Training on Data for a Two-Phase DPSK Modem
Original Publication Date: 1988-Jul-01
Included in the Prior Art Database: 2005-Feb-15
Training on data is the way by which a modem recovers from line drops, or initializes its receiver after power-on. In all these cases, the modem has to retrieve the coefficients of the adaptive equalizer which compensates for the amplitude and phase distortion introduced by the telephone channel. With a two-phase DPSK modem, the two-phase signal contains no quadrature component. The effect of amplitude and delay distorsion is to introduce such a component. This undesirable component may be amplified by the adaptive equalizer which, at the initialization, may converge into a stable state, exhibiting, for example, a four-phase received signal instead of the two expected phases.