Patent ID: 7215222

Claim:
A low-noise block (LNB) for use with a satellite dish receiving signals broadcast by a satellite which includes two incident signals orthogonally polarised in the same frequency band, said LNB comprising: a feedhorn, a waveguide coupled to said feedhorn, said waveguide having a printed circuit board support surface and a short circuit end plate, a printed circuit board mounted on said support surface and having first and second probes extending into said waveguide, said probes being disposed along a common longitudinal plane, a signal rotator structure disposed within said waveguide between said second probe and said short circuit end plate, said signal rotator structure comprising a wedge-shaped protruding surface extending from an interior surface of said waveguide partly across said waveguide, said signal rotator structure narrowing the waveguide with respect to a first component of one of the two polarised incident signals to increase the wavelength of the first component and reflect the first component at a frequency dependent cut-off point before said first component reaches the short circuit end plate, and permitting an orthogonal second component of said one of said two incident polarised signal to be reflected by said short circuit end plate, the reflected first and second components being recombined within said waveguide to provide a recombined polarised signal before reaching said second probe whereby the recombined polarised signal rotates 90° from the polarisation of the other of the two incident signals into the longitudinal plane common with said probes.