Patent GB-881748-A (GB)
Title: Radiant energy system
IPC: H01Q21/00
Filed: 1959-10-01
Abstract: 881,748. Aerials. HUGHES AIRCRAFT CO. Oct. 1, 1959 [Oct. 21, 1958], No. 33374/59. Class 40(7). [Also in Group XL(b)] An aerial system comprises first means for modulating the energy fed to the aerial, second means for periodically varying as a function of time at least one characteristic parameter of the aerial whereby a plurality of predetermined frequency components representing different space-correlated factors are introduced to the radiated or received energy, and a frequency segregation network in the receiver responsive only to one or more of said frequency components, whereby spacecorrelated information and information derived from the modulation provided by the first means are obtained independently. Low side lobe system, Fig. 1. A slotted waveguide array 20 is provided with simultaneously operated switches 24, 26 so that the effective lengthof the aerial may be varied. A radar pulse source 28 is coupled to the guide 20 and generates pulses under the control of a synchronizer 29, which also feeds timing signals to modulator 30 to operate the switches 24, 26. The modulator operates during the time that the echo signals are being returned to the guide 20 and operates at a frequency considerably higher than the repetition frequency of the pulse source 28 so that a number of cycles of modulation is applied to each R.F. echo pulse. The pulses then pass via a receiver 32 and detector 33 to a filter 34. The resultant signals are fed to a utilization circuit 36. It is stated that sidelobes are reduced because of the modulation of the guide length, and hence of the polar diagram, the effective diagram of the modulated aerial being: more sharply defined in terms of side-lobe level than the diagrams of either the full length or the shortened length aerials separately. A mathematical dissertation is made. Dual beam conical lobing system, Fig. 5. In this embodiment the conventional conical lobing operation of the aerial is used to provide concurrent sum and difference patterns equivalent to those produced by a monopulse aerial system. The aerial comprises a reflector 40, a pair of waveguide feed arms 41, 42, and a rotating lens assembly 43, the assembly providing a nutating beam with a frequency, for example, of 133 c./s. A unit 46 keeps the aerial directed at the target. The signal appearing at the detector output includes a D.C. component, which represents the component provided by the unmodulated beam pattern, and a 133 c./s. modulation. By extracting these components sum and difference patterns are obtained which are used in a conventional monopulse utilization circuit. Miscellaneous. By suitable modulation of an aerial it is possible to obtain simultaneous dual pattern operation, for example to obtain the characteristics of both a pencil beam and a fan beam. More than one region at a time may be scanned simultaneously. General time-modulated aerial system. In this system each element in an array is individually controlled in amplitude and phase. In the embodiment shown, Fig. 12, the aerial comprises a number of linear and parallel arrays 74. Each array has its own arrangement of slots 76, each slot having a different associated modulating element 80 which controls the radiation from the slot in amplitude and phase. A transmitter and receiver are coupled to the arrays via a duplexer, and signals detected at 97 are fed to band-pass filters 101-105 and from thence to a utilization circuit. The manner of operation of the aerial system is controlled by units 110 and 112 which control the effect of each modulating element 80.