Patent GB-622455-A (GB)
Title: Improvements in radio-receiving apparatus for steering aircraft in a predetermined path
IPC: G01S1/02
Filed: 1944-11-16
Abstract: 622,455. Radio navigation; radiolocation. SPERRY GYROSCOPE CO., Inc. Nov. 16, 1944, No. 22766. Convention date, Nov. 23, 1943. [Class 40 (vii] In radio receiving apparatus used in steering an aircraft to follow a landing path defined in relation to a radio beam in which the deviation from the path is indicated on the screen of a cathode-ray tube, the beam of the cathode-ray tube is recurrently deflected by appropriate control signals to produce on the screen traces which, when the aircraft is on the landing path, simulate the appearance of a physical structure as viewed from a point on the landing path and in such a way that the relationship between these traces, or the parts of the traces, is altered in response to signals measuring deviation of the aircraft from the landing path so that the modified traces represent the physical structure as seen from a point displaced from the landing path in the direction of the aircraft's displacement therefrom. In the arrangement described, the physical structure simulated is a tunnel represented by a series of concentric rings 18 ... 26 modified to provide a perspective view at a plane located at a predetermined distance from an observer in the aircraft 16 and a stereoscopic representation may be produced. A pattern comprising a number of concentric rings, Fig. 7 (not shown), on the screen 31 of a cathode-ray tube 32 is scanned by a beam moved in circles of decreasing diameter by the combined operation of a sawtooth generator 38 controlled from a polar generator 36 driven by a motor 35 and an oscillator 39 producing sinusoidal waves of a frequency much greater than that of the sawtooth waves together with an arrangement 42 producing a phase shift of-90 degrees between the inputs to the amplifiers 41, 43 controlling vertical and horizontal deflection. The output from the tube 32 is applied to a cathode-ray tube 34 whose horizontal and vertical deflection amplifiers 64, 67 are fed from summation circuits 63, 66 which are supplied with sinusoidal components from the oscillator 39 and balanced modulator 62, a 90 degrees phase shifter 65 being associated with the circuit 63. A non- linear sweep generator 61 producing pulses of hyperbolic waveform and synchronized with the sawtooth generator 38 is connected through balanced modulator 62 and also to modulators 68, 69 so that the circles produced by the tube 34 will not be equally spaced on to screen 33. Signals from a localizer receiver 72 and a glide-path receiver 74 corresponding to deviations from the glide path are applied through switch arms 71, 73 to the balanced modulators 68, 69 and to the circuits 63, 66 to modify the normal trace. The object in employing a hyperbolic waveform is demonstrated in connection with Figs. 2, 3 (not shown). Deviations of pitch relative to a stabilized horizon provided by a gyroscope 75 are derived from a potentiometer 82 and applied to the vertical direction amplifier 67 and yaw deviations relative to a gyroscope 76 are derived from a potentiometer 91 and fed to the horizontal direction amplifier 64. The arrangement is modified for stereoscopic presentation by a control arrangement 101 fed with the non-linear waveform produced by generator 61 and applied in opposite phase over leads 115, 116 and commutator 117 to the horizontal deflection arrangement 64. A screen polarized in two directions at right angles and intermittently rotated through 90 degrees by gearing driven from the motor 35 enables alternate images to be viewed by the right or left eye of the observer through polarizing glasses 124. The system may be modified to provide an indication of distance by connecting the sawtooth generator 38 through a switch 29 to the circuit 125 which is arranged to provide a voltage corresponding to the distance of the aircraft from a pulse-transmitting apparatus located on the ground and arranged to send signals dependent on the reflection time of the pulses-the distance-indicating voltage controlling the amplitude of the sawtooth wave and consequently the number of rings appearing on the screen 33, thus providing an indication of the distance of the aircraft from the landing point on the airport. The system may be used for constant-altitude flying by substituting a beacon receiver 128 for the localizer receiver 72 and an altimeter 129 for the glide-path receiver 74. The indications on the cathode-ray tube and the modified traces corresponding to deviations of the craft from the desired path are illustrated in Figs. 10 to 15 (not shown). Specifications 496,521 and 536,090 are referred to.