Design and optimization of the cascaded band-stop filters using vertically coupled open-loop ring resonators

Abstract

In this paper, we proposed several compact bandstop filters using C-open-loop ring topology. In the first step a minimize bandstop using single C-ring resonator is simulated optimized and realized. The triple ring BPF consists of two cascaded C-ring resonators, which are placed on the RO4003 substrate, while the third ring is etched as DGS resonator on the ground plane. The both top resonators are connected with input and output through microstrip feed lines. The both filters are simulated, optimized and partially realized using MWR simulator and Anritsu E5072A vector network analyzer VNA. In order to reduce the size and to improve the filter characteristics, novel compact filter topologies are designed basing on the previous structures. The proposed multi-band band stop filters consist of several open-loop ring resonators placed vertically behind each other. Using this idea, the filter topologies with design flexibility, close size and excellent results are reached. The novel compact multi-band band stop filters produce several stopband along a frequency range from DC to 9 GHz, in which each separate band exhibits an acceptable and useful bandwidth. Each stopband has regenerated two reflexion zeros, what leads to a good sharpness factors in the transition domains. Good agreement between the experimental results, full-wave simulation has been achieved. This new filter idea can be very attractive for the nowadays multilayer and compact radio frequency integrated circuit design.