Low-loss wide-band microwave filter

A microwave filter comprising:

• a series of cavities interconnected in a cascade fashion between an input port and an output port of said filter, each of said cavities having a circular cylindrical shape;
• a plurality of irises, individual ones of said irises being located at interfaces between successive ones of said cavities, each iris having an aperture configuration for coupling two orthogonal electromagnetic waves between cavities;
• a first of said cavities being bounded at one end thereof by an end wall located at said input port and, at a second end thereof, by an iris located at the interface with the next cavity;
• a last one of said cavities being bounded at a second end thereof by an end wall located at said output port and, at a first end thereof, by an iris located at the interface with the preceding cavity;
• an input transition located at said input port and an output transition located at said output port, each of said transitions comprising a section of rectangular waveguide opening into an end wall of a cavity;
• and wherein
• each of said cavities has a length selected to sustain a TE.sub.113 mode of electromagnetic wave within the cavity, and
• in each cavity, the diameter of a cavity is smaller than the length thereof by a factor of 0.26 for increased bandwidth and decreased transmission loss.