Patent GB-1005318-A (GB)
Title: Radar target-acquisition control apparatus
IPC: G01S13/66
Filed: 1962-11-19
Abstract: 1,005,318. Electric analogue computers. ELECTRONIC ASSOCIATES Inc. Nov. 19, 1962 [Nov. 20, 1961], No. 43689/62. Heading G4G. [Also in Division H4] In the control of the range, azimuth, and elevation adjusting means in a first targettracking radar station so as to place the radar " on-target," the target is initially tracked by a second radar station which generates target range, azimuth and elevation signals, translates such signals into cartesian co-ordinate signals X, Y, Z, Fig. 7, and transmits the latter signals to the first station at which the radar adjusting means positional data is compared in cartesian form with that received from the second station, after allowance for geographical station separation, to generate error signals which control the adjusting means. The invention is particularly described as applied to a missile range in which the position of the missile is continuously measured by a chain of radar stations with overlapping tracking ranges; the continuity of measurement is achieved by controlling an adjacent station from a presently tracking station whilst the missile is passing through the overlapping tracking range. General arrangement, Fig. 1.-A " local " radar 10, Fig. 1, receives in a " target acquisition" " computer 48 (i) signals X R , Y R , Z R  representing the cartesian co-ordinates-as corrected to axes originating at radar 10-of the target being tracked by a " remote " radar, (ii) signals X L , Y L , Z L  from a polar-to-cartesian converter 11 utilizing sine/cosine potentiometers, Fig. 2 (not shown), and representing the positions of servomotors which control slant range D, azimuth A and elevation E, and (iii) signals representing slant range D and plan range R = D cos E. The above signals are D.C.; the error-correcting signals # D , # A , # E , which are applied to the local range, azimuth and elevation servomotors, are conveniently made A.C. Target acquisition computer, Figs. 3, 4, 5a, 5b.- Cartesian error-correcting signals # x , # y , # z , are defined by the equations:- and it is demonstrated that sine and cosine functions of angles A, E, may be approximated by the " square " functions as illusttated in Figs. 5a, 5b to give thereby the following values of # D>  # A  and # A  in simpler terms than would arise from exact calculations:- Fig. 3 shows a schematic diaargm of the computer. Quantities # x , # y , # z , appear as A.C. signals at the outputs of the transformers 60 due to modulators 58 the field coils of which are fed with the same frequency as the radar servomotors ; capacitors 63 afford approximately sinusoidal voltages at the transformer outputs. Units 62 and 68 are described in more detail below with reference to Fig. 4. Those amplifiers 64 which lie in the A (azimuth) and E (elevation) channels are gain-controlled to perform requisite respective divisions by factors R, D. In the circuit of Fig. 4 appropriate selection and polarization of the cartesian quantities # is effected by the identification and selection of the sector in which the azimuth and elevation angles occur. The " square " function approximations are generated by circuits including units CX, CY, CXY, CZR which incorporate amplitude-limiting diode pairs 84, pre-amplifiers 74, and modulators-demodulators 76. Each amplifier 72 gives D.C. push-pull outputs but only one of these is utilized from the amplifier in unit CY. Devices SS1-SS8 switch the modulated cartesian error signals # x , # y , # z , in accordance with the above tables, to the primaries of transformers 98 and each transistor 100 has its collector connected to the, secondary of a corresponding transformer 98 the transistor emitters being earthed. Each transistor 100 is normally biased so as to conduct and the switching signals are applied via resistors 101. The switching operation is described with reference to Figs. 6a, 6b (neither shown). The A.C. output signals from amplifiers 64 are equal in amplitude to the signals # A , # E , # D , and signal phase reversal for giving the appropriate sign in the above tables is accomplished by AND gates, e.g. 108, 110, 112, transistors 104 and transformers 70. The local radar is placed in the automatic tracking mode when the error signals # x , # y , # z , are reduced to zero.