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Power Budget

Go to Results > Power Budget/RCS in the main menu to display the Power Budget dialog box, Fig. 1. The following list of parameters versus frequency will be shown when discrete sources are used as the excitation:

  • The Input Power column shows the total input power provided by the discrete sources in the structure.
  • The Radiated Power column shows the total radiated power from the structure.
  • The Structure Loss column shows the total consumed power (ohmic losses) in the structure.
  • The Efficiency column is the radiated power to the input power ratio. When the structure is lossless, an efficiency of 100% is obtained.
  • The Directivity column is the peak directivity (dimensionless) .
  • The Directivity [dBi] column is the peak directivity in decibels with reference to an isotropic source .
  • The Gain column is the peak gain (dimensionless).
  • The Gain [dBi] column is the peak gain in decibels with reference to an isotropic source.
  • The Pav column is the average power density. This value is calculated averaging the power density over all directions in space.
  • The Pmax column is the maximum value of the radiated power density.
  • The Theta (max) and Phi (max) columns are the zenith and azimuth angles, respectively, in the direction of maximum radiation.
  • The Error column is the error in the power balance of the system. A necessary, but not sufficient, condition for a model to be valid is that the input power must be equal to the sum of the radiated and lost powers, so the Error is defined as follows:

Error % = 100 x (Input Power – Lost Power – Radiated Power) / (Input Power – Lost Power)

  • The Average Gain Test (AGT) column represents the same information as the Error column, but the AGT must be close to 1 to validate a model, since it is given by

AGT = (Radiated Power + Lost Power) / Input Power

Select an item from the list in the upper right corner of the window and then press the Plot button to plot the selected item versus frequency. Click on the Export button to export the list to a CSV file.

Fig. 1: The Power Budget dialog box.


  • A power budget error of about ±1% is permissible from the engineering point of view.
  • When a real ground plane is set, this column shows the percentage of power lost in the ground due to its finite conductivity.
  • When an infinite substrate slab is set, this column shows the percentage of power transferred to the dielectric material in the substrate.
  • AGT = 1 means that the power balance is exact. An AGT between 0.99 and 1.01 is comparable to achieving an error of ±1%.


When there is a real ground plane or an infinite dielectric substrate, the directivity and the average power density (Pav) are meaningful quantities only if the Theta and Phi angles in the Far-Field panel > of the Setup tabsheet are set in the following ranges:

:: If the environment is free space (there is no ground plane):

0 <= Theta <= 180 deg.


0 <= Phi <= 360 deg.

:: If the environment has a ground plane:

0 <= Theta <= 90 deg.


0 <= Phi <= 360 deg.

This is because the average power density must be computed averaging the power density or Poynting vector by considering all directions in free space. If there is a ground plane, directions must be considered in half-space.

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