Patent GB-795537-A (GB)
Title: Improvements in or relating to radar display apparatus
Inventor: SIMMONS RONALD ERIC GEORGE
IPC: G01S7/24
Filed: 1955-05-27
Abstract: 795,537. Radar; cathode-ray tube circuits. DECCA RECORD CO., Ltd. June 12, 1956 [May 27, 1955], No. 15478/55. Drawings to Specification. Class 40 (7). Relates to a pulse radar C.R.T. P.P.I. for use on a craft in which a fixed direction on the display, e.g. upwards, corresponds to the heading of the craft, i.e. the display is relative, and in which smudging of displayed echoes due to changes in the heading of the craft is prevented by rotating the tube in accordance with said changes in heading. According to the present invention the origin of the display is displaced at a rate and in a direction corresponding to the rate and direction of movement of the craft. As described, the tube is rotated by a motor controlled by the craft's compass and the relative display may be produced by (1) fixed X and Y scan coils energized by sweep components resolved in accordance with the relative bearing of the aerial, Fig. 1; (2) X and Y scan coils fixed relative to a housing which is rotated with the tube, the coils being energized by sweep components resolved in accordance with the true bearing of the aerial, Fig. 2; (3) a single scan coil rotated in accordance with the relative bearing of the aerial, Fig. 4; or (4) a single scan coil rotated relative to a housing in accordance with the true bearing of the aerial, said housing being rotated with the tube, Fig. 3. As illustrated in the Figure, a voltage proportional to the speed of the craft is resolved by a compasscontrolled resolver into E-W and N-S components and integrated to give corresponding E-W and N-S displacement voltages which are applied to (a) X and Y shift coils fixed relative to a housing rotated with the tube, Figs. 2 and 3; or (b) compass-controlled combining and resolving circuits producing voltages proportional to the components of the craft displacement resolved along the longitudinal and transverse axes of the craft, said voltages being applied to fixed X and Y shift coils, Figs. 1 and 4. When the scan and shift coils are of the same form and are mounted in the same manner, e.g. Figs. 1 and 2, the two sets of coils may be interwound or replaced by a single set of deflection coils fed with combined scan and shift signals as in Specification 737,519. In any embodiment employing X and Y scan or shift coils, these may be replaced by three coils mutually inclined at 120 degrees, the inputs thereto being modified accordingly. In the embodiments, Figs. 2 and 3, comprising shift coil arrangement (a), the tube and the shift coils are mounted in a single housing which is rotatable by the compass-controlled motor and the display can be converted to an azimuth-stabilized display, with or without off-centring, by means of suitable switches. The speed voltage may be generated automatically as in Specification 795,288, or the speed may be determined by manual adjustment of the speed voltage so that an echo from a known stationary object appears as a stationary response on the screen. If the craft is to travel a straight course the speed voltage may be integrated directly and applied to a single fixed shift coil. A transparent plotting surface may be fixedly or rotatably mounted on the screen of the C.R.T. Reference has been directed by the Comptroller to Specification 599,889, [Group XL].