US 5,122,810 AGranted

Feed waveguide with ferrite rod polarizer and stepped dielectric support for matching

AssigneeRacal-Mesl Limited

InventorsWilliam T. Nisbet, Robert M. Ferguson, Andrew P. Baird

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Abstract

An antenna arrangement for receiving television signals from a satellite comprises a parabolic dish which collects the signals and feeds them through a feedhorn, then through a polarization switch and to a low noise block to the receiver. The polarization switch comprises a ferrite rod supported in a dielectric holder within a circular waveguide. The ferrite rod is surrounded by a solenoid coil which is energizable to rotate the plane of polarization of the signals passed along the waveguide, so as to enable the switch to select either horizontally or vertically polarized signals. The current in the coil is switchable between two values, one having a predetermined magnitude in one direction through the coil and the other having the same predetermined magnitude but in the opposite direction through the coil. The current levels are seleced such that the corresponding angular positions for the plane of polarization are +45.degree. relative to the datum position for the polarization plane and -45.degree. with reference to this datum position. The dielectric holder has a stepped configuration so as to match the loaded waveguide to the empty waveguide.

Claims8

Dependent claims

A polarisation switching arrangement responsive to polarised radio signals and capable of selecting signals having either one of predetermined states of linear polarisation comprising,

a waveguide,
a ferrite rod having a longitudinal axis and having flat end surfaces normal to the longitudinal axis,
a dielectric support means axially and dielectrically supporting the ferrite rod in the waveguide,
electrically energisable field generating means for generating a magnetic field directed axially along the ferrite rod and energisation means for supplying electrical current to the electrically energisable field generating means whereby to control energisation of the field generating means so as to switch the plane of linear polarisation in the waveguide between two positions which are orthogonal to each other,
the dielectric support means comprising a dielectric holder directed axially of the waveguide and whose opposite axial ends are of stepped configuration and the opposite axial ends of the ferrite rod projecting axially beyond the opposite axial ends of the dielectric holder so as to be situated externally of the dielectric holder, whereby the combination of the stepped configuration of the opposite axial ends of the dielectric holder and the projecting ends of the ferrite rod compensates for the loading effect of the ferrite rod on the waveguide.

2 more elements

Dependencies are inferred from the claim text.