Patent GB-746629-A (GB)
Title: Improvements relating to radar apparatus
Inventor: STAAL MARCUS
IPC: G01S7/10
Filed: 1954-02-26
Abstract: 746,629. Radar. NAAMLOOZE VENNOOTSCHAP HOLLANDSE SIGNAALAPPARATEN. Feb. 26, 1954, No. 5746/54. Class 40 (7). To search and determine the position with a fair degree of accuracy of a target whose position is to be determined very accurately, or which is to be followed, by a narrow beam conical scan radar a separate horizontal fanbeam radar scanned in elevation is used. The two radars may be separate and have separate transmitters and receivers or they may be partially combined and in either case arrangements are provided to enable the automatic or manual alignment of the conical scan aerial system with a target determined by the use of the search aerial. The aerial arrangements may be as shown in Fig. 1, wherein the framework 101 is rotatable about a vertical axis for aligning both aerials in azimuth. The framework carries the aerial for conical scanning 102 which consists of a reflector with an eccentricallyrotating radiator 105. This aerial is mounted as a whole for adjustment in elevation about a horizontal axis 103. The search aerial consists of a radiator 104, which is relatively high to limit the beam width in the direction of scan, and a primary element 106 at the end of a jointed wave-guide 108. The scanning of the search aerial is effected by moving the element- 106 and wave-guide 108 about an axis parallel to the axis 103 by means of a crank mechanism 107. The framework is first aligned by rotation about the vertical axis so that the aerials are directed in approximately the correct azimuthal direction and then the search aerial is scanned in elevation for the location of the desired object. The conical scan aerial may be scanned along with the search aerial so that it is automatically aligned in elevation with the object or it may be automatically aligned after the object has been located by the search radar or, finally, it may be aligned manually under the guidance of displayed information as to the difference between its direction and that of the object. To speed up the search and assist in obtaining a sharply focused search beam the elevation scan may be limited in extent and the search aerial system as a whole be capable of a preliminary adjustment about a horizontal axis. As the conical scan radar and the search radar are never required simultaneously a single combined transmitter-receiver equipment may be provided which can be switched from one aerial system to the other. The output of the receiver must also be switched over at the same time. The output of the conical scan radar is used to indicate the co-ordinates of a particular target and also, if desired, for fully or partly automatic tracking whilst that of the search radar provides alignment information. The conical scan radar will normally work with a range gate for the selection of one particular object whereas the search radar is concerned with all possible objects of interest and has no gate. Where there is no automatic system aligning the two radar systems the display system shown in Fig. 2 may be used. In this arrangement pulses applied at 202 from the transmitter trigger saw-tooth generator 201 to provide a horizontal range time base for cathode-ray tube 203. The vertical deflecting plates obtain a potential dependent on the position of the search aerial from potentiometer 204 coupled thereto and the trace is brightened by the application of signals corresponding to received echoes from receiver 206 to grid 205. Thus the range and elevation of all objects in the field of view of the search radar are displayed. The display also carries a horizontal line elevation marker, indicating the elevation angle of the conical scan radar, obtained by comparing the potential derived from unit 204 with that derived from a similar potentiometer 207 coupled to the conical scan aerial in circuit 208 and, when these are equal, delivering a brightening pulse to the grid 205. Finally there is displayed a vertical line range marker indicating the range of the gate in the conical scan radar. This may be obtained either by using the gate pulses themselves if the conical scan radar uses pulses synchronous with those supplied at 202 or by comparing a potential derived from potentiometer 209 adjusted in accordance with the gate position with the time-base waveform in circuit 210 at releasing a very short brightening pulse each time these are equal.