Adaptive detection of digital suppressed-carrier A.M. signals
thesisposted on 2013-04-10, 12:54 authored by John D. Harvey
The thesis describes various detection processes which are suitable for use in a synchronous serial data-transmission system operating at a transmission rate of up to 20,000 bits per second over a slowly time-varying channel, The methods of operation of different detection processes are first described, with reference to binary and quaternary baseband signals, which includes the case when V,S,B,signals are transmitted over ·telephone circuits or H,F,radio links. The results of computer simulation tests are presented, comparing the tolerances of the detection processes to additive white Gaussian noise with the tolerances of conventional linear and non-linear equalisers. Several different time invariant channels are used in the tests. It is shown that two relatively simple detection processes can achieve a considerable improvement in tolerance to noise over both linear and non-linear equalisers of optimum design, Several of the most promising detection processes and a few new detection processes are then modified to use 4-point, 16-point and 32-point Q,A,M,signals. The methods of operation of the different detection processes are then described for the signal format being considered. The results of computer simulation tests are presented comparing their tolerances to additive white Gaussian noise with those · of the linear and non-linear equalisers of optimum design. It is shown that these detection processes operate most efficiently, in terms of tolerance to noise and in the number of sequential operations, if the transmitted signal contains the smallest number of possible signal levels. Finally, several simple methods of estimating the sampled impulse response of the channel are presented. One of these channel estimation techniques gives a very low error in the estimated response, while giving a good rate of adaptation to a time-varying channel.
- Mechanical, Electrical and Manufacturing Engineering