Hi Kai,

Okay, I'm really hurting my brain trying to recall this stuff. Still, it's good to get some exercise sometimes.



You no doubt recall that maximum power transfer happens when a load (in this case free space) and source (your circuit) have equal impedances. Antennae are the impedance matching devices which, to the extent possible, achieve this result. Of course, I realize you already know this, but I include it nonetheless for completeness.

As for compensating elements (e.g. stubs), they create fortuitous reflections. You'll recall that anytime a signal propogates down a line, any of the signal that does not transfer is reflected back at the source. Compensating components produce extra reflections which interfere with (add destructively) to that reflected signal, canceling it out.

Now think about the effect of those uncancelled reflections on the source. In a worst case scenario, reflected signals can add constructively with the principle signal and fry the transmitter. Even if they don't, they can still interfere, adding destructively, with the principle signal cancelling it out. By preemptively cancelling out the reflections, you "clear the way," so to speak, for the principle signal.

And now, by once again working in the phrase "Smith chart" (just the name, with no elaboration about how to use them), I will have fully exhausted the remnants of the knowledge I once held on this subject.

Joe