Transmission zero realization in E-plane filters by means of I/O resonator tapping

A new topology for E-plane filters compatible with the traditional low-cost single metal insert in a split-block housing is proposed. Improved out-of-band rejection is achieved by virtue of the transmission zeros. The overall length of the input and output resonators is reduced by ~45%, resulting in saving the length of a resonator. A synthesis procedure is outlined. A 4pole filter is demonstrated that implements 2 out-of-band TZs. The technique is well suited to be combined with an extracted pole technique further improving the out-of-band characteristics of the filters. The same 4pole filter is then adopted to accommodate for extra 4 TZs by means of extraction. The simulated loss of the two 4 pole filter presented is 0.22 dB and 0.24 dB, respectively.