By means of a signal representation in a signal space spanned by a few time-limited exponential basis-functions, and data-aided maximum-likelihood techniques, novel methods for the joint and nonjoint estimation of carrier-phase and symbol-timing for general coherent CPM (continuous phase modulation) receivers are proposed. The estimators are quite simple, especially in obtaining symbol-timing. Simulation results show that synchronizers using such estimation structures exhibit an excellent steady-state behavior. Whereas a fast acquisition of the carrier-phase is always possible, joint synchronizer loops tend to hang up for CPM-schemes with partial response signaling. Several ways to overcome the hang-up problem are discussed.
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