Back in 2011, I used something called FEKO Lite to model a PCB bowtie antenna with a tapered matching feedline that had to function both as an antenna and a rudder for an autonomous submarine. Periodically the sub would stick its rudder in the air to get a GPS fix and exchange satellite data. I sure wish I had a VNA for that project! Now I have the nanoVNA but FEKO may be beyond my budget.
Douglas Butler