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Ansoft HFSS — Radiation Menuics:
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Radiation MenuUse the commands on the Radiation menu to:
• 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.
When you choose Radiation from the menu bar, the followin
Radiation CommandsThe commands on the Radiation menu are:
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
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
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
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.
Radiation/Compute/Near Field> To compute the radiated fields in the near-field region:
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:
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.
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.
iation Menuiation Commandsiated Fieldsiation/Computeiation/Display Dataadiation/Display Data/ar FieldMaximum Field DataAntenna ParametersExporting the Far Field Values
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
.
Ansoft HFSS — Radiation Menuics:
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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.
e that the Accepted Power our problem. If no port is
area (steradians) is the total y the peak power radiated
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
Ansoft HFSS — Radiation Menuics:
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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.
nds on the accuracy of E is possible that the com-ctual radiated power. To
he mesh on the absorb-eters — if ports have
Ansoft HFSS — Radiation Menuics:
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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.
iation Menuiation Commandsiated Fieldsiation/Computeiation/Display Dataadiation/Display Data/ar Fieldadiation/Display Data/ear FieldMaximum Field DataExporting the Near Field Values
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
Ansoft HFSS — Radiation Menuics:
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Index
iation Menuiation Commandsiated Fieldsiation/Computeiation/Display Dataadiation/Display Data/Far ieldadiation/Display Data/ear FieldMaximum Field DataExporting the Near Field Values
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|.
iation Menuiation Commandsiated Fieldsiation/Computeiation/Display Dataadiation/Display Data/ar Fieldadiation/Display Data/ear FieldMaximum Field DataExporting the Near Field Values
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.
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.
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.
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.
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.