Figure 1: [[Propagation Module]]'s Transmitter dialog with a user defined radiator selected.
Â
=== Multiple Transmitters vs. Antenna Arrays ===
Â
[[EM.Cube]]'s SBR simulations are fully coherent and 3D-polarimetric. This means that the phase and polarization of all the rays are maintained and processed during their bounces in the scene. Your propagation scene can have more than one transmitter. During an SBR simulation, all the rays emanating from all the transmitters are traced in the propagation scene. All the received rays at a given receiver location are summed coherently and vectorially. This is based on the principle of linear superposition. All the transmitters belonging to the same transmitter set have the same radiation properties. They are either parallel short dipole radiators with the same current amplitudes and phases, or parallel user defined radiators with identical radiation patterns. As these transmitters are placed at different spatial locations, they effectively form an antenna array with identical elements. The array factor is simply determined by the coordinates of the base points. If you want to have different amplitude or phases, then you need to define different transmitter sets.
Â
If that radiators are indeed the elements of an actual antenna array with a half wavelength spacing or so, we recommend that you import the radiation pattern of the array structure instead and replace the whole multi-radiator system with a single point transmitting radiator in your propagation scene. This case is usually encountered in MIMO systems, and using an equivalent point transmitter is an acceptable approximation because the total size of the array aperture is usually much smaller than the dimensions of your propagation scene and its representative length scales. In that case, you need to position the equivalent point radiator at the radiation center of the antenna array. This depends on the physical structure of the antenna array. However, keep in mind that any reasonable guess may still provide a good approximation without any significant error in the received ray data.
=== Defining Receiver Sets ===