الفهرس 
SummaryOnly 14 pages are availabe for public view
 |  | from | 130 |  |  |
| | | from | 130 | | |
Abstract
The presen-c thesis gives a proposed method for synthesising an all pole transfer function approximating the constant group delay response with a wide bandwidth and a reasonable amplitude characteristic with poles freely to move \dthout any constraint on an ellipse in the com~lex frequency plane (S-plane). The same method can be used to compensate for the dispersive delay encountered in wave propagation via the ionosphere~
The minimization procedure is carried out by optimally locating the poles in the S-planc~ An analytical e::tpression for the delay function is obtained from the pole locations. The class of functions is g~nerated by varying the major a:d..s A, the minor a:dsB, and the angles of the pole locations ~k’ these parameters are varied so as to minimize the square of’the difference between the resulting group delay and the ideal constant delay. The minimization procedure is carried out using Davidon, Fletcher-Powell conjugate gradient method.
In order to make the cOLrputational time a minimum possible we selected the case in which the ideal constant delay is normalized to unity. TIe also considered the case where the mean delay 1’m is variable, and the value of this mean delay is also optimized, this case takes a relatively large amount of compu-ca-i;ional time.
The present ”thesis consists of two main parts. Part one deals with a studies of the effect ~f ·the ionosphBre on the delay distortion of the propagated waves, and
a detailed studies of prev:ious author’ a work in connection with the needed mathematics of the approximation methods of the del~ functions. This part contains three chapters. Chapter one is concerned with the effect of ionosphere on ~ve propaga-Gion~ Chapter two is concerned vIi th a general studies of oche optimization techniques. Chaptt.ir thr0e is concerned with the approximation methods (f °the group delay
characteris-i;ic. ,
Part two contains our minimiza-1;ion technique used to obtain an all-pole :function approima-Ging the idealoonstan:t
group del~ with a wide bandwidth wld a reasonable amplitude characteristic. This part contains -GWO chapters. Chapter four is concerned with the theore-Gical analysis of -t;he
proposad m6”l;hod. In chapter five numerical computation and results associated with tables and figures are reported to facilitate the comparison between the present method and the previous other’s li1cthods. The computer programs are included in the appendix, and a list”ng of the refrences used is
given at the end of the thesis.