Novel microstrip bandpass filter with multiple transmission zeros and wide stopband

This paper proposes a fourth-order microstrip bandpass filter with better frequency selectivity and harmonic suppression, which composes of two half wavelength resonators and a dual-mode resonator. A new coupling topology is realized by embedding a dual-mode resonator between two half wavelength resonators. Two anti-coupled structures are added at the tapped input and output to achieve a wide stopband which is up to 4.9 times of the fundamental frequency. The filter sample is fabricated using single-layered printed circuit board (PCB) technology, and the measured S-parameters agree well with the simulated ones.