GB1234751A - Improvements in or relating to aerials - Google Patents

Abstract

1,234,751. Aerials. GENERAL ELECTRIC CO. Ltd., S. CORNBLEET, and J. BROWN. 22 Jan., 1968 [30 Nov., 1966], No. 53733/66. Heading H4A. A radar aerial array utilizing the static-split principle comprises a shallow cup-shaped metal member 2 having its open end closed by a metal plate 3. The interior of the member 2 is divided by four partitions 4 into quadrants, each quadrant being divided by two arcuate partitions 6 to form a rectangular cross-section waveguide in the configuration of a serpentine channel 7 having three limbs. The outer end of each waveguide 7 is coupled to a respective rectangular cross-section feed waveguide 9, the inner end adjacent the centre boss 5 being short-circuited. The outer surface of plate 3 carries four groups of eight linearly polarized radiators 10, each group being associated with a respective quadrant. The radiators 10 are spaced apart along a waveguide channel 7 a distance equal to ¢#, their positions being denoted by crosses 11. Each radiator 10, Fig. 3, incorporates a dipole radiating element 12 formed by photo-etching a copper layer on the face of a dielectric disc 13. The disc 13 fits in a recess 14 in a copper tube 15, the other end of the tube being flush with the surface of the plate 3 to form a resonant cavity. Each element 12 is coupled to its waveguide 7 by an air-filled coaxial line 16 incorporating a slot excited balun. The outer conductor 17 of the line 16 is bifurcated by slots 18, the ends of the bifurcations having lugs 19 fitting into slots 22 in the disc 13. The other end of the conductor 17 fits in an aperture (not shown) in the plate 3. The inner conductor 21 is connected at one end to the conductor 17 in the slotted region to generate the H 11 coaxial mode, this mode in combination with the existing T.E.M. mode exciting the bifurcations to form a balanced transmission line. The other end of the conductor 21 has a probe 22 extending into the waveguide 7. Inductive irises 23 match out admittances presented by the probes 22. The linearly polarized array may be converted to circular polarization by a polarizing grating placed in front of the array. In an alternative arrangement for obtaining circular polarization, the radiator 24 of Fig. 4 may be used, this radiator comprising two interleaved copper spirals 25 photo-etched on a PTFE disc 26. In a modified construction (Figs. 5, 6, not shown), each quadrant is divided into three separate arcuate waveguides by three concentric circular partitions extending through 360 degrees.