Second‐order reflective‐type, absorptive notch filter with lumped elements

Abstract

ABSTRACTIn this article, a design methodology and equations necessary for a second‐order absorptive, reflective‐type, transmission zero notch filter are introduced, derived, and described in detail. Initially, a single (first order), absorptive, reflective‐type transmission zero notch filter is described. Based on this, improvements to the first‐order reflective‐type notch filter are discussed and a novel circuit that achieves a second‐order absorptive, reflective‐type, transmission zero notch response is proposed. The necessary conditions for the achievement of the second‐order absorptive, reflective‐type, transmission zero from the proposed circuit are derived. As an experimental verification, first‐ and second‐order absorptive, reflective‐type, transmission zero circuits are fabricated and their performance measured. It is shown that the first‐order notch circuit introduces a zero into the response of a main filter with a depth of over 12 dB in the frequency range 2.19–2.27 GHz, while the second‐order notch circuit introduces a transmission zero with a depth of over 20 dB GHz, in the same frequency range as its first‐order counterpart. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2542–2545, 2014