Hfss Spherical Coordinate System

[Eunice Beady]

Inthe data generation, I set up a relative coordinate for my radar array that the radar array as well as the relative coordinate for the array moves around the global coordinate system. The antennae are defined in the relative coordinate system. The object being detected lies still on the origin of the global coordinate system. I am moving the relative coordinate system in a spherical coordinate with a fixed radius and azimuth and elevation angles are the variables.

At each azimuth and elevation angle, I get the cartesian coordinate of the radar array from the spherical system and point the radar to the object by setting the x-axis of the relative coordinate system to the negative of the position of the origin of the relative coordinate system in the global coordinate system. The "y-point" variable was kept (0,1,0) as default.

Now I am trying to calculate the position of the antennae in Python but with only the origin of the relative coordinate system and the x-axis of the coordinate system, I only know the plane on which the y and z axes of the relative coordinate system live. In order to find the orientation of the y and z axes of the relative coordinate system, I need to reduce a degree of freedom by correctly interpreting the setting of the y-point in the coordinate system as shown in the screenshot below.

Y-point in similar sense orients the Y-axis of Relative CS to that of Global CS. For example Y-value (0,1,0) orientes Y-axis of Relative CS in same direction as Y-axis of Global CS, and (0,0,1) means Y-axis of Relative CS aligns as Z-axis of Global CS.

The X Axis and Y point works in combination and are dependent on each other. For example keeping X Axis and Y point values same (1,0,0) & (1,0,0) tool will throgh the error saying "RelativeCSParameters: X and Y vectors are parallel."

To assign a tangential magnetization to a permanent magnet in 2D and 3D using the magnet material properties in Ansys Electronics Desktop, you can follow the steps outlined in the document titled "How to model multi-directional magnetization of PMs in Maxwell?".

The document explains how to specify the magnetization direction according to different types of coordinate systems such as Cartesian, Cylindrical, or Spherical. The coordinate system type is specified in the material characteristics under "Material Coordinate System Type". The setup is based on vectors, which are defined by a magnitude and a direction. This information will be specified separately.

For example, if you are using a Cartesian coordinate system, you would specify the Cartesian coordinate system option, indicate the Magnitude (a value), and indicate the direction (X, Y, or Z). This information can be introduced using 1 or -1, depending on the direction.

For Cylindrical and Spherical coordinate systems, the procedure is the same but the direction will be R, Phi, and Z axes for Cylindrical and Rho, Theta, and Phi axes for Spherical.

The document also provides examples of how to set up multiple magnets, like in a PM motor, using the Cylindrical coordinate system.

References:

[1] Title: 'How to model multi-directional magnetization of PMs in Maxwell?', URL: '/knowledge/forums/topic/how-to-model-multi-directional-magnetization-of-pms-in-maxwell/'

Coordinate systems are one of those things that are fundamental to Finite Element Analysis, but that most of us do not think about a lot. They are there, but some users never fiddle with them. And some users are constantly futzing around with them. We thought it would be a good idea to do a quick review of how coordinate systems in ANSYS Mechanical work. We will also go over the basics for Mechanical APDL (MADL) in case you need to work with snippets.

ANSYS cares a lot about coordinate systems because they allow the program to solve in a standard, global, Cartesian system while allowing loads, constraints, material directions, layer information, beam sections, joints, result values, and a whole slew of other important aspects of the model to be specified in unique coordinate systems. This avoids making the user do coordinate system transformations. At solve time, everything gets converted.

In ANSYS Mechanical, coordinate systems reside in the Model Tree between Geometry and Connections. Once you define a coordinate system it becomes available for use with any other object that can use a coordinate system. This allows you to define it once, and then use it many times.

You always get a Global Cartesian coordinate system, called Global Coordinate System. It is Cartesian, has an ID of 0, and sits at 0,0,0. You can not change any of these values. Any imported coordinate systems will show up underneath the global.

This is the easiest part. You simply choose one of your defined coordinate systems from a dropdown list when you create an object that is dependent on a coordinate system. Usually this is when you can define a value based Components rather than on geometry:

Do note that you can also use coordinate systems to transform directional result values. Simply pick the Coordinate system from the dropdown list. This is especially important when looking at hoop or radial stresses in a cylindrical part.

Coordinate systems are huge in MAPDL. Nodes have them, elements have them, sections have them. Plus you can make a coordinate system active and every command you execute is done in that active coordinate system, and converted for you to the global. Very powerful.

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The antenna element pattern is defined based on [1] and it only supports a uniform rectangular array (URA) positioned on the Y-Z plane. This option is only available in Data Flow phased array models; it is not available in the RF Design ArrayAnt model.

When element pattern data is captured using an EM tool or real measurements in a chamber, the element of interest is excited while all other elements are terminated, but the array is not moved so that the element of interest is not located at the origin of the coordinate system. The result is that the "array factor" (phase shift caused by the element location being away from the coordinate system origin) will be embedded in the pattern data captured for it. In this case, the Element array factor included in pattern data must be selected, so that the embedded array factor is processed properly and not double counted when the overall array pattern is computed.

When File Map is 2: Custom and Element array factor included in pattern data is YES, the array factor embedded in element patterns must be removed according to their original locations before applying new array factor. In this case, the following parameters are available to specify the locations of the elements where the pattern files were captured.

Following parameters are used to transform antenna element pattern from LCS (Local Coordinate System) to GCS (Global Coordinate System). Refer to Phased Array Configuration Parameters for the description of α, β, and γ rotation.

Usually, antenna engineers design antenna element radiation patterns with maximum power pointing to the z-axis (θ = 0), but communication engineers used to make the maximum power radiation directing to around the x-axis.

These three parameters support arbitrary rotation of the antenna pattern in the spherical coordinate system to accommodate the requirements. In communication systems, the downtilt angle is frequently used. In the following picture, the left graph is the original antenna pattern and the right graph is the resulting antenna pattern rotated by downtilt angle of 30 degrees. In this use case, we set parameter Rotation Around Y for each antenna element to 30 and set both Rotation Around Z and Rotation Around X to 0 degrees for each antenna element.

When Pattern Type is Three Sector Antenna for Y-Z URA or when Pattern Type is Pattern File and Pattern File Type is EMPro, HFSS, CST or FFIO, this parameter specifies whether to normalize its pattern to its directivity pattern. If Pattern File is .ffd HFSS, GRASP, its element pattern will be normalized regardless of this parameter.

For patterns from some files, the Etheta/Ephi field is measured radiation strength when excited by a certain power. To get a directivity pattern, this exciting power should be excluded by normalization. When PatternNormalization is the Sum of Input Power for BeamPattern model and Phased Array Analysis, this parameter is forced to Yes internally.

To complete the setup, the Element array factor included in pattern data should be set to YES and the locations (coordinates) of the elements in the 5 x 5 array must be provided using the parameters

This option is similar to 0: Individual for Each Element except that it allows users to "change" the files' indices (numerical suffix in the name) without really changing the file names but by using File Map to specify a mapping matrix. The pattern file names must follow the naming convention described in 0: Individual for Each Element. As explained in Phased Array Configuration Parameters, each array element is assigned an index based on its location and the chosen configuration (Custom, ULA, URA, Circular, etc.). When the element pattern files are not indexed using the same ordering rule described in Phased Array Configuration Parameters, using 0: Individual for Each Element would result in the wrong pattern files assigned to the different elements. In such cases, you need to use 3: Individual for Each Element with Reordering and explicitly specify the mapping between the files and the elements using the File Map in a similar way as described in 2: Custom.

Let's look at an example using a 4 x 4 uniform rectangular array. On the left, you see SystemVue's ordering convention for elements of a URA placed on the X-Y plane. Now assume that when the element pattern files were captured in your EM tool of choice, the ordering/indexing used is what is shown on the right. If this set of patterns files is used with the option 0: Individual for Each Element, the pattern file for the element at location (0.015, 0) in the EM simulation (index 2 on the right) will be used for the element at the location (0, 0.015) in the SystemVue simulation (index 2 on the left).

To make the correct assignment of pattern files to elements, in this case, we need to use 3: Individual for Each Element with Reordering and set the File Map parameter to [1 5 9 13 2 6 10 14 3 7 11 15 4 8 12 16]. The way to get this vector of values is to traverse/record the numbers shown on the right following the sequence of numbers shown on the left. Another way to define the map is using the 4 x 4 matrix shown below

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