Free you say? Ah, well now...

Although at work I'm spoiled by access to the like usual suspects, MWO, Axiem, Analyst, HFSS, Cadence Allegro etc there are a couple open-source GPL licensed tools that are worth a look:

Qucs - does Spice-like things, S-parameter stuff, harmonic balance and a touch of ADS about some aspects of the interface: http://qucs.github.io/ - if you're not wanting to call up Modelithics libraries or foundry PDKs it's not bad.

openEMS - EM solver based on FDTD, C++ solver back-end, Octave/Matlab front-end: http://openems.de/start/index.php - has some nice examples to get you going.

If you're going completely 'off-grid' with your EDA tools, then there's at least one effort to make PCB footprints for the open-source PCB tool KiCad from openEMS simulation structures.

I've used openEMS as yet-another-simulator-method to check something I had in HFSS. There is a bit of a learning curve but retired engineers have plenty of free time, right? ;)

R.