Electric Circuits and Networks

16.10 CONSTANT-k LOW-PASS FILTER

We commence our discussion on passive filters designed using symmetric reactive two-port networks from this section onwards. The constant-k low-pass filter is taken up first. It is also called the 'Prototype LPF Section'. The T-network and Π-network versions of prototype low-pass filter section are shown in Fig. 16.10-1.

The characteristic impedance and propagation constant of these two prototype sections can be determined by substituting Z₁ = jωL and Z₂ = 1/jωC in the corresponding expressions arrived at in Sect. 16.9.

Note that the product of Z₁ and Z₂ in both sections is a constant, independent of angular frequency. This is the reason behind the name ‘constant-k low-pass filter’. Let this constant be designated ...