Synthesis of Extracted Pole Filters With Transmission Zeros in Both Stopbands and Nonresonant Nodes of the Same Nature

Abstract

Extracted pole filters alternating transmission zeros (TZs) above and below the passband are intrinsically related to the use of nonresonant nodes (NRNs) of different nature (inductive and capacitive). This work demonstrates that it is possible to synthesize an extracted pole filter showing TZs on both sides of the passband but implementing all NRNs of the same reactive nature, overcoming the limitations imposed by some technologies. The proposed feature is achieved by special consideration of the input reflection phase of the generalized Chebyshev filter function, affecting input and output resonators and placing at most two zeros at the opposite band. A third-order all-capacitive prototype filter has been synthesized and fabricated to validate the proposed statement. The concept allows us to achieve all-capacitive or all-inductive filters.