Performance Analysis of a Second Order Delay-lock Loop with Application to a Cdma System with Multipath Propagation

AB!3TRACT CDMA systems require synchronization between the received sequence and the locally generated sequence. This is done by means of a Delay-Lock Loop (DLL). The differential equation of an incoherent secondorder DLL has been programmed. The Mean Time to Lose Lock (MTLL) of the DLL is a very important design parameter. We have obtained this parameter by computer simulation and we are able to plot the MTLL as a function of the signal to noise ratio in the data bandwidth. In a narrow-band system, our simulation shows that the effect of the fast Rayleigh fading is a remarkable performance degradation even with high mean signal to noise ratio. Assuming a wide-band system, so that the receiver has enough bandwidth to resolve the different propagation paths, we propose a modified DLL scheme. The MTLL of the proposed DLL is evaluated using a dynamic simulation of the multipath channel. The results show an improvement with respect to the conventional DLL.