You might start at the ARRL's Antennas page [0] and consider the ARRL Antenna Book [1]. Most of that is aimed at amateur radio in particular but the theory is the same.

There's tons of free and/or open-source software (of varying quality) for modeling antennas and such as well.

[0]: http://www.arrl.org/antennas

[1]: https://www.arrl.org/shop/ARRL-Antenna-Book-23rd-Softcover-E...

Take a microwave design class. This would be a second or third course after electrostatic, electrodynamics, then something like microwave theory. At my school we had to petition for the course as a special section. It was great, we built cavity resonators, and final project was an antenna design. All the way from theory, then using modern fea antenna software, and then building it and testing performance. If you have any interest take it. I was not going to but the professor said: "Phil, what's the lower end of the microwave spectrum?", I said "1 GHz", he then asked "How fast is your computer?", I replied "2.8 GHz", He said "I'll see you next semester then?". these days having an understanding of microwave theory will help you no matter your specialization.

1. Find a university course on RF, look up the course textbooks.

In my university we had several courses on "analog electronics" which covered topics like free space path loss and RF concepts (e.g. bandpass filters).

2. Use Google or another search engine (DDG) to find the book in PDF or EPUB version.

3. Enjoy reading the book without forking over hundreds of dollars to a greedy publisher.

balanis