US2424982A - Directional radio antenna lobe switching system - Google Patents

Description

ugQS, 3947. v w. H. c. HIGGINS ETAL 2,4243@ DI-RECTIQNAL RADIO 'ANTENNA SWITCHING SYSTEM l Filati Aug. 3, 1942 '7l Sheets-Sheet l "WHC-H/GG/Ns-- "NVWQARS :GAMME/v f ATTORNEY Aug. 5, 1947. H. c. HIGGINS ETAL i 2,424,982

l DIRECTIONAL RADIO ANTENNA LOBE SWITCHING SYSTEM Filed Aug. 3, 1942 7 Sheets-Sheet 2 F/G. 3/ l o/Poz. es ar |/30 o/PoL E: .as

lo [32' BN 1mm. on Rec. ATTORNEY 5, 147. w. H. c. HIGGHNS ETAL DIRECTIOAL RADIO ANTENNA LOBE SWITCHING SYSTEM Filed Aug. 5,' 1942 7 Shets-Sheet 3 vos Ion.

RESE .S no graft l o2 l o u M w K K og ON- o@ o@ omvN SNIOVB'L w h1 `c. H/GG/Ns c: A. WARREN /NVE N TORS 5, 47. w. H. Hlesms ETAL 2,4219 DIRECTIONAL RADIO ,ANTENNA LOBE SwI-TCHING SYSTEM Filed Aug.. 5, 1942 7 Sheets-,Sheet 4 FIG. [0

X l ATTORNEY C A. WAR/17 N w. H. c. HlGGlNs; Erm.

DIRECTIONAL RADIO ANTENNA LOBE SWITCHING SYSTEM.

Aug. 5, 1947.

7 sheets-'sheet 5 Filed Aug... s, 19:42

T0 IRANSHITIER RECEIVER nu mw um P Lann z. i Pmasou /60 /60 s 'A /Nvflvroks W H C- H/GG/NS Aug. 5, i947.

` wH. c. 'HIGGINS Erm.

DIRECTIONAL, RADIO ANTENNA LOKBE SWITCHING SYSTEMr -Sheetsfsheet 6 Filed' Aug. 5. 1942 Lowe Museu t n mm Aug. 5', v1947.

W, H. C. HIGGINS ETAL DIRECTIONAL RADIO ANTENNA LOBE SWITCHING SYSTEM 7 sheets-'sheet '7 Filed Aug. 3, 1942 l u WENT-msn. c; H/GG//vs Patented Aug. 5, 1947 ZAZitZ IHRECTEONAL RADIO ANTENNA LOSE SWITCHING SYSTEM William H. C. Higgins, West Orange, and Cliiord A. Warren, Watchung, N. J., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application August 3, 1942, Serial No. 453,390

(Cl. 25d-41) 11 Claims. l

This invention relates to improved high-precision direction iinding antenna systems. More particularly it relates to antenna systems having unidirectional, sharply-defined directive characteristics, commonly designated as lobes, and to improved arrangements for switching or displacing the unidirectional sharply-defined directive lobe of such antennas alternately between two positions in a given plane, or in each of several planes, a few degrees in opposite directions from the normal axis of directivity, for the purpose of resolving the flat bearing obtained with stationary lobe antennas of thi-s type since the diierential quotient of the signal strength with respect to the orientation is nearly zero in the neighborhood of maximum reception.

As it is above suggested, the sharpness of the bearing obtained can be increased by switching the lobe alternately from a position a few degrees on one side of its normal axis yto a like position a few degrees on the opposite side of the axis. if this is done without affecting the amplitude or shape of the lobe and the shift of the lobe is discretely chosen, a, signal of constant intensity will be received i. e. equal signal strength for alternate lobe positions will be obtained when the normal axis of the antenna system is directed precisely at the signal source. The signal source can be a, beacon radiator, an ordinary radio transmitter. or an object from which radio waves are being reflected toward the antenna system.

Numerous arrangements for effecting increased sharpness of directive indications by the general method above described, have been devised by others and the present invention is therefore directed toward improved arrangements of this type.

In the prior art, for example, the mechanical (rotary) movement of a reflector to effect lobeswitching is taught in Fig. 2 of United States Patent 2,083,242, issued June 8, 1937, to W. Runge. Electrical lobe-switching by conductive contacting devices is taught, for example, in Fig. 3 of the above-mentioned patent and in United States Paten-ts 1,959,708, issued March 13, 1934, to G. Von Arco, 2,045,849, issued July 7, 1936, to W. Runge et al., and 2,160,857, issued June 6, 1939, to A. Gothe.

In general, because of inertia, the mechanical lobe-switching schemes of the prior art must operate at relatively slow rates and therefore they are not satisfactory except where the direction indicating signals are of relatively very long duration and of substantially uniform amplitude.

Electrical lobe-switching schemes of the prior art,

2 are, on the other hand, frequently subject to two sources of difculty, the rst arising from possible poor electrical contacts in switching mechanisms and the second arising from a disturbance of impedance relations as the lobe is switched such that the power distribution throughout the antenna system is changed and the amplitude or shape of the lobe changes as it is switched from one position to the other with the result that the'- line of precisely equal intensity for the two (or more) lobe positions is not readily determinable. The median line or normal axis of the antenna system, being a conveniently determinable parameter, is preferable as a natural axis of precisely equal intensity for direction nding systems.

In the electrical lobe-switching arrangements oi the present invention Contact diiculties are avoided by eliminating conductive switching mechanisms. impedance diniculties of the type described above are avoided by structural arrangements which produce precisely controlled and balanced impedance changes during lobeswitching operations.

The principal object of the invention is, therefore, to provide lobe-switching arrangements which will be suitable for obtaining highly accu. rate bearing indications on signals of relatively very short duration. A further object is to provide lobe-switching Varrangements which will be iree from electrical contact troubles.

Another object is to provide lobe-switching arrangements which will not objectionally alter the impedance relations within the antenna system, the lobe of which is being switched Other and further objects will become apparent during the course of the following description and in the appended claims. The principles of the invention will be readily understood from the following description of preferred illustrative embodiments in conjunction with the Kaccompanying drawings, in which:

Fig. l illustrates one arrangement for lobe switching electrically without employing mechanical contacting members;

Figs, 2A and 2B illustrate a second arrangement for lobe switching electrically without employing mechanical contacting members;

Figs. 3 to 9, inclusive, are diagrams employed in connection with an analysis of the principles involved in an electrical lobe-switching arrangement which provides equal power distribution between the two antenna sections and avoids the of mechanical contacting members;

Figs. 10A, 10B and 10C illustrate an embodiment of a lobe-switching device of the invention;

Iig. ll illustrates schematically the use of a single-plane lobe-switching device of the invention with a linear array of eight dipole antennas;

Fig. l2 illustrates schematically the use of a two-plane lobe-switching device of the invention with two linear arrays of four dipole antennas each;

Figs. 13A and 13B illustrate further features of the arrangement schematically indicated in Fig. l2; and

Figs. 14A and 14B illustrate an adaptation of a lobe-switching mechanism of the invention to a relatively lower frequency directional system.

In more detail, in Fig. 1 two dipole antennas comprising radiating members Il and i8 respectively are spaced one-half wave-length apart so that when energized precisely in phase they will produce a symmetrical directive lobe of radiated energy having a maximum normal to the Common plane of the two dipole antennas Conducting members I3 and i4 provide identical electrical paths for the transmission of energy to the two dipole antennas from their center points to which a feed line comprising conductors il and i2 are electrically connected. A half disc i@ of dielectric material is supported on shaft i5, which is driven by motor I6. Shaft I5 may be of non-conducting material or it may be electrically insulated from conductors Il to ifi, inclusive. As the half disc le of dielectric material is rotated about shaft l5 it is introduced alternately to the left and right of the center points of conductors i3 and It. This is, of course, electrically equivalent to alternately inserting to the left and right of the Center point of conductors l 3 and ifi a section of transmission line of diiferent impedance from that of the line formed by conductors it and i@ and will alternately change the relative phases of the two energy components radiated by dipole antennas H and I8 causing the lobe maximum to shift alternately between a position a few degrees to one side of its normal position to one a few degrees to the other side, i. e., the lobe will switch and equal intensities of the two lobes will be received along an axis midway between the two lobe positions. The amount of shift will depend of course upon the radius of the semi-disc iii, its dielectric constant and the change in impedance which it effects. Ob ously, such an arrangement will completely avoid contact difficulties.

In Figs. 2A and 2B a somewhat similar arrangement is shown but in this case a semi-disc 2o of metal is employed and the center portion of upper conductor 23 is raised to increase its separation from the lower conductor 2li. Shaft i5 is again preferably of insulating material'or is insulated from conductors Il, i2, 23 and 2li.

As shown in Fig. 2B, metal disc 20 is electrically insulated frcm conductors 23 and 24, a layer oi insulation 25 being inserted in the raised portion of conductor 23 to avoid possible conductive contact. As semi-disc 29 is rotated, it is alternately inserted on the left and right of the center points of conductors 23 and 2E and has the eiect as indicated in Fig. 2B of switching alternately trom a small section of transmission line having impedance 1/2Z0 to a like small section having an impedance 22o, the dimensions of the over-all arrangement being assumed to have been proportioned so that if conductors 23 and 2liv over their major portions have an impedance of Zo the section in the center in the absence of the semi-disc is will have, because of its greater spacing, an impedance of 22o and with semi-disc l0 inserted therein it will have an impedance of 1/2Z0. Again the relative phases of the radiations from antennas il and i8 will be alternately changed and lobe switching will result, the extent of lobe deilection being a function of the phase change which in turn is dependent upon the radius of semi-disc i8.

The systems of Figs. l and 2 are convenient and satisfactory where relatively small shifts of the lobe will sufce, for example shifts in the order of 2 or 3 degrees each side of the normal axis of an antenna array of approximately 4 wave-lengths in breadth. Where larger shifts are desired, however, the impedance may have to be altered ct such an extent that the power distribution between the halves of the antenna array is substantially altered, in which case the shape of the radiated lobe may be adversely affected and the axis of equal intensity for the two lobe positions may be undesirably shifted from the normal axis of the array. Moreover, the axis of equal intensity for one position of the lobe-switching mechanism may not coincide with that for the other position.

To avoid these difculties, a modiiied arrangement will be evolved below and the principles upon which it is based will now be discussed,

In Fig. 3 an array of a plurality of dipole antennas, or similar directive antenna units, is assumed to have an axis of symmetry as indicated by center-line Se, one group 3l being to the left and the other group 38 being to the right. Leads 32 and 33 are likewise precisely symmetrical with respect to centerline Si! at which point leads Sli and 35 are connected, bringing power from a transmitter or leading received energy to a receiver.

The impedance or the line formed by conductors 32 and 33 should be substantially equal to that of the dipole antenna groups to which it is connected. For high frequency systems. for

l example, systems employing energy having a wave-length less than one meter, o, convenient impedance is ohms.

For the two 1/4 wavelength sections of the transmission line comprising conductors 32 and 33 on each side of the axis of symmetry 36, i. e., a first section extending from axis or point O to point A on the left, and a second section tending from axis 3@ or point O to point B on the right, the phase shift or each of these sections, assuming condenser 36 to be temporarily discone nected, is 14 of 360 degrees or 9G degrees. This follows from the well-known fact that a uniform transmission line terminated in its own impedance has a phase shift of 360 degrees per wavelength.

Assuming now that condenser 3e is connected across the line at point A, the section O-A represented in Fig. d is obtained. The capacity of condenser 36 is cho-sen so that its impedance at the operating frequency ci the system is i 'io ohms, i. e., e. negative purely reactive impedance of 70 ohms. In Fig. Li resistance do represents the remainder of the system to the left ci p t A and is assumed to be substantially 7i) ohms and purely resistive.

Next, consider a section of line having a Zn of 'i0 ohms as shown in Fig. 5. By standard formulae, if the line is terminated at its left end A by a pure resistance t2 equal to 2.6 Zu, at a point A .152 wave-length from this resistance the impedance is equivalent to a resistance Zo and reactance -Zo in parallel, i. e., an impedance equivalent to that o-f a capacity 36' and a resistance Y 40' in parallel, will be found. It should be understood that capacity 36 and resistance 49 represent the impedance of the line at point A of the lineof Fig. 5 and are not discrete elements. In other words, in Fig. 4 we could remove condenser 36 and resistance 40 and substitute therefor an additional section of line .162 wave-length long with a resistance of '2.6 Zo shunting the far end. This process of analysis discloses reference points at which purely resistive impedances exist and from which the phase shift along the section of Fig. 4 may be determined. By standard formulae, another purely resistive impedance point A" on the line of Fig. 5 which is l@ wave-length from A' is found and the impedance of the line at this point A" is found to be .38 Zo. On the basis of this information the curves of Fig. 9 can be used to determine the phase shift of the section of line shown in Fig. 4.

In Fig. 9 the electrical length or distance along the line from a point X to a load or impedance across the line is given in degrees, one wavelength being 360 degrees. Values of load imped ances Zr between Zr= and Zr= are indicated for curves i6|), 52, 64, 65, 68, '|2, M and lli,l

curve '69 corresponding to Zr=0, curve `|2 corresponding to Zr=%Zo, curve B4 corresponding to Zr=1/5Z0, curve 65 corresponding to Zr=1/2Zo, ycurve 68 corresponding to Zr=1Zu, curve l0 corresponding to Zr=2Zo, curve 12 corresponding to Zr=Zo, curve 14 corresponding to Zr=10Zo and curve TS corresponding to Zr=, respectively.

The phase shift corresponding to a particular length of line and termination may then be read from the scale at the left of Fig. 9.

For example, in the above case where the length of line was .162 wave-length or 58.4 clegrees (electrical length) and the termination or load was 2.6 Zo the curves of Fig. 9 show that the phase shift from A to A', Fig. 5, is 32 degrees. Since the phase shift from A to A" is 90 degrees the phase shift from A to A" IFig. 5 is 90-32: 58 degrees.

In the same manner considering the section of line from center-line 30 to A, Fig. 5, the effective termination at A" is, as above stated, .38 Zu and its distance from center-line 30 is 1/4 wave-length minus .088 wave-length equals .162 wave-length. From the curves of Fig. 9 the phase shift from center-line 39 to A" is 74 degrees. The total phase shift from center-line 30 to point A, Fig. 5, is then 132 degrees (58+74) and the difference in phase shift between the sections to points A and B on opposite sides of the center-line 30 in Fig. 3 is then 132-90:42 degrees. This demonstrates that a substantial phase shift can be conveniently introducedby merely shunting a capacity across the line comprising conductors 32 and 33 of Fig. 3 at a distance which is short with respect to the wave-length from the center line 3B By further adjustment of the position of capacity 3S it was found that for a distance of .18 wave-length from the center-line 30, as illustrated in Fig. 6 the parallel resistive components of the impedances looking each way from the center-line 3U toward the dipoles 21 and 28 respectively were both the same and were equal to the characteristic impedance Zo of the line comprising conductors 32 and 33. This feature assures equal power division in the two branches. Furthermore, the phase shift in the branch including capacity 36 is found for this condition to be 54 degrees greater than for the branch having no capacity therein. This phase shift is greater than that for a spacing of the condenser of 1A; wave-length from the center line and, as will be described hereinunder, lends itself very conveniently to a lobe-switching arrangement which will alternately insert a capacity equivalent to capacity 36 in first the one and then the other of the two branches leading to the two groups of dipoles, the capacity in each case being at an electrical distance of .18 wave-length from the center line of electrical symmetry. Moreover, equal power distribution and therefore substantially zero lobe distortion is realized by this arrangement.

Alternatively, an inductive reactance equal to +720 could be substituted for the capacity 36 as illustrated by inductance i5 ofiFig. '7 and if placed at .18 wave-length from the center line of symmetry would produce equivalent results, except that the lobe shift would be in the opposite direction. Such an arrangement would, however, usually involve conductively contacting switching members to effect lobe switching. Such arrangements are preferably to be avoided if possible. It would of course be feasible to inductively couple an inductive reactance alternately to corresponding points on opposite sides of the line of symmetry but in most instances it is more convenient to employ capacitative reactances as described in detail below.

Fig. 8 illustrates a circuit of the same type as shown in Fig. 3 except that it employs concentric rather than simple two-conductor transmission lines and the capacity 36 is applied to a section of line 1/2 wave-length long comprising conductors 5| and 52, this section in turn connecting to the main horizontal line comprising conductors 41 and 48, at a point which is electrically .18 wave-length from the center-line 3B of electrical symmetry of the system. As is well known in the art, this is electrically equivalent to connecting capacity 36" directly across line All, 48 at the .18 wave-length point, but as will presently become apparent the use of the 1/ wave-length stub 5|, 52 lends itself -more conveniently to use in a practicable mechanism for effecting lobe switching in accordance with the principles of the invention.

In Figs. 10A and 10B a practicable mechanism for effecting lobe switching in one plane is illus* trated. In Fig. 10B a concentric line system com prising a T-fltting 88, two T-i'lttings 92 and units of coaxial line 98 including inner conductor 9|, joining the three above-mentioned T-ttings 88 and 92 and extending to the left and right from T-ttings 92 (shown in Fig. 10A) is shown, to'

gether with two stub concentric line members comprising outer conductors 83 and inner conductors 84 are shown.

This concentric line system is of the type shown in Fig. 8 and described above.

The vertical stub lines 83 and 84 are each 1/2 wave-length long and are made to have a lower characteristic impedance than the concentric line 9|) and 9| so that the stray capacity of the metallic fingers |02 do not appreciably affect the electrical length of the line. The upper ends connect electrically to mounting members 8S and through the last-stated members to metallic finger members |92, the latter members having a central portion removed as shown in Fig. 10A to facilitate centering the beam of the antenna when the lobe-switching device is not being used, as will be explained in more detail presently. An insulating member |24 provides mechanical sup- 7 port forthe upper: end ofmemb'erltpin each instance.

The concentric line, QQ, 9i extends to the left and to the right/from T-members 92, respectively, to connect to the left and right halves of the antenna system in accordance with the arrangement schematically indicated in Fig. 3 above. The centerline Sli of electrical symmetry for the system passes through the center of T-member 83 as shown in Fig. 10B, the verticalleg of T- member 88 serving to connect to transmitting or receiving apparatus or to a dupleXing-arrangement where the antenna system is to be employed alternately for transmitting and receiving. An impedance matching member 19. comprising an enlarged section or" the inner conductor is provided in the vertical leg of the T-member 83. Like impedance matching sections are employed at other points in the multiple antenna arrangements to be described hereinunder. The principles involved in the use of such impedance matching members are well known to those skilled in the art and are, briefly, when a load impedance differs by a moderate amount from the characteristic impedance of the line it is possible to transform the load impedance to the characteristic impedance of the line by connecting the two with a quarter wave-length transmission line having a characteristic impedance of \/Z1-Zo Where Zr is the load impedance and Zo is the characteristic impedance of the transmission line to which the load is to be matched. Y

A semicircular rotor member I9@ of' conductive material having a vertical web with three horizontal semicircular fins extending therefrom, as shown in plan view in Fig. 10A and in elevation in Fig. 10B, is fastened to shaft It@ by key lill'. The horizontal iins of member lili! interleave in spaced relation with the metallic finger members H12 as shown in Fig. 10B as the rotor Hill is rotated forming a capacity which for alternate half rotations is transferred from the end of one of the vertical stub lines 83, Bil to the end of the other vertical stub line. When the linger members t2 are fully interleaving the webs of member lil the capacity between them is such that its reactive impedance as seen from the point of connection between line 95B, tl and the vertical stub lines 83, Sil, will be equal to the characteristie impedance of line 9?, Si. The points at which the stub lines connect to line 9G, Si are of course .18 wave-length to the left and right of the center line of electrical symmetry 3Q, respectively, so that, in accordance with the theory discussed in detail hereinbefore, a discrete phase shift Will alternately be introduced to the left and right of axis t@ without disturbing the power distribution to the two halves of the antenna system.

Rotor mii has, as shown in Fig. 10B, very small clearance with respect to the lower surface ille of its housing member El) which provides a relatively very low impedance path (high capacity) for high frequency currents and effectively shortcircuits at high frequencies the relatively high resistance of the conductive path through the rotor and the rotor shaft and bearings to the housing 8i?, to which the outer conductors of the stub .lines connect.

Motor shaft l22 of motor l2@ is coupled through iiexible coupling H5 to shaft lll@ and serves,V

of course, to drive rotor Hifi. Motor Wtl is supported on a mounting bracket 55B and enclosed by housing member 82 which is secured to the lower housing member 8B' by bolts 8l.

Membersv Ill), H2 and. I Illk andfassociated det-- tails shown .in Fig. lC'icomprise a-stoppingmech--- anism for stopping thelobe-switching rotor IDU; precisely in the position in which itv is-.shown1in-. Fig. 10A. This position is chosen since it provides equal capacities-at the upper ends of the two stub lines 83, iflcompletingthe electricalsymmetry of.' the antenna system so that maximum radiation or reception will coincide with the normal axis` of the antenna array when the lobe-switching.

mechanism is not in use.

Members Il!) and H4 are single-tooth ratchet:

type cams. Member Hffis keyed to shaftf IDBsbytaper pin H3. Member lis free to turn on(r shaft il'. Member l l2 is a spiral type flat spring similar to the main springs employed to drive large clocks and is fastened at one endxto member Mil and at its other end to member. Hi When power is removed from the` motor l2!) tostop the' lobe-switching action, a solenoid, not shown, whose windingy is connected across the'motor: winding is Clo-energized to release member., l'lSiof Fig. 10C and permit springs ll9.to move pawls. EEE and E23 against members lill-and llt, respectively. The tooth of member HS engagespawli- 223 and ceases its rotation. The inertiaof motor iro, rotor mi) and shaft H36 is thenexpended inY winding up spring H2 until shaft |06 is broughti to a stop whereupon spring H2 starts to rotate, shaft lllin the opposite directionuntil pawl I'Zl. engages the single tooth ofv member l I4; stopping shaft Ilf in the position shown in-Fig. 10A. Thespace between fingers; B52l permits small variations in the position of rest without seriously af;- fecting the electrical balance ofthe systerrlVV and' thus makes it possible to employ reasonable tolerances in manufacturing the parts of the stopping mechanism; When powerv is again'applied to motor l2@ the solenoid withdrawsAV the pawls from members Il@ and IM. and permits free operation of the lobe-switchingmechanism.

Housing 8l, directly under the lobe-switching rotor los, encloses a simple cam-o-perated-switching mechanism, the cams being drivenfby an extension of shaft ESE, the position-ofy the cams indicating by closing appropriateV circuits and opening others, the direction in which the lobe is being deflected atV any particular instant during operation of the lobe-switching mechanism; This arrangement is employedusually to provideY a double image of a signal of particular interest on the indicator, which-is usually a cathode ray oscilloscope, one image being the signal as re-k ceived with the lobe switched in onedirectiom. the other image being the signal as received with. the lobe switchedY in the other direction, the two images being laterally displaced a short distanceso as to appear side by side whereby the antenna system may be turned until the two imagesare of equal amplitude and-the antenna systemwill. then be pointing directly toward the source from whichthe signa-ll of particular interestd is being received.

Details of this arrangement are no-t illustrated in the drawings of this application since it doesI not relate directly tothe invention forwhich protection is being sought. However, theA abovev brief description will, itis felt, suliice to substantially assist in makingv clear the advantagesy to' be gained by the use of lobe-switching arrange-v ments in radio direction determiningsystems.

Fig. ll shows in schematic diagram formV an antenna array arranged for single-planeflobee switching in accordancel with the principlesV of' the linvention; InFig. lleight dipolevantennas |30 are shown aligned end to end in a row with uniform spacing between antennas. The length of each radiator of the dipoles |30 is preferably a half wave-length of the frequency to be employed. The system is electrically symmetrical with respect to the axis 30. Enclosure |32 is for the purpose of providing a balanced to ground feed for dipoles |30 by making the impedance of the outer conductor of coaxial line |54 high with respect to ground at the point where the dipole connection is made. Members |36 are reiiectors spaced 1A; wave-length behind the dipoles |30 and as is well known in the art increase the eii'iciency and directivity of their associated dipoles. Members |34, |38, |40, Hill and |48 ccmprise enlarged sections of the inner conductor of their respective concentric lines and function as above described to improve the impedance matches at the junctions where they are situated.

Member |42 is a lobe-switching mechanism, preferably of the type illustrated in Figs. A and 10B and described in detail above.

In a further form of the arrangement of Fig. 11 the individual reflectors `|36 can be replaced by a single semi-cylindrical reflector of parabolic cross section, the line of antennas being situated along the focal line of the reflector. Rerlectors of this type are indicated in Fig. 13B for a twoplane lobe-switching system and are described below.

Fig. 12 shows in sch'ematic diagram form an antenna array arranged for two-plane lobe switching in accordance with the principles of the invention. Figs. 13A and 13B illustrate further features of the arrangement of Fig. 12. The array oi Fig. 12 is similar to that of Fig. 11 except that two rows of dipoles |80 are employed, one row being positioned above the other so that by alternately introducing additional phase shift in the lines leading to the upper and lower rows the lobe can be switched in the vertical plane.

'I'he rows are each subdivided horizontally into two equal parts and by alternately introducing additional phase shift in the lines leading to the right and left halves respectively of both rows the lobe can be switched in the horizontal plane. As for Fig. 11, so in Fig. 12, each dipole |60 is provided with reectors |66 which can be individual or which can be replaced by a single semicylindrical reflector of parabolic cross section for each row of dipoles as indicated in Fig. 13B. Enclosures |82 are provided around the end of each line adjacent to a dipole antenna and impedance matching elements such as |64, |82 and |19 are provided at the several line terminals as for the system of Fig. 11.

As a matter of mechanical convenience the lobe-switching mechanism |80 of Fig. 12 can be, in the majority of its structural details, very much like the lobe-switching mechanism described above and illustrated in Figs. 10A and 10B. The chief and sole important difference will of course follow from the necessity of lobe switch'- ing in two planes and as indicated in Figs. 12 and 13A four sets of members |02 spaced at 90-degree intervals with respect to each other and connected by half wave-length concentric line stubs to the four branch lines |10, |12, |14 and |18 respectively at a distance of .18 wave-length from the center of electrical symmetry of the system are employed, in lieu of two sets of members |02 spaced at 180 degrees from each otheras for the single plane arrangement of Figs. 10A and 10B.

* The rotor |00 may be identical with that employed for single-plane operation and as it rotates it will engage successive pairs of adjacent sets of members |02. Starting from the position indicated in Fig. 12 and assuming clockwise rotation; the beam for the position indicated in Fig. 12 will be deflected up; as the rotor turns to engage members |02 of line |14 and drops member |02 of line |10 the beam will be deflected to the right; as the rotor proceeds further to engage members |02 of lines |10 and |16 only the beam will be deflected down and finally when the rotor is engaging members |02 of lines |18 and |10 only the beam will be deflected to the left.

A stopping mechanism is preferably provided to stop the rotor at a position in which the beam is deflected up, i. e. with the rotor approximately 180 degrees from th'e position indicated in Fig. 12, when it is desired to operate without lobe switching.

The cam-operated switches cooperating with the indicating system for a two-plane lobeswitching system such as that illustrated by Fig. 12, preferably connect a left-right indicator for the left and right beam deilections and an updown indicator for the up and down beam deflections respectively, so that a signal of particular interest may be located and followed in azimuth employing th'e left-right indicator and in elevation by employing th'e up-down indicator.

In the side view schematic diagram of Fig. 13B, the upper and lower dipole arrays of Fig. 12 are shown aligned on the focal lines of upper and lower semicylindrical reflectors of parabolic cross section, respectively. Lines |10 and |12 will in this view lie in a common plane as will also lines |14 and |16.

In Figs. 14A and 14B the details of a capacity switching unit for a lobe-switching mechanism intended for use in a relatively low frequency.

(200 megacycles) and low impedance system are shown. In this system larger capacities are required so that the rotor 202 for the unit of these Iigures comprises ten capacity members in the form of semicircular plates, and the linger members 200 are assembled in groups of nine interleaving in spaced relation with the rotor plates. To obtain the high capacity (low impedance) desired between the rotor 202 and the housing 200 in this instance, a set of nine members 206 fastened to the housing 200 is provided to project in interleaved arrangement spaced with respect to rotor elements 202 as shown in Fig. 14A and spaced between each pair of the sets of finger members 2 04 as shown in Fig. 14B. Because of the lower frequency, also, the distance of the .18 wave-length points from the electrical center of symmetry for the antenna and lobe-switching systems is great enough so that the half wavelength stub lines of the higher frequency systems may be omitted and the four branch lines may be brought directly to the lobe-switching mechanism from the center of symmetry and proceed from the mechanism to their respective subgroups of the antenna array. For example, in Fig. 14A the bottom end 230 of member 208 at the left of the figure may connect to the inner conductor of a length of line .18 wave-length long coming directly from the electrical center of symmetry and a second connection to member 208 may be made, as by member 2|0, from which the inner conductor of a line to one subgroup of the antenna array may be connected. Members 2|8 and 220 serve to insulate the assembly supported on member 208 from housing 200 and threaded extensions 2| 2 and 232 of housing 200 facilitate the fastening of the outer conductors of the re- 1l spective concentric lines to the housing 298.Y In other respects the lobe-switching mechanism and associated circuit arrangements of Figs. 14A and 1413r may be substantially the same as for similar mechanisms and arrangements described in detail above for higher frequency systems.

Numerous other arrangements embodying the principles of the invention will occur to those skilled-in the art. The scope of the invention is dened in the following claims.

What is claimed is:

l. In a high frequency radio directional system, an antenna-system comprising a plurality of radiating and receiving antenna members symmetrically arranged with Vrespect to a particular Vaxisa-system'of electrical transmission lines providing electrical symmetry between a common electrical input point and the corresponding portions of said antenna system on'opposite sides-of said axis of symmetry, the antenna system being proportioned to provide a sh'arply directive lobe characteristic along said axis of symmetry and lobe-switching means comprising means for introducing a predetermined discrete reactive impedance non-conductively connecting to said antenna system, alternately at two portions of said transmission line system, said two portions being the corresponding portionsofisaid transmission line system on opposite sides of said axis of symmetry, the value of said reactive impedance being not less than the characteristic impedance of said transmission line whereby lobe-switching, that is-delection of the lobe a1- ternately fromja position a Yfew degrees on one side of said axis of symmetry to. a position a like few degrees on the opposite side vof said axis, can be leffected with-rapidity and without encountering contact; resistance dinculties.

2. The arrangement of claim 1 the point of introduction of said discrete reactive impedance being chosen to provide substantially no disturbance ofthe normal equal distribution of powerV to the portionsof said antenna system on both sidesfof said axis of symmetry when said impedance is introduced on eitherfside of said system wherebythe shape 'of the lobe characteristic of said antenna system is not altered by the introductionof'said impedance on either side of said axis-of symmetry and themaking of precision bearings by the use of said system 'is facilitated. -Sf In a high frequency radio directional system em-loying asymmetrical antenna system having a sharply directivecharacteristic, means for increasing thesharpnessrof bearing indications obtained by uthepointing of said antenna system comprising a dielectric member, andA means for alternately introducing said member between conductors of said antenna system on one side of -its axis of symmetry and between correspondingconductors of said antenna system on the other-side of its axis of symmetry, the length of the Yconductors affected in each case being between l; and 1A; wave-length of the energy being radiated, wherebsr a relatively small changein the phase relation between the energy of the two halves of the antenna system is effected and the directional characteristic of said'antenna system is shifted alternately from a position a few degrees on' one side of th'e normal axis of Ysaid characteristic to a corresponding position on the other side o f said lnormal axis without encountering substantial "impedance unbalance or electrical contact resistance diiculties.

Y `4, a high frequency radio directional system, a symmetrical antenna system having a sharply directive response characteristic and phase changing means "adapted to' be vnon-conductively coupled` Yalternately to corresponding points of said antenna system ony opposite Vsides of the axis of symmetry thereof whereby the `directive characteristic of said antenna systemis alternately switched between a, positiona few degrees to one side of its normalaxis to a like position a few degrees to the opposite side of its Vnormal axis and the accuracy of the bearing obtained by pointing said antenna system at a source radiating or reflecting radio wave energy, can be substantially increased.

5. In a radio systemya multielement antenna system having electrical symmetry about aparticular axis, identical transmission lines'connecting the portions of said antenna system on opposite sides of said axis to a common junction, means for introducing at corresponding points of said transmission lines a particular discrete'impedance which is alternately and non-conductively coupled with said two lines, the impedance alternately coupled with said two lines being substantially equal in magnitude to the characteristic impedance 0f the lines.

6. In a radio system, amultielement antenna system having electrical symmetry about aparticular axis, identical transmission lines connecting the portions of said antenna system on o pposite sides of said axis to a common junction, means for introducing at corresponding points-'of said transmission lines ap'articular discrete fimpedance which is alternately andA non-conductively coupled Vwith'isaid two'lines, the point on each of said'lines to which :said impedanceis coupledbeing at adistance of `substantially '.18 wave-length from the" common junction of said lines.

7. In a radio: system, a multielement antenna system having electrical symmetry Vabout'a' particularly axis, identical Vtransmission lines-con necting the portions of said antenna system on opposite sides of saidaxis toa common junction, means for introducingat corresponding points of said transmission lines a particular discrete impedance which is alternately and non-conductively coupled 'with said two lines,y the impedance alternately vcoupled with said twolines bein'gvsubstantially equal in` magnitude to' the' characteristic impedance of the lines and thepoint on each line to which saidfimpedance is coupled'being ati-a distance of substantially .18 wave-length from the common Vjunction of said lines.

8. An .antenna system for directive radiosystems'c'ompri'sin'g a pluraltiy of antenna elements arranged in two like groups, the groups being symmetrically disposed'about a commonaxis, apair or substantiaily identical' transmission line systems connecting said' .two groups of'an'te'nna'i elements to acommonju'nction point, a capacitative device comprisingta'rotary element and two stator elements, th'e rotary elementc'apacitativelyengaging the4 two stator "elements Vfor alternate halves of keach complete rotation, respectively, one stator being conductively connected across one of said transmission :line systemsfthe Vother stator being vconductively connectedfacross" the other of said transmission linesystems vthecapacity between 'each `stator and v theY rotor when fully engagedther'ewithbeiiglof the valuec'orresponding to a reactive limpedance of substantially 'the same magnitude as the characteristic impedance of the transmission line to 'whichthe' Vstator is connected, 4'whereby fa" predetermined electrical impedance" can be' alternately introduced in shunt across rst one and then the other of said transmission line systems by rotating said rotor element Without making or breaking conductive connections to said lines and lobe-switching of said antenna system to enhance the accuracy of directive determinations dependent upon the directive properties of the antenna system is more satisfactorily effected.

9. The arrangement of claim 8, the connection of each stator to its respective line being such that the impedance appears eiectively at an electrical distance of .18 wave-length of the energy employed, from the junction point of the two transmission line systems.

10. An antenna system for directive radio systems comprising a plurality of antenna elements arranged in a plurality of like groups, the groups being symmetrically disposed about a common axis, a transmission line system connecting each group of antenna elements to a common junction point, the respective transmission line systems being substantially identical, a capacitative device comprising a rotor element and a plurality of stator elements, one stator element being associated with and conductively connected across each of said transmission line systems, respectively, the capacity of each stator element when fully engaged by the rotor element being such that its impedance is substantially equal to the characteristic impedance of the transmission line system, the stator elements being regularly spaced and the rotor capacitatively engaging each stator for approximately half of each complete rotation whereby when the rotor is turned impedances are successively placed and removed from the transmission line systems in a regular rotative manner and lobe-switching of the directive beam of said antenna system is effected in several planes.

11. The antenna system of claim 10, the stator element for each transmission line system being effectively connected thereto at a distance' which is electrically .18 wave-length of the energy employed from the common junction point of the line systems.

WILLIAM H. C. HIGGINS. CLIFFORD A. WARREN.

REFERENCES CITED The following references are of record in thele 0f this patent:

FOREIGN PATENTS Number Country Date 802,756 France June 13, 1936i 114,047 Australia Oct. 14, 1941

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