A microwave cavity filter is configured for operation in the dual TE22N mode to realize a very high Q factor at very high frequency ranges. The microwave filter is formed from using one or more cylindrical cavities in which two orthogonal field polarizations of the TE22N mode are excited and coupled together by means of a coupling element. Different combinations of inter-cavity irises provide for both direct and cross-coupling of aligned field polarizations in adjacent cavities, as required, to realize complex filter functions. The irises may be formed in either a side or end wall of the cavities for both collinear and planar mount configuration. Negative mode coupling also allows for transmission zeros to be realized on either side of the filter passband.