Thank you for your help!
I'm using two SteamVR Base Stations 2.0 and the interference occurs, as soon as I increase the exposure time of the IR-Tracking Cameras (Qualysis). A link cable between both Vive sensors didn't help. You already pointed out, that a modulation of the frequency wouldn't make a change, so would you confirm that there's no chance to let the IR-System and the Vive Sensors operate alternatingly? So that while the IR-Signal stops, the Vive sensors do their sweep?
@Synthesis @VibrantNebula