Balun filter based on stub-loaded resonator

The invention relates to the technical field of filters, and discloses a Balun filter based on branch knot loading resonators. Comprising a first coupling micro-strip line, a second coupling micro-strip line, a third coupling micro-strip line, a fourth coupling micro-strip line, a fifth coupling micro-strip line, a first micro-strip resonator, a second micro-strip resonator, a first open-circuit branch knot, a second open-circuit branch knot, a first capacitor sheet and a grounding plate. The fourth coupling microstrip line is coupled with the first microstrip resonator in parallel, and the first open-circuit branch knot is connected with the fourth coupling microstrip line; the fifth coupling microstrip line is coupled with the second microstrip resonator in parallel, and the second open-circuit branch knot is connected with the fifth coupling microstrip line; the grounding plate is provided with a defected ground structure. The microstrip resonator and the circuit generate multi-mode resonance, and the open