DGS resonator with two transmission zeros and its application to lowpass filter design

A novel defected ground structure (DGS) with two transmission zeros and a sharp cutoff frequency response is proposed. Both the two transmission zeros generated by the new DGS are lower than the one generated by a dumbbell-shaped DGS etched the same square area dimensions. On the basis of the proposed DGS, a lowpass filter has been designed, fabricated and measured. The filter with 3 dB cutoff frequency at 4 GHz exhibits a very sharp cutoff frequency response and an ultra wide stopband with rejection better than 25 dB from 4.2 to 23 GHz. Measured results show good agreement with simulated ones.