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The theory of decision-aided carrier tracking loops as developed by Lindsey and Simon is extended to include the effects of intersymbol interference. A major theoretical result is the solution of the Fokker-Planck equation for the probability density function (pdf) of the phase error for a first-order tracking loop. This function is used to average upper and lower bounds on the demodulator error rate so that an estimate of the overall system error rate may be obtained. The modulation technique analyzed is double-sideband-pulse-amplitude pulse-amplitude modulation. Curves are presented which display the threshold performance of the system error rate at low modulation index.