Realization of practical lumped element all-pass networks for delay equalization of microwave filters

All-pass networks of the second order used for delay equalization are described in various textbooks, but are frequently quite unrealizable due to impractical circuit element values. This problem has now been solved using new network transformations having simple design equations. An example is given of an all-pass network used in the design of a delay-equalized filter having a passband from 1250 to 1500 MHz.