Tunable waveguide bandpass filter

A waveguide filter, comprising:

• waveguide means including an input port adapted to be coupled to a source of signals to be filtered and also including an output port adapted to be coupled to utilization means, said waveguide means including conductive first and second broad walls spaced apart by conductive first and second narrow walls, thereby defining a rectangular waveguide having cross-sectional dimensions;
• a flat elongated rectangular conductive septum including first and second long edges, first and second short edges, and mutually parallel broad sides, said septum being oriented within said rectangular waveguide means with said broad sides parallel to and substantially equidistant from said first and second narrow walls, and with said first and second long edges in electrical contact with said first and second broad walls, respectively, with said first short edge facing in the direction of said first port for splitting said signals to be filtered into first and second portions propagating in the regions between said first narrow wall and said septum, and second narrow wall and said septum, respectively, said septum further defining at least one aperture symmetrically located between said first and second broad walls, whereby said first and second portions of said signals propagate past said aperture and recombine in the region between said second short edge of said septum and said output port to form an output signal filtered in a frequency range;
• and
• dielectric tuning means located to least between said first narrow wall and said septum for differentially affecting said first and second portions of said signal to be filtered for causing an interaction between said first and second portions at said aperture whereby said frequency range is affected.

A waveguide bandpass filter, comprising:

• elongated conductive walls enclosing an elongated waveguide having a longitudinal axis and substantially constant interior cross-sectional dimensions along its length, and in which electromagnetic energy can propagate, said conductive walls being symmetrically disposed about at least one plane of symmetry;
• an elongated flat conductive first septum including first and second elongated edges, first and second ends, and first and second mutually parallel broad sides, said first septum extending across said waveguide, perpendicular to said longitudinal axis, each end of said first septum being in contact with said conductive walls, said first septum being located so that said one plane of symmetry is parallel with said first and second broad sides of said first septum and lies within said first septum, said first septum further being located at a predetermined first location along said elongated waveguide, the distance between said first and second elongated edges being much less than the length of said elongated conductive walls;
• an elongated flat conductive second septum including first and second elongated edges, first and second ends, and first and second mutually parallel broad sides, said second septum extending across said waveguide, perpendicular to said longitudinal axis, each end of said second septum being in contact with said conductive walls, said second septum being located so that said one plane of symmetry is parallel with said first and second broad sides of said second septum and lies within said second septum, said second septum further being located at a predetermined second location along said longitudinal axis of said elongated waveguide, said second location being spaced at a predetermined distance from said first location such that said first and second septa are separate to define an aperture, whereby said first and second septa and said aperture have bandpass characteristics about a frequency for signals flowing through said waveguide;
• and
• dielectric means located continguous with said aperture and movable in a direction orthogonal to said one plane of symmetry for controlling said frequency about which said bandpass characteristics occurs.