Patent GB-1069381-A (GB)
Title: Radar system
IPC: G01S7/08
Filed: 1964-05-20
Abstract: 1,069,381. Radar system. BOFORS A.B. May 20, 1964 [May 24, 1963], No. 20897/64. Heading H4D. In a radar system comprising a primary P.P.I. display 5 of the scanned area wherein a selected portion of the scanned area is displayed on an enlarged scale on a secondary display 14, manually controlled means are provided to produce a movable marker 25 on the secondary display 14, and generate signals representative of the movement of the manually controlled means whereby the said portion of the scanned area may be selected. The radar antenna 1 is rotated on a shaft connected to the rotor of a resolver R1 fed with scanning waveform A, to produce two resolved deflecting voltages A Sin y and A Cos y, where y is the azimuth angle of the antenna with respect to a reference direction O. These voltages are fed to the x and y deflecting plate terminals of display 5, to produce the normal rotating radial sweep. The target 23 which is to be displayed on display 14 is distance L from the centre of display 5 and is angularly disposed from the reference line 7, by angle #. A circular marker 22 is superimposed on the display 5 by signals from generator SG1 applied to x and y terminals 21. A shaft 9 carries sine and cosine potentiometers P4 and P5 respectively and is rotated by a hand wheel 12, via differential gear D1, to represent the angle #. A shaft 16 is connected to a potentiometer P1 and is rotated by a hand wheel 19, via differential gear D2, until potentiometer P1 produces a voltage representing distance L. This voltage is fed to potentiometers P4 and P5 such that they produce voltages representing L Sin # and L Cos # respectively, which are fed to the x and y terminals 21 respectively, such that the marker 22 moves to approximately enclose the target response 23. Shaft 9 also carries two orthogonally disposed rotor windings of a resolver R2 having two orthogonal stator windings, respectively fed with the voltages representing A Sin y and A Cos y. The arrangements is such that the two rotor windings produce voltages representing A Sin (y - #) and A Cos (y - #) which are respectively fed to the x and y deflecting plate terminals 13 of display means 14, the voltage representing distance L being first subtracted from the voltage representing A Cos (y - #) in means 15. The amplification of display means 14 is such that the area of display 5 containing response 23 is reproduced on display 14 as a much enlarged off-centre P.P.I. section display. Due to the inaccuracy of display 5 response 23 on display 14 is usually not in the centre 26 of the display. An oval marker 25 is produced by generator SG2 feeding orthogonal signals to terminals 24. A control stick 27 is freely movable and is connected to a gear assembly 28 which resolves its movement into two orthogonal components in x and y directions and translates these components into rotations of shafts 30 and 29 respectively. Each shaft is provided with a potentiometer P2 and P3 which provide signals representative of the total displacement of the stick Y 1  and X 1  in the two directions y and x from respective neutral positions and techogenerators T1 and T2 which provide signals dy representative of the rate of movement - and dt dx - of the stick in the two directions. The dt signals from the techo-generators are fed to integrating circuits, each comprising a resistor 31, an amplifier and a feedback capacitor 33, to produce signals representing ##<SP>t</SP> o  dx and ##<SP>t</SP> o  dy. These are fed to terminals 24 such that movement of the stick 27 causes corresponding movement of marker 25. By this means marker 24 is made to coincide with response 23. The signals representing Y1 and dy/dt are summed in means 41 and are fed to drive a motor M2 which rotates at a speed proportional to the signal applied thereto. Since the signal representing dy/dt is only present from time 0 to t 1  while the stick is be ng moved, this signal will cause the motor to turn by an amount ##<SP>t</SP>1 o  dy representing the displacement Y 1 . The signal representing Y 1  remains after the stick movement has stopped and causes the motor to continuously rotate through an angle instantaneously represented by ##<SP>t</SP> o  y 1 dt. The output shaft of motor M2 is coupled to shaft 16 via differential gear D2 to produce a corresponding change in distance L, the change having a constant component and a changing component. dx The signals representing X 1  and - are similarly dt fed to energize a motor M1 coupled to shaft 9, and produce a change in angle having a constant component and a changing component. Marker 23 on display 5 is thus caused to first encircle response 23 by means of the two constant component changes of L and #, and also commences to move at a constant speed in a fixed direction by means of the two changing components of L and #. This movement of the marker 22 assumes a constant movement of the response 23. The off screen centre of the display 14 is similarly moved such that response 23 is first brought to the centre 26 of the display and remains there if the assumed movement of the response is correct. The response 23 is displayed at 14 once per antenna scan and just before a new response is to be displayed, marker 25 is returned to the centre 26 of the display by.means of capacitor 33 being shorted under the action of relays 35 which are controlled by cam switch 36 coupled to a shaft 38 measuring the time when the area containing the response 23 is swept. If the assumed movement of the response is correct, the new response should be at the middle 26 of the display 14 and no movement of stick 27 should be necessary. If the assumed movement is incorrect, movement of the stick will be required. The valves of # and L may be fed to a fire control computor for a weapon which is to fire at the selected target, by means of generators Gland G2 geared to shafts 9 and 16.