h ( t ) = Vpp ??? tanh ( ( 3.4154 t ) ( ?? ??? K ??? T b ) ) - Vpp ??? tanh ( 3.4514 ( t - T b ) ( ?? ??? K ??? T b ) ) ( 1 ) in which Vpp is the amplitude of the signal, K is a parameter that determines the width of the leading edge and Tb is a bit time interval.