Resistance in parallel with inductors in a series leg of the low-pass
filter facilitates changing input and output resistance of the filter with little
or no change in the reactance of the inductors. Furthermore, the reactance of the
capacitors in the shunt legs of the filter will be substantially unaffected. This
assists the designer in matching the impedance of the filter in the pass-band while
still providing substantial impedance mismatching in the stop-band without substantially
affecting the characteristics of the filter. Facilitating impedance matching in
the pass-band and impedance mismatching in the stop-band is accomplished without
the need for more complex active components. POTS splitters making use of such
filters can facilitate impedance matching of line and load termination in a telecommunications
system in response to signals within the frequencies of typical analog telephony
service while providing impedance mismatching in response to signals within the
frequencies of typical xDSL service.
