A dielectric resonator having variable cross-section, preferably varying monotonically, and, most preferably, the resonator being in the shape of a truncated cone. Such shapes displace the H.sub.11 mode from the TE mode in the longitudinal direction of the cone. Truncating the cone to eliminate the portion of the cone where the H.sub.11 mode exists, virtually eliminates the H.sub.11 mode. A circuit comprising a plurality of these resonators may be arranged in an enclosure with each resonator longitudinally inverted relative to adjacent resonator(s) to provide a compact design with enhanced coupling and adjustability. A spiral coupling loop provides high magnetic flux in a small physical volume for coupling energy into or out of the circuit. Alternately, the resonator can coupled to a microstrip by placing the resonator upside-down near the microstrip, whereby the TE mode is immediately above the microstrip, providing enhanced coupling there between.