US2473421A - Search antenna array - Google Patents

Description

June 14, 1949.- FU IN. ETAL 2,473,421

SEARCH ANTENNA ARRAY Filed May 30, 1945 2 Sheets-Sheet 1 INVENTORS MORTON HAMERMESH EUGENE FUBINI '/M-'W Q 4 (LC.

AT TORNEV June 14, 1949. E. FUBINI ETYAL 2,473,421

SEARCH ANTENNA ARRAY Filed May 30, 1945 2 Sheets-Sheet 2 INVENTORS MORTON HAMERMESH EIBIGENE FUBINI B M Mg-M .4 T TOR/VEV Patented June 14, 1949 SEARCH ZXNTENNA Z-KRRAY Eugene Fubini, New York, N. Y., and Morton vJ-Iamermesh, Cambridge, Mass, assignors to the 'United'States'of America as-represented by the Secretaryof War dipplication May 30, 1945,-Serial-No.596,720

9 Claims. L1

This invention relates .to.-an antenna system for radio signaling apparatus and is useful with both-receiving and transmitting apparatus.

"More-specifically the ipresent -invention relates to an antenna .array comprising at least one antennaelectrically connected to the remainder of the apparatus-and rotating about a center external to .it and other antennas not electrically connected to thelapparatus-and adiustably arranged outsideoflthecircle about which the con- ,nected-antennarotates.

:W-hen a'n array of antennas (includes some antennaselectrically connected to the receiving or the -transmitting apparatus andothers not connected thereto, the-electrically connected antennasare normallydesignatedinthe art as driven antennasand.thosenotelectricallyconnected are ordinarily designated as ,paras-iti-c antennas. Althoughin a receiver.anantennaisvnot accurately speaking driven by. the. receiving apparatus, this usual terminology of the art will be used hereinbelowa-ndis to .be understood in. accordance with the foregoing explanation. The performance of parasitic antennas is well known in the art. In .a transmitter ithese parasitic antennas absorb power radiated by the drivenn-an'teim-a and reradiate it inaphaserelation to the original radiation dependent. upon their length and position with relation toithe driven antenna, so that the fieldsuadd l'in .onewdire'c'tion and subtract in the other vproducing a radi-ationfpattern or radiation lobe having a definitedirectionpf "maximumra'diation and a narrow angle of radiation.

It is one of, the objects of "the present invention to improvefup'on the con'venti'onal array of driven and parasitic antennas "by producing a "long and narrow lobe 'and to provide means for sweeping that lobe *overa wide angle -without being required 'to'rot'at'e the "entire antenna array.

'An object 'of this invention "is to olza't'ain over a wide range ffrequen'cies a relatively narrow and sharp directive lobe may be scanned continuously or intermittently at any desired rate of. speed over a predetermined wide area of search. In the case where the-antenna system of the present "invention is used with receiving apparatus, this directive lobe represents a minimum area within :which the 'antennawill pick up and deliver to the receiving apparatus signals of a predetermined minimum "intensity, when attached to transmitting apparatus this lobe represents direction 'ofradiation of equal minimum strength. I

V .Inapreierred embodiment "of the invention, three parasitic antennas are used which are ar- '2 ranged in a semi-ellipse having its shortfaxis along the major aiiis "6f wave.propagatronpf tne driven antenna and its ldngjaxisat'rightaiigles thereto. The center of "this slfihellibse coinaides with the center around which'tlie -driven antenna rotates. It has been foun -for inbst satisfactory operation that'the "radiu's'of rotation of the driven antenna should be asmaurraction of the average'tundamental wavelen'gm'eoverea by the array and that'the parasitic.aiite'iina's"be spaced from the center of that-circle '"at a distance no greater than ahalf of that wavelength.

One advantage of the...prese'rit invention is its use for navigational .purposeson ships and aircraft for locating homing signals. Previously, it had been necessary, when searching 'forhorri ing signals, to turn either the-shipitsel f'or the entire antenna array -to-locate the direction of the homingsignals. Particularly on aircraft, the mechanical difficulties of rotating the entire array present'serious obstacles. v

@ther advantages and novel features of this invention will beoon e apparent to those skilled in the art from the iollowing description of the invention taken in connection with theaccompanying drawingsi-n which:

Fig. 1 is a schematic representation of a-preierred embodimentof the present invention;

-Ei-g-. 2 is a drawing of the #patterns covered by the antenna array of the :present inventionior various positions of the driven antennapesighated in Fig. -1;

Fig. 3 is 'a drawing-partially in section and :partially isometric showing a preferred mechanical arrangement for the mounting of the antenna array of the present invention Fig. 3a is a drawing showing 'details -of.-the mounting ofthe driven antenna; and

Fig. 4 is a *dr-awi-ng showing details "of the mounting ofthe -parasitic airtennas.

Referring to Fig. 1, the driven antenna 40 is fixe dly mounted "upon a rotatable "disc H- by any suitable means such as aslot 42; The driven a'ni tenna i0 is substantially perpendicular to the disc H. The slot I2 provides means --for adjusting the distance of the driven antenna II] from the center 13 of the disc '11 which ma be fastened in anydesired position by any suitable device. The disc 'H maybe rotated "by 'any'well known means such as a hand crank or d'rivir'ig motor, hereinafter F01 lfidst S'IIIGEES'STI II operation, it been found that the radius of rotation of the driven antenna Should be approximately one-tenth of the average fundamental wavelength of the signal to be transmitted or received by the antenna array.

The driven antenna is preferably a dipole, that is, an antenna having an electrical length one-quarter the average fundamental wavelength of the signals to be transmitted or received.

The electrical length of the parasitic antennas i i, 15, and i6 are preferably one-quarter of a wavelength and are of sufficient thickness to permit a wide variation in the frequencies of the transmitted or received signals without adverse effect upon the efficiency of the array. Antennas i4, i5, and it are mounted to a rigid member I! of insulating material with low dielectric loss. They are securely fastened to member [1 in slots 58 by any well known means, such as screws, which permit adjustment of their position along the member H. The longitudinal axes of the parasitic antennas are substantially parallel to that of the driven antenna in and substantially perpendicular to the face of the rotatable disc I i. Antennas l4 and are spaced one-half of the fundamental wavelength of the driven antenna If! and antenna l6 one-quarter of that wavelength from the center [3 of the disc II. The antennas i4 and i5 are centered on a straight line passing through the center I 3, and the antenna i6 is centered on a line passing through center it and at a right angle to the line on which antennas l4 and [5 are centered.

In designing both the driven antenna and the parasitic antennas so that their effective electrical lengths are of proper dimensions, there should be taken into consideration the effect upon that length of the means employed to mount the antennas on the framework.

In order that an operator may determine the direction from which a signal is received, he will, upon reception of the signal, stop the rotation of the driven antenna [0. If the antenna is rotated by a motor or other mechanical means the driving means should be equipped with a fast operating brake so that when the rotating motor is cut off the driven antenna will come to an immediate stop. The direction from which signals are received may be determined by the angle between the axis 33, 34 or 35 (Fig. 2) of the lobe at the time of reception and a fixed axis, such as the longitudinal axis of a ship or airplane. This can be indicated by any usual means such as a dial and pointer.

With the driven antenna H1 in the position shown in Fig. 1, the antenna pattern for the system is indicated by curve 30 shown in Fig. 2. When the rotatable disc II is moved in a clockwise direction through an angle of 90 the driven antenna to will be at the position indicated by 20 on Fig. 1. Since the driven antenna I0 is now in a different position relative to the parasitic antennas l4, l5, and IS, the antenna pattern of the array will change in both direction and shape. The pattern obtained with the driven antenna It at the position 2%} is that of the curve 3|, Fig. 2. When the driven antenna is in the position 2!, the antenna pattern will be that of curve 32, Fig. 2. Curves 32 and 3| are substantially congruent and the respective angles of their axes 33, 34 with the axis 35 of the antenna pattern for the original position of the driven antenna, are substantially equal. It is seen that the rotation of the driven antenna It] results in a much wider coverage than that obtainable without rotating the driven antenna but for any given position of the driven antenna, the lobe is not widened. The angle of sweep for the arrange- 4 ment hereinabove described has been found to approximate 70.

For fixed dimensions of the driven antenna l0 and fixed dimensions and relative positions of the parasitic antennas l4, l5, and N5, the system will operate satisfactorily over a band of frequencies of of the center frequency, producing the fairly sharp unidirectional antenna patterns shown in Fig. 2. When it is desired to change the operating frequency to a greater extent than the above, the radius of rotation of the driven antenna l0, and the relative electrical distance from it of the parasitic antennas l4, l5, and it are adjusted to compensate for the change of frequency.

When the driven antenna 10 is rotated from the position 2%, Fig. 1, through the position 22 to the position 2 l, the varying antenna pattern produced is not as narrow and contains a magnitude of range less than that for rotation through the other 186 of the circle. Hence, when desirable, only the more effective of rotation is used. This may be accomplished by suitable switching of the driven antenna ID from the operative to the inoperative state, and vice versa, as it passes through positions 29 and 21 during its rotation. such an arrangement allows searching for onehalf the time. An alternate arrangement is to provide conventional mechanical means to rotate the driven antenna i0 over only a semi-circle, from position 2 I, Fig. 1, through its original position to position 20 and likewise back through its original position to position 2 I. By this arrangement continuous searching over the predetermined area of space is accomplished.

The angular magnitude of the area of search may be altered by changing the angular positions of the parasitic antennas [4, I5, and IS with relation to the driven antenna Ill. Likewise, the width of the lobe may be varied by varying the number of parasitic antennas used.

A preferred form of mechanical construction for the mounting and operation of the antenna array of the present invention particularly suitable for aircraft is shown in Fig. 3. The input to the driven antenna I0 is introduced at terminal posts an, 483 to a stationary coaxial line 4|. In the case of a receiving antenna array terminals 453, 4c are the connections of the array to the receiver. Coaxial line 4| connects the receiving or transmitting apparatus to rotatable coaxial line 42 through electrically continuous joint 43. Rotatable coaxial line 42 is mechanically but not electrically connected to hollow rotatable shaft 44 surrounding stationary coaxial line 4 l. Rotatable shaft 44 may be grounded and is suitably supported along its length as at 45, 45, and mechanically connected to disc ll. Coaxial line 42 may be mechanically connected to rotatable shaft 44 by any well known means such as a locking key or tongue and groove that will provide electrical insulation between coaxial line 42 and shaft 44. A portion 46 of rotatable coaxial line 42 is continued at right angles by an adapter n in the proximity of rotatable disc H and follows under slot l2 in that disc. Its end is connected to driven antenna In by means of a conducting ring 48 (Fig. 3a) clamped in close contact with the base of antenna [0 by screw 49 (Fig. 3a) or other suitable means. Portion 46 of coaxial line 42 is flexible to provide for adjustment of antenna In in slot l2.

Shaft 44 is rotated by an electric motor or other driving means, not shown, through motor shaft 5% and a suitable gear train and clutch mechanism to-;permitmannalirotation when desired. suitable arrangement of gearing. is

shown "in Fig. 3. Assuming rotatable Shaft M .to be vertical, there is keyed to it at its bottom a bevel gear l,"meshing'with bevel gear 52 on the endofmotor shaft 50. Suitable clutch and clutch Shaft 58-rotates bothduring motor andmanual --operationand therefore therernay be convenient- -lyplaced on its free end a dial I60 by which the angular position of antenna III to a reference axis may be indicated.

, r Fig. .4 shows one method of mountin the parsitic antennas to permit thee-desired angular and linear adjustment. Each parasitic antenna is mounted on a stationary member 63 supported on the array structure or directly on the ship or aircraft carrying the array. A rigid non-conductive member 6| is attached to stationary member 63 by a screw 62 which provides adjustable means for the angular adjustment of member 6| with respect to driven antenna I 0. The parasitic antennas I4, I 5, and I6 are fastened to members Bl' in any suitable manner. Slot 64 provides for variation of the distance between the parasitic antennas and the fixed position of vertical member 63. By utilization of the two above-described adjustments it is possible to place the parasitic antennas in any desired position with relation to the driven antenna.

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

What is claimed is:

' -1. An antenna array for radio signaling comprising a driven antenna arranged to travel along a substantially circular path in a horizontal plane, means for causing said travel, a pair of parasitic antennas fixedly mounted on the same horizontal plane and on a line representing an extended diameter of said circular path at points equidistant from the center of said circular path, and a third parasitic antenna fixedly mounted in the same horizontal plane at a point along an extended radius at right angles to the line on which said pair of parasitic antennas are mounted and at a distance from the center of said circular path substantially one-half the distance of each of the pair of parasitic antennas from said center.

2. An antenna array for radio signaling over a relatively wide working range of frequencies comprising a driven antenna adapted to travel on a horizontal plane along a substantially circular path having a radius of the order of one-tenth of the average wavelength of the working range of the array, means for causing the continuous travel of said driven antenna, a pair of parasitic antennas fixedly mounted in the same horizontal plane as said driven antenna, each of said pair being equi-distant from the center of said circular path on a line representing a continuation of a diameter of said circular path and at a distance of the order of half the average wavelength of the working range, and a third parasitic antenna mounted on the same horizontal plane at a point 6 "aicngan extended :axis at right angles at!) line on which said pair of parasitic :antennastare inbunted and at a. distance of the :order ref a quarter of the wavelength of the working range.

horizontal plane at a point along an extended radius at right angles to the line on whic-hsaid pair of parasitic antennas are mounted and at a distance from the center of said circular :path substantially one-half the distance of eachof the pair of parasitic antennas from the center. v

4. An antenna array for radio signaling comprising a driven antenna arranged to travel along a substantially circular path in a horizontalplane, means for causing said travel; a pair of parasitic antennas linearly adjustable on the same'horizontal-plane and'on a line representing an extended diameter of said circular path at points equidistant from the center of said circular path, and a third parasitic antenna linearly adjustable in the same horizontal plane at a point along an extended radius at right angles to the line on which said pair of parasitic antennas are mounted and at a distance from the center of said circular path substantially one-half the distance of each of the pair of parasitic antennas from said center.

5. An antenna array for radio signaling comprising a driven antenna arranged to travel along a substantially circular path in a horizontal plane, means to vary the radius of said circular path, means for causing said travel; a pair of parasitic antennas linearly adjustable on the same horizontal plane and on a line representing an extended diameter of said circular path at points equidistant from the center of said circular path, and a third parasitic antenna linearly adjustable in the same horizontal plane at a point along an extended radius at right angles to the line on which said pair of parasitic antennas are mounted and at a distance from the center of said circular path substantially one-half the distance of each of the pair of parasitic antennas from the center.

6. An antenna array for radio signaling comprising a driven antenna arranged to travel along a substantially circular path in a horizontal plane, means for causing said travel, a pair of parasitic antennas fixedly mounted on the same horizontal plane and on a line representing an extended diameter of said circular path at points equidistant from the center of said circular path, and a third parasitic antenna fixedly mounted in the same horizontal plane at a point along an extended radius at right angles to the line on which said pair of parasitic antennas are mounted and at a distance from the center of said circular path substantially one-half the distance of each of the pair of parasitic antennas from said center, said parasitic antennas having suificient cross-section to allow a change in operation frequency of plus and minus 25% without substantial adverse change in the resulting antenna pattern.

7. The device as set forth in claim 6 wherein said driven antenna and said parasitic antennas are substantially one-quarter wavelength in length with relation to the average operating frequency of the operating frequency range.

8. An antenna array for radio signaling comprising a driven antenna arranged to travel along a substantially circular path in a horizontal plane, means to vary the radius of said circular path, means for causing said travel, a pair of parasitic antennas linearly adjustable on the same horizontal plane and on a line representing an extended diameter of said circular path at points equidistant from the center of said circular path, and a third parasitic antenna linearly adjustable in the same horizontal plane at a point along an extended radius at right angles to the line on which said pair of parasitic antennas are mounted and at a distance from the center of said circular path substantially one-half the distance of each of the pair of parasitic antennas from said center, said parasitic antennas having sufiicient cross-section to allow a change in operation frequency of plus and minus 25% without substantial adverse change in the resulting antenna pattern.

9. The device as set forth in claim 8 wherein said driven antenna and said parasitic antennas are substantially one-quarter wavelength in length with relation to the average operating frequency of the operating frequency range.

EUGENE FUBINI. MORTON HAMERMESH.

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

UNITED STATES PATENTS Number Name Date 1,714,864 Galletti May 28, 1929 1,745,342 Yagi Jan. 28, 1930 1,828,705 Kolster Oct. 20, 1931 2,073,085 Wells Mar. 9, 1937 2,113,136 Hansell et a1. Apr. 5, 1938 2,199,050 Jenkins Apr. 30, 1940 2,215,785 Gallant Sept. 24, 1940 2,225,456 Koschmieder Dec. 17, 1940 2,243,523 Davis May 27, 1941 2,405,281 Bemis Aug. 6, 1946 OTHER REFERENCES The Corner Reflector Antenna, by J. D. Kraus,

published in Proceedings of the I. R. E., November 1940, pp. 513-519.

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