US2589813A

US2589813A - Antenna positioning system

Info

Publication number: US2589813A
Application number: US596724A
Authority: US
Inventors: Jr Robert I Hulsizer
Original assignee: US SEC WAR
Current assignee: United States, WAR, Secretary of; US SEC WAR
Priority date: 1945-05-30
Filing date: 1945-05-30
Publication date: 1952-03-18
Anticipated expiration: 1969-03-18

Description

March 18, 1952 R. 1. HuLslzER, .1R

ANTENNA POSITIONING SYSTEM Filned May `50, 1945 ooooooo mi Patented Mar. 18, 1952 ANTENNA PGS'EINING SYSTEM Application May 30, 1945, Serial No. 596,724

`3 Claims.

This invention relates to electrical control means particularly as employed in radio objectlocating systems.

In some radio systems the antenna array is made to move back and forth through a small angle in azimuth. In many systems known in the prior art the sector scanned by the antenna may be selected 'by suitable controls on the radio set. This selection is done manually by the operator of the radio set.

In many applications it would be desirable to have the antenna move automatically in azimuth so that the sector scanned is center-ed about the target once the antenna array has been positioned so that the sector scanned contains the selected target.

It is an object of the present invention, therefore, to present a system for automatically centering the sector scanned by an antenna array on a selected target.

In accordance with the present invention there are provided energy radiating means and means for causing said radiating means to oscillate through a predetermined angle. The amplitude cf the angle of oscillation is determined by suitable control means associated With the means for causing the radiating means to oscillate. Means are provided in said control means for causing the radiating means to oscillate at an angular position with respect to a given reference indicated by information derived from the signals from a selected target.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, in which:

Fig. 1 is a schematic diagram of the invention; and

Fig. 2 is a detail view of a commutator and a cam shown in Fig. 1.

Referring now more particularly to Fig. l o the drawing, there is shown a source of automatic gain control or AGC voltage Ill, connected to a selector means I I. In this embodiment of the invention the selector means II comprises relays I2 and I3, and vacuum tubes I5 and I5 connected as cathode followers. The input from AGC source Ii) is applied to contact arm Il of relay I3 and contact arm I8 of relay I2. Relay l2 has a winding 2|, and when a voltage is applied to terminal I9 of this winding, contact arm I8 of the relay engages the contact point 22. When no voltage is applied to terminal I9, there is no connection between contact arm I8 and Point 22 is connected to grid 23 of point 22. vacuum tube I5 by means of resistor 24. A capacitor 26 is connected from grid 23 to ground. Resistor 2l, connected between cathode 28 of tu-bc l@ and ground, serves as the cathode load for the cathode follower circuit of tube I6. Relay i3 is similar to relay I 2 in that Contact arm il engages the point 30 when a voltage is applied to terminal 3l of the winding 32. When no vol*- age is applied to terminal 3|, there is no connection betweenl contact arm Il and point Si). Point 3B is connected to grid 33 of tube I5 by resistor 34. A capacitor S6 is connected from grid 35 to ground. Resistor 3l is connected from cathode 38 of tube I5 to ground and serves as a cathode load for the cathode follower circuit of tube I5.

Terminal I9 of relay winding 2| is connected to contact arm 4I of a relay 42, and terminal 3'I of relay winding 32 is connected to contact arm 43 of relay 42. Relay 42 is so constructed that when a voltage of a given polarity is applied to terminal 44 of coil 45, contact arms 4I and 43 will make contact with points 4l and 48, respectively. When a voltage of polarity opposite to the above mentioned polarity is applied to terminal 44, contact arms 4| and 43 make contact with points 45 and 50 respectively. When no voltage is applied to terminal 44, contact arms 4I and 43 remain in a neutral position so that no contact is made. Points 4l and 50 of relai7 42 are return-ed to a source of positive potential represented by the plus sign in Fig. 1. No connection is made to terminals 49 and 48 of relay 42.

Relay 4-2 has a second set of contact arms 52 and 53. Relay 42 is so constructed that contact arms 52 and 53 engage the Contact points 55 and 5l respectively when the above mention-ed voltage of given polarity is applied to terminal 4 4 of coil 45. When this voltage is removed from 55 and 51. When a voltage of a polarity opposite to the given polarity is applied to terminal 44, contactk arms 52 and 53 make contact with terminals 53 and 59 respectively. When that voltage is removed from terminal 44, contact arms 52 and 53 remain in contact with points 58 and 5S. Points 55 and 59 are returned to a point of positive potential represented by a plus sign in Fig. l, and points 58 and 5l are returned to a point of negative potential represented by a minus sign in Fig. 1. Contact arms '52 and 53 are connected to terminals of a motor 52. rive motor52 is mutator 65.

mechanically connected to antenna structure S3. A Selsyn generator 54 or other suitable anguiar position transmitter is mechanically connected to antenna structure G3. A Selsyn motor 65 or suitable angular position receiver is electrically connected to Selsyn generator 64. Commutator 66 has two conducting segments 5l' and 68, more clearly shown in Fig. 2. Segment l' is connected to the negative terminal GEB of a source of direct-current potential l2. Positive terminal 'I3 of source 'I2 is maintained at ground potential. Segment 63 is connected to the positive terminal 'lli of a source of directcurrent potential l5. The negative terminal -'i of source 'e6 is maintained at ground potential.

A contact 'i8 mounted on cam 'I9 makes contact with a segment El or G8 when cam 'I9 and commutator 65 are in certain relative positions. Contact 'I8 is connected to terminal 44 of relay coil 45.

Cathode 23 of tube I5 in the selector means II is connected to terminal 93 of a controlled power supply means 9i, and cathode 38 of selector means I I is connected to terminal 92 of controlled power supply means QI. In this embodiment of the invention terminals 9! and 92V are the input terminals of a converter 93. This converter is preferably of the type known to the art as a Brown converter. Output terminals 94 and 35 of converter 33 are connected to input terminals, 95 and 97, respectively of a servo-ampliiier 9B. The output terminals 99 and IIJ@ of servoamplier |33 are connected to a motor IDI. Motor Iili has a second set of input terminals I02 and E33, the purpose of which will be eX- plained presently. Motor IUI is mechanically connected to cam 'i9 through gear train 464. A control vhandle IE is mechanically coupled to a suitable Vdiierential in Vgear train |04.

larms 52 and 53 inthe positions shown in Fig. 1,

contact arm 52 is at a positive potential, and contact arm 53 -is 4at a negative potential. It will ba assumed that this causes antenna 63 to rotate in a clockwise direction when viewed from vthe top. As Vantenna 53 rotates, Selsyn generator 64 which is mechanically coupled thereto also rotates. Selsyn motor 65 rotates in synchronism with Selsyn generator 64, and in so rotating it causes ya segment, for example .seg-- ment 68, on commutator 65 to come in contact 'with contact 'I8 on cam 79. A positive potential ifs now 'applied to terminal -44 of relay lcoil 46, 4causing thecontact arms 52 and 53 to move so that they make contact with points 58 and V59, re-

spectively. Contactarm 52 is now .at a negative l potentialand contactarm 53 is at a positive potential. The direction of rotation of motor IG is thus reversed so that antenna 63 rotates in a I counterclockwise Ydirection when viewed from Vthe top. The direction of rotation of Selsyn motor 65 is also Vreversed so that commutator 65 is driven inthe opposite direction to bring Contact 18 into engagement with vsegment El 'on com- Terminal 43 of relay coil 45 is now at a negative potential, and contact arms 52 and 53 areactuated-to make contact with points 5B and 5l, respectively. This causes motor `E52 to again reverse direction, and the cycle will be repeated. Thus, it will be seen that antenna 63 oscillates through an Aangle jointly rdetermined by the spacing of segments 6l and 68 on commue tator 66, the ratio of the movement of Selsyn generator S4 to the movement of antenna S3, and the ratio of the movement of ASelsyn motor to the motion of commutator St.

The location of the sector scanned is determined by the position of contact 'I8 on cam i9. The position of cam 'I3 is controlled by motor I all which turns cam 19 through the medium of a reduction gear train |04. The direction in which motor IUI turns, and hence the direction in which contact 'I8 on cam 19 moves, is controlled by selector II; controlled power supply 9| and relay 42.

Automatic gain control source IB produces an automatic gain Vcontrol or AGC voltage in any manner well known in the art. This AGC voltage is a direct-current potential that has an amplitude dependent on the strength of the signals received by the AGC generator. 1n the usual system this AGC voltage is applied to a receiver in such a manner that the amplitude of the output signals are constant even though the amplitude of the input signals are varying. It should be understood, however, that an AGC voltage may be produced without actually applying this voltage to a receiver. As is well understood in the art, the Ysignals received by a directional antenna array such as antenna 63 are of maximum strength when the axis of the array is pointed at the source of the received signals.

This YSource may be a reflecting object which re turns echoes of the pulses transmitted by antenna array 6.3, or it may .be any signal source emitting .signals of constant amplitude. When the axis of the antenna is moved away from the source of the received signals, the amplitude of the signals at the input of the receiver is reduced, requiring that the AGC voltage change in order to maintain the signals in the output of the receiver constant. In the present embodiment of the invention'it will be assumed that the AGC voltage produced in source IB becomes more positive ia's the received signal decreases in amplitude and becomes less positive as the received signal increases in amplitude.

AGC 'source I!! is connected in parallel to contact arms I8 and Il in selector II. vWith relay 42 .in the normal 'or unenergized position the AGC voltage is not applied to relay contact 22 nor is :it applied to relay contact 38. Continuing the original assumption that antenna 63 is rotating clockwise, contact arms 4l and 43 will make contact withjpoints 4'! and 48, respectively, when relay coil 4.5 Vis energized by contact 'I coming in contact with segment 68. Since antenna 33 has inertia., it will take a small vtime interval for contact 'I8 .to move off segment V6,8 in the ensuing reversal of rotation. During this time interval contact arm 4I is connected to a source of positive Apotential through Vpoint 41. Coil 2I of relay ,I2 is now energized, and contact arm L8 'connects the AGC voltage source to point 22. Resistor 24 and capacitor`26 act as a smoothing iilter Yso that the potential on grid 23 is the average value of lthe pulses of VAGC voltage applied to point 22 everytime relay I2 closes. Relay I.3 remains open when contact 'f8 is Vin contact with segment 68 because point 48 is open. However, when commutator 63 moves so that contact 'I8 ,touches segment 6Fl, relay I3 will then be closed; and relay i2 will be released. Re- "sistor 34 and capacitor 3G lact `as a smoothing ilter for the :pulses of -AGC voltages applied to and I3 is closed for only a short time interval and that this time interval occurs at the moment when motor 62 is reversing its direction of rotation.

The converter 93, which may be of the type known as a Brown converter, is a type of vibrator circuit that produces a square wave output of a predetermined repetition frequency. The vibrator is so designed. that the polarity of the output is determined by the relative polarity of the input terminals. Referring now to the converter shown as unit 93 in Fig. 1, if terminal 92 is at a higher direct-current potential than terminal Gil, the output at

terminals

94 and 95 will be a square Wave of a first polarity. If, on the other hand, terminal Sii is at a higher potential than terminal 92, the output at terminals 9d and 95 will be a square wave having a polarity exactly opposite to the rst polarity. If terminals 9|] and 92 are at equal potentials, the output at

terminals

94 and 95 is zero. The output of converter 93 is fed to servo-amplier 9S. Amplifier 98 is any of the types of amplifiers Well known to the art that will produce a substantially sine wave voltage wave form at terminals S9 and |00 when a square wave is applied to input terminals 9E and Sl. The output at points 99 and |80 is either of two sine waves that differ in phase by 180 depending on the polarity of the square wave at points 96 and 9?. It is understood that the output at points 99 and |06 will be zero when the input at

points

96 and 97 is zero. Motor lili in this embodiment of the invention is a two-phase alternating current motor. One eld of motor |01 is energized by amplier 98, and the second is energized by an alternating voltage applied to terminals |52 and |13 that is of the same frequency as the output of amplier 98. The phase of the voltage at points |02 and |03 differs by ninety electrical degrees from the phase of either output of amplifier 98. It can be seen that the direction of rotation of motor Will be determined .by the phase of the output of amplifier 98 and hence by the relative polarity of terminals 90 and 92. It is also obvious that motor IBI will not rotate if terminals 90 and 92 are at the same potential.

As will be apparent to those skilled in the art, the controlled power supply 9| may be a type of diiierential amplifier and motor itl may be a type of direct-current motor without affecting'the operation of the invention.

Suppose now the center line of the sector scanned by antenna $3 contains the source of received signals. The axis of the array will be displaced by an equal angle from the direction of the target at each end of the sector, and, therefore, the ypulses of AGC voltages applied to points 22 and 3U will be of equal magnitude. Since the time that relay 2 is closed is substantially equal to the time relay 3 is closed, the average voltage at point 22 will be the same as the average voltage of point 3|?, so grid 23 will be at the same potential as grid 33. Since the two cathode follower circuits containing tubes |5 and I6 have substantially identical characteristics, cathode 28 will be at the same potential as cathode 38 when grid 33 is at the same potential as grid 23. Since cathode 2B is at the same potential as cathode 38, no field exciting voltage will be supplied to motor by amplifier 98; hence, motor |0| will not rotate.

Suppose now the center line of the scanned sector is oir center with respect to the target. The axis of the antenna array will make a smaller angle with the target line at one end of the sector than it does at the other. This would mean that the magnitude of the AGC voltage pulses applied to points 22 and 3|! would not be equal, and, therefore, the potential of grid 23 will not be equal to the potential of grid 33. Controlled power supply 9| is designed so that the output at points 99 and l will be such that motor lili will move cam 'I9 in a direction to yplace the center of the scanned sector on the target.

Using the assumed directions of motion of antenna 63 and commutator 66, that is, when antenna moves clockwise when viewed from the top, commutator 66 moves clockwise when viewed from Selsyn motor 65, assume further that the target or source of the received signals lies to the left of the center of the scanned sector as viewed from the antenna. When relay |2 closes, the axis of antenna 63 will make a greater angle with the line to the target than it will when relay |3 closes. This means that grid 23 will be at a higher potential than grid 33. Controlled power supply 9| now furnishes motor IUI with energy of such a polarity that it will move cam 'IS in a counterclockwise direction when viewed from Selsyn 65. Moving cam 'i9 in this direction will move the center of the scanned sector back to the target line. It will now be apparent that if the target is on the right side of the center of the scanned sector, grid 33. will be at a higher potential than grid 23 and controlled power supply 9| will furnish energy of such a phase that cam 'I9 is moved in a clockwise direction by motor IUI W hen searching for a target, the sector scanned may be selected by turning control handwheel |05 which moves cam 'I9 through a suitable differential mechanism in gear train |04. It may be convenient in some embodiments of the invention to make the connection to segments 6l and 68 through slip rings so that antenna 63 may be rotated continuously if desired.

While there has been described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention.

What is claimed is:

l. An antenna positioning system, comprising a directional signal receiving antenna having a beam pattern adapted to scan thru an angle in a given plane sector, a motor for driving said antenna, a source of energizing potential for said motor; a relay, having contacts in the circuit `between said motor and said source, for controlling the polarity of the potential with respect to said motor; a second source of energizing potential, a circuit including a rotatable commutator connecting said second source and said relay, an angular position transmitting device connecting said antenna and said commutator, a contact controlling the connection between said commutator and said relay, a cam for controlling the position of said contact, motor means for displacing said cam to effect a shift in the position of said contact; an automatic gain control circuit for supplying a signal, the relative value of a given polarity of which is inversely proportional to the intensity of the signals received thereby, a circuit for periodically transducing signals from said gain control circuit including actuating means therefor, circuit control means for said actuating means controlled by said relay; and

means for converting the output of said transducing means into a sine wave, the presence and relative phase of Which depends on the comparative polarity of said output, Vsaid last named means being connected to energize said second motor.

2. An antenna positioning system, comprising a directional antenna having a beam-like pattern adapted to scan a sector having a given angle, a driving motor for said antenna to normally effect an oscillation thereof thru said angle, a source of energizing potential for said motor, means to yeffect a reversal in the polarity of said source with respect to said motor connected to said potential source and said motor, means for controlling said reversal effecting means as a function of 'the angular position of said antenna; a source of signals the amplitudes of which are a `function of the Vcentering of said scanning sector with respect to a point in a given direction within said sector, means for periodically supplying a signal which inrespect to sign and amplitude is 'afunction of the difference ofthe extreme values of said signal amplitudes connected to be supplied from said signal source, and means connected to be energized from said signal difference supplying means for effecting a shifting of said controlling means by an amount in accordance with said signal diieren'ce.

-.3. klan antenna 'positioning system, comprising a directional receiving antenna having a beam pattern, means for effecting an oscillatory movement of said 'antenna in a given plane through a vsectorhaving a given angle, means for shifting the direction of said scanning sector connected with said last named means, and means including :a source of signals the sign and amplitudes of 'which are a function of the centering Vof said scanning sector with respect to a point Yin a given direction within said sector for controlling said shifting means; wherein said means for controlling said shifting means includes a normally inoperative motor and said means for controlling sad last named motor includes an automatic gain control circuit for supplying a signal, the relative value of a given polarity of which is inversely lziroportienal to the intensity of the signals received thereby, means for periodically transducing signals from said gain control circuit in synchronism with the extreme limits of the oscillatory movement 'of said antenna, and means for converting the said transduced signals into a sine Wave the presence and relative phase of which depends von the comparativeV tpolarity of said two transduced signals, and means for applying said sine Wave signal to said shifting motor.

ROBERT I. HULSIZER, JR.

REFERENCES CITED The following references are of record in the ile of this patent:

UNITED ESTATES PATENTS Number Name Date 1,915,328 Mirick June 27, 1933 2,138,966 Hafner Dec. 6, 1938 2,247,029 Luck June 24, 1941 Y2,257,757 Moseley Oct. 7, 1941 2,415,166 Farrow Feb. 18, 1947 2,446,024 Porter et al July 27, 1948 2,458,175 Kolding Jan. 4, 1949