GB1446850A - Signal converters - Google Patents

Abstract

1446850 Cartesion to polar co-ordinate converter PLESSEY CO Ltd 21 Nov 1973 [1 Dec 1972] 55540/72 Headings H3H and H4D A circuit for converting analogue cartesian co-ordinates X, Y to polar co-ordinates R, # (# digital) comprises a clocked counter providing a signal representing a progressively variable angle α, means receiving the angle signal and providing sine α and cosine α signals, multiplier means producing digital signals representing X cosine α and Y sin α, comparator means inhibiting further variation of the angle α when X cos α = Y sin α, the angle α then being #; means for producing complement signals X sin # and Y cos # and means for summing the complement signals giving R. Clock pulses are fed to 11 bit binary counter 16, the output of which represents the variable angle. The angle signal is fed to two true / complement devices which provide, under control of signals on lines 22, 23 either the angle or its complement to Read only memories 26, 27, which give as output the sine of the input angle. Initially the complement is supplied by 20 and the output of ROM26 is the cosine of the angle, while 21 supplies the true value and ROM27 the sine of the angle. The sine and eosin signals, together with the analogue co-ordinate values are supplied to respective multiplying D/A converters 30, 31 as shown and the output signals are passed to comparator 34. At equality of the X cosine and Y sine signals, the flow of clock pulses to counter 16 is stopped. The true and complement devices 20, 21 are then switched to their other states and the resulting X sine and Y cosine signals are summed at 36 to give R. The converter may be used in numerical control machines, gun turret control, video map generation and CRT deflection systems. It may also be used in a height finder radar system (Fig. 1) in which the X and Y co-ordinates of a target are generated from a plan position indicator display by potentiometers connected to a joystick or rolling ball marker. The bearing # is used to direct a nodding height finder radar aerial and the range information for distinguishing between several targets in line and to control the angle of nod which can be less for more distant targets.