A serial search process achieved by reference code clock frequency offset suffers from a degraded autocorrelation function between the two codes because of the differing chip rates. In this thesis a computer simulation is used to investigate the code decorrelation, and the results are employed to obtain the mean acquisition time for the serial search process. The analysis is extended to include a CCD. type of matched filter following the integrate and dump detector, and to investigate the improvements in acquisition time that may be achieved over the simple serial search process if a search-lock strategy is employed. The effects of jitter and phase offset upon the error probability of the recovered data are investigated both theoretically and by measurement for the particular case of code modulation by sequence inversion keying. A tracking loop is presented that has been shown to maintain reference code phase offset to within ~ 0.01 chips under conditions where the noise on the communications link has made the recovered data unusable for most purposes. Finally, an application of spread spectrum techniques to small local area networks is presented, and a discussion of the effects of the crosscorrelation noise from the other user spreading codes upon the tracking loop's discriminator characteristic is given.
|Date of Award||1985|