I've used the Johanson 2450AT07A0100 chip antenna on several boards recently (five that I can think of). These were all revs of two boards. Changing the ground plane geometry at all changes the antenna's matching. On some of the boards it started pretty far from matched.
So first I cal'ed out my cable and tried it with a zero-ohm resistor. (A cap at its SRF might be better, but I like a zero-ohm at 2.4GHz so I can look at 250MHz worth of spectrum. Zero-ohm is almost as good anyway.)
What!? Back at UF we'd say it was matched right from the git-go.
I turned off the cal, just in case I had made a mistake during cal'ing. Just as expected I got the same resonant frequency with a slightly better SWR at the band edges. This looks real.
Johanson's antenna cheated me out of billable engineering hours. 
We'll see if it's preformance, which has been good for its size on other boards, is similar.
