To access the Power Budget dialog box (see Fig. 1), go to Results > Power Budget/RCS in the main menu. The following list of parameters versus frequency is displayed when discrete sources are used for 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, representing ohmic losses in the structure.
- The Efficiency column displays the radiated power-to-input power ratio. When the structure is lossless, it results in an efficiency of 100%.
- The Directivity columns display the peak directivity, dimensionless and in decibels (dBi) with reference to an isotropic source.
- The Gain columns display the peak gain, dimensionless and in decibels (dBi) with reference to an isotropic source.
- The Av. EIRP (Effective Isotropic Radiated Power) columns display the average EIRP in Watts and dBW. This value is equal to the Radiated Power.
- The Peak EIRP (Effective Isotropic Radiated Power) columns display the peak EIRP in Watts and dBW.
- The Av. Power Density column is the average power density. This value is calculated averaging the power density over all directions in space.
- The Peak Power Density 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 F/R H and F/B H columns are the front-to-rear and front-to-back ratios, respectively, in a horizontal slice of the radiation pattern given by Theta = Theta (max).
- The F/R V and F/B V columns are the front-to-rear and front-to-back ratios, respectively, in a vertical slice of the radiation pattern given by Phi = Phi (max).
- 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 – Lost – Radiated) Power / (Input – Lost) Power
- The Average Gain Test (AGT) column represents a similar indicator to the Error column. To validate a model, AGT should be close to 1, as it is calculated using the formula:
AGT = (Radiated + 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.
- A power budget error of about ±10% is permissible from the engineering point of view.
- When a real ground plane is used, the Error column shows the percentage of power lost in the ground due to its finite conductivity.
- When a substrate slab is used, 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%.