The invention discloses a double-
frequency band-pass filter based on electromagnetic mixed
coupling. The double-
frequency band-pass filter is structurally characterized in that the lower surface of a medium substrate (7) is completely covered with a
metal layer, the portion, on the upper surface, of the
metal layer comprises a first input / output
feeder line (1), a second input / output
feeder line (2), a first double-frequency
resonator (3), a second double-frequency
resonator (4), an
interdigital capacitor (5) and a
short circuit branch knot (6), and metalized through holes (34) in the medium substrate (7) connect the portion, on the upper surface, of the
metal layer with the portion, on the lower surface, of the metal layer. The first double-frequency
resonator (3) and the second double-frequency resonator (4) generate electrical
coupling through the
interdigital capacitor (5) and generate magnetic
coupling through the
short circuit branch knot (6). The mixed coupling has the advantages that the electrical coupling can independently adjust
first pass-band bandwidth, and the magnetic coupling can independently adjust second pass-band bandwidth. The filter is compact in structure, easy to integrate, short in process cycle, and capable of being used for a double-frequency
transceiver for
frequency selection.