Crossed tee-fed slot antenna

Claim 1

A variable-polarization microwave antenna for reception and transmission of microwaves within a predetermined range of frequencies, said antenna comprising: A. first and second generally planar ground-plane conductors spaced apart and extending generally parallel to each other, said first conductor forming a generally cruciform aperture having first and second arms extending transversely of each other; B. shorting elements extending between said ground-plane conductors to short them together and surrounding said aperture to form a cavity defined by said ground-plane conductors and said shorting elements, the distances across said cavity in the directions of said aperture arms being between one-half and one wavelength at frequencies within the predetermined frequency range; C. a first feed line including a first generally tee-shaped feed conductor whose stem extends between and generally parallel to said ground-plane conductors and into said cavity out of registration with said second aperture arm, the crosspiece of said first feed conductor being disposed in said cavity in registration with said first aperture arm and shorted to said ground planes at its ends; and D. a second feed line including a second generally tee-shaped feed conductor whose stem extends between and generally parallel to said ground-plane conductors and into said cavity out of registration with said first aperture arm, the crosspiece of said second feed conductor being disposed in said cavity in registration with said second aperture arm and shorted to said ground planes at its ends, said first and second feed lines being independently driveable for variation of the plane of polarization by variation of the amplitude ratio of the drive signals on said first and second feed lines.