Microwave waveguide window having the same cutoff frequency as adjoining waveguide section for an increased bandwidth

Claim 1

In a microwave waveguide window for propagation of microwave frequencies within a selected bandwidth, hollow waveguide means, microwave dielectric window means hermetically sealed across said waveguide to define a first dielectric window-filled waveguide section interposed between second and third waveguide sections, said first, second and third waveguide sections are dimensioned to have approximately the same cutoff wavelength, whereby each of said first, second and third waveguide sections will support approximately the same number of waveguide transmission modes, said first waveguide section having a dielectric-filled length l1 which is less than one wavelength long at the center frequency of said selected bandwidth, said second section of waveguide having substantially less characteristic impedance than said first section of waveguide, and including a transition section of waveguide interposed between said first and second sections of waveguide, said transition section of waveguide dimensioned to have approximately the same cutoff wavelength as said first and second waveguide sections and being substantially shorter than said first section of waveguide, and wherein said dielectric window material protrudes from said first section of waveguide into said transition section of waveguide by an amount substantially less than the length of said transition section of waveguide, whereby wave reflections from the waveguide transition from said second to said first waveguides are effectively cancelled.