A Novel Technique for Controlling Transition Steepness and Rejection Bandwidth in DGS Filters

In this paper, we present a novel technique for controlling the passband to stopband transition steepness and the rejection bandwidth of DGS filters. The technique is based on controlling at least two dimensions of the DGS elements in order to adjust its equivalent inductance and capacitance. We showed that when maximizing the equivalent inductance, the rejection bandwidth of the DGS element increases and thus the filter will have a wide reject band at the expense of a less sharp transition from pass-band to stop band. When maximizing its capacitance, the cutoff frequency and resonance frequency of the DGS elements become near to each other, resulting in a steep transition from the passband to the rejection band at the expense of a narrower reject band. Two fifth order low pass filters were designed using the proposed technique and their simulation results confirmed the validity of the technique. One of them was fabricated and measured and showed good agreement with the simulation results.