Stability requirements of oscillators used for synchronization loops in communication systems

Abstract

Abstract. An imperfect clock timing recovery in receivers of modern communication systems degrades the performance of synchronization loops and, hence, the overall system reliability and data transmission quality. In this paper, the phase-locked loop (PLL) for the carrier recovery and the delay-locked loop (DLL) for the clock timing recovery of the pseudonoise (PN) code in directsequence spread-spectrum systems are analyzed regarding the impacts of imperfect oscillators (including phase noise and a frequency offset between transmitter and receiver) and channel noise on the mean exit time. The optimal design considerations to achieve a maximum mean exit time for second-order synchronization loops can be used to find the required oscillator stability, Le., the maximum tolerable frequency offset and oscillator phase noise.