CST2013: Monitor

Simulation: Monitors Field Monitor

This dialog box gives you the opportunity to define field monitors that you might need to obtain additional information on the electromagnetic field distribution inside your structure. It is possible to define frequency as well as time monitors. After a calculation, you can observe your field monitors by selecting them in the navigation tree.

Labeling frame

Name: Displays the name for the field monitor either as a user input or automatically generated.

Automatic labeling: This check button enables or disables the automatic labeling for the defined field monitor. The automatically generated label consists of  the selected monitor type, including either the specified frequency or time sample settings of the frequency or time monitor, respectively.

Type frame

E-Field: The electric field vectors will be stored.

H-Field and Surface current: Selecting this monitor creates two monitor entries in the result tree. The first one shows the magnetic field vectors. The second one (labeled with "Surface Current") uses the magnetic fields on the surfaces of  "PEC" or "lossy material" solids to calculate the surface currents there.

Surface current (TLM only): Just the surface currents will be calculated. Only supported by TLM Solver.

Powerflow: This monitor stores  the Poynting vector of the electromagnetic field. The monitor represents the maximum value (peak value) of the power flow at every spatial point, encountered within one period of time. Therefore, this type of monitor is time independent.

Current density: If there are electric losses inside of the calculation domain, the currents inside of these materials are stored in this type of monitor.

Power loss density/SAR: See SAR calculation overview for detailed information.

Electric energy density / Magnetic energy density: Choose one of these monitors if you want to store the electric/magnetic energy density throughout the monitor volume. These monitors represent the maximum values (peak values) of the energy density within one period of time. Therefore they are time independent.

Farfield/RCS: For RCS calculations use a plane wave excitation. See Farfield Overview for detailed information.

Note: Farfield monitors must not have two parallel magnetic/electric boundaries&endash;one of two parallel boundaries must be of the type open (PML).

Field source: This monitor records the tangential fields on a prescribed box surface. The recorded data can be used as a near field source for the time domain solver in other projects.

Note: The data is saved in the results folder as "name of the source.fsm". This monitor is available for the time domain and the tetrahedral frequency domain solvers. It records the data at the specified frequencies. It is recommended to use the proprietary FSM nearfield data format in software products of CST.  In order to use the recorded fields outside of CST products it is recommended to use the NFS nearfield scan data exchange format. See here for more details.

Note: The minimum frequency Fmin is required to be an integer multiple of the sampling frequency (Fmax -Fmin) / (Freq. Samples-1).

Specification frame

Here, the field monitor domain can be specified, selecting between frequency and time.

Frequency: The monitor records the chosen field type only for a specific frequency. If the transient solver is used, this is done by use of a DFT.
Information about a possible normalization can be obtained in the section Spectral results from transient solvers.

Frequency: Enter a valid expression to specify the recording frequency of the frequency field monitor. It should be within the frequency range entered in the Frequency Range Settings dialog box, otherwise this monitor will be ignored during the calculation.

Freq. samples: For field source monitors, you can choose a number of equidistant frequency samples between Fmin and Fmax where frequency domain field sources are monitored.

Fmin/Fmax: This shows the minimum and maximum frequencies available for the monitors. It can be adjusted for the field source monitors.

Time: The monitor records the chosen field type at several equidistant time samples. Note that  this feature is not available for farfield monitors for frequency domain solvers.

Start time: Enter here the start time for the time monitoring.

Step width: Enter here the desired step width for the time monitoring. Together with start and end time this value determines the full number of recorded time samples. Note that time monitors possibly need a great amount of disk memory if the step width is chosen too small.

End time: Selecting this check box offers the possibility to define a specific endtime for the recording. If it is not selected, the recording will continue up to the end of the calculation.

Broadband: If a farfield monitor was selected in the type frame a broadband farfield can be calculated during the transient solver run. The broadband farfield monitor is based on an expansion of the farfield in terms of spherical waves. The origin of the expansion is the center of the bounding box. It allows to obtain the farfield at any frequency in the specified range as well as at any time of the simulation. Frequency domain and time domain results can be accessed by selecting plots of a broadband farfield monitor and by the plot properties dialog.

Freq. samples: Choose a number of equidistant frequency samples between Fmin and Fmax where frequency domain farfields are calculated. Results for any frequencies in between are interpolated to obtain broadband information. For a more accurate interpolation over the frequency band increase this value e.g. to "31". An odd number assures that the result at mid frequency is not obtained by interpolation.

Accuracy: Defines the desired accuracy of the farfield. Together with the Fmax and the size of the structure it determines the number of modes required to represent the farfield.

Note that leaving out higher order terms by choosing a lower accuracy is equivalent to low pass filtering the farfield solution. This saves memory and computation time. However, the farfield result has usually less detail.

Transient farfields: This check button activates the additional calculation of transient farfield information which can be displayed afterwards for a certain time in the post processing. Note that in order to accurately obtain time domain farfields the computational effort is higher than for broadband farfields only.

2D Plane frame

Activate: Select this check box  to define a 2D field monitor recorded on a specified plane, otherwise the field is recorded considering the complete calculation domain as a 3D monitor. 2D monitors are only available for electric or magnetic field type, either as a frequency or a time monitor.

Orientation: You can choose the 2D plane normal parallel to any global coordinate axis X,Y or Z.

Position: Enter the position along the chosen direction here.

Position frame

This frame is only active for field source and single frequency farfield/RCS monitors.

Use subvolume: Select this check box to define a subvolume with Xmin, Xmax, Ymin, Ymax, Zmin, and Zmax for the field source monitor. Otherwise, the field is recorded on the boundary of the calculation domain.

Invert orientation: Select this check box to record the fields as a source direct inwards. Otherwise, the fields are recorded for an outward directed source.

Export farfield source

Activates the automatic generation of a farfield source from the corresponding farfield monitor after a solver run. All farfield source exports from the same excitation are collected into a single broadband farfield source file.

OK

Accepts your settings and leaves the dialog box.

Apply

Accepts your settings without closing the dialog box so that you can enter another field monitor.

Cancel

Closes this dialog box without performing any further action.

Help

Shows this help text.