On the performance of extended tracking range delay-locked loops

Spread spectrum techniques have become very popular for various terrestrial and satellite based applications. Mobile communications based on code division multiple access (CDMA) and global positioning systems (GPS) are considered or already in operation. Good synchronization is crucial for the operation of spread spectrum systems. For direct sequence spread spectrum systems (DS-SS) the exact code phase timing estimate is essential. The timing is influenced by clock offsets and by Doppler effects especially in mobile satellite environments. In spread spectrum synchronization systems the delay-locked loop (DLL) is widely used for PN-code tracking. The detector error characteristic (S-curve) of the DLL has a major impact on its performance. Using a generalized detector characteristic for the DLL offers new design parameters. The design trade-off regarding the main performance criteria of tracking jitter and loop robustness against loss of lock is discussed