Two-band microwave antenna with nested horns for feeding a sub and main reflector
First Claim
1. A two-band multimode microwave source for the simultaneous radiation of waves in a lower-frequency band and in a higher-frequency band, comprising a waveguide structure forming a first cavity of rectangular cross-section and including two first pairs of waveguides which terminate at a discontinuity plane and are separated from each other by a first block projecting convergingly beyond said discontinuity plane into said first cavity, said first pairs of waveguides emitting into said first cavity a lower-frequency first wave, said first block being hollow and containing two second pairs of waveguides separated by a second block, said first block forming a second cavity communicating with said second pairs of waveguides and opening into said first cavity for emitting a higher-frequency second wave into the latter, said first cavity having an output aperture spaced from said second cavity in the direction of wave propagation for radiating both said first and second waves.
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Accused Products
Abstract
A two-band multimode microwave source for an antenna of a low-elevation-tracking radar comprises a higher-frequency section nested in a lower-frequency section, the two sections having E-planes perpendicular to each other. The lower-frequency section includes two outer pairs of waveguides separated by a block which convergingly projects beyond their output ends and is bisected by the E-plane of that section. The higher-frequency section includes two inner pairs of waveguides disposed within that block and separated by an obstruction lying in the last-mentioned E-plane. The higher-frequency wave emitted by the inner waveguides is made planar by a lens disposed at n output aperture of the structure which is transparent to the lower-frequency wave. In a Cassegrain-type radar antenna the lower-frequency wave emitted by the source is returned by a semitransparent intermediate reflector toward a main reflector provided with a grid which rotates its plane of polarization to let it pass out through the intermediate reflector along with the higher-frequency wave which, passing unattenuated through the intermediate reflector, is returned by a solid outlying reflector to the main reflector.
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Citations
8 Claims
- 1. A two-band multimode microwave source for the simultaneous radiation of waves in a lower-frequency band and in a higher-frequency band, comprising a waveguide structure forming a first cavity of rectangular cross-section and including two first pairs of waveguides which terminate at a discontinuity plane and are separated from each other by a first block projecting convergingly beyond said discontinuity plane into said first cavity, said first pairs of waveguides emitting into said first cavity a lower-frequency first wave, said first block being hollow and containing two second pairs of waveguides separated by a second block, said first block forming a second cavity communicating with said second pairs of waveguides and opening into said first cavity for emitting a higher-frequency second wave into the latter, said first cavity having an output aperture spaced from said second cavity in the direction of wave propagation for radiating both said first and second waves.
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8. A radar antenna adapted to radiate waves in a lower-frequency band and in a higher-frequency band, comprising:
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a waveguide structure forming a first cavity of rectangular cross-section and including two first pairs of waveguides which terminate at a discontinuity plane and are separated from each other by a first block projecting convergingly beyond said discontinuity plane into said first cavity, said first pairs of waveguides emitting into said first cavity a lower-frequency first wave, said first block being hollow and containing two second pairs of waveguides separated by a second block, said first block forming a second cavity communicating with said second pairs of waveguides and opening into said first cavity for emitting a higher-frequency second wave into the latter with a plane of polarization perpendicular to that of said first wave, said first cavity having an output aperture spaced from said second cavity in the direction of wave propagation for radiating both said first and second waves; a forwardly concave main reflector centered on said waveguide structure; a rearwardly convex intermediate reflector forwardly of said main reflector, said intermediate reflector being transparent to said second wave while directing said first wave back onto said main reflector; a rearwardly convex outside reflector forwardly of said intermediate reflector sending back said second wave substantially unaltered through said intermediate reflector to said main reflector; and a polarization-rotating grid adjacent said main reflector for making the polarization of said first wave codirectional with that of said second wave and enabling both said waves to be redirected forward by said main reflector via said intermediate reflector and past said outside reflector.
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Specification