I'm attempting to use the CST asymptotic solver to compute the farfield pattern of a reflector antenna illuminated by a farfield source. In my case, the main lobe is very narrow (~0.01 degrees), so I require a fine angular grid to resolve the individual lobes. I've attempted to do this by specifying the following (fixed phi) theta sweep in the observation sweep tab of the solver settings:
thetamin = 0
thetamax = 0.1
thetastep = 0.001
However, once the results have been computed, the farfield is plotted with a theta step size of 0.006 degrees, not the 0.001 degrees that was specified above. Strangely, the step size entry in the farfield plot window shows the step size to be 0.001 degrees, but it's grayed out and not adjustable. Same for the corresponding entry in the farfield plot properties dialogue box. If I now increase thetastep in the solver settings to 0.01 degrees and recompute the results, the farfield angular step size matches the 0.01 degrees I specified.
Another observation to note is that if I do a theta and phi sweep, where the thetastep = 0.001 and phi goes from 0 to 360 at 1 degree increments, a 1D constant phi slice is plotted with the specified thetastep of 0.001. Furthermore, I'm freely able to adjust the step size parameter in the farfield plot window (seems able to be varied even below 0.001).
So what ultimately sets the plotted farfield angular step size? In the CST help page titled 'Farfield Plot - General,' it does mention a minimum angular step size of 0.01 degrees for Cartesian plots, but that clearly doesn't reflect the results above.
