Robust H-infinity control of phase-locked loops with polytopic type uncertainties

A robust H-proportional to control method is applied in the design of loop filters for phase-locked loop (PLL) carrier phase tracking. The proposed me thod successfully copes with large S-curve slope uncertainty and with a sig nificant decision delay in the closed loop that may stem from the decoder a nd:or the equalizer there. The design problem is transformed into a state-f eedback control problem where phase and gain margins should be guaranteed i n spite of the uncertainty. Of all the loop filters that achieve the requir ed margins the one that minimizes an upper bound on the effect of the phase and the measurement noise signals is derived. Copyright (C) 2001 John Wile y & Sons, Ltd.