Hi,

I'm trying to learn about software defined radio, obviously, and writing
the necessary code to do so - I like to prove concepts to myself by
simulating them in Matlab, or Python. I run into trouble when it comes
to control loops like PLLs and lately Poly Phase Filter Blocks - which I
still don't really understand, because of the feedback and how to handle
error and stability in code. I'd like to ultimately simulate
PLLs, PFB, and Costa's loop in the time domain, with a stream of input
samples going into the recovery block. By the way, I've seen some PLL
tutorials on the internet, but they cheat by simulating it in the phase
domain, that's not good enough, I want time domain!

But right now, I'd like to learn about Poly Phase Filter Block Clock
Recovery and perform a miniature simulation to learn it. Can anybody
point me to some references and maybe some advice. I just pulled up the
pfb_clock_sync code from the source and oh my god, I don't think I can
hang. Any advice on how to start learning from the code too would be
helpful.

I have a B.S. in Electrical Engineering, and know a B.S. worth amount of
RF, mainly Smith charts and matching, which won't help me here!