A novel slow-wave ladder dual-mode bandpass filter

A novel type of slow-wave dual-mode bandpass filter with periodic ladder microstrip lines is presented. This filter has better stopband rejection and wider stopband, in comparison with the conventional square ring dual-mode bandpass filter. It is designed at the operating frequency of 6 GHz with the bandwidth of 500 MHz. Size reduction has been achieved by means of the slow-wave structure. A dual-mode bandpass filter using this structure was fabricated and measured, and the measured results agree well with those of simulation.