Carrier Recovery Systems for Arbitrarily Mapped APK Signals

This paper introduces new carrier recovery techniques for general amplitude-phase keying (APK) modulation signals. The APK´s include not only normal QAM but also arbitrarily mapped APK´s, including an unsymmetrical APK. Difficulty in phase error detection due to signal mapping complexity, undesirable stable-lock point existence, and the contradiction between a fast acquisition and an accurate steady state performance can be overcome. For that purpose, an acquisition mode and a steady-state mode are used. Furthermore, read-only memories (ROM) are used for recognizing various system states. Random sampling controlled PLL noise performance and acquisition mode carrier recovery circuit pull-in performance with hysteresis property was obtained.