Waveguide branching filter having compensating cavities

Claim 1

IN COMBINATION, A WAVEGUIDE FOR CONDUCTING A PLURALITY OF BANDS OF FREQUENCIES, SAID WAVEGUIDE HAVING FIRST AND SECOND WALLS OPPOSITE ONE ANOTHER WITH A FIRST COUPLING APERTURE IN THE FIRST WALL; A PASS-BAND BRANCHING FILTER LOCATED EXTERIOR TO SAID FIRST WALL FOR SELECTING ONE OF SAID BANDS OF FREQUENCIES AND FOR PASSING THE SELECTED BAND OF FREQUENCIES THEREFORM, SAID FIRST APERTURE PROVIDING COMMUNICATION BETWEEN SAID WAVEGUIDE AND SAID FILTER; A SECOND APERTURE IN ONE OF SAID WALLS OF SAID WAVEGUIDE; MEANS DEFINING A WAVEGUIDE CAVITY LOCATED EXTERIOR TO THE LAST SAID WALL FOR MATCHING SAID PASS-BAND FILTER TO SAID WAVEGUIDE, SAID SECOND APERTURE PROVIDING COMMUNICATION BETWEEN SAID WAVEGUIDE AND SAID CAVITY; THE AXES OF SAID FILTER AND SAID CAVITY WHICH EXTEND THRUGH SAID APERTURES BEING DISPLACED AT A DISTANCE OF AN ODD NUMBER OF QUARTER GUIDE WAVE LENGTHS WITH SAID DISTANCE MEASURED ALONG THE WAVEGUIDE AXIS; SAID CAVITY BEING SO TUNED THAT THE COMBINATION OF THE FILTER AND CAVITY PROVIDES A MATCH FOR WAVES WHICH ARE REJECTED BY THE FILTER AND ALLOWS ALL OF SAID PLURALITY OF BANDS OF FREQUENCIES OTHER THAN SAID SELECTED BAND OF FREQUENCIES TO BE CONDUCTED VIA SAID WAVEGUIDE WITH MINIMUM ATTENUATION.