In the params file, the W0 parameter is defined as the transmit beam radius, but it also modifies the pupil_mode variable. This effectively modifies the fibre size from its optimal value for the specified D_GROUND, used for the reciprocity calculations.
Example where I noticed this issue:
If I want to model the uplink of a bidirectional link configuration, I will have my downlink aperture size set to some large value e.g. 1m. I will then set W0 to be my uplink beam radius (e.g. 5cm). Now, when I want to compute received power at the satellite, pupil_mode will be a gaussian with waist W0 within the much larger aperture diameter, and so my atmospheric losses will be incorrect.
In the params file, the
W0parameter is defined as the transmit beam radius, but it also modifies thepupil_modevariable. This effectively modifies the fibre size from its optimal value for the specifiedD_GROUND, used for the reciprocity calculations.Example where I noticed this issue:
If I want to model the uplink of a bidirectional link configuration, I will have my downlink aperture size set to some large value e.g. 1m. I will then set
W0to be my uplink beam radius (e.g. 5cm). Now, when I want to compute received power at the satellite,pupil_modewill be a gaussian with waistW0within the much larger aperture diameter, and so my atmospheric losses will be incorrect.