A filter comprises a dielectric resonator element and a cylindrical waveguide cavity having a corrugated tube structure that surrounds the dielectric resonator element such that an outer encircling wall surface of the dielectric resonator element is in contact with an inner sidewall of the corrugated tube structure. The corrugated tube structure includes one or more spaced-apart corrugations configured to provide a spring-like action to controllably expand and contract the corrugated tube structure so that the dielectric resonator element can be controllably inserted and clamped within the cylindrical waveguide cavity. The geometry of the spaced-apart corrugations can be selected to define a rotationally asymmetric corrugated tube structure configured to split a plurality of fundamental modes of electromagnetic waves within the filter.