Ultra-wide stopband low-pass filter with bowtie defected ground structure

A bowtie defected ground structure (DGS) unit is proposed in this paper. For using the same length and width, the proposed DGS unit can provide wider stopband than the conventional square and dumbbell DGS. A 3.8GHz microstrip low-pass filter with six non-uniform cascaded bowtie DGS units is designed and compared with conventional DGS low-pass filters. The proposed low-pass filter is fabricated and measured. Measured results show that the low-pass filter achieves an ultra-wide stopband with overall 30dB attenuation up-to 20GHz, and the insert loss is less than 1.2dB over the passband.