0ε0r'

G ejk0r–

ejk0 r̂ r'⋅

r--------------------------------------≈ .

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elds that result have an r

h is a key feature of far

FSS uses the general ecify the radial coordinate r. s from the radiating struc-

usly discussed far-field points in the far-field region.

calculate the fields in a hich the fields are calcu-

ution region, then the ttered fields depending the radius is outside the e scattered fields.

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When this form of G is used in the far-field calculations, the fidependence in the form of

This r dependence is characteristic of a spherical wave, whicfields.

When you choose Radiation/Compute/Near Field, Ansoft Hexpressions given in (eq. 1). For this command, you must spBecause it can be used to compute fields at an arbitrary radiuture, this command can be useful in EMC applications.

When you choose Radiation/Compute/Far Field, the previoapproximations are used, and the result is valid only for field

Note: If you are using Radiation/Compute/Near Field to problem containing an incident wave, the radius at wlated is very important. If the radius is within the solfields calculated are either the total fields or the scaupon which is selected using Data/Edit Sources. Ifsolution region, then the fields calculated are only th

e jkr–

r---------- .

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ated fields in the far-field or

dow appears:

n a spherical grid, this is , refer to Plotting

region.ld region.

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1. Choose Radiation/Compute/Far Field. The following win

2. Leave Sphere selected. Since far fields are only plotted othe only option available. For a more detailed explanationSpherical Cross-Sections.

Far Field Computes the radiated fields in the far-fieldNear Field Computes the radiated fields in the near-fie

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ed. For each phi point

ndary specified in the 3D lds, select Custom

ist window appears, etry/Create/Faces List

d fields.to cancel the operation.otations for the specified

ears. For information on

nter a value in degrees. than one.er a value in degrees. The lue and less than 360.r example, to divide a ou would enter 18 steps.

s the sweep to consist of

Enter a value in degrees.

nter a value in degrees. rt value and less than 90.For example, to divide a you would enter 12 steps. s the sweep to consist of

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3. Specify the following for Phi from x-axis:

4. Specify the following for Theta from z-axis:

5. Choose View Points to view the points which will be plottthere are corresponding theta points.

6. If you wish to select a surface other than the radiation bouBoundary Manager over which to integrate the radiated fieSurface and do the following:a. Choose Set to select the surface. The Select Faces L

containing a list of the surfaces created with the Geomcommand.

b. Select the faces list over which to compute the radiatec. Choose OK to accept the selected surface or Cancel

7. Choose OK to compute the field at each of the specified rnumber of points or Cancel to cancel the computation.

After the far field is computed, the Plot Far Field window appplotting the far field, see Plot/Far Field.

start The point where the rotation of phi begins. EThe start value must be equal to or greater

stop The point where the rotation of phi ends. Entstop value must be greater than the start va

steps The number of steps on the sweep of phi. Fosweep from 0° to 180° into 10° increments, yEntering zero for the number of steps causeone point, the start value.

start The point where the rotation of theta begins.The start value must be greater than -90.

stop The point where the rotation of theta ends. EThe stop value must be greater than the sta

steps The number of steps on the sweep of theta. sweep from -60° to 60° into 10° increments, Entering zero for the number of steps causeone point, the start value.

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ear Field window

ld region, you may elect Select how you wish to r the appropriate

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1. Choose Radiation/Compute/Near Field. The Compute Nappears.

2. When you are computing the radiated fields in the near-fieto compute them over a spherical surface or along a line. compute the near field from one of the following and enteinformation:

SphereLine Segments

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ce. For a more detailed Cross-sections.

ed. For each phi point

ndary specified in the 3D lds, select Custom

ist window appears y/Create/Faces List.d fields.

nter a value in degrees. than one.er a value in degrees. The lue and less than 360.r example, to divide a ou would enter 18 steps.

s the sweep to consist of

Enter a value in degrees.

nter a value in degrees. rt value and less than 90.For example, to divide a you would enter 12 steps. s the sweep to consist of

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SphereSelect Sphere to compute the near field on a spherical surfaexplanation on spherical surfaces, refer to Plotting Spherical

> To compute the near field over a sphere:1. Specify the following for Phi from x-axis:

2. Specify the following for Theta from z-axis:

3. Enter the radius (in meters) at which to compute the radiafrom origin field.

4. Choose View Points to view the points which will be plottthere are corresponding theta points.

5. If you wish to select a surface other than the radiation bouBoundary Manager over which to integrate the radiated fieSurface and do the following:a. Choose Set to select the surface. The Select Faces L

containing a list of the surfaces created with Geometrb. Select the faces list over which to compute the radiate

start The point where the rotation of phi begins. EThe start value must be equal to or greater

stop The point where the rotation of phi ends. Entstop value must be greater than the start va

steps The number of steps on the sweep of phi. Fosweep from 0° to 180° into 10° increments, yEntering zero for the number of steps causeone point, the start value.

start The point where the rotation of theta begins.The start value must be greater than -90.

stop The point where the rotation of theta ends. EThe stop value must be greater than the sta

steps The number of steps on the sweep of theta. sweep from -60° to 60° into 10° increments, Entering zero for the number of steps causeone point, the start value.

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to cancel the operation.otations for the specified

appears.

ong from the Line /Create/Line appear in

ndary specified in the 3D lds, select Custom

ist window appears y/Create/Faces List.d fields.to cancel the operation.ified number of points or

appears.

n you first create the line

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c. Choose OK to accept the selected surface or Cancel 6. Choose OK to compute the field at each of the specified r

number of points or Cancel to cancel the computation.

After the near field is computed, the Plot Near Field window

Line SegmentsSelect Line to compute the near field along a line segment.

> To compute the near field along a line:1. Select the line segments to compute the radiated fields al

segment list. Only line segments created with Geometrythe list. You may select multiple line segments.

2. If you wish to select a surface other than the radiation bouBoundary Manager over which to integrate the radiated fieSurface and do the following:a. Choose Set to select the surface. The Select Faces L

containing a list of the surfaces created with Geometrb. Select the faces list over which to integrate the radiatec. Choose OK to accept the selected surface or Cancel

3. Choose OK to compute the field along the line for the specCancel to cancel the computation.

After the near field is computed, the Plot Near Field window

Note: The number of points along the line is specified whesegment with Geometry/Create/Line.

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fields in the far-field region. fields in the near-field

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Radiation/Display DataUse the Radiation/Display Data commands to view the comfields in the far-field or near-field region.

Far Field Displays the computed data for the radiatedNear Field Displays the computed data for the radiated

region.

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uted data for the far fields.

ilar to the following

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iation Menuiation Commandsiated Fieldsiation/Computeiation/Display Dataadiation/Display Data/ar FieldMaximum Field DataAntenna ParametersExporting the Far Field Values

> To view the maximum field data:1. Choose Radiation/Display Data/Far Field. A window sim

appears:

2. Choose Export to export the field data to a file.3. Choose OK.

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ld, and the coordinates — r (R,Phi,Theta). The values

component, which is equal

component, which is equal

Vmain, for an x-polarized oss polarization. This is

Vmain, for a y-polarized oss polarization. This is

distance r is factored out Field Data values are

.

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iation Menuiation Commandsiated Fieldsiation/Computeiation/Display Dataadiation/Display Data/ar FieldMaximum Field DataAntenna ParametersExporting the Far Field Values

Maximum Field DataThe value of the maximum rE-field data is listed under rE Fieradius, phi, and theta — of the maximum value are listed undeare given in volts.

The following parameters are listed:Total The maximum of the total rE-field.X The maximum rE-field in the x direction.Y The maximum rE-field in the y direction.Z The maximum rE-field in the z direction.Phi The maximum rE-field in the φ direction.Theta The maximum rE-field in the θ direction.LHCP The maximum left-hand circularly polarized

to

RHCP The maximum right-hand circularly polarizedto

Ludwig 3/X dominant

The maximum of the dominant component, aperture using Ludwig’s third definition of crequal to |Eθcosφ - Eφsinφ|.

Ludwig 3/Y dominant

The maximum of the dominant component, aperture using Ludwig’s third definition of crequal to |Eθsinφ + Eφcosφ|.

Note: When calculating the maximum far field values, the of the E-field. Therefore, the units for the Maximumgiven in volts.

12------- Eθ jEφ–( ) .

12------- Eθ jEφ+( )

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e that the Accepted Power our problem. If no port is

na. Directivity is the peak ed by the power radiated tor having total radiated

antenna. This is the total a radiating antenna struc-nd is computed by integrat-

ross all radiation and daries. the antenna. This is the net ng a radiating antenna struc- is computed by integrating oundaries.

na. This is the ratio of the er and is therefore a mea-a.

the radiation from the ted power per solid angle.

ectivity depend on the computation of the radi-l peak intensity of the e parameters will be

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iation Menuiation Commandsiated Fieldsiation/Computeiation/Display Dataadiation/Display Data/ar FieldMaximum Field DataAntenna ParametersExporting the Far Field Values

Antenna ParametersAnsoft HFSS displays the following antenna parameters. Notand Radiation Efficiency require that a port be defined for ypresent, they do not appear.

Beam Area Displays the beam area. The beam integrated radiated power divided bper solid angle.

Directivity Displays the directivity of the antenradiated power per solid angle dividper solid angle of an isotropic radiapower equal to that of the antenna.

Radiated Power Displays the power radiated by the time-averaged power (watts) exitingture through a radiation boundary, aing the complex Poynting vector acperfectly matched layer (PML) boun

Accepted Power Displays the net power accepted bytime-averaged power (watts) enteriture through one or more ports, andthe Poynting vector across all port b

Radiation Efficiency Displays the efficiency of the antenradiated power to the accepted powsure of ohmic loss within the antenn

Max. U (theta, phi) Displays the maximum intensity of antenna. This is the maximum radia

Warning: The computed values of max U, beam area, and diruser-determined set of aspect angles chosen for theated fields. If this set does not encompass the actuaradiated pattern, the displayed results for these threinaccurate.

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ameters to a file. The file h of the antenna

th two rows. The top row w the value. The table

nds on the accuracy of E is possible that the com-ctual radiated power. To

he mesh on the absorb-eters — if ports have

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iation Menuiation Commandsiated Fieldsiation/Computeiation/Display Dataadiation/Display Data/ar FieldMaximum Field DataAntenna ParametersExporting the Far Field Values

Exporting the Far Field Values> To export the maximum field data:

1. Choose Export from the Far Field Parameters window.2. Use the file browser that appears to export the far-field par

contains the maximum field values and positions, and eacparameters. These parameters are arranged in a table wiwill contain the name of the parameter, and the second rocan be read into any spreadsheet program.

3. Choose OK.

Note: The accuracy of the computed radiated power depeand H on the absorbing boundary. In some cases itputed radiated power may deviate slightly from the aincrease the accuracy of the radiated power, seed ting boundary. As a check, you can use the S-parambeen defined — to calculate the radiated power.

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puted data for the near

g window appears:

. The values displayed

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> To view the maximum field data:1. Choose Radiation/Display Data/Near Field. The followin

2. Select the geometry on which you computed the near fieldremain the same; only the units and coordinates change.

3. Choose Export to export the field data to a file.4. Choose OK.

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remain the same regardless coordinates displayed

under E Field, and the coor- listed under (R,Phi,Theta).

nder E Field, and the coordi-r (X,Y,Z). The values are

ters.

component, which is equal

d component, which is equal

Vmain, for an x-polarized oss polarization. This is

Vmain, for a y-polarized oss polarization. This is

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Maximum Field DataThe parameters listed in the Near Field Parameters window of the geometry — Sphere or Line — selected. However, thechange depending on the geometry selected.

On a sphere, the value of the maximum E-field data is listed dinates — radius, phi, and theta — of the maximum value areThe values are given in volts per meter.

Along a line, the value of the maximum E-field data is listed unates — x, y, and z — of the maximum values are listed undegiven in volts per meter, and the coordinates are given in me

The following parameters are listed:Total The maximum of the total E-field.X The maximum E-field in the x direction.Y The maximum E-field in the y direction.Z The maximum E-field in the z direction.Phi The maximum E-field in the φ direction.Theta The maximum E-field in the θ direction.LHCP The maximum left-hand circularly polarized

to .

RHCP The maximum right-hand circularly polarize

to .

Ludwig 3/X dominant

The maximum of the dominant component, aperture using Ludwig’s third definition of crequal to |Eθcosφ - Eφsinφ|.

Ludwig 3/Y dominant

The maximum of the dominant component, aperture using Ludwig’s third definition of crequal to |Eθsinφ + Eφcosφ|.

12------- Eθ jEφ–( )

12------- Eθ jEφ+( )

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.arameters to a file. The

se parameters are name of the parameter,

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Exporting the Near Field Values> To export the maximum field data:

1. Choose Export from the Near Field Parameters window2. Use the file browser that appears to export the near field p

file contains the maximum field values and positions. Thearranged in a table with two rows. The top row contains theand the second row the value. The table can be read intoprogram.

3. Choose OK.

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d fields to a disk file.This file

By default, files with the

.

diated field solution file.

y default, files with the

3D Post Processor.

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> To save the radiated field solution:1. Choose Radiation/Save Fields.2. Use the file browser that appears to save the plot to a file.

.fld file extensions appear in the window.

The data is then saved and can be accessed by Ansoft HFSS

.fld file extensions appear in the window. 3. Choose OK.

Note: Loading a previously saved solution overwrites anycalculated during the current post-processing sessio

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theta, you are specifying the ry value of phi there is a cor-ates a spherical grid. Each s from the center of the

in this direction. The number d theta. The relationship

grees. The start value must

rees. The stop value must

ide a sweep from 0° to 180° for the number of steps

y

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hetaertical Cross-Sectionsorizontal Cross-Sections

Plotting Spherical Cross-SectionsWhen you specify the range and number of steps for phi and directions in which the radiated fields are calculated. For everesponding range of values for theta, and vice versa. This cregrid point indicates a unique direction along a line that extendsphere through the grid point. The radiated field is calculated of grid points is determined by the number of steps for phi anbetween phi and theta is shown below.

PhiEnter the following values under Phi from x-axis:

StartThe point where the rotation of phi begins. Enter a value in debe equal to or greater than one.

StopThe point where the rotation of phi ends. Enter a value in degbe greater than the start value and less than 360.

StepsThe number of steps on the sweep of phi. For example, to divinto 10° increments, you would enter 18 steps. Entering zero

x

zφ is rotated away from the x-axis.θ is rotated away from the z-axis.

φ

θ

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degrees. The start value

grees. The stop value must

divide a sweep from -60° to ero for the number of steps

eds at least two direc-f the number of steps for greater than zero, and d in at least two direc-

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hetaStartStopSteps

ertical Cross-Sectionsorizontal Cross-Sections

causes the sweep to consist of one point, the start value.

ThetaEnter the following values under Theta from z-axis:

StartThe point where the rotation of theta begins. Enter a value inmust be greater than -90.

StopThe point where the rotation of theta ends. Enter a value in debe greater than the start value and less than 90.

StepsThe number of steps on the sweep of theta. For example, to 60° into 10° increments, you would enter 12 steps. Entering zcauses the sweep to consist of one point, the start value.

Note: When the system computes the radiated fields, it netions along which to compute the fields. Therefore, iphi is zero, then number of steps for theta must be vice versa. This ensures that the fields are computetions.

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eping theta through a range ion of the vertical cross-sec-

dow and, if necessary,

y

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Vertical Cross-SectionsA vertical cross-section results from holding phi fixed and sweof values. The figure shown below demonstrates the orientattion when φ is the fixed variable:

> To plot a vertical cross-section:1. Specify the range and number of steps for phi and theta.2. Select phi as the fixed variable from the Plot Options win

select the value of phi from the list of values.

θ values are an infinite radial distance away from the origin for far-field plots.

x

z

φ

θ

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d sweeping phi through a rientation of the sphere on

indow and, if necessary,

y

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Horizontal Cross-SectionsA horizontal cross-section results from holding theta fixed anrange of values. The figure shown below demonstrates the owhich the field is computed when θ is the fixed variable:

> To plot a horizontal cross-section:1. Specify the range and number of points for phi and theta.2. Select theta as the fixed variable from the Plot Options w

select the value of phi from the list of values.

x

z

θ

φ

φ values are an infinite radial distanceaway from the origin for far-field plots.