| 摘要 |
952,897. Aerials; radar. MARCONI CO. Ltd. Sept. 14, 1961 [March 9, 1961], No. 8659/61. Headings H4A and H4D. The invention relates to an aerial system for use in a secondary radar station with control radiation, i.e. one from which is radiated an interrogation pulse having a radiation pattern in the form of a narrow beam accompanied by side lobes which pulse precedes in time a control pulse in a beam of breadth and intensity sufficient to cover the radiation pattern of the side lobes of the interrogation beam, the co-operating transponders of the system being arranged to respond only on receipt of a predetermined minimum level of an interrogation pulse over that of the succeeding control pulse. The aerial comprises a radiation concentrating element 1 (which may be either a lens or a reflector either of which may be curved in two mutually perpendicular planes) at a focus of which is disposed an interrogation component aerial system 2 and a control component aerial system which includes at least two directional aerials 4 and 5 fed in phase opposition to each other and directed towards the element 1 but being defocused relative thereto and being symmetrically offset from an axis of the element 1 through the said focus. Any of the aerials 2, 4 and 5, may be either Fagi arrays or horns and the feeders to the aerials 4 and 5 may be waveguides or lines, there being a difference of an odd number of half-wavelengths in the feeder lengths to obtain the required phase opposition. In operation the aerial system 2 is periodically energized by interrogation pulses and the directive aerials 4 and 5 are pulsed a short time after each interrogation pulse. The feed of aerials 4 and 5 in phase opposition is stated to result in the control beam radiation pattern having a minimum or " notch " in the direction of the principal lobe of the interrogation beam, Fig. 2 (not shown). |
