Analogue lossless ladder networks have long been used in communication
engineering because of their low element-value sensitivity and reduce
d network complexity. In low-frequency applications, in order to avoid
the use of bulky and often lossy inductors, active RC devices are the
preferable form of realization. However, component tolerances and par
ameter sensitivities associated with an active device usually border o
n or exceed the practical limits of realizability at high frequencies.
As a result, one has to resort to the passive LC design. Moreover, ac
tive filters with the best performance are usually those which are bas
ed on direct simulation of the resistively terminated LC ladder networ
ks.(1,2) For these reasons, the study of LC ladder circuits should sti
ll deserve some attention. An analogue ladder circuit which may be rep
resented as a general two-port network composed of a cascade of two-po
rt subnetworks, has traditionally been analysed by the ABCD-matrix (or
transmission matrix) approach.(3-6) The T-matrix (or wave-chain matri
x) approach,(4,5) while popular with some people, has tended to be avo
ided by others because the use of voltage-wave parameters can be mathe
matically more unwieldy. In this paper, both approaches to the derivat
ion of recursive algorithms for computing the transfer-function coeffi
cients of an analogue ladder circuit are described and compared.