Patent GB-1424841-A (GB)
Title: Digital antenna positioning system and method
IPC: G01S7/02
Filed: 1973-07-11
Abstract: 1424841 Aerials; radar WESTINGHOUSE ELECTRIC CORP 11 July 1973 [31 July 1972] 33014/73 Headings H4A and H4D In a method of directionally positioning an aerial of a radar system mounted on a movable platform having a platform axes system signals are generated representing platform attitude relative to a fixed co-ordinate axes system and aerial position relative to the platform axes system, the signals being related in amplitude to a reference voltage. All of the signals, and the reference voltage, are simultaneously sampled at a first time, and are temporarily stored as a first block of data signals. A first reference normalization constant is generated which is equivalent to the square root of the sum of the squares of each of the data signals in the first block, and each of said signals is normalized in response to said constant. The normalized data signals are temporarily stored in a buffer memory until the process of normalization has been completed, when they are transferred as a block into an operational memory. Aerial positioning signals are generated responsively to the said block of normalized data signals. The invention also provides apparatus for performing the above method, and is described as applied to an airborne radar system of the kind featured in Specification 1,424,842 (Fig. 1). The various angular quantities from the aircraft altitude signal generator 20 and from the aerial drive unit 18 are processed in suitable conventional resolvers and are supplied therefrom to the computer 22 as analogue signals representing the sines and cosines of the angular quantities. Thus, the sines and cosines of the aircraft altitude angles # #, # are supplied to an input unit 104, Fig. 6, of the computer 22. The resolvers of the angular quantities Ad, Ed of the aerial reflector 28, Fig. 1, are driven through twice those angles, respectively and provide the sines and cosines of 2Ad, 2Ed to the computer 22. The direction cosines O, # A -# E  of the tracking error signal are provided from a suitable conventional digital signal processor 100 which, together with a target tracking error computer 50 is synchronized in response to a clock signal C 1  (e.g. at 166 Hz) from a timing control unit 102, which also provides clock signals C 2  (e.g. at 249 Hz) to the input unit 104 and to a twist reflector angle error computer 56, which provides error signals # Ad , # Ed  to the drive unit 18, Fig. 1, and C 3  (e.g. at 83 Hz) to an aerial monitoring unit 106, which provides target information signals TGT to the pilot display and control unit 24, Fig. 1. The alternating current line voltage ACLINE supplied to the various resolvers is also taken to the input unit 104. A particular target may be selected by means of a DESIG signal applied to the twist angle error computer 56. In operation, the angle input signals and the A.C. line voltage which are applied to the input unit 104 are sampled at the rate of the C 2  clock signal, are quantized and normalized, and are then stored in digital form in an operational memory 105. The digital signal processor 100 supplies the tracking error signals in the form of digital direction cosines to the computer 50, which samples this data at the rate of the C 1  clock signal and which provides fixed co-ordinate axes system referenced line-of-sight error' positions X s , Y s , Z s  (and rates X s , Y s , Z s  if desired) for storage in the operational memory 105. Flow diagrams of the functioning of the' computer 50 are given in Figs. 7a, 7b (not shown). The input unit 104 comprises analogueto-digital converter means 164, Fig. 10, a buffer store 166, a calculator 168, a second buffer store 170, and a timing signal generator 165. The C 2  clock signal is received by the generator 165 which produces phased signals C#1, C#2, C#3 for controlling respectively read-in and read-out to and from the buffer 166, and readout from the buffer 170. In the calculator 168 the normalization of the input data is effected and signals representing the sines and cosines of the angles Ad and Ed are also produced (Fig. 11, not shown). Data from the input unit 104 is stored in the operational memory 105, and is applied to the twist reflector angle error computer 56 for calculation of the error signals # Ad , # Ed À A flow diagram of the functioning of the computer 56 is given in Fig. 8 (not shown). Data relative to the angles #, #, #, Ad, Ed is also applied from the operational memory, 105 to the target tracking error computer 50 and to the aerial monitoring unit 106. A flow diagram of the functioning of the unit 106 is given in Fig. 9 (not shown).