Tables for pseudo-elliptical and phase equalized microwave filters - II

Odd-degree microwave filters with symmetrical structures and auxiliary couplings between nonadjacent resonators are discussed. These couplings give transmission zeros both at real and complex frequencies. It is shown that if frequency-independent cross-couplings are properly introduced in the filter low-pass prototype, the resulting transfer function exhibits an odd number of finite-frequency transmission zeros, which are not symmetrically allocated with respect to the zero frequency. The low-pass filter therefore cannot be physically realized, but can still be utilized as a low-pass prototype of the microwave filter. It is shown that an equiripple transfer function can be achieved with an odd-degree network, if the resonators are tuned at different frequencies with respect to the filter midband frequency. The element values of the 52 odd-degree low-pass prototype networks are collected in six tables, and the amplitude and group delay response behavior for some of them are shown.