An Introduction To The Effect Of Data Modulation On Time-Shared Noncoherent Code Tracking Loop Operation

The effect of data modulationoncodetracklng loop operation has been ignored inthebchnical literatwe upto now [1],[2]. This paper uses computer simulations to examine the effects of data modulation on the discriminator output of time sharednoncoherentdeby-lockedloopsThe~LshowhowdatamodulatiolFkrducedtransientsintherecehredslgnaldeaact from the performance of loops by forcing the discriminator IF filters Into a continuous transient state, even though dithering transients can be ignored. This may affect the performance of tau dither code tracking loops more severely than that of a double dither kop. Timeshared code tracking loop operation highlights the importance of proper selection of the code phase usedforspreadng data bits. OtheWse theexternal gain imbalance problem is merely replaced with an internal gain imbalance. Theetfect of data moddationcan be compensated for to a certain extent by choosing an m a t e COmMnationof spreading code~and~deby ,espec ia l ly i f thedu le l lng interval isequaltoosysymboltime.