Compact lowpass filter with ultra-wide stopband rejection using meandered-slot dumbbell resonator

A novel meandered-slot dumbbell resonator for designing a compact lowpass filter (LPF) with ultra-wide stopband rejection is presented. Compared with some other reported compact and wide stopband rejection LPFs, the proposed LPF using the novel meandered-slot dumbbell resonator has great improvement on size reduction and stopband width. Delivering a 3 dB cut-off frequency at 2.2 GHz, the designed LPF achieves an ultra-wide stopband of 12.8 times the cut-off frequency with overall 20 dB attenuation. The compact dimension of this filter is as small as 0.15 lambda g x 0.37 lambda g, where lambda g is the guide wavelength at the cutoff frequency. The proposed filter is fabricated and tested. Measured results show good agreement with simulated ones.