SNOAA04A March 2020 – June 2021 FDC1004 , FDC1004-Q1 , FDC2112 , FDC2112-Q1 , FDC2114 , FDC2114-Q1 , FDC2212 , FDC2212-Q1 , FDC2214 , FDC2214-Q1 , LDC0851 , LDC1041 , LDC1051 , LDC1101 , LDC1312 , LDC1312-Q1 , LDC1314 , LDC1314-Q1 , LDC1612 , LDC1612-Q1 , LDC1614 , LDC1614-Q1 , LDC2112 , LDC2114 , LDC3114 , LDC3114-Q1
Figure 2-1 Create a New Problem Dialog BoxWhen choosing between the two problem types, consider the geometry of the coil. For both planar and axisymmetric problems, the FEMM workspace forms a cross section of the coil and target. The workspace is a slice of the PCB coil such that all layers and traces of the PCB are visible. Keep this in mind while constructing the coil. It is important to construct the cross section such that the simulation will create a coil shape. See how each problem type turns the 2D workspace into a 3D solution:
Planar problems expand along the axis perpendicular to the plane. The user must specify the distance of this expansion. This type of problem is most often used to simulate racetrack coils. However, planar problems cut off the rounded edges of the coils, leaving only the long parallel section. This makes the simulation much less accurate than spiral coil simulations using axisymmetric problems.
Figure 2-2 Example Planar Problem Workspace With Labeled Traces and TargetAxisymmetric problems rotate around a user-specified axis. This type of problem is the most useful for inductive sensing simulations and should be used for all circular coils. Note that coils simulated with this problem type will not be true coils, but will be a series of concentric circles. Even so, the coils are fairly accurate simulations.
Figure 2-3 Example Axisymmetric Problem Workspace With Labeled Traces and TargetUse the Spiral Inductor Designer in LDC Tools to calculate a frequency and enter that frequency in the problem Frequency (Hz) field. If the FEMM simulation includes a target, use the sensor frequency with target interaction.
Figure 2-4 Problem Definition Dialogue Box
to place nodes. Use either segments
or arcs
to connect them. At least two nodes must be placed before placing segments. These will form the boundaries of your shape(s). Use the trace width, trace spacing, and trace thickness from the Spiral Inductor Designer to create a cross section of each trace. Here are key tips for placing objects:
button to move objects.
button to copy objects.
button to select a group of
objects. Then click the
button to highlight objects in a
rectangular area or the
button to highlight objects in a
circular area. Press the space bar to join the objects into a
group.
button to scale
button to open the Boundary Builder.
Figure 2-5 Boundary Builder Dialogue Box
Figure 2-6 Axisymmetric
Problem With Boundaries
Figure 2-7 Planar Problem
With Boundaries
to place block labels. Place a block label
inside each boundary area, including the white space inside the outer
boundary. The result should look something like Figure 2-8:
Figure 2-8 Axisymmetric
Problem Workspace With Block Labels
Figure 2-9 Default Materials Library
Figure 2-10 Materials Library With Air and Copper Added to Model Materials
Figure 2-11 Block Properties Menu
Figure 2-12 Properties for
Selected Block Menu
Figure 2-13 Axisymmetric
Problem Workspace With Defined Materials
Figure 2-14 Circuit Property Menu
Figure 2-15 Example Planar Problem Workspace With Defined Circuits
for Racetrack Coil
Figure 2-16 Properties for Selected Block Menu
Figure 2-17 Axisymmetric
Problem Workspace With Defined Circuits
to generate the answer file.