A design method of closed ioop resonator filter to reduce size and adjust pole

This paper presents a new design method of closed loop resonator filter by using multiple sub-networks that connects transmission line to capacitor in parallel. This method gives an advantage to reduce the size of closed loop resonator without changing permittivity of printed circuit board (PCB) or resonance characteristics. The value of parallel capacitor is used as a design factor to reduce the size of closed loop resonator. Also, this paper introduces the method of positioning attenuation pole at desired frequency by adjusting impedance ratio between sub-networks. This paper presents the implementation of 2 pole closed loop resonator filter that using the same impedance, 50 ohms, between sub-networks. The filter has 70 % reduction in size by adding parallel Cp=1 pF to the designed close loop filter. Also, the 2 pole closed loop resonator filter was designed by the use of 50 ohms and 54.6 ohms that is impedance between sub-networks, respectively in order to put the attenuation pole at 1.8 GHz and 2.5 GHz.