Small size third order coupled resonator band-pass filter using capacitor loaded slots

In this paper, we present a small size third order band pass coupled resonator filter. The filter consists of defected ground structure resonators (DGSs). The reduction of the size is achieved by loading the resonator with lumped capacitor. The insertion of lumped capacitor within resonator increases the effective capacitance and reduces the resonant frequency, so the dimensions of the filter will reduce and the performance of the filter will improve by enhancing the energy stored in the resonator. A third order band pass filter with center frequency of 2.4GHZ with single transmission zero at 2.61 GHz is designed and simulated. The filter has pass band from 2.3 to 2.52 GHz and wide stop band with rejection higher than 20dB up to more than 8GHZ, and insertion loss lower than 1 dB is achieved within pass band.