Patent GB-1367216-A (GB)
Title: Phased array system
IPC: H01Q25/02
Filed: 1972-09-28
Abstract: 1367216 Aerials; pulse radar RAYTHEON CO 28 Sept 1972 [4 Oct 1971] 44903/72 Headings H4A and H4D An aerial system comprises a first means containing a plurality of regions each receiving a portion of an incident wavefront and transmitting it with a respective phase shift, which may be varied in relation to the phase shifts of other regions. The reconstructed modified wavefront impinges upon a second means (reflector or refractor) which alters the relative directions of the constituent rays of said wavefront such that said second means presents a substantially uniform aperture independently of the direction in which transmission or reception takes place. As described, a horn 42, Fig. 1, co-operates with a reflector 38, a lens 40, which is made up of a plurality of phase-shifting elements 48, being interposed. The horn 42 is of four-channel monopulse type, and is connected by waveguides 76 to an electronic unit 74. The lens 40 is curved so that it approximately conforms to the wavefront from the horn 42. The phase shifters 48 are of ferrite latching type, and are controlled by pulses on lines 54. The reflector 38 may be of hyperboloidal form, and is substantially larger than the active area 46 illuminated by the beam 44 from the lens 40. Said active area is moved on the surface of the reflector by angular scanning of the beam 44, and a collimated beam 56 from the aerial system is correspondingly scanned, but with reduced angular movement and tracks a selected aircraft 34 which may carry a transponder 234 and which is in the vicinity of a runway 36. The reflector 38 is mounted on a base 58 by means of a frame 60, and the horn 42 and the lens 40, which may be protected by a radome, are carried on an arm 64 which is pivotally connected to an extension 62 from said base. A motor 72 enables the distance between the lens 40 and the reflector 38 to be adjusted. In a second embodiment, the reflector 38 is replaced by a lens made from a ceramic or by a plastics material, or comprising a plurality of parallel spaced waveguides (Fig. 2, not shown). In a third embodiment, the lens 40 is replaced by a sub-reflector which comprises a plurality of phase shifters (Fig. 3, not shown). The reflector 38, Fig. 1, is preferably situated within the near field region of the lens 40, and a procedure is described whereby the configurations of the various elements may be obtained by a ray tracing programme utilizing a computer. Circuit arrangements.-The waveguides 76 couple the horn 42 to a comparator 78 which provides elevation/azimuth difference, and sum signals for a receiver 82. A duplexer 84 in the sum channel enables pulses from a transmitter 80 to be radiated. A computer 86 receives angle information from the receiver 82, and range information from a processor 84, which is coupled both to the transmitter and to the receiver. Said computer controls the operation of the system in a sequence determined by a timing unit 94, including control of a beam steering unit 88 for providing signals over the lines 54 for the phase shifters 48. Target selection is effected at a console 92, which receives information from an area surveillance radar 120. A display 90 is coupled both to the console 92 and to the computer 86. Each ferrite phase shifter 48 has a "reset" and a "set" coil, and in each cycle the "reset" coils of all phase shifters are first energized together, and then the "set" coils receive pulses of durations corresponding to the phase shifts required (Figs. 9, 10, 11, not shown). Shorter auxiliary pulses are also directed to some "set" coils to provide compensation for temperature rises within the lens 40. Said rises are at a maximum at the top of the lens, and decrease to a minimum at the bottom. No compensation is provided for phase shifters at the top but is provided, in increasing steps, for those below (Fig. 12, not shown).