The invention relates to the field of
microwave and
millimeter wave circuits, and discloses a
microstrip band-pass filter, which comprises a substrate, input ports and a
resonator group consisting ofresonators, wherein the
resonator group is arranged on the substrate in a mirror symmetry manner, the input ports are respectively connected to the resonators at the two ends of the
resonator group, and the input ports are connected to the resonators at the two ends of the resonator group. A folding resonator pair is arranged in the middle of the resonator group; the folding resonator pair comprises two folding resonators which are in mirror symmetry; the equivalent
electrical length of each resonator and each folding resonator is a quarter
wavelength, and the shape of each folding resonator can be changed according to actual conditions. According to the
microstrip band-pass filter provided by the invention, at least one group of folding quarter-
wavelength resonator pairs are embedded in the middle of a traditional interdigital
microstrip band-pass filter, so that a transmission zero point is generated at the low end of a filter
passband, and the out-of-
band rejection capability of thelow end of the
passband is further improved, and out-of-
band rejection of the low pass-band end and the high pass-band end is promoted to be relatively symmetrical.