Patent GB-1042822-A (GB)
Title: Radar system
IPC: G01S13/58
Filed: 1963-04-05
Abstract: 1,042,822. Radar. CANADIAN PATENTS & DEVELOPMENT Ltd. April 5, 1963 [Aug. 31, 1962], No. 13561/63. Heading H4D. [Also in Division G4] A radar system comprises an aerial affording two mutually divergent pencil beams P1, P2, Fig. 1, rapidly scanning sequentially the azimuthal arc SR, Fig. 6a, a type-B display, Fig. 6c, displaying echoes E, E<SP>1</SP> of a mortar projectile as it passes through the beams, and an analogue computer which determines the range R m  and azimuth A m  of the source M<SP>1</SP>, Figs. 2, 3, of the projectile by extrapolation of the points a, b corresponding to projectile echo ranges R1, R2, and azimuths A 1 , A 2 , in accordance with the equations: where the synbols having the meanings: #R = R 1  - R 2 , #A = A 1  - A 2 , α is the angle between beams P1, P2, # is the angle beam P1 makes with the horizontal plane HP through the radar, # is the estimated angle of the projectile source below the horizontal, g is gravitational acceleration, and #T is the time interval between echoes E, E<SP>1</SP>. Aerial system. Fig. 1.-The aerial system affords a 1 degree pencil beam scanning alternately in planes P1, P2 separated (α) in elevation by some 2“ degrees, to produce effectively two fan-shaped beams each scanned 20 times per second, by means of a Foster.type soanner SC (see U.S.A. Specification 2,832,936) modified as described in " Electronics," Sept. 18, 1959, pages 34-36. Scanner SC is at the focus of a semi-parabolic cylinder RF, and the assembly is mounted on a platform AP on vehicle V, the platform being maintained horizontal as described in Specification 1,042,826; the assembly can be inclined relative to the platform to tilt the fan beams whilst maintaining α constant, and is rotatable in azimuth. Echo display and operator's procedure, Figs. 6c, 7d.-After detection of a firing on a smallscale type-B display, Figs. 6a, 6b, the operator enlarges the display scale, Fig. 6c; the composite display of all received echoes is as depicted in Fig. 7d. The operator chooses the points CML, CMU corresponding to lower and upper beams, each point being the mean of the centres of the lower leading edges of the first and last echoes. Screen S is provided with a writing surface. A hand switch HS is used to record the interval #T, taken between respective first echoes, by timer TM. An electronic marker, Fig. 7e (not shown), the position of which is adjustable conjointly by azimuth marker hand wheel AMH and range marker hand wheel RMH by means described in Canadian Specification 580,247, is first set on point CML and foot switch FS then depressed thus bringing the computer into operation (see below); switch FS is of the kind which remains closed until an ensuing depression which takes place when the electronic marker has been aligned with point CMU. Quantities #R, #A are thus fed into the computer. Analogue computer, Figs. 8, 10.-The analogue computer is shown schematically in Fig. 8 and comprises an electro-mechanical arrangement utilizing shaft rotations, mechanical differentials for adding purposes, and servo-controlled potentiometer wipers. The inputs set into Fig. 10 are: #, by shaft H10; #, by shaft H11 from hand wheel WPH; #T, by shaft H15 from the timer; and R m  by shaft H9 from the apparatus of Fig. 9 (not shown); shaft H7 produces K<SP>1</SP> according to the aforementioned equation. In the apparatus of Fig. 10, shaft H12 represents (# + #) and a gear ratio is chosen to give (# + #)/α. The factor is derived in a bridge servo loop the inputs to which are R m  at resistor R11, (K<SP>1</SP>+¢) at resistor RR12, and #T at resistor RR13; resistors RR12, RR13 are wound in a square-law manner, and resistors RR11, RR14 are linear. By appropriate proportioning of circuit constants the factor g/2α is taken into account. The apparatus of Fig. 11 (not shown) accepts A 1 , #A and K<SP>1</SP> to form A m  and the apparatus of Fig. 9 forms R m . The computed values of A m  and R m  are displayed on respective counters CT1, CT6. Conversion of these polar coordinate quantities to cartesian co-ordinate is carried out utilizing a resolver, Fig. 12 (not shown), and the cartesian co-ordinates of the radar are added by handwheels REH, RNH; the final values are displayed on counters CT10, CT12 and are transmitted to the " friendly " gun site. Computation may be modified by neglecting curvature of the projectile trajectory and using a straight line extrapolation to f<SP>1</SP>, Fig. 2. Directing own fire, Figs. 2 and 8.-To facilitate control of the " friendly " gun when the shells used are fused for air bursting the operator inclines the working plane WP, Fig. 2, until the corresponding height appears in target elevation counter CT4. Re-setting of computer.-The computer is reset by further operation of foot switch FS and hand switch HS; completion of re-setting is indicated by a lamp LP2, Fig. 10. The azimuthal scan may be arranged to centralize the echoes on the display, Fig. 11 (not shown). The radar pulse repetition frequency is selectable, corresponding to long and short range operation.