A lowpass filter filters out the high frequencies. This filter is designed with the impulse invariant methode. Only a simple first ordersection is designed. Four of those sections can be cascaded (N=number of cascades). The left outputchannel will contain the lowpass filtered signal. The right outputchannel is the original minus the lowpass filtered signal. The Following figure illustrates a calculated frequency transfer function (cutoff = 1 kHz).

Simulated in Matlab V5.3:
-- ChristiaanGelauff - 30 Jan 2006