S11_rho and S11_centre correspond to the smith chart area where you will sweep, you should try to set the smith chart centre for beginning with a large S11_rho.
Hi jayce3390
How do you get these(S11_rho=0.9 S11_center=polar(0.1,-180) )?if I change the LDMOS MRF281 to MRF282,How can I get the S11_rho and S11_center?
Thank.
these values are not linked to the transistor, this is for the load sweep. At the first load pull time you set values that make the sweep large and after several load pull simulations you will restrict a small area on the smith chart where you will find optimum load for your device.
These values are not fixed, they serve to locate the centre and the radius of the circle area (of smith chart) where the load will sweep.