Dual-mode bi-pass filter based on capacitance loading square resonant rings

The invention discloses a dual-mode bi-pass filter based on capacitance loading square resonant rings, mainly solving the problems of poor out of band rejection and uncontrollable coupling between cavities of traditional bi-pass filters. The filter comprises a micro-strip dielectric substrate (11), a metal earth plate (12), two same capacitance loading square resonant rings (13), a perturbation metal sheet (16) and a pair of input/output feeder lines (17). A symmetrical cascade mode is adopted between the capacitance loading square resonant rings (13), each capacitance loading square resonant ring comprises one square metal ring (14) and four loading metal sheets, and a pair of input/output feeder lines (17) adopt a symmetrical distribution mode, are arranged mutually parallel above the micro-strip dielectric substrate (11), and penetrate into the insides of the square resonant rings (13) for feeding. The dual-mode bi-pass filter based on capacitance loading square resonant rings can improve the out of band transmission characteristic, control the strength of coupling between cavities, realize highly symmetrical bi-pass frequency response, and be used in a wireless communication system.