Differential carrier loop estimation for digital vestigial side band modulation

In this paper we address the problem of phase recovery for a digital VSB modulation. Two criteria, a Constant Modulus and MSE, which exploit the properties of VSB signaling in the presence of noise are proposed and analyzed. The extrema of the objective functions and their domains of attraction are derived. Under mild conditions on the statistics of the input sequence, it is shown that the derivative of these functions can be used as a new phase detector in a Phase Locked Loop (PLL) implementation. An effective semi-blind solution which consists of a combination of the MSE and CM phase detectors is introduced and analyzed.