NOV» l2, 1946 T. M. GLuYAs, JR., ET AL LOBE SWITCHING ANTENNA Filed Feb. 24, 1943 @Se (Ittorneg ' Patented Nov. 12, 1946 UNETED STATES PATE. @FETEQE 2,411,034 Lona SWITCHING ANTENNA Thomas M. Gluyas, Jr.,`CollingsWood, and Lester J. Wolf, Audubon, N. J., assignors to Radio Cor poration of America, a corporation of Delaware Application February 24, 1943, Serial No. 476,888 5 Claims. ( Cl. 250-11 ) l 2 This invention relates to directive antennas and more particularly to an antenna system for matic diagram of an antenna array and its as providing alternately overlapping directive lobes. sociated circuits arranged according to the pres In some applications it is desirable to radiate or pick up energy alternately in two relatively nar ent invention, Fig. la is a side view of a radiating element mounted in front of a screen, Figs. 2 row overlapping lobes. This may be accom plished by an array of spaced dipoles energized or coupled together in such phase relationships that the resultant directive pattern comprises a beam whose axis may be shifted by suitable vari ation of the phase relationships between the sev eral elements. In such applications as require two discrete lobes, without any intermediate di rectivity, the changes in phasing may be provided by a switching mechanism of some sort. The arrays used for this purpose generally comprise at least one central group of radiating elements, - and one or more groups of side elements disposed symmetrically with respect to said central group and phased in opposite senses with respect to said accompanying drawing, of which Fig. 1 is a sche and 2A are schematic diagrams of antenna ar rays explanatory of the operation of the system of Fig. 1, Fig. 3 is a group of curves representing the components of a radiation ñeld produced by the eiïect of the -in-phase currents in the system cf Fig. 1, and Fig. 4 is a group of curves illustrat ing the production vof the directive iield by all of the currents in the system of Fig. 1. Referring to Fig. 1,-the antenna array to be ¿ described comprises a central group I of radi ator elements and two side groups 3 and 5, symmetrically located with respect to the central group. A concentric line 'l is connected to a ractive effect on the other side. The problem of switching radio frequency energy, particu larly when relatively large peak power is in radio device, not shown,l which 'may be a re ceiver, a'transmitter, or both. The line 1 is con nected directly by a concentric line 9 to the cen tral >group I. .In'order to convert from the elec trically unsymmetri'cal concentric line to a cir cuit which is symmetrical with respect to the ground, suitable for connection to dipole anten volved, has been met to some extent by the em na elements, a concentric line transformer II is central group so as to provide an additive effect on one side of the axis of the array and a sub provided. This device comprises a relatively large cylindrical conductive section 1A Wave ing movable make-and-break contacts. Another problem which arises in the design and opera length long, connected at its base to the outer tion of directive arrays of the above described 30 conductor of the line 9. The central group com prises two parallel dipoles spaced apart IÁQ Wave type is the elimination of undesired secondary lobes in the radiation pattern. In order to length and connected in parallel as shown. Each or" the side groups comprises a similarly arranged achieve the desired sharpness of directivity While avoiding secondary lobes it is usually neces pair of dipoles. The center line of each side sary to use an array comprising a large number group is 5A; wave length from that of the central ployment of capacitor type switches, thus avoid of elements, and on ship board and in other Ino group. bile installations there is usually a definite limit through concentric line transformers I3 and I5 and lines I'l and I9 respectively to the switching circuit at the junction points 2I and 23. The to the size of the array which can be tolerated. It is the principal object of the present inven tion to provide an improved method of and means for providing alternately overlapping ra diation directive patterns.. Another object is to provide a directive antenna array for the above- purpose which is relatively simpleand compact in construction. A further" object is to provide an improved method of and means for changing the ener gization of the various elements of an antenna Aarray for the purpose of controlling the directive pattern thereof. A further object is to provide an improved capacitor type switch. i The side groups 3 and 5 are coupled points 2I and 23 are connected together by a line 25 of a length‘equivalent to 50 electrical degrees. The point 2I is connected through a, line 21, 1A; wave length long, to a, junction point 29. The point 29 is connected through a line 3l to a stationary capacitor plate 33 and through a 1A; wave line 35 to a junction point 37. The junc tion point 23 is similarly connected through a 1A; wave line 39 and lines 4I and 43 to a stator plate 4G' and to the junction 3l. YA stub line 45 60 is connected to thejunction point between the lines 39, 4I and 43 and a similar stub Ill is con nécted to the opposite junction point 29. The These and other objects will become apparent vcapacitor switch @9 includes the stator plates 33 to those skilled in the art upon consideration of and Lida pair of stator plates 5I and 53, and a the following description with reference to the 55 single rotor plate 55. The stator plates 5I and 2,411,034 3 53 are connected to stub lines 51 and 59 respec tively. The rotor plate 55 is mechanically con nected to a motor 6I provided with a suitable power supply, not shown. 4 operation is the solid line curve 11, which rep resents the resultant ñeld produced by the corn plete array with one position of the switch 49. When the switch lis is in its opposite position, Referring to Fig. 2, the radiation from pairs of the quadrature current component represented radiators along a line symmetrically disposed with respect to the midpoint of the line is of by the curve "il is reversed, providing a resultant similar in shape to the resultant 11 but inverted with respect to the bearing axis. With the de the form: ' sign illustrated in Fig. 1 the ñeld pattern is 30° 10 wide at the half energy point and the lobe dis placement is 6° from the center line. -It should be noted that the curves 1l and 13 are approxi Where K is a constant, I1, Iz . . . are the radiator currents, of phase angles ai, «x2 . . ., and B1 B2 . . are the radiator spacings in radians. For an add number of radiators (Fig. 2A) : mately tangent at their point of nearest ap proach, which occurs at an angle of about 45°. 15 If the currents and phases of the radiator ele ments are so arranged that these curves do not cross, no spurious radiation lobes are produced. The rotating capacitor ¿l5 is part of a series resonant circuit which alternately grounds the The actual field pattern may be determined by junction points 29 and lill. A short circuit at multiplying the above expression by the direc 20 the junction point 29 reflects an open circuit at tivity pattern of the radiator element, including junction points 2l and 31 as a result of well the effect of the reflecting screen. This factor lrnown impedance inversion characteristics of may be determined experimentally with a single quarter wave transmission lines. Similarly a radiator element. In the array of Fig. l the short circuit at the junction point ¿lll reilects open dipole elements are supported 1/8 wave length in 25 circuits at points 23 and 31. The inductance iront of a screen ‘53, as illustrated in Fig. 1A. of the stub line ¿il together with the capacitance When the array is used for transmitting, the between the condenser plates ¿l5 and 55 is series current in the central group is maintained con resonant at the frequency of antenna operation. stant. The current in each element of the side The rotor plate 55 is effectively grounded by 30 group is 1/2' that of each element of the central means of the stub 51 which, together with the group, and inA one position of the switch 49, the capacitance of the plates 5l and 55 is series current in the side group 3 leads the current resonant. The residual capacitances at the un in the center group l by 25°. The current in grounded points 29 and ¿lo are brought to par the side group 5 lags that in the central group by the same amount. For the opposite position 35 allel resonance by the stub lines 41 >and ¿i5 re spectively so that these capacitances have no of the switch ¿l5 these conditions are reversed, net eñect on the normal transmission path and the current in the side group 5 leads while through the ungrounded junction point. When that of the side group 3 lags. the point ‘29 is grounded, current flows over the Referring to Fig. 3, the field components re sulting from the in-phase components of the 40 line sections ¿i3 and 39, so that the side group 5 leads the side group 3 in phase by an angle pro antenna currents are illustrated. This ñgure portional to the length of the line section 25. neglects the individual directivity of the radiators When the point 44 is grounded current flows and the effect of the screen which will be taken over the path including sections 2.1 and 35 into account in Fig. 4. The field component caused by the central antenna is represented by 45 and the side group 3 leads. Thus the beam is displaced from left to right as the rotor of the the dotted line 55. rl‘his is seen to be independent capacitor ¿i9 is turned. The rotor of the capaci of the bearing angle 0. The field component tor 49 is grounded through series resonance with produced by the currents in the side groups 3 and 5 is indicated by the dash line 61. This is 50 the stub lines to avoid necessity for rotating ground connections which are diiilcult to achieve a function of the angle 9 as described above. at high frequencies. This arrangement also pre It is to be understood that the curve 61 repre vents radio frequency currents from flowing sents only that portion of the field which is down the motor shaft and through the motor` produced by the in-phase components of the bearings. currents in the antennas. The resultant field is merely the sum of the fields produced by the 55 Thus the invention has been described as an antenna system for providing alternately over side and center groups and is thus represented lapping directive radiation lobes. A relatively simple array is employed, comprising a central Referring to Fig. 4, the resultant due to the radiator group and two symmetrically disposed quadrature phase components of the side antenna side groups. The central group is excited con 60 currents is represented by the dotted line 1|. tinuously and the side groups are excited out The resultant field caused by the in-phase com of phase with the central group, one side leading ponents, represented by the curve 69 in Fig. 3, and the other side lagging by the same angle. is shown by the dash line curve 13 in Fig. 4. This The phase angles of the side groups are inter curve is equivalent to the curve 69 but is repre 65 changed periodically to displace the radiation lobe sented on a different scale and is extended to from left to right. An improved switch is pro both sides of the zero bearing axis. The direc vided for this purpose, comprising a rotating tivity factor produced by the use of a screen capacitor provided with a single rotor and a plu and the directivity of the individual radiators is rality of stator plates. The rotor is grounded represented by the alternate dot and dash curve 15. I. e. a single radiator, with a screen, has 70 through a series resonant circuit including the by the solid line curve 69. a directivity pattern like the curve 15. To de termine the resultant field, the quadrature and in-phase component curves 1I and 13 are added together graphically and multiplied by the di rectivity factor curve 15. capacitance to one of said stators. We claim as our invention: l. An antenna system for providing alternately overlapping directive pattern lobes, lcomprising The result of this 75 a central radiator group and two side radiator 2,411,084 groups symmetrically disposed with respect there 6 one leading, and one lagging, with currents in each side group radiator equal to one half the to, each of said radiator groups comprising a pair of horizontal dipoles spaced 1/2‘ wave length current in each center group radiator, and means apart vertically and electrically` connected in for periodically reversing the phase relations of parallel, said side groups being separated hori 5 the energization of said side groups with respect zontally from said central group by 5/8 wave to that of said central group. length, a main transmission line adapted to be 3. The invention as set forth in claim 1, in connected to a utilization circuit, said trans cluding a screen of conductive material disposed mission line being connected directly to said in a plane parallel to all of said radiator elements central radiator group and through branch cir 10 and spaced substantially 1/8 wave length there cuits to said side radiator groups, a section of from. transmission line of a length equivalent to 50 4. A radio frequency distribution circuit in electrical degrees and switching means arranged cluding a main supply line, two branch lines, to alternately include said line section in the two transmission line sections 1/5 wave length paths to said side radiator groups, said switching long, each connecting one of said branch lines means comprising quarter wave length trans 15 respectively to said main line, and a transmission mission line sections connected in series between line section of predetermined length connecting said main line and each of said branch circuits, said half wave transmission line sections to each stub lines, and motor driven capacitor means other, switching means arranged to alternately connected to said quarter wave sections and to short circuit said half wave length sections at 20 said stub lines, whereby said quarter wave sec their midpoints, said switching means compris tions are alternately short-l circuited through series ing cyclically variable capacitor means connected resonant circuits including said capacitor means to said midpoints and stub lines connecting said and said stub lines. variable capacitor means to ground, said stub 2. An antenna system for providing alternately overlapping directive pattern lobes, comprising 25 lines being of such lengths that said stub lines, a central radiator group and two side radiator groups symmetrically disposed with respect there together with the maximum capacitance of said variable capacitor, comprise series resonant cir to, each of said radiator groups comprising a pair of horizontal dipoles spaced 1/2' wave length apart cuits. 5. The invention as set forth in claim 4 in from said central group by 5A; wave length, means cuits which are parallel resonant with the mini mum capacitance of said variable capacitor at vertically and electrically connected in parallel, 30 cluding inductive elements connected to said midpoints and so proportioned as to form cir said side groups being separated horizontally for constantly energizing _said central group. means for energizing each of said side groups 25 degrees out of phase with said central group, the frequency of operation of said system. THOMAS M. GLUYAS, J R. , LESTER J. WOLF.