Patent GB-1424842-A (GB)
Title: Antenna positioning system and method
IPC: H01Q3/08
Filed: 1973-07-11
Abstract: 1424842 Automatic control of attitude WESTINGHOUSE ELECTRIC CORP 11 July 1973 [31 July 1972] 33018/73 Heading G3R [Also in Division H4]  In positioning a radar system aerial mounted on movable means an initialization signal is generated by a suitable means which represents a radar beam line-of-sight relative to a predetermined beam lineof-sight co-ordinate axes system which is defined relative to said movable means. An error signal is generated by a means, which represents an angular error between the radar beam line-of-sight and a target line-of-sight referenced to said predetermined beam line-of-sight co-ordinate axes system. Means references said error signal and said initialization signal to a predetermined fixed co-ordinate axes system defined relative to a predetermined fixed point (such as a point on the earth). Means responsive to the said referenced error and initialization signals generates a least one line-of-sight positions signal representing the angular positions of the target line-of-sight relative to said fixed co-ordinate axes systems. Finally, means responsive to said or each line-of-sight position signal, and to aerial position signals, drives the aerial in a direction tending to null the generated error signal. As described, a radar system which is installed on an aircraft 10, Fig. 1, includes an aerial assembly 12, a transmitter/receiver unit 14, a tracking error detector 16, an aerial drive unit 18, an aircraft altitude signal generator 20, a computer 22, and a pilot display and control unit 24. The aerial assembly 12 comprises a feed horn 36; a fixed polarization sensitive sub-reflector 26, and a main twist reflector 28 which is rotatable about two orthogonally disposed axes 30, 34. The horn 36 may be located either behind the reflector 26 (as shown), or on the other side thereof. It emits radiation which (with the aircraft in normal trim) is horizontally polarized and which is reflected from the reflector 26 to the reflector 28, where its polarization sense is changed to vertical. The radiation is then transmitted through the reflector 26 along a line-of-sight axis 38. A target 40, which lies along a line-of-sight axis 42, reflects a part of the transmitted energy back to the feed horn 36.  Said horn actually consist of a cluster of four horns Fig. 2a (not shown) and the detector 16 develops from their respective received energies error signals EA, EE corresponding respectively to the angular differences in azimuth and elevation between the linesof-sight 38, 42, which are fed to the computer 22. The aircraft altitude signal generator 20 is of conventional type, and from it signals #, #, ° representative of the disposition of a system of co-ordinate axes (X A , Y A , ZA) which are fixed relative to the aircraft, in relation to a system of co-ordinate axes (X, Y, Z) which are fixed in space, are fed to the computer 22. The aerial drive unit 18 provides signals Ed, Ad, to the computer 22 which are representative of the angular position of the reflector 28 in relation to the (X A , Y A , Z A ) co-ordinate axes system. The computer 22 develops signals E Ed , E Ad  in response to its various inputs, which are fed to the drive unit 18 and cause it to rotate the reflector 28 so that the error signals E A , E D  are reduced towards zero, with the line-of-sight 38 co-inciding with the line-of-sight 42. The computer 22 comprises a target tracking error computer 50 Fig. 31 which provides calculated target line-of-light direction cosines X s , Y s , Z s  relative to the fixed co-ordinate axes system (X, Y, Z), and also rate direction cosines X s , Y s , Z s  which may be applied to a line-of-sight angular rate computer, together with the X s , Y s , Z s  signals, for producing signals W xs , W ys , W zs  for utilization in a gun fir control system, for example. The X s , Y s , Z s  signals are applied through contacts of a track/designate relay 54, by means of which a particular target may be selected, to a twist reflector angle error computer 56, which also receives the Ed, Ad, #, #, ° signals, and which calculates the E Ed  and EAd signals. The target tracking error computer (40), Fig. 4 (not shown) comprises two matrix calculators, three rate generators, and three rate integrators. The twist reflector angle error computer (56), Fig. 5 (not shown) comprises a matrix calculator, a commanded direction cosines calculator, a reflector direction cosines calculator, and a  reflector direction cosine to reflector angle error calculator.