The disclosure relates to a filter including dielectric substrate, ground and microstrip line layers, and signal and ground vias. The ground layer is formed on the dielectric substrate and has a ground plane and signal terminal contacts. The microstrip line layer is located on the dielectric substrate and includes microstrip resonators, common electrode and input and output terminal contacts. The input and output terminal contacts are connected to the microstrip resonators. The signal and ground vias extend among the ground layer, the dielectric substrate, and the microstrip line layer. The signal terminal contacts are connected to the input and output terminal contacts through the signal vias. The ground plane is connected to the common electrode through the ground vias. The filter further includes at least one capacitive coupling unit capacitive-coupled with two of the microstrip resonators adjacent to each other.