== Defining Dielectric Objects ==
Of the two simulation engines of EM.Cube's MoM3D Module only the Surface MoM solver can handle dielectric objects as dielectric materials cannot be modeled by wireframe structures. Dielectric objects are created under the '''Dielectric''' node in the '''Physical Structure''' section of the Navigation Tree. They are grouped together by their color and material properties. You can insert different dielectric groups with different colors and different permittivity εe<sub>r</sub> and electric conductivity Ïs. Note that a PEC object is the limiting cases of a lossy dielectric material when Ï â âσ → ∞.
To define a new Dielectric group, follow these steps:
* Right click on the '''Dielectric''' item of the Navigation Tree and select '''Insert New Dielectric...''' from the contextual menu.
* Specify a '''Label''', '''Color''' (and optional Texture) and the electromagnetic properties of the dielectric material to be created: '''Relative Permittivity''' (εe<sub>r</sub>) and '''Electric Conductivity''' (Ïs).
* You may also choose from a list of preloaded material types. Click the button labeled '''Material''' to open EM.Cube's Materials dialog. Select the desired material from the list or type the first letter of a material to find it. For example, typing '''V''' selects '''Vacuum''' in the list. Once you close the dialog by clicking '''OK''', the selected material properties fill the parameter fields automatically.
* Click the '''OK''' button of the dielectric material dialog to accept the changes and close it.
# Verifying the mesh.
The commercial release of EM.CUBE's MoM3D Module provides a Wire MoM solver. In this simulation engine, all the metallic objects are discretized as a wire-frame structure. Wires, line and curves are discretized as polylines made up of small linear cells (segments).Surface and solid objects are discretized as a wire-frame mesh with triangular cells. The MoM3D mesh generator meshes the wires based on a specified mesh sampling rate expressed in cells/?&lambda<sub>0</sub>. Curves are first polygonized and converted into '''Polyline''' Objects, whose edge lengths follow the specified mesh sampling rate. In the case of solid objects, only their surface and faces are discretized using a triangular wireframe mesh, which is regarded as a grid of interconnected wires. Two algorithms are offered for generation of a triangular wireframe mesh. The default algorithm is '''Regular Wireframe'''. This mesh generator creates wireframe elements that have almost equal edge lengths. The other algorithm is '''Structured Wireframe''', which usually creates a very structured wireframe with a large number of aligned wireframe elements.
To view the MoM3D Module's wire-frame mesh, click on the [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/mesh-generation/creating-and-viewing-the-mesh/mesh_tool_tn.png]] button of the '''Compute Toolbar''' or select '''Menu [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Compute [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Discretization [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Shoe Mesh''' or use the keyboard shortcut '''Ctrl+M'''. When the wire-frame mesh is displayed in the Project Workspace, EM.CUBE's mesh view mode is enabled. In this mode, you can perform view operations like rotate view, pan, zoom, etc. However, you cannot select or move or edit objects. While the mesh view is enabled, the '''Show Mesh''' [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/mesh-generation/creating-and-viewing-the-mesh/mesh_tool.png]] button remains depressed. To get back to the Normal View mode, click this button one more time, or deselect '''Menu [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Compute [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Discretization [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Show Mesh''' to remove its check mark or simply click the '''Esc Key''' of the keyboard."Show Mesh" generates a new mesh and displays it if there is none in the memory, or it simply displays an existing mesh in the memory. This is a useful feature because generating a wire-frame mesh may take a long time depending on the complexity and size of objects. If you change the structure or alter the mesh settings, a new mesh is always generated. You can ignore the mesh in the memory and force EM.CUBE to generate a mesh from the ground up by selecting '''Menu [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Compute [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Discretization [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Regenerate Mesh''' or by right clicking on the '''3-D Mesh''' item of the Navigation Tree and selecting '''Regenerate''' from the contextual menu.
== Customizing the Mesh ==
To set the wire-frame mesh properties, click on the [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/mesh-generation/creating-and-viewing-the-mesh/mesh_tool_tn.png]] button of the '''Compute Toolbar''' or select '''Menu [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Compute [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Discretization [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]] Mesh Settings...'''or right click on the '''3-D Mesh''' item in the '''Discretization''' section or the Navigation Tree and select '''Mesh Settings...''' from the contextual menu. The MoM3D Mesh Settings Dialog opens up. You can change the mesh generation algorithm from the drop-down list labeled '''Mesh Type''' and select one of the two options: '''Regular Wireframe''' or '''Structured Wireframe'''. You can also set the '''Mesh Sampling Rate''', whose default value is 20 Cells/ ?λ<sub>0</sub>.By default, surface objects or solids are wire-framed at the mesh cell size. Therefore, each wire segment of the wire-frame mesh contains one cell. Another parameter that can affect the shape of the mesh especially in the case of solid objects is the '''Curvature Angle Tolerance'''. This parameter expressed in degrees determines the apex angle of the triangular cells of the structured mesh. Lower values of the angle tolerance will results in more pointed triangular cells.
[[Image:/files/images/manuals/emagware/emcube/modules/mom3d/mesh-generation/customizing-the-mesh/wire_pic4.png]]
* In the case of a gap on a line object, in the box labeled '''Offset''', enter the distance of the source from the start point of the line. This value by default is initially set to the center of the line object.
* In the case of a gap on a polyline object, first choose the '''Side''' of the polyline where you want to place the source. Then, in the box labeled '''Offset''', enter the distance of the source from the start point of that side. By default, a gap source is placed at the center of the first side of the polyline object. You can also change the offset value using the spin buttons. If you keep pushing the spin buttons, the gap source moves from one side to the next, and its side index and offset value are adjusted automatically.
* In the '''Load Properties''' section, the series and shunt resistance values Rs and Rp are specified in Ohms, the series and shunt inductance values Ls and Lp are specified in nH (nanohenry), and the series and shunt capacitance values Cs and Cp are specified in pF (picofarad). The impedance of the circuit is calculated at the operating frequency of the project. Only the elements that have been checked are taken into account. By default, only the series resistor has a value of 50? Σ and all other circuit elements are initially grayed out.
* If the lumped element is active and contains a gap source, the '''Source Properties''' section of the dialog becomes enabled. Here you can specify the '''Source Amplitude''' in Volts (or in Amperes in the case of PMC traces) and the '''Phase''' in degrees.
* If the workspace contains an array of line or polyline objects, the array object will be listed as an eligible object for gap source placement. A lumped element will be placed on each element of the array. All the lumped elements will have identical direction, offset, resistance, inductance and capacitance values. If you define an active lumped element, you can prescribe certain amplitude and/or phase distribution to the gap sources. The available amplitude distributions include '''Uniform''', '''Binomial''' and '''Chebyshev'''. In the last case, you need to set a value for minimum side lobe level ('''SLL''') in dB. You can also define '''Phase Progression''' in degrees along all three principal axes.
== Defining Ports ==
Ports are used to order and index gap sources for S parameter calculation. They are defined in the '''Observables''' section of the Navigation Tree. Right click on the '''Port Definition''' item of the Navigation Tree and select '''Insert New Port Definition...''' from the contextual menu. The Port Definition Dialog opens up, showing the total number of existing sources in the workspace. By default, as many ports as the total number of sources are created. You can define any number of ports equal to or less than the total number of sources. This includes both gap sources and active lumped elements (which contain gap sources). In the '''Port Association''' section of this dialog, you can go over each one of the sources and associate them with a desired port. Note that you can associate more than one source with same given port. In this case, you will have a coupled port. All the coupled sources are listed as associated with a single port. However, you cannot associate the same source with more than one port. Finally, you can assign '''Port Impedance''' in Ohms. By default, all port impedances are 50?Σ. The table titled '''Port Configuration''' lists all the ports and their associated sources and port impedances.
NOTE: In EM.CUBE you cannot assign ports to an array object, even if it contains sources on its elements. To calculate the S parameters of an antenna array, you have to construct it using individual elements, not as an array object.
* RCPz
The direction of incidence is defined through the ? θ and ? φ angles of the unit propagation vector in the spherical coordinate system. The values of these angles are set in degrees in the boxes labeled '''Theta''' and '''Phi'''. The default values are ? θ = 180° and ? φ = 0° representing a normally incident plane wave propagating along the -Z direction with a +X-polarized E-vector. In the TM<sub>z</sub> and TE<sub>z</sub> polarization cases, the magnetic and electric fields are parallel to the XY plane, respectively. The components of the unit propagation vector and normalized E- and H-field vectors are displayed in the dialog. In the more general case of custom linear polarization, besides the incidence angles, you have to enter the components of the unit electric '''Field Vector'''. However, two requirements must be satisfied: '''ê . ê''' = 1 and '''ê à k''' = 0 . This can be enforced using the '''Validate''' button at the bottom of the dialog. If these conditions are not met, an error message is generated. The left-hand (LCP) and right-hand (RCP) circular polarization cases are restricted to normal incidences only (? θ = 180°).
To define a plane wave source follow these steps:
* The direction of the Plane Wave is determined by the incident '''Theta''' and '''Phi''' angles in degrees. You can also set the '''Polarization''' of the plane wave and choose from the five options described earlier. When the '''Custom Linear''' option is selected, you also need to enter the X, Y, Z components of the '''E-Field Vector'''.
NOTE: In the spherical coordinate system, normal plane wave incidence from the top of the domain downward corresponds to ? θ = 180<sup>o</sup>°.
[[Image:/files/images/manuals/emagware/emcube/modules/mom3d/excitation-sources/plane-waves/po_phys15.png]] [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/excitation-sources/plane-waves/po_phys16_tn.png]]
== Setting Wire MoM Numerical Parameters ==
A Wire MoM simulation involves a number of numerical parameters that normally take default values unless you change them. You can access these parameters and change their values by clicking on the '''Settings''' button next to the "Select Engine" drop-down list in the '''Run Dialog'''. This opens up the Wire MoM Engine Settings Dialog. In the '''Solver''' section of the dialog, you can choose the type of linear solver. The current options are '''LU''' and '''Bi-Conjugate Gradient (BiCG)'''. The LU solver is a direct solver and is the default option of the MoM3D Module. The BiCG solver is iterative. Once selected, you have to set a '''Tolerance''' for its convergence. You can also change the maximum number of BiCG iterations by setting a new value for '''Max. No. of Solver Iterations / System Size'''. The Wire MoM simulator is based on Pocklington's integral equation method. In this method, the wires are assumed to have a very small radius. The basis functions are placed on the axis of the "wire cylinder", while the Galerkin testing is carried out on its surface to avoid the singularity of the Green's functions. In the "Source Singularity" section of the dialog, you can specify the '''Wire Radius''' . EM.CUBE's MoM3D Module assumes an identical wire radius for all wires and wireframe structures. This radius is expressed in free space wavelengths and its default value is 0.001?λ<sub>0</sub>. The value of the wire radius has a direct influence on the wire's computed reactance.
[[Image:/files/images/manuals/emagware/emcube/modules/mom3d/running-wire-mom-simulations/setting-the-numerical-parameters/wire_pic21.png]]
== Visualizing Wire Current Distributions ==
At the end of a MoM3D simulation, EM.CUBE's Wire MoM engine generates a number of output data files that contain all the computed simulation data. The main output data are the current distributions and far fields. You can easily examine the 3-D color-coded intensity plots of current distributions in the Project Workspace. Current distributions are visualized on all the wires and the magnitude and phase of the electric currents are plotted for all the PEC objects. In order to view these currents, you must first define current sensors before running the Wire MoM simulation. To do this, right click on the '''Current Distributions''' item in the '''Observables''' section of the Navigation Tree and select '''Insert New Observable...'''. The Current Distribution Dialog opens up. Accept the default settings and close the dialog. A new current distribution node is added to the Navigation Tree. Unlike the [[Planar Module]], in the MoM3D Module you can define only one current distribution node in the Navigation Tree, which covers all the PEC object in the Project Workspace. After a Wire MoM simulation is completed, new plots are added under the current distribution node of the Navigation Tree. Separate plots are produced for the magnitude and phase of the linear wire currents. The magnitude maps are plotted on a normalized scale with the minimum and maximum values displayed in the legend box. The phase maps are plotted in radians between -? π and ?π.
Current distribution maps are displayed with some default settings and options. You can customize the individual maps (total, magnitude, phase, etc.). To do so, open the '''Output Plot Settings Dialog''' by right clicking on the specific plot entry in the Navigation Tree and selecting '''Properties...''' or by double clicking on the surface of the plot's legend box. Two '''scale''' options are available: '''Linear''' and '''dB'''. With the '''Linear''' (default) option selected, the current value is always normalized to the maximum total current in that plane, and the normalized scale is mapped between the minimum and maximum values. If the '''dB''' option is selected, the normalized current is converted to dB scale. The plot limits (bounds) can be set individually for every current distribution plot. In the '''Limits''' section of the plot's property dialog, you see four options: '''Default''', '''User Defined''', '''95% Conf.''' and '''95% Conf.'''. Select the user defined option and enter new values for the '''Lower''' and '''Upper''' limits. The last two options are used to remove the outlier data within the 95% and 99% confidence intervals, respectively. In other words, the lower and upper limits are set to ? ± 1.96? and ? ± 2.79? , respectively, assuming a normal distribution of the data. Three color maps are offered: '''Default''', '''Rainbow''' and '''Grayscale'''. You can hide the legend box by deselecting the box labeled '''Show Legend Box'''. You can also change the foreground and background colors of the legend box.
* The initial size of the sensor plane is 100 Ã 100 project units. You can change the dimensions of the sensor plane to any desired size. You can also set the '''Number of Samples''' along the different directions. These determine the resolution of near field calculations. Keep in mind that large numbers of samples may result in long computation times.
After closing the Field Sensor Dialog, the a new field sensor item immediately appears under the '''Observables''' section in the Navigation Tree and can be right clicked for additional editing. Once a Wire MoM simulation is finished, a total of 14 plots are added to every field sensor node in the Navigation Tree. These include the magnitude and phase of all three components of E and H fields and the total electric and magnetic field values. Click on any of these items and a color-coded intensity plot of it will be visualized on the Project Workspace. A legend box appears in the upper right corner of the field plot, which can be dragged around using the left mouse button. The values of the magnitude plots are normalized between 0 and 1. The legend box contains the minimum field value corresponding to 0 of the color map, maximum field value corresponding to 1 of the color map, and the unit of the field quantity, which is V/m for E-field and A/m for H-field. The values of phase plots are always shown in Radians between -? π and ?π.You can change the view of the field plot with the available view operations such as rotating, panning, zooming, etc.
[[Image:/files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/near-field-visualization/wire_pic30.png]] [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/near-field-visualization/wire_pic31_tn.png]]
[[Image:/files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/radar-cross-section/rcs_equation.png]]
EM.CUBE calculates three RCS quantities: the ? φ and ? θ components of the radar cross section as well as the total radar cross section: ?σ<sub>?θ</sub>, ?σ<sub>?φ</sub>, and ?σ<sub>tot</sub>. In addition, EM.CUBE MoM3D Module calculates two types of RCS for each structure: '''Bi-Static RCS''' and '''Mono-Static RCS'''. In bi-static RCS, the structure is illuminated by a plane wave at incidence angles ?θ<sub>0</sub> and ?φ<sub>0</sub> and the RCS is measured and plotted at all ? θ and ? φ angles. In mono-static RCS, the structure is illuminated by a plane wave at incidence angles ?θ<sub>0</sub> and ?φ<sub>0</sub> and the RCS is measured and plotted at the echo angles 180°-?θ<sub>0</sub>; and ?φ<sub>0</sub>.It is clear that in the case of mono-static RCS, the Wire MoM simulation engine runs an internal angular sweep, whereby the values of the plane wave incidence angles ?θ<sub>0</sub> and ?φ<sub>0</sub> are varied over the intervals [0°, 180°] and [0°, 360°], respectively, and the backscatter RCS is recorded.
To calculate RCS, first you have to define an RCS observable instead of a radiation pattern. Right click on the '''Far Fields''' item in the '''Observables''' section of the Navigation Tree and select '''Insert New RCS...''' to open the Radar Cross Section Dialog. Use the '''Label''' box to change the name of the far field or change the color of the far field box using the '''Color''' button. Select the type of RCS from the two radio buttons labeled '''Bi-Static RCS''' and '''Mono-Static RCS'''. The former is the default choice. The resolution of RCS calculation is specified by '''Angle Increment''' expressed in degrees. By default, the ? θ and ? φ angles are incremented by 5 degrees. At the end of a Wire MoM simulation, besides calculating the RCS data over the entire (spherical) 3-D space, a number of 2-D RCS graphs are also generated. These are RCS cuts at certain planes, which include the three principal XY, YZ and ZX planes plus one additional constant ?φ-cut. This latter cut is at ?φ=45° by default. You can assign another phi angle in degrees in the box labeled '''Non-Principal Phi Plane'''.
At the end of a Wire MoM simulation, the thee RCS plots ?σ<sub>?θ</sub>, ?σ<sub>?φ</sub>, and ?σ<sub>tot</sub>are added under the far field section of the Navigation Tree. These plots are very similar to the three 3-D radiation pattern plots. You can view them by clicking on their names in the navigation tree. The RCS values are expressed in m<sup>2</sup>. For visualization purposes, the 3-D plots are normalized to the maximum RCS value, which is also displayed in the legend box. The 2-D RCS graphs can be plotted from EM.CUBE's data manager exactly in the same way that you plot 2-D radiation pattern graphs. A total of eight 2-D RCS graphs are available: 4 polar and 4 Cartesian graphs for the XY, YZ, ZX and user defined plane cuts. At the end of a sweep simulation, EM.CUBE calculates some other quantities including the backscatter RCS (BRCS), forward-scatter RCS (FRCS) and the maximum RCS (MRCS) as functions of the sweep variable (frequency, angle, or any user defined variable). In this case, the RCS needs to be computed at a fixed pair of phi and theta angles. These angles are specified in degrees as '''User Defined Azimuth & Elevation''' in the "Output Settings" section of the '''Radar Cross Section Dialog'''. The default values of the user defined azimuth and elevation are both zero corresponding to the zenith.
NOTE: Computing the 3-D mono-static RCS may take an enormous amount of computation time.
[[Image:/files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/radar-cross-section/wire_pic51_tn.png]][[files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/radar-cross-section/wire_pic51.png|files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/radar-cross-section/wire_pic51.png]] [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/radar-cross-section/wire_pic52_tn.png]][[files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/radar-cross-section/wire_pic52.png|files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/radar-cross-section/wire_pic52.png]] [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/radar-cross-section/wire_pic53_tn.png]][[files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/radar-cross-section/wire_pic53.png|files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/radar-cross-section/wire_pic53.png]]
The RCS of the wire-plate structure: (Left) ?σ<sub>?θ</sub>, (Center) ?σ<sub>?φ</sub> and (Right) total RCS..
== Customizing 3D Plots ==
Reading far field values from a 3-D radiation pattern plot by mouse-over.
You can change the type of the 3-D radiation pattern plot through the '''Radiation Pattern Dialog'''. The plot type change applies to all the three nodes: theta component, phi component and total field patterns. In the 3D Display Type section of this dialog you can choose from three options: '''3D Polar''', which is the default choice, '''Spherical Map''' and '''Cone'''. In the last two cases, the far field values are plotted on the surface of the unit sphere, where each point correspond to a (? θ, ?φ) pair. In the spherical map, the curved cells of the unit sphere are colored based on their field value. In the cone-type plot, a vectorial visualization of the far fields is generated. In the last case, you can also set the size of the cones that represent the far field vectors.
[[Image:/files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/customizing-3-d-pattern-plots/wire_pic42_tn.png]] [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/customizing-3-d-pattern-plots/wire_pic43_tn.png]]
== 2D Radiation Graphs ==
At the end of a Wire MoM simulation, the radiation pattern data E<sub>?θ</sub>, E<sub>?φ</sub>, and E<sub>tot</sub> in the three principal XY, YZ and ZX planes as well as an additional user defined phi plane cut are available for plotting on 2-D graphs. There are a total of eight 2D pattern graphs in the data manager: 4 polar graphs and 4 Cartesian graphs of the same pattern data. To open data manager, click the '''Data Manager''' [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/visualizing-simulation-data/scattering-parameters-and-port-characteristics/data_manager_icon.png]] button of the '''Compute Toolbar''' or select '''Compute [[Image:/files/images/manuals/emagware/emcube/modules/mom3d/the-metal-structure/moving-objects-between-pec-groups-or-transferring-to-other-modules/larrow_tn.png]]Data Manager''' from the menu bar or right click on the '''Data Manager''' item of the Navigation Tree and select Open Data Manager... from the contextual menu or use the keyboard shortcut '''Ctrl+D'''. In the Data manager Dialog, you will see a list of all the data files available for plotting. These include the four polar pattern data files with a '''.ANG''' file extension and the four Cartesian pattern data file with a '''.DAT''' file extension. Select any data file by clicking and highlighting its '''ID''' in the table and then click the '''Plot''' button to plot the graph.
At the end of a Wire MoM sweep simulation, other radiation characteristics are also computed as a function of the sweep variable (frequency, angle, or any other user defined variable). These include the '''Directivity (D0)''', '''Total Radiated Power (PRAD)''' and '''Directive Gain (DG)''' as a function of the theta and phi angles. Another radiation characteristic of interest especially in circularly polarized scenarios is the Axial Ratio. In EM.CUBE, the axial ratio is always defined in the LCPz or RCPz sense based on the X- and Y-components of the electric field. In order to calculate the directive gain or axial ratio, you have to check the boxes labeled '''Axial Ratio (AR)''' or '''Directive Gain (DG)''' in the "Additional Radiation Characteristics" section of the '''Radiation Pattern Dialog'''. Four 2-D Cartesian graphs of the axial ratio as functions of the theta angle a generated in the three principal XY, YZ and ZX planes as well as the additional user defined phi plane cut. At the end of a Wire MoM sweep simulation, the directive gain and axial ratio can also be plotted as functions of the sweep variable. In this case, either quantity needs to be computed at a fixed pair of phi and theta angles. These angles are specified in degrees as '''User Defined Azimuth & Elevation''' in the "Output Settings" section of the '''Radiation Pattern Dialog'''. The default values of the user defined azimuth and elevation are both zero corresponding to the zenith.