US2415678A

US2415678A - Antenna

Info

Publication number: US2415678A
Application number: US460590A
Authority: US
Inventors: Martin A Edwards
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1942-10-03
Filing date: 1942-10-03
Publication date: 1947-02-11
Anticipated expiration: 1964-02-11

Description

Feb. 11, 1947. M. A. EDWARDS ANTENNA Filed Oct 3, 1942 3 Sheets-s 1 Martin A. Edwards Feb. 11, 1947. w bs I 2,415,678

ANTENNA Filed Oct. 3, 1942 3 Sheets-Sheet 2 Inv entor" Martin A. Edwards,

b5 WW EJ His AttoT'Tweg Feb. 11, 1947. M. A. EDWARDS 2,415,678

ANTENNA Filed Oct. 5, 1942 $Sheets-Sheet 3 Inventor: Martin A. Edwards,

y x MMZM i ZAttoT'he Patented Feb. 11, 1947 UNITED ANTENNA Martin A. Edwards, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application October 3, 1942, Serial No. 460,590

6 Claims.

The present invention relates to directional scanning antennas, known as scanners or spinners, for use in radio locating equipment.

In use the antenna is rotated in azimuth while the elevation may be continuously varied so the antenna transmits or receives radio waves from a sector of a spherical sector coordinated with the azimuth and elevation of the antenna.

It is desirable that the antennabe rotatable in azimuth at a high speed, that the elevation be controllable through a wide angle, and that the support for the antenna, cause a minimum of interference with the radio waves. In prior constructions the desired speed has been prevented by excessive vibration, and the support has caused interference with the radio waves at some elevations.

The object of my invention is to provide an improved antenna construction which is mechanically balanced so as to permit the desired high speed rotation, which has an improved control, which has a support causing a minimum of interference.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and m thod of operation, together with further objects and advantages thereof, may best be run derstood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 is a perspective rear view of an antenna embodying my invention; Fig. 2 is an elevation, partly broken away, of the turntable; and Figs. 3 and 4 are control diagrams.

Referring to the drawings, there is shown an antenna projecting along the axis of a parabolic reflectorfi. The antenna and its associated reflector comprise a parabolic antenna unit which transmits or receives radio waves along a narrow l beam concentric with the axis of the reflector. The antenna and reflector, which preferably is parabolic in form, are supported for tilting about horizontal axis so as to vary the elevation of the antenna by trunnions 3 and 4 associated with brackets 5 and 8 fixed to a reinforcing channel lid on the back of the reflector. The trunnions are at the upper ends of standards I rising from a turntable 3 journaled for rotation on a, vertical s in azimuth) by ball bearings 9 (Fig. 2)

ed. in a base ill. The antenna is rotated in muth a motor I l on the base having a, pinion 5 in driving a crown gear l2 fixed to the turn table. The antenna is tilted about the axis of the trunnions 3 and 4 to vary its elevation by a reversible motor I3 driving a, countershaft l4 through reduction gearing l5 and connected to the antenna through a crank arm l6 fixed to the countershaft which moves a link ll connected to a crank arm l3 fixed to the channel 5a, on the back of the reflector 2.

The elevation of the antenna is controlled by a cam shaft 2a carried in a frame 2| on the housing for the reduction gearing l5 and having a gear sector 22 which meshes with a gear sector 23 fixed to the countershaft l4. Ihe cam shaft 28 accordingly moves through the same angle as the countershaft l4 and at any instant has a position corresponding to the elevation of the antenna. The cam shaft 20 is connected through bevel gears 24 to a rotating potentiometer 25 supported on the turntable and connected through slip rings 25 and 21 (Figs. 3, 4) to coils 28 and 29 which shift the beam of a cathode ray tube 353 vertically in accordance with the elevation of the antenna. A similar rotating p0- tentiometer 3|, supported on the base Ill, driven at the same speed and in phase with the turntable by reduction gearing having a pinion 32 meshing with the gear [2 on the turntable, is connected to coils 33 and 34 which shift the beam of the cathode ray tube horizontally in accordance with the azimuth of the antenna. Through the rotating potentiometers 25 and SI the position of the trace on the cathode ray tube screen is directly related to or coordinated with the azimuth and elevation of the antenna.

The electrical connection to the antenna is through a coaxial transmission line 555 which extends up through the center of the turntable and in through the center of the trunnion 3 and the back of the reflector 2 to the antenna. A rotating joint 35 at the trunnion E5 and a similar rotating joint (not shown) at the turntable permit the necessary relative movement between the parts Of the transmission line.

The antenna presents a difficult balance problem. For effective scanning it must be rotated at a high speed and the elevation must be capable of continual change between rather wide limits. In the particular antenna illustrated the antenna is rotated in azimuth at a speed of 360-400 R. P. M. and is tilted in elevation between limits of 10 and from the horizontal at a rate of 30 sec. (5 R. P. M.). The structural parts, as obvious from the drawings, are not symmetrical about the axis of rotation. The mechanism for varying and controlling the elevation of the antenna (the motor 13, gearing l5, cam shaft 25 and its associated gearing, link ll, potentiometer 25, etc.) is mounted back of the axis of the tumtable as viewed from the front of the reflector so as to provide a clearance permitting tilting of the reflector to an angle below the horizontal (or above the horizontal if the antenna is inverted and suspended from a top support). For the same reason the standards I may be shifted or bent toward the back of. the turntable. The center of gravity of the antenna 5 and its associated reflector 2 is forward of the axis of the turntable. The link ll and the associated crank arms I5 and It occupy different positions for each elevation of the antenna and accordingly intro duce a variable unbalance.

It has been found that the antenna can be balanced for satisfactory operation at the desired high speeds by counterbalance weights El, 38, 39, The counterbalance weight .i'l is carried by arms 43E projecting from the back of the reflector and holding the weight in line with the antenna l. The counterbalance weight 3? shifts the center of gravity of the antenna and reflector to a point slightly forward of the turntable axis as viewed from the front of the reflector. The balance weight 3?, the antenna I, and the reflector 2 are equivalent to a weight directly over the of the turntable and an additional weight on the antenna l in front of the reflector. If the counterbalance weight 3i is large enough to bring the center of gravity of the weight of the antenna and the reflector directly above the axis of the turntable, the operation will be improved if an additional balance weight is fastened to the antenna in front of the reflector. In the present construction the balance weight ill is accordingly equivalent to this larger balance weight and the additional weight on the antenna. The balance Weight on the trunnion t acts as a counterbalance for the transmission line and the rotating joint 35. The balance Weight 39 carried by an arm d2 depending from the channel to at right angles to the arms il acts as a counterbalance for the link ll since it has a movement opposite that of the link. The counterbalance weight is fixed to the front edge of the turntable, it, together with the unbalanced weight of antenna reflector and weight ill (in front of the turntable axis as described above), counterbalances the Weight of the motor it and the associated parts. on the back of the turntable. The unbalance due to the motor iii and its associated part should theoretically be counterbalanced by an equal and opposite weight at the iro-ntoi the turntable. If this were done the Weight would be above the turntable and would interfere with the tilting of the reflector unless trunnions 3 and l were raised further above the turntable. Since space is at a premium 2. ore compact antenna assembly is obtained by counterbalancing the motor 53 and its associated parts with the balanceweight it (below the center of gravity of the motor it, etc.) and the unbalanced weight of the antenna l, reflector 2, and weight ill (above the center of gravity of the motor 83, etc.).

Because the center of gravity of the antenna, reflector, and balance weight 3? is in front of the turntable axis, the counterbalancing effect varies with the elevation of the antenna. This i compensated by the weight 39 which has an effect cancelling the variation due to the elevation of the antenna.

With the balance weights as shown is possible to distribute the weight so the moment of inertia of the entire rotating system about the mechanica] axis of rotation is greater than the moment of inertia about a cross axis through the center of gravity of the system so the system rotates stably about its mechanical axis. As indicated in the description, the functions of the balance weights not limited to counterbalancing cerparts, and for best results the weights should varied experimentally for each antenna syscm. location of the balance weights and the arrangement of the parts is, however, such that only a mall amount of experimentation should be required.

control diagrams of Figs. 3 and i are quite similar except in the arrangement for selecting the of elevation of the antenna. Corresponding parts the control diagra" 1S accordingly indicated by the same reference nu.- merals.

In each of the control diagrams the azimuth. motor ii is a direct current motor having field sanding shunted across the armature terminals, one of which is grounded and the other of which i connected through conductors and to a switch it in the high side of a direct current power supply ll. The azimuth motor accordingly operates continuously when the switch is closed. In addition to rotating the antenna in azimuth, as described above, the azimuth motor it through a suitable connection indicated by the dotted line is rotates a cam 43 which controls switch 56 in circuit with the transmitter, indithe blocl: 5i, and arranged the is cut off during part of the azimuth e of the antenna. For example, the antenna, got be mounted on a ship in a position such that the structure of the ship blocked the antenna beam during part of its azimuth range. In 2 the cam .8 and the switch til comprise a slip ring with a suitable brush (not shown) at bottom of a stack of slip rings fixed to the underside of the turntable 3 around a supporting sleeve 52. The other slip rings in the stack are connected to the parts on the turntable. The

receiver, indicated by the block is not controlled by the switch 5&3 but is on at all times there i no need for cutting the receiver off.

During the rotation of the antenna in azimuth the transmitter is effective to transmit direetional pulses of radio waves throughout the sired azimuth range. Reflections of the transted waves picked up by the receiver are stated in frequency and rectified and supplied to the grid 5 of the cathode ray tube 36 to modulate the beam of the cathode ray tube so to provide the desired indication on the v cathode ray tube screen. As explained above, the position of the cathode ray tube beam is controlled by the coils 28, 2t, and so that is coordinated with the azimuth and elevation of the antenna.

The elevation motor it has a field winding connected through

slip rings

56 and 57! and

conductors

35 and 58 to the high and grounded sides of the power supply ll.

The difference between the control diagrams of Figs. 3 and 4 lies in the manner of controlling the connections to the armature of the elevation motor is so as to control the elevation of the antenna.

In Fig. 3 the armature of the elevation motor is is controlled by reversing relays 58 and 6% bay ing an interlock EH which prevents simultaneous energization. When the relay 5%) is energized, its armature s2 is raised from the normal position i1- lustrated, completing a circuit to the elevation motor armature which extends from one side of the armature through conductors '63, 64, slip ring 55, conductor 56, contacts 61, and conductor 68 to the high side of the power supply, and from the other side of the armature through conductor 69, limit switch I0, conductor II, slip ring 12, conductor l3, and contacts '14 to ground. Energizing the relay 59 causes the elevation motor I3 to run in the direction to depress or lower the antenna. When the relay 60 is energized, its armature T6 is raised, completing a circuit to the elevation motor armature which extends from one side of the armature through conductors 93 and B4, slip rings 65, conductor 06, and contacts 11 to ground, and from the other side of the armature through conductor 69, limit switch I0, conductor H, slip ring I2, conductor I3, contacts I 8, and conductor 68 to the high side of the power supply. When the relay 60 is energized, the elevation motor runs in the direction to raise the elevation of the antenna.

The limit switch I is controlled by a cam I on the cam shaft 20. If the antenna should pass its upper lower limit of elevation, the cam 15 moves the switch I0 to contact I9, short circuiting the elevation motor armature and bringing it quickly to rest by dynamic braking so as to prevent travel beyond the desired limits. The limit switch is a safety device which is not normally in use.

The elevation of the antenna is controlled by normally closed switches 80, 8|, 92, 83, and 84 which are controlled by

cams

85, 89, 31, 88, and 89 on the cam shaft arranged to open the switches at the arbitrarily selected degrees of ele- 1- vation indicated above the respective cams. The switch 80 which controls the upper limit of elevation of the antenna is in series with the coil of the relay 60 which causes elevation of the antenna and at the upper limit opens the circuit through the relay and causes it to open the circuit to the elevation motor. The circuit through the switch 80 extends from conductor 90, connected to the high side of the power supply through the slip ring 56, through conductor 9i, switch 80, conductor 92, slip ring 93, and conductor 94 to the relay B0. The switch 84 which controls the lower limit of elevation of the antenna is similarly in series with the coil of the relay 59 which causes lowering of the antenna through a circuit which extends from conductor 90 through switch 84, conductor 95, slip ring 55, and conductor 91 to the relay 59. The switches BI, 82, and 83 which control the elevation of the antenna intermediate its upper and lower limits are connected to common ground conductors 98 respectively in series with conductors 99, I90, and IOI, slip rings I02, I03, and I04, and conductors I05, I06, and I01 to contacts I08, I09, H0 of an upper limit selector switch III and contacts H2, H3, and I I4 of a lower limit selector switch H5. The contacts of the selector switches I II and H5 are labeled in degrees corresponding to the switches so as to aid in understanding the operation. It is obvious that the degrees are arbitrarily chosen.

In use the elevation motor runs in one direction until the desired limit of travel is reached, at which it is reversed and runs to the other limit. The extreme upper and lower limits are controlled as described above by the

switches

80 and 84 which open at the respective limits. At the upper limit. the switch opens the circuit to the relay 69, and when the armature I6 drops to the position illustrated the relay 59 is energized through a circuit which extends from conductor 90, connected to the high side of the power supply, through switch 84, conductor 95, slip ring 96, conductor 91, relay 59, contacts H6, conductor Ill, and lower limit selector switch H5 to ground. When operating between the extreme upper and lower limits the selector switches III and I I5 will be connected to the grounded contacts corresponding to the upper and lower limits. When the relay 59 picks up, the elevation motor is energized in the direction to lower the antenna. Upon reaching the lower limit the switch 84 opens, opening the circuit to the relay 59 and causing its armature '62 to return to the illustrated position. In this position the relay B0 is energized through a circuit extending from the high side of the power supply through conductors 90, 9|, switch 80, conductor 92, slip ring 93, conductor 94, relay 60, contacts H8 and selector switch III to ground.

It is sometimes desirable that the scanning be limited to a range of elevation intermediate the upper and lower limits. This intermediate range is controlled by the selector switches I I I and H5 through the normally closed switches SI, 82, and as which are opened at the designated limits.

The operation of the switches will be explained for the position illustrated in which the upper limit selector switch I I I is set at 20 and the lower limit selector switch H5 is set at 5. When the antenna is moving toward the 20 position, the

. relay 59 is deenergized and the relay 60 is energized through a circuit extending from the high side of the power supply through conductors 90, 9|, switch 30, conductor 92, slip ring 93, conductor 94, relay 60, contacts I I8, selector switch II I, contact I09, conductor I06, slip ring I03, switch 82, and ground conductor 98. At the 20 limit the switch 82 opens, deenergizing the relay 00 and causing the energizing of the relay 59 through a circuit which extends from the high side of the power line through conductor 90, switch 84, conductor 95, slip ring 95, relay 59, contacts I I6, conductor II'I, lower limit selector switch H5, contact H2, conductor I01, slip ring I04, conductor IOI, switch 83, and ground conductor 90. At the 5 limit the switch '83 opens, deenergizing the rel y 9 n en r izing the rela 60 through the circuit described above.

When it is desired that the antenna be kept at any one of the designated limits, both selector switches I I I, I I5 are moved to the same position, thereby opening the circuits to the

relays

59 and 60 at the selected position. Both relays then move to the position illustrated in which the conductors 66 and I3 in series with the elevation motor armature are short circuited through a. dynamic braking resistor H9 and contacts I20 and I2 I. The dynamic braking quickly brings the elevation motor to rest at the desired angle.

The control of Fig. 4 is not so flexible as Fig. 3 since the upper limit of elevation of the antenna is fixed and only the lower limit is variable.

As in Fig. 3 the elevation motor armature I3 is connected through the safety switch I0 which is controlled by the cam "I5 on the cam shaft 20 so that the safety switch opens when the antenna moves beyond the upper and lower limits.

The circuit to the elevation motor slip rings 65 and i2 is controlled by a reversing relay I22 having contacts I29 and I25 energizing the motor in the direction to raise the antenna, contacts I26 and I21 energizing the motor in the direction to lower the antenna, and holding contacts 528 for holding the relay in its raised position in which the contacts I26 and I21 are closed. The circuit to the motor extends from the slip ring 65, connected to one side of the motor, through a conductor E23 to either the contacts 25 or I27 and from the slip ring T2, connected through the safety switch iii to the other side of the motor, through a conductor Hill, a selector switch I35, and a conductor I32 to either the contacts E24 or lZfi. The contacts E25 and E26 are alternatively connected to the high side of the power supply, and the contacts I24 and i2? are alternatively connected to the low side of the power supply.

The elevation motor is controlled at its upper limit by a normally open switch H3, and at the selected lower limits by normally open switches I35, I35, 835, Hi, each of the switches being controlled by cams 3311, ls la, 835a, idiia, and i-E'lo; on the cam shaft Ell each of which causes its respective switch to be closed only at the designated angular position of the antenna. For convenience the switches are labeled in the arbitrarily selected degrees of elevation of the antenna corresponding to the positions at which the switches are closed.

When the relay E22 is in the deenergized position illustrated, the elevation motor I3 is rotating in the direction to raise the antenna. When the antenna reaches its upper limit, the switch 33 closes and energizes the relay I22 through a circuit which extends from the high side of the power supply through switch 66, conductor I33, resistance its, the coil of relay I22, conductor slip ring Mi, switch I33, and, conductors M l and 8 55 connected to the slip ring 5! which is connected to the grounded side of the power supply. This causes the relay to pick up, opening the contacts 524 and H25 and closing the contacts I27, and I28. The contacts I28 are holding contacts which hold the relay in its raised position. The elevation motor now runs in a direction to lower the antenna, and the switches Iii-i l, E35, N56, and i3! will be momentarily closed at the designated positions. The switches lil l to it? are respectively connected to selector switches hi6, Ml, M8, and M9 which are moved in unison with the selector switch HM, and each of which has a contact connected through a conductor I59 to one side of the relay coil I223. The other side of the relay coil I22 is connected through the conductor Md and slip ring It! to a conductor i555 connected to the other side of each of the switches. When the antenna reaches a position corresponding to the setting of the lower limit selector switches Hit-M9, the closure of the corresponding switch short circuits the coil of the relay and causes it to drop to the position illustrated in which the elevation motor is energized in the direction to raise the antenna.

In the Fig. 4 construction the antenna accordingly is continuously raised and lowered between the upper limit and the selected lower limit. Each of the selector switches has an off position in which the elevation motor is deenergized. When the selector switches are moved to the off position the antenna accordingly will remain in the position to which it has been moved.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an antenna, a reflector therefor, bearings supporting said antenna and reflector for tilting about a horizontal axis, a turntable carrying the bearings for rotating the reflector about avertical axis, mechanism carried by the turntable for varying the tilting of the reflector. within -predetermined. angular limits, said mechanism having a moment of inertia about said vertical axis variable with the tilt of said reflector, a balance weight on the reflector for counterbalancing forces due to the tilting of the reflector, and a second balance Weight movable laterally of said vertical axis in accordance with the tilt of said antenna to compensate for variations insaid moment of inertia.

2. In combination, an antenna reflector unit for rotation in azimuth and tilting in elevation so as to scan an are determined by its elevation, a turntable rotatable on a vertical axis supporting the antenna unit for rotation in azimuth, mechanism carried on and rotatable with the turntable for tilting the antenna unit in elevation within predetermined angular limits, said mechanism being behind said vertical axis with respect to the front of said reflector and having a horizontal component of movement, a balance weight mounted on the back of the reflector and so proportioned that the combined center of mass of said weight and said units lies in front of said vertical axis, a second balance weight on the front of said turntable to balance said unit and said first Weight about said vertical axis, and a third balance weight mounted upon said reflector and having a horizontal component of movement therewith opposite to that of said mechanism.

3. In combination, a turntable rotatable on a vertical axis, a directional antenna supported on the turntable for tilting on a horizontal axis, means for rotating the turntable, a reversible motor on the turntable for rotating the antenna on its horizontal axis, and a control for reversing the motor at upper and lower limits whereby the antenna scans a sector of a sphere comprising means on the turntable responsive to the tilt of the antenna, means remote from the turntable for selecting the limits, and reversing means con trolled by said tilt responsive and limit selecting means.

4. In combination, an antenna and reflector unit, a turntable rotatable about a vertical axis and having trunnions supporting said unit for tilting about a horizontal axis, mechanism carried by said turntable for varying the tilt of said unit within predetermined angular limits, said mechanism having a moment of inertia about said vertical axis variable with said tilt, and a 0 balance weight mounted upon said turntable for horizontal movement in accordance with the tilt of said unit and in a direction to compensate for variation of said moment of inertia.

5. In combination, an antenna and reflector unit, a turntable rotatable about a vertical axis and having trunnions supporting said unit for tilting about a horizontal axis, mechanism mounted upon said turntable on one side of said vertical axis and having a horizontal component of movement to vary the tilt of said unit within predetermined angular limits, and a balance weight mounted upon said reflector on the opp0 site side of said vertical axis and having a horizontal component of movement opposite to that of said mechanism, whereby variation of the moment of inertia of-said mechanism about said vertical axis is compensated by a similar varia tion of the moment of inertia of said balance weight.

6. In combination, an antenna and reflector unit having the antenna in front of the reflector, trunnions supporting the unit for tilting about a horizontal axis, a turntable rotatable about a vertical axis, and supporting said trunnions, a motor mounted upon said turntable behind said whereby-its moment of inertia about said vertical UNITED STATES PATENTS axis varies in accordance with said tilt, a balance Number Name Date weight arranged in conjunction with said unit to 231,929 Lyman Feb 13, 9 1

counterbalance the weight of said motor about 2,257,320 Williams Sept. 30, 1941 said vertical axis, and a weight mounted upon 10 2,136,323 DeTar Jan 9, 1940 said reflector and movable horizontall in accordance with the tilt of said reflector to compensate FOREIGN PATENTS said variation of said moment of inertia. Number Country Date 9 10 vertical axis with respect to the front of said reflector, a link connected between said motor EFERENCES CITED and said reflector for Varying the tilt of said unit The following references are of record in the within predetermined angular limits, said link file of this patent: having a horizontal component of movement 5 MARTIN A. EDWARDS. 497,147 British Dec. 9, 1938