  The total impedance of a ladder-shape network consisting of inductors and
capacitors does not converge to a certain value when the steps of the network
increased. In this paper, we analyze this effect in frequency domain. We find
that in some band the impedance converge to a limit value while in other band
it doesn't. Based on this property in frequency, we propose a filter that
exhibits excellent performance both in amplitude and phase response. As a
validation of our result, the simulation of this filter was carried out on the
EDA software Multisim with respect to a practical circuit.
