TCAS and slow moving/stationary targets?

Hi,

Quick google search on "TCAS filter slow" and similar didn't get me
what I wanted, so here goes... Do TCAS systems filter out targets
which have slow/no ground speed?

Reason for asking... I got into wave yesterday, and while climbing
through 11,000 MSL NW of Allentown PA had an American Airlines CRJ
pass nearby. I would guesstimate that he was about 500 above and a
half mile horizontal. It wasn't really close - I had him in sight
for over a minute and was edging away laterally to gain separation.
But, it was a little closer than the published TA/RA numbers I've seen
in manuals. I was essentially stationary for 20 minutes.

By comparison, later in the flight I watch an A300 make a sweeping
turn around me at 9,000 as I crossed a well-published STAR. I also
checked in with Allentown approach, and they painted me just fine on
their ground radar.

Curious...

P3