steng,
Just a shot-in-the-dark here, but the square waves you see are coming from the NC terminals of the motion? If that's the case, you may be seeing the "double pulse" (for pet immunity), to circumvent false alarms. Most motions I deal with give you the ability to shut that feature off. Generally, 360 degree PIR's don't have that feature. Hope that helps?

Good Luck,
C