Design of small size coupled resonator band pass filters with capacitor loaded slot Using FDTD method

In this paper, we present a design of a small size second order band pass coupled resonator filters by using finite difference time domain method (FDTD). The filter consists of defected ground structure resonators (DGSs). The reduction of the size of the filter 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 be improved by enhancing the energy stored in the resonator. A Second order band pass filter with centre frequency of 2.4 GHz has been designed, fabricated and measured. The filter has a wide stop band with a rejection higher than 20 dB up to more than 10 GHz. Insertion loss of less than 0.7 dB is achieved within the pass band. Another Second order band pass filter with centre frequency of 3.1 GHz has been designed, fabricated, and measured. The filter has a wide stop band with a rejection higher than 20 dB up to more than 10 GHz. Insertion loss of less than 0.8 dB has been achieved within the pass band. Finally, it is found that, the experimental results agree well with the EM-simulation and FDTD simulation results.