  Plane wave illumination without the scatterer
The present example considers a plane wave illumination in a free space without a scatterer.

Simulation model considers a cubic volume of free space (cube side = 40 mm), with absorbing exterior boundaries (marked as blue box), a surface for near-to-far field transformation (NTF box, marked as reen box) with each wall placed 4 mm from an absorbing boundary and a surface for plane wave excitation (plane wave box, marked as red box) with each wall placed 10 mm from an absorbing boundary. Plane wave illumination without the scatterer project in QW-Editor.
QuickWave enables free space excitation with a plane wave (available as TEM illumination). For this excitation type there are three angles to be chosen:
φ (Phi) - azimuthal angle of the direction of wave propagation,
θ (Theta) - elevation angle of the direction of wave propagation,
Polarisation - polarisation angle of the electric field.

With all these angles set to zero, the incident wave travels along the Z-axis and its electric field vector is oriented along the X-axis. In general, the direction of propagation determines a modified Z' axis, and the electric field orientation determines a modified X' axis, of the modified X'Y'Z' coordinate system obtained from the original XYZ coordinate system by rotation with Euler angles Phi, Theta, Polarisation in the ZYZ Euler convention. For more details about Euler angles refer to Radiation patterns section.

It is advised to refer to Free space incident wave for detailed discussion regarding free space excitation with a plane wave or Gaussian beam.

With the settings of Phi=0 degrees, Theta=90 degrees and Polarisation=0 degrees, the wave propagates in the +X direction and positive E-field is in the -Z direction. Configuration dialogue of a plane wave box excitation (free space incident wave). Ez field component of plane wave excitation (Phi=0 degrees, Theta=90 degrees and Polarisation=0 degrees) at 10 GHz.
Time dependent Ez field distribution of plane wave excitation (Phi=0 degrees, Theta=90 degrees and Polarisation=0 degrees) at 10 GHz.
Now we change the settings to Phi=45 degrees, Theta=90 degrees and Polarisation=0 degrees. Configuration dialogue of a plane wave box excitation (free space incident wave). Ez field component of plane wave excitation (Phi=45 degrees, Theta=90 degrees and Polarisation=0 degrees) at 10 GHz.
Time dependent Ez field distribution of plane wave excitation (Phi=45 degrees, Theta=90 degrees and Polarisation=0 degrees) at 10 GHz.