Single and Multiple-Band Bandpass Filters Using Bandstop Resonator Sections

In this paper, the design methodology and implementation of single-band and multiple-band elliptic function bandpass filters (BPFs) are presented, based on the concept of bandstop resonator (BSR) sections. One or more single-mode and multiple-mode BSRs can be dangled from a non-resonant node. Each BSR can generate one reflection zeroes (RZ) and one transmission zeroes (TZ). Multiple BSR sections are used to flexibly and independently control the location and bandwidth of the stop bands and therefore the same of the passbands. The method to design single- and multiple-band elliptic function BPFs has been detailed using a number of examples based on waveguide technology. For proof of concept, a 6th-order single-band BPF with six BSR = 2 sections and a 3^rd-order dual-band BPF using three BSR = 3 sections are designed and fabricated monolithically using a selective-laser-melting (SLM) 3-D printing technique. Excellent agreement between simulated and measured results verifies the proposed design methodology and its versatility as well as the additive-manufacture approach.