Dual polarization waveguide probe system with wedge shape polarization rotator

• US 7,215,222 B2
• Filed: 02/18/2005
• Issued: 05/08/2007
• Est. Priority Date: 05/17/1999
• Status: Expired due to Fees

• Current Assignee: Skyware Technologies (Uk) Ltd.
• Original Assignee: Channel Master LLC (CommScope Holding Company, Inc.)
• Inventors: Baird, Andrew Patrick, Stokes, Jamie
• Primary Examiner(s): LEE, BENNY T
• Application Number:
  US11/061,582
• Publication Number:
  US 20050140461A1
• Time in Patent Office: 809 Days
• Field of Search: 333/21.A, 333/137
• US Class Current: 333/137
• CPC Class Codes: H01P 1/161 sustaining two independent orthogonal modes, e.g. orthomode transducer combining or separating polarisations and frequencies H01P1/2131
• CPC Class Codes: H01P 1/165 for rotating the plane of polarisation

Abstract

There is disclosed herein a waveguide rotator for use with a dual polarization waveguide probe system. The waveguide has an internal structure that protrudes into the waveguide such that a first orthogonal component of the incident polarized signal propagates to the end of the waveguide and is reflected therefrom and the second orthogonally polarized component is cut-off by the protruding structure which narrows the waveguide, at a distance from a short circuit at the end of the waveguide, and is reflected substantially at the cut-off point, the cut-off point being frequency dependant. At some predetermined distance from the reflecting means and the cut-off point, the first component and the second component are recombined such that the polarization of the recombined structure is rotated 90° from the incident polarization. The protruding interior surface creates a pocket or cavity behind the waveguide into which components from a circuit board can be inserted.

Claims

1. 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.

2. A waveguide rotator for use with a dual polarisation waveguide probe system for receiving at least first and second orthogonally polarised incident signals, said system having a waveguide into which the at least two orthogonally polarised signals are received for transmission therealong, said waveguide having:

a first probe extending from a wall of the waveguide into the interior of the waveguide, said first probe being adapted to receive said first orthogonally polarised signal traveling along a common longitudinal plane thereof,

a signal isolator extending from the wall of the waveguide, said signal isolator being located downstream of said first probe and lying in said longitudinal plane for reflecting the first orthogonally polarised signal in said longitudinal plane back to said first probe and allowing said second orthogonally polarised signal, orthogonal to said first polarised signal to pass along said waveguide,

a second probe located downstream of said signal isolator and extending from the wall of the waveguide in said longitudinal plane,

a signal rotator disposed in said waveguide downstream of said second probe and having a wedge-shaped planar inclined protrusion extending from an interior surface of said waveguide partly across said waveguide towards a rear reflecting wall disposed at an end of said waveguide, said signal rotator being dimensioned and proportioned such that a first incident polarisation component of said second orthogonally polarised signal propagates to the rear reflecting wall at the end of the waveguide and is reflected therefrom and a second incident polarisation component of said second orthogonally polarised signal is cut-off by said protrusion before reaching the rear reflecting wall, and is reflected substantially by said protrusion at a frequency dependent cut-off point whereby said reflected first and second components recombine within said waveguide such that the polarisation of the recombined reflected signal is rotated by 90°

from the polarisation of the second orthogonally polarised signal such that the recombined reflected polarised signal is polarised in said longitudinal plane for detection by said second probe.

3. A waveguide rotator as claimed in claim 2 wherein the waveguide cross-section is substantially square.

4. A waveguide rotator as claimed in claim 2 wherein the waveguide cross-section is rectangular or circular.

5. A waveguide rotator as claimed in claim 2 wherein the wedge-shaped protrusion extends substantially across the waveguide and narrows to a common location on the waveguide wall to provide a substantially planar surface between the waveguide wall and the rear reflecting wall of the waveguide.

6. A waveguide rotator as claimed in claim 2 wherein the wedge-shaped protrusion has cut-outs so that it does not extend completely across the width of the waveguide at the rear reflecting wall.

7. A waveguide rotator as claimed in claim 2 wherein the wedge-shaped protrusion is stepped, the wedge-shaped protrusion being comprised of a series of triangular protrusions of increasing waveguide width.

8. A waveguide rotator as claimed in claim 2 wherein the signal rotator is provided by dual wedge-shaped protrusions on opposed sides of the waveguide.

9. A waveguide rotator as claimed in claim 8 wherein one or both dual wedge-shaped protrusions may be stepped.

10. A method of rotating an incident polarised signal traveling in a waveguide having a short circuit at one end thereof by substantially 90°

, said method comprising the steps of,

providing a wedge-shaped inclined protrusion in the waveguide, said protrusion extending partially across said waveguide,

allowing a first component of said incident polarised signal to travel to the short circuit at the end of said waveguide and be reflected from said end back along the waveguide,

increasing the wavelength of a second component of said incident polarised signal by decreasing the cross-section of said waveguide by said protrusion,

reflecting said second component from the protrusion at a frequency dependent cut-off point before said second component reaches said short circuit,

recombining the reflected first and second components in said waveguide to form a recombined polarised signal rotated substantially 90°

from the polarisation of the incident signal.