# Post-Simulation Data Analysis

## Discretized Fourier Transform (DFT) and Fast Fourier Transform (FFT)

As a time domain simulation method; FDTD can get all the relevant spectral response with a single simulation. To get the spectral response, you need to use the DFT, FFT, and Analysis. Discretized Fourier Transform gets a single wavelength response from a time series. where s(n) are the time domain response, N is the number…

## Power Calculation and Poynting Vector

For the z-direction propagation wave. The total power in x-y plane can be divided into two power values: x-direction polarized z-direction propagation power (Pz-x) and y-direction polarized z-direction propagation power (Pz-y). The corresponding formulas are: x-polarization power y-polarixation power Total power where the cap dot indicates the complex value that comes from the DFT calculation, and…

## Far Field Transform

Fraunhofer approximation Narrow angle far-field transform being used in OptiFDTD is based on the Fraunhofer approximation: At a large distance d, the far field position can be expressed by the far field angle, Where the x-directional angle (θx) is the angle between the original yz-plane and the shortest straight line connecting the point and the Y…

## RCS Calculation

Consider figure 21, which depicts an observation point in the far field many wavelengths away from the near field path . In this case, the Far Field can be identified as: for TE simulation and for TM simulation. Then the bistatic radar cross section (RCS) in two dimension can be defined as: Figure 23: Geometry…

## References

 Justin Peatross and Harold Stokes, “Physics of Light and Optics”