Patent GB-748623-A (GB)
Title: Radar simulating apparatus
Inventor: CUTLER ALBERT ERNEST
IPC: G01S7/40
Filed: 1953-10-01
Abstract: 748,623. Trainers for radar. COMMUNICATIONS PATENTS, Ltd. Sept. 21, 1954 [Oct. 1, 1953], No. 26971/63. Drawings to Specification. Class 40 (7). A training device simulating radar equipment having an angularly movable aerial beam, possibly aircraft mounted, includes computing means, fed with positional and directional information for the " radar" , directional information about the aerial beam, and positional information for a target, which provides simulated echo pulses delayed in accordance with the range of the target from the aerial when the target falls within the aerial beam. The first stages in the computor are fed with x, y and z co-ordinate information about the radar position and the target position, using a convenient frame of reference, and the coordinates of the target from the radar are then determined. These co-ordinates are then modified so as to bring the x axis of the reference frame into alignment with the zero bearing direction of the radar, which may be the heading direction if the radar is supposedly aircraft mounted. The next stages are fed with the pitch and roll angles of the craft or radar mounting and resolve the target co-ordinates last determined into the equivalent co-ordinates relative to the longitudinal, transverse and " vertical " axes of the radar frame of reference. The next information to be fed in is the elevation and train angles for the simulated aerial beam relative to the radar reference axes and these are used in conjunction with the co-ordinate information to determine the value of R cos a and R<SP>2</SP> sin<SP>2</SP> a where R is the range of the target and a the angle between the direction of the aerial and the direction of the target from the radar. The value for R cos a obtained is squared and multiplied by a constant factor representing sin<SP>2</SP> b where b is the half angular width of the aerial beam. When the R2 sin<SP>2</SP> a output is less than the resultant R<SP>2</SP> cos2 a sin<SP>2</SP> b output a gate is opened (the target then being within the beam) and a signal representing the computed quantity R cos a (which is then almost the same as R) fed to a coincidence detector. If the aerial beam is assumed to be performing a scan the output of the gate circuit to the coincidence detector will be a series of pulses of a width dependent on the beam width and amplitude dependent on the target range. The coincidence circuit may also be fed with the saw-tooth scanning waveform of a radially scanned display tube and pass brief brightening pulses to produce an indication on the display when the amplitudes of the two inputs are equal. The amplitude of the brightening pulse may be controlled inversely in accordance with fourth power of range so that the indications of distant objects are less bright in accordance with actual practice. The radar position information fed to the computor may, in the case of an airborne radar, be the resultant of integrating the components of craft speed along the respective axes. The craft speed being regarded as the sum of the air speed and the wind speed. The signals representing the air speeds may be obtained from the flight controls of a dummy aircraft as may also be the angular information representing the attitude of the aircraft which is used at a later stage in the computor. Modifications may be made to simulate a stabilized scanning aerial or one having a fan-shaped beam. One form of computor is described with reference to Figs. 1, 2 and 3 (not shown).