Patent GB-814392-A (GB)
Title: Improved radar simulating apparatus
Inventor: SWIFT JAMES WALTER
IPC: G06G7/78
Filed: 1955-08-25
Abstract: 814,392. Radar simulators. COMMUNICATIONS PATENTS Ltd. Aug. 25, 1955, No. 24471/55. Class 40 (7). In a radar trainer simulating a mobile, e.g. airborne, scanning radar with a P.P.L. display, an A.C. voltage of amplitude proportional to the slant range rs, Fig. 1 (not shown), of a target is produced by combining in an amplifier 7 A.C. voltages X1 sin wt, Y1 cos wt; - X2 sin wt ; - Y2 cos wt proportional to the x and y co-ordinates of the radar and target respectively to give a resultant first voltage rg sin (wt+0) where rg=#(X2 - X1)<SP>2</SP>+(Y2 - Y1)<SP>2</SP>= plan range and 0 is the bearing of the target, deriving from said first voltage a second voltage h sin (wt+#+#/2) where h is the vertical separation of the target and radar (i.e. h= Z2 - Z1) and combining in an amplifier 23 said first and second voltages to give a resultant voltage rs sin (wt+#+#) where # is the elevation of the target. As shown, the voltage h sin (wt+#+#/2) is produced between the tappings of two potentiometers 19 and 20, the tappings being set in accordance with the vertical co-ordinates Z1 and Z2 of the radar and target and the potentiometers being energized by a voltage sin (wt + # + #/2) of constant amplitude obtained by applying the output of amplifier 7 through a limiting and phase shifting circuit 18. A three-phase 1,600 c/s. supply is applied to the stator 4 of a synchro 5 whose rotor 4a is electrically coupled via leads a, b, c to the stator 25 of a synchro 26 having a single coil rotor 27, the rotors 4a and 27 being positioned in accordance with the assumed instantaneous azimuth #<SP>1</SP> and elevation #<SP>1</SP> respectively of the radar scanner, so that the outputs from rotors 4a and 27 are proportional to sin (wt+#<SP>1</SP>) and sin (wt+#<SP>1</SP>+#<SP>1</SP>) respectively. The voltages X1, Y1, X2, Y2 may be derived from potentiometers associated with a chart for plotting the tracts of the radar and the target, the potentiometers being energized by a two-phase 1,600 c/s. supply derived from the three-phase supply. An output from a time-base generator 34 is applied (1) to the rotating coil 35 of a P.P.L. C.R.T. 36 and (2) together with the rectified range voltage rs from amplifier 23 to a circuit 37 to generate a delayed target pulse which is applied to the grid 40 of the tube 36 through horizontal and vertical gates 17 and 33 and amplifier 38, the horizontal gate 17 being opened when #=#<SP>1</SP> by a gate pulse output from a coincidence circuit 16 responsive to the squared and differentiated outputs from synchro rotor 4a and amplifier 7 and the vertical gate 33 being opened when (#+#)=(#<SP>1</SP>+#<SP>1</SP>) by a gate pulse output from a coincidence circuit 32 responsive to the squared and differentiated outputs from synchro rotor 27 and amplifier 23 since the gate pulse outputs from coincidence circuits 16 and 32 are displaced by # degrees, the horizontal gate 17 must be held open for a corresponding period. Signals representing noise, permanent echoes, range markers, &c. may be applied to amplifier 38 from a source 39. The simulated aerial scan may be helical, spiral or combined spiral and conical; for a simple azimuthal scan the synchro 26 and vertical gate 33 are omitted. The simulated aerial beam width may be varied by altering the duration of the gate pulses from coincidence circuits 16 and 32.