The thesis investigates techniques for the adjustment of pre-detection filters employed
by high speed serial digital modems operating over both time-invariant and timevarying
Various techniques for the adjustment of these pre-detection filters have been
considered in previous investigations. The more recent ones enable such filters to be
adjusted in a simple and accurate way using an estimate of the sampled impulse
response of the linear baseband channel, together with a prior knowledge of the roots
that lie outside the unit circle in the z-plane. A root finding algorithm is an integral
part of these techniques.
Algorithms for the location of the required roots are presented here, and compared
with previous ones in an attempt to optimise the operational speed and accuracy of the
adjustment of these filters.
Alternative algorithm have also been considered, that operate directly on the sampled
impulse response of the linear baseband channel, without the need for locating any
roots, thus enabling a faster and more accurate adjustment of the pre-detection filter.
The relative performances of all the algorithms are then evaluated over different
telephone channels, at transmission rates of 9600 and 19200 bits/sec. The algorithms
are also tested over fading channels (such as HF radio links), so as to select the one
which offers the best compromise between performance and complexity for hardware
Finally, various aspects of the hardware implementation of the selected algorithm have
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.