Pi networks use two outer parallel components and a middle series component.
For comparison purposes, a pi filter is effectively two L filters back-to-back but simplifies the two series components in the middle to a single entity.
After finding the constraints of the pi network, designers need to calculate the equivalent impedance to match the source.
Building filter networks is necessary for signal conditioning that separates desired signal bandwidths from noise that can harm signal quality or damage components at high enough frequencies. Filter networks also have a secondary but equally valuable role in aiding power delivery: impedance matching the source to maximize power transferability. In purely resistive networks, circuit designers can accomplish this with only resistors, but more sophisticated applications require reactive elements (i.e., capacitors and inductors) to achieve this setting. Pi network impedance matching is one implementation designers can use that affords considerable flexibility over the more rudimentary L networks.