Compact microstrip lowpass filter with ultra-wide stopband

A compact microstrip lowpass filter with an ultra-wide stopband is proposed. To achieve wide stopband suppression and compact size, both symmetrically loaded resonant patches and meander transmission line are adopted. A demonstration filter with 3 dB cutoff frequency at 1.3 GHz has been designed, fabricated and measured. The proposed filter also exhibits a very wide stopband of 152%, and is able to suppress the eleventh-harmonic response together with a small size of 0.12λg × 0.071λg, where λg is the guided wavelength at 1.3 GHz.