US2410666A

US2410666A - Orienting mechanism for pulse echo systems

Info

Publication number: US2410666A
Application number: US398057A
Authority: US
Inventors: George W Leck
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1941-06-14
Filing date: 1941-06-14
Publication date: 1946-11-05
Anticipated expiration: 1963-11-05

Description

Nov. 5,1946. G. w. LECK 2,410,666

ORIENTING MECHANISM FOR PULSE EQHO SYSTEMS Filed June 14, 1941 3 Sheets-Sheet 1 l l l l l i 3nventor BB l/ NOV. 5, 1946. w CK 2,410,666

ORIENTING MECHANISM FOR PULSE ECHO SYSTEMS Filed June 14, 1941 I s Sheets-Sheef 5 Mame Q d-c. Harm 6 m; 7965 Z SnveFtor Patented Nov. 5, 1946 ORIENTING MECHANISM FoR PULSE ECHO sYs'rEMs George W. Leek, Collingswood, N. J assignor to Radio Corporation of America, a corporation of Delaware 1 Application J me 14, 1941, Serial No. 398,057

' vThis invention relates to scanning devices and particularly to improvements in devices for Varyin'g-f the direction of a beam of energy from a pulse echo system and for directing in synchronism therewith the scanning beam of a cathode ray indicator.

Pulse echo systems are usedto detect'objects and to indicate the'direction and distance of the object. In such systems a directive antenna is generally used for the pulse transmission and a non-directive antenna may serve for reception or ,vice versa, or directive antennas may be used forboth transmission and reception. While separate antennas may be used, the instant invention is described by referring to a single directive antenna which may be used for both transmissionand reception. {Such an antenna system is described in the copending application Serial No. 184,354, filed January 11, 1938, by Wolff and Herschberger, for Signaling system. One of the objects of the instantinvention is to'provide improved means for'scanning a region by a beam of pulse energy. Another object is to provide iniprovedmeans for moving a beam of pulse energy andja cathode ray beam in synchronism. .Another object is to provide means for directing a beam of pulses throughout a conical region and for synchronously directing a cathode ray beam in a helical pattern;

' The invention will be described by referring to the accompanying drawings in which Figures 1 and 2 are front and side views, respectively, of one embodiment of the invention; Figure 2a, is a fragmentary sectional View along the line IId-Ha; Figure 3 is a sectional view of another embodiment of the invention; Figure 4 is a schematic diagram of amo'dification for conical scanning; and Figure 5 isa circuit diagram of a modification of Figure '4. Similiar reference characters'are applied to similar elements in'the several figures. V Referring to Figs. 1, 2 and 2a, a motor l is mounted on 'a base-3 which supports a directive antenna system .5. The antenna system is pivotally mounted in a yoke T. The yoke is oscillatably'mounted on a-hollow bearing member 9. The oscillations of the yoke are produced by means of a driving gear H which is securedtoa shaft. l3 extending from the motor I through the hollowbearing member 9. The driving gear engages a driven, gear l5.. A, pair of links. I1, 19 or a cam slot or the like, connect the driven gearto-the yoke so that as the gear rotates the yoke gisflloscillated through the desired angle: A second set. of; link members v21,: 23 .lare =usedto 3 Claims. (01. 250- 11) connect the gear shaft 25 with a potentiometer arm 21 so that the potentiometer arm oscillates in synchronism' with the antenna system 5; The output leads from the potentiometer 29 are connected to the horizontal deflecting electrodes of a cathode ray tube 3i.

The antenna system 5 is oscillated about the yoke pivots by an eccentric 33 which is driven" in. the following manner: A first bevel gear 35 is connected to the motor shaft l3 and is arranged to engage a second bevel gear 31 which is mounted on a stub shaft 39. A cam M is secured to the shaft 39 and is arranged to engage the inside surface of an aperturein a'connecting rod 33, The connecting rod 43 is pivotally connected to a member 45 which terminates in the antenna system. The eccentric 33 is also connecte'dto a potentiometer arm 41. The potentiometer arm is arranged to oscillate in synchronism with the antenna system as'it moves'about its horizontal axis on the yoke. The output of thev potentiometer 48 is applied to the vertical deflecting electrodes of the cathode ray tube 3i. v

The antennasystem is connected by} a transmission line lllto a' pulse transmitter Friend-to a pulse'receiver '53. Theoutp'ut of the pulse'receiver is applied tothe control electrodes ofthe cathode ray tube 3! so that received signals may brightenor dim the cathode ray trace.' The trace is moved horizontally in synchronism with the oscillations of the antennasystem about its vertical axis. The trace is movedvertically in synchronism with'the oscillations'oi the antenna system about itshorizontal axis. The ratio of horizontal toverticaloscillations is dete'rminedby the several gear ratios.

The cathode ray screen may beprovided with a'suitable calibration so that'the azimuth and elevational angles at which'an' echo pulse is "observed may be indicated. From the nature of the antenna movements, it follows that the directive beam will explore a substantially pyramidal form. The cathode ray trace the base of the pyramid) I h In some installations it may-be-desirable-to explore a conical region. --One"suitable arrangement for scanning conically is shown in Fig-3; In'this arrangement the antenna-system (Si is mounted on a cylindrical member 63 whichis journalled in bearings 65, B1. The antenna sys-' tem is rotated by a motor 69 which may be connected by a belt, chain drive 1!, gearing or 'the like, to the cylinder 63. A ringgear '13 is secured to the" base. l5 which supportsa. synchronous motorc69 andbearings 65, -61. Alpinion .gear fll',

will correspond to mounted on the cylinder 63, engages the ring gear I3. A pair of cranks I9 are connected to the pinion gear shaft on either side of the bearings 8| therefor. The cranks I9 are connected by links 83 to the antenna system 6|.

The synchronous motion of the cathode ray is effected by'therollowing means: The currents applied to the synchronous motor are also applied to a phase splitter 85 and hence to the cathode ray deflecting electrodes of the cathode ray tube 81 to produce a circular trace. The radius of the trace is controlled by deriving biasing voltages from a potentiometer 89 which is operated in synchronism with the radial movements of the antenna system. The potentiometer '89 is operated as follows: A link Si is used to connect the antenna system to the potentiometer arm93. As the antenna system moves on its pivotal mounting 95, the arm 93 will move to vary-the potentiometer output voltage, which is applied to a radial deflecting electrode 92 of the cathode ray tube 81.

It should be understood that as the antenna system is rotated about the axis 91 of the cylinder 63, the gear I? through the movements of the crank I9 and connection lever 63, slowly tilts the antenna system about its axis. 95. Thus the beam ofpulse energy from the antenna traverses a conical region, or expressed another way, the axis of the beam traverses a. spiralpath. The cathode ray also traverses a spiral path and it moves in synchronism with the beam from the antenna.

The ratioof the twomovements which make up the conical scanningby means of the radio beam is determined by the. ratio of the ring gear I3 to the pinion gear 11. This ratio maybe selected to obtain the required definition of scanning. While the arrangement has been shown for scanning a conical region in which the axis of the cone lies between the horizon, and the zenith and including a definite azimuth angle, it should be understood thatbymounting the base I5 in a vertical plane the device may be used to scan throughout the azimuth as willqbe shown in a modification of the invention.

A modification of the foregoing arrangement is shown in Fig. 4 in which an electromechanical drive is substituted for the mechanical system of:Fig. 3. In the modified arrangement the directive antenna system IIII is mounted in va'ball and socket or other universal joint IIIB which is supported by a post I05 extending from the-base member IIII. Three solenoid type motors I99 are preferably mounted at 120 intervals. The motors each include a polarized magnetic armature or movable member III.

a The movable members III are connected ,by suitablelinks II 3 to bearings I I5 on the .outer portion of the antenna reflector or other antenna member. The field coils of the -motors are. energized by a-three phase alternator'I II, -w.hich is driven bya motor H9. The shaft-k200i the alternator, or the driving motor II9,iis connected through suitable gearing I ZI' to .arheostat I23. in

the generator exciter circuit I24. The generator output is thus varied according to any desired pattern so that the three phase output voltage .follows, for example, a sawtooth pattern. The motors I09 are successively energizedby the three phase currentsso that theantenna system undergoes a circular. rockingzmovement, ofjan amplitude varying according to -the generator. output, The resulting antenna beam deflections follow a spiral pattern. That. is, as the applied: voltages .in-

crease because of the sawtooth wave form of the generator exciting voltage, the motors I09 produce larger and larger movements and since the movements are preferably at intervals in space and in time, the axis I26 of the antenna I28 traces a helical pattern and the beam of pulses from the antenna scan a conicalor hemispherical region. The three phase currents may be applied to a three coil deflecting system I39 arranged around the cathode ray indicator I32 to rotate the cathode ray in synchronism with the rotations of the antenna, and the sawtooth voltages may be applied to produce radial movements. The cathode ray will trace a helical pattern on the fluorescent screen of the indicator, which may be provided with a suitable calibrated scale I34 to indicate the position of the reflecting obiect with respect to predetermined coordinates.

Instead of using polarized magnetic armatures in the solenoid motors I09 and applying sawtooth exciting voltages to the three phase generator, the movable motor members III may consist of a second solenoid I I2 to which the sawtooth voltages from the potentiometer I23 may be applied, as shown in Fig. 5. Under these circumstances, the three phase currents are applied to thefixed windings and the direct currents are appliedto the movable windings, or vice versa, so that the antennas will be deflected by variable amounts so that its axis follows a helical path as before. In either arrangement the connecting rods may be provided with biasing springs I25 to maintain the zero or central position of the antenna, which has been omitted to avoid complicating the diagram.

Thus the invention has been described as an improved means for scanning a region by means of a beam of pulses. A cathode ray is moved in synchronism with the scanning beam. Received pulse echoes are applied to modulate or vary the cathode ray so that an object will be indicated according to predetermined coordinates on the cathode. ray tube screen. Inthis manner the sky from the horizon upwardly may be continuously scanned and refiections'from an aircraftor surface vessel coming over the horizon will'indicate the azimuth and elevationof the craft.

I claim as my invention:

1. A pulse echo scanning device including a directive antenna for radiating a beam of pulses and for receiving reflected pulses returning substantially along said beam, means for moving said antenna so that said beam traces a spiral ina plane normal to said beam so thatsaid beam scans a conical region, a receiver connected to said antenna and responsive to said reflected pulses, a cathode-rayindicator including ray defiecting and ray varying elements, means for deriving from said antenna movements currents.

corresponding to said spiral, meansior applying said currents to said ray deflecting elementssc that-said ray is synchronously moved ina spiral pathgcorresponding tothe said beamspiral, and means: for.v applying to said ray varying element currents deriving from said receiverand corresponding to'said reflected; pulses to indicate-the position of a pulse. reflecting object.

2..A;pulsev echo scanning deviceincludingin combination,:.a directive antenna'for radiatinga beam of pulses and for receiving echo pulses from objects in saidbeam, av rotatable support forsaid antenna,.means for pivotally mounting said antenna on saidsupport, means forrotating :said support, aring. gear and a. pinion gear. cooperat ing with said rotatable support so that said pinion gear is rotated as said support is rotated, a crank member operated by said pinion gear, a link member connecting said crank and said antenna for moving said antenna back and forth on said pivotal mounting as said antenna support is rotated, the movements of said support and said antenna directing said beam of pulses in a spiral path, a receiver connected to said antenna and responsive to said echo pulses, a cathode ray indicator connected to said receiver for indicating said echo pulses, and means responsive to said antenna support and antenna movements for synchronously moving said cathode ray along a path corresponding to said spiral.

3. A radio beam scanning device including an antenna system for establishing a sharply defined beam, a rotatable support including a pivotal mounting for said antenna system, means for rotating said support, a ring gear and a pinion gear cooperating with said rotatable support so that said pinion gear is rotated as said support is rotated, a crank member operated by said pinion gear, and a link member connecting said crank and said antenna system for moving said antenna system back and forth on said pivotal mounting as said antenna support is rotated.

GEORGE W. LECK.