The effect of data modulation on sigma delta and modifieddelay-locked loop operation

摘要

Computer simulations were used to examine the effects of datamodulation on the discriminator output of the sigma-delta and modifiednoncoherent delay-locked loops. The results show howdata-modulation-induced transients in the received signal detract fromthe performance of the tracking loops by forcing discriminator IF(intermediate frequency) filters into a continuous transient state.Furthermore, the loops are somewhat vulnerable to an internal gainimbalance resulting from an improper choice of the code phase used forspreading the data bits. A measurement approach is applied to both loopsto combat the effect of data modulation