6.1.12                    Time integral of power dissipated

 

The calculations of power dissipated, energy stored, and Q-factor are physically meaningful in the steady-state sinusoidal excitation regime. However sometimes we are interested in the total power dissipated in the circuit when it is excited by a pulse of limited duration. This requires performing time integration of power dissipated. Such information is available in Integral of Power Dissipated window. This feature delivers Space & Time Integral of Pdiss in [nJ], given for both electric and magnetic fields.

At each FDTD iteration the software performs the following operations:

Note that the space integration is time consuming thus the suppress option for the integration of electric or magnetic space & time integral of Pdiss are available.

 

It should be noted that by space & time integral of Pdiss we understand the total energy converted into heat during the simulated process. The time domain integration mentioned above is performed when the Integral of Power Dissipated window is opened or when the space & time integral of Pdiss calculation process is activated from a tasker file. Thus if we want to integrate the Pdiss over the entire duration of the input pulse we should activate the Integral of Power Dissipated window immediately after starting the simulation.

The value of space & time integral of Pdiss becomes meaningful when it is compared to the total energy available from the input source. The energy available from the source is available in the Integral of Power Dissipated window (it it also delivered by Power Available post-processing).

 

Note that the integration can be performed in all media in the circuit or in the chosen media using Dense regions only and Selected Dense Media options. In typical cases the space and time integral of power dissipated is calculated through the integration over the whole circuit. However, in some applications we would like to know the value of this integral only in a particular object or group of objects. QuickWave enables such functionality with Dense regions only and Selected Dense Media options.

The Dense regions only option allows space-selective integration of dissipated power. When this option is enabled the software takes into account only the regions composed of the media that were previously declared as having non-zero density. The density value has no significant meaning here and it is treated only as a marker for dissipated power calculation. Thus, if one wants to calculate the space and time integral of dissipated power in a particular region one should fill this part with a medium of non-zero density and use Dense regions only option.

 

Let us further consider a simulation scenario with several lossy objects, where it is required to calculate the space and time integral of power dissipated separately in each of the objects or in some groups of the objects. For that purpose Dense regions only option needs to be activated (non-zero density must be set for appropriate media), what additionally enables Selected Dense Media option. Selected Dense Media option allows selecting which dense media will be used in the calculations. The user may choose any combination of the media for space and time integral of dissipated power calculation but at least one medium must be chosen.

 

Note that medium density is specified in the Project Media window of the Input Interface. Since QuickWave allows FDTD cells filled by more than one medium, ambiguity of "density" to be assigned to such cells has to be resolved. Since the criterion is, that the dielectric medium of the highest "conductivity" decides whether a cell is "dense", the density of this medium is treated as "density" of the cell. Density assigned to metallic and PEC media is ignored in this consideration. "Conductivity" is understood as the sum of X, Y, and Z components of Sigma and SigmaM. The medium of highest "conductivity" in the above sense also becomes a dominant cell medium for QW-BHM operation.

 

 

The Integral of Power Dissipated window delivers the power dissipated in the circuit over the entire duration of the input pulse as a value. The user can also take advantage from the displays showing the distribution of the time integral of power dissipated in the circuit, as discussed in Dissipated power and dissipated power density.