Wideband slot antenna with low VSWR

A slot antenna comprising:

• a waveguide having a first side a second side a third side and a fourth side a closed end and an open end, wherein the second side extends substantially perpendicularly from a first end of the first side and wherein the third side extends substantially perpendicularly from a second end of the first side and wherein the fourth side extends between the second side and the third side, the fourth side being substantially parallel to the first side, the sides and the closed end forming a cavity;
• a feeding point located substantially midway between the first end of the first side and the second end of the first side;
• a T-Bar located inside the cavity the T-bar having a center member extending from the feeding point into the cavity and a cross member having a length extending across the cavity between the second side and the third side wherein the cross member is shaped as a stepped cylinder having a first diameter in a central portion along the length of the cross member and having a second diameter in an outer portion along the length of the cross member;
• a ground screen attached to the open end of the waveguide and extending substantially perpendicularly away from the four sides of the waveguide;
• and
• a plurality of conductive probes extending substantially perpendicularly from the ground screen in a direction away from the cavity.

A slot antenna comprising:

• a waveguide having a first side a second side a third side and a fourth side a closed end and an open end, wherein the second side extends substantially perpendicularly from a first end of the first side and wherein the third side extends substantially perpendicularly from a second end of the first side and wherein the fourth side extends between the second side and the third side the fourth side being substantially parallel to the first side, the sides and the closed end forming a cavity;
• a feeding point located substantially midway between the first end of the first side and the second end of the first side;
• a T-Bar located inside the cavity, the T-bar having a center member extending from the feeding point into the cavity and a cross member having a length extending across the cavity between the second side and the third side wherein the cross member is shaped as a stepped cylinder having a first diameter in a central portion along the length of the cross member and having a second diameter in an outer portion along the length of the cross member;
• and
• a ground screen attached to the open end of the waveguide and extending substantially perpendicularly away from the four sides of the waveguide;
• wherein the second side includes a first cavity extension at a point where the cross member extends to the second side, the cross member extending into the first cavity extension and wherein the third side includes a second cavity extension at a point where the cross member extends to the third side, the cross member extending into the second cavity extension.

A slot antenna comprising:

• a waveguide having a first side a second side a third side and a fourth side a closed end and an open end, wherein the second side extends substantially perpendicularly from a first end of the first side and wherein the third side extends substantially perpendicularly from a second end of the first side and wherein the fourth side extends between the second side and the third side, the fourth side being substantially parallel to the first side, the sides and the closed end forming a cavity;
• a feeding point located substantially midway between the first end of the first side and the second end of the first side;
• a T-Bar located inside the cavity the T-bar having a center member extending from the feeding point into the cavity and a cross member having a length extending across the cavity between the second side and the third side wherein the cross member is shaped as a stepped cylinder having a first diameter in a central portion along the length of the cross member and having a second diameter in an outer portion along the length of the cross member;
• a ground screen attached to the open end of the waveguide and extending substantially perpendicularly away from the four sides of the waveguide;
• a dielectric radome covering the open end;
• and
• a first cover extending from the second side over the opening and a second cover extending from the third side over the opening for the purpose of compensating for the dielectric radome.

A slot antenna comprising:

• a waveguide having a first side, a second side, a third, side, and a fourth side, a closed end and an open end, wherein the second side extends substantially perpendicularly from a first end of the first side and wherein the third side extends substantially perpendicularly from a second end of the first side and wherein the fourth side extends between the second side and the third side, the fourth side being substantially parallel to the first side, the sides and the closed end forming a cavity;
• a feeding point located substantially midway between the first end of the first side and the second end of the first side;
• a T-Bar located inside the cavity, the T-bar having a center member extending from the feeding point into the cavity and a cross member having a length extending across the cavity between the second side and the third side;
• a ground screen attached to the open end of the waveguide and extending substantially perpendicularly away from the four sides of the waveguide;
• and
• a conductive probe extending substantially perpendicularly from the ground screen in a direction away from the cavity.

A slot antenna array comprising:

• a plurality of slot antennas each slot antenna comprising:
• a waveguide having a first side a second side, a third, side, and a fourth side, a closed end and an open end, wherein the second side extends substantially perpendicularly from a first end of the first side and wherein the third side extends substantially perpendicularly from a second end of the first side and wherein the fourth side extends between the second side and the third side, the fourth side being substantially parallel to the first side, the sides and the closed end forming a cavity;
• a feeding point located substantially midway between the first end of the first side and the second end of the first side;
• a T-Bar located inside the cavity, the T-bar having a center member extending from the feeding point into the cavity and a cross member having a length extending across the cavity between the second side and the third side wherein the cross member is shaped as a stepped cylinder having a first diameter in a central portion along the length of the cross member and having a second diameter in an outer portion along the length of the cross member;
• and
• a ground screen attached to the open end each of the waveguide and extending substantially perpendicularly away from each of the four sides of the waveguide;
• wherein the plurality of slot antennas are arrayed about the circumference of a circle in a circular array with the open ends of the slot antennas facing radially outward and the ground screens form a ground screen cylinder with the open ends of the waveguides defining slots in the ground screen cylinder.