A filter, comprising a dielectric resonator and a substrate, wherein the dielectric resonator comprises a body and an encirclement wall, wherein the body is a dielectric material whose dielectric constant is greater than 1, the encirclement wall is saliently disposed on a surface of the body, the encirclement wall encircles the surface of the body to form a cavity area, the encirclement wall isolates the cavity area from external space of the encirclement wall, and the encirclement wall comprises a top surface, an inner side surface, and an outer side surface, wherein the inner side surface and the outer side surface are disposed opposite to each other and both connected between the top surface and the body, the top surface is located on a surface, away from the body, of the encirclement wall, the inner side surface is a surface, which faces the cavity area, of the encirclement wall, the outer side surface faces the external space of the encirclement wall, the top surface is covered with a metal layer, and the outer side surface is covered with a metal layer, wherein the outer side surface of the encirclement wall and a surface, which is connected to the outer side surface, of the body are coplanar, wherein the body is further provided with a resonant hole on a bottom wall of the cavity area, wherein the resonant hole is in communication with the cavity area, wherein the surface of the body comprises a dielectric exposed area of a ring shape and other surfaces of the body except the dielectric exposed area are all covered with a metal layer; the dielectric exposed area is disposed on the bottom wall of the cavity area surrounding the resonant hole and adjacent to the resonant hole, characterized in that the top surface is a non-planar structure and is connected to a matching structure disposed on the substrate, wherein the matching structure matches the shape of the non-planar structure of the top surface. wherein the body is a dielectric material whose dielectric constant is greater than 1, the encirclement wall is saliently disposed on a surface of the body, the encirclement wall encircles the surface of the body to form a cavity area, the encirclement wall isolates the cavity area from external space of the encirclement wall, and the encirclement wall comprises a top surface, an inner side surface, and an outer side surface, wherein the inner side surface and the outer side surface are disposed opposite to each other and both connected between the top surface and the body, the top surface is located on a surface, away from the body, of the encirclement wall, the inner side surface is a surface, which faces the cavity area, of the encirclement wall, the outer side surface faces the external space of the encirclement wall, the top surface is covered with a metal layer, and the outer side surface is covered with a metal layer, wherein the outer side surface of the encirclement wall and a surface, which is connected to the outer side surface, of the body are coplanar, wherein the body is further provided with a resonant hole on a bottom wall of the cavity area, wherein the resonant hole is in communication with the cavity area, wherein the surface of the body comprises a dielectric exposed area of a ring shape and other surfaces of the body except the dielectric exposed area are all covered with a metal layer; the dielectric exposed area is disposed on the bottom wall of the cavity area surrounding the resonant hole and adjacent to the resonant hole, characterized in that the top surface is a non-planar structure and is connected to a matching structure disposed on the substrate, wherein the matching structure matches the shape of the non-planar structure of the top surface.