Design of Multilayer Type 2-Pole Band Pass Filter with Additional Poles using Closed Loop Resonator

This paper presents the design method of BPF using closed loop resonator, analyzed on the basis of TEM mode [1] and broadside coupled lines. The closed loop resonator has been analyzed with manly different methods; magnetic wall method, numerical solution, field solution and so on. However, these method take large amounts of calculations due to using field theories and it is difficult to build application circuits including other elements[2]. but the analysis method given in this paper is more simple and faster and the analysis of other elements in resonator is possible. The BPF using closed loop resonator is possible to put the number of additional poles equal to the number of closed loop resonator by assigning resonance frequency of each closed loop resonator differently. By taking advantage of the presented design method, the BPF containing good attenuation slope and wide rejection band characteristics can be realized by proper assignment of poles. In this paper, the 2-pole, 3-pole BPFs have been designed with the presented design method and the 2-pole BPF has been realized on 1.72 ~ 1.75 GHz frequency band.