US2458885A

US2458885A - Directive antenna system

Info

Publication number: US2458885A
Application number: US568248A
Authority: US
Inventors: Clifford A Warren
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1944-12-15
Filing date: 1944-12-15
Publication date: 1949-01-11
Anticipated expiration: 1966-01-11
Also published as: FR934847A; GB624876A

Description

Jan. 11, 1949. c, WARREN Z,458,8$5

DIRECTIVE ANTENNA SYSTEM Filed Dec. 15, 1944 8 Sheets-Sheet 1 //v l/EN TOR C. A. WA RREN Jan. 11, 1949. c. A; WARREN DIRECTIVE ANTENNA SYSTEM 8 SheetsSheet 2 Filed Dec. 15, 1944 Elks uWSi IN l/E N TOR y c.,4. WARREN 0.3

A 7' TOR/V5 V Jan, 11, 1949. c. A. WARREN 2,453,385

/ DIRECTIVE ANTENNA SYSTEM Fi led Dec. 15, 1944' 8 Sheets-Sheet 5 FIELD STRENGTH POWER GAP-AXIS THEORETICAL DIRECTIVE PATTERNS OFF AXIS THEORETICAL DIRECTIVE PA TTERNS wvavron CA. WARREN ATTORNEY C. A. WARREN DIRECTIVE ANTENNA SYSTEM Jan. 11, 1949.

Filed Dec.

8 Sheets-Sheet 4 asmom Him/381$ 073/1 lNl ENTOR By C A. WARREN Jan. 11, 1949.

c. A. WAR REN DIRECTIVE ANTENNA SYSTEM Filed Dec. 15, 1944 8 Sheets-Sheet 5 83 89 e um? 83 be? (Hanna 8) H19N381S 073/1 INVENTOR' CA. WARREN BY I 8 A TTORNE Y c. A. wAREN DIRECTIVE ANTENNA SYSTEM Jan. 11, 1949.

8 Sheets-Sheet 6 1- Filed Dec. 15, 1944 asmoap mouse/1s 073/1 -4 m at IN VENT'OR By CA. m4 RREN ATTORNEY C. A. WARREN DIRECTIVE ANTENNA SYSTEM Jan. 11, 1949.

Filed Dec. 15, 1944- 8 Sheets-Sheet 7 /Nl/N7'OR 6 A. WARREN Q y.

A T TORNE Y Patented Jan. 11, 1949- DIRECTIVE ANTENNA SYSTEM Clifford A. Warren, Watchung, N. 1., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 15, 1944, Serial No. 568,248 16 Claims. (Cl. 250-3335) This invention relates to antenna systems and particularly to directive antenna systems.

the amplitudes of the antenna currents, as disclosed in Patent 2,419,205, granted on April 22, 1947, to C. B. H. Feldman. In the case of a single parabolic reflector, the desired minor lobe reduction may be secured by tapering the energization or illumination of the reflector, as described in Patent 2,422,184, granted on June 1'7, 1947,

' antenna pattern, the single'primary lobe of the to C. C. Cutler. While these prior art methods have been successfully employed, they are not entirely suitable for reducing the minor lobes obtained in the double antenna or dual refiector system disclosed in the copending joint application of W. H. C. Higgins and applicant, Serial No. 453,390, filed on August 3, 1942, now Patent No. 2,424,982, dated August 5, 1947. The dual reflector system comprises two parallel horizontal arrays of colinear dipoles and a separate large cylindrical parabolic reflector associated with each array, and it is especially suitable for use in a dual plane lobe switching radar antenna system. Accordingly, it appears desirable to reduce the minor lobes, in the directive pattern of a dual reflector system, in a more satisfactory manner than heretofore effected.

It is one object of this invention to secure, in an antenna system, a highlysatisfactory directive characteristic.

It is another object of this invention to reduce, in a directive antenna system, the minor lobes of the directive characteristic of the antenna.

It is another object of this invention to reduce, in a dual plane lobe switching antenna system, the first minor lobes of the directive patterns taken in the two perpendicularly related switching planes, without materially increasing the half power widths of the major lobes in said patterns.

It is a further object of this invention to eliminate, in a dual plane lobe switching antenna system, false cross-overs ,in each switching plane.

In accordance with one embodiment of the invention, an auxiliary antenna system is positioned adjacent to the dual reflector or main antenna system disclosed in the eopending Higgins-Warren application and is utilized for securing the desired minor lobe reduction. For convenience, the single primary lobe of the main .minor lobes.

have opposite phases.

auxiliary antenna pattern and the single primary lobe of the resultant or combined pattern are termed herein the major" lobe, the maximum" lobe and the principal lobe, respectively; and the secondary lobes of the main, auxiliary and resultant patterns are termed herein the "minor," the minimum" and the "subsidiary" lobes, respectively.

The auxiliary antenna system comprises a single cylindrical parabolic reflector and a: pair of colinear dipoles aligned with the horizontal focal line of the small reflector. The auxiliary antenna system and the main antenna system are connected to the same radar transceiver. The vertical aperture dimension of the auxiliary reflector and the horizontal dimension of the auxiliary antenna system are relatively small compared to the corresponding dimensions of the main antenna system and are such that, in each switching plane, the width of the maximum lobe pattern of the auxiliary antenna system is at least as great as the total width of the major lobe, the nulls adjacent thereto and the first Amplitude control means are provided for regulating the currents supplied to or received from the two antenna systems, whereby the intensities of the maximum lobe of the auxiliary antenna and the aforementioned minor lobes may be equalized substantially. In each plane the two first minor lobes of the main antenna system are cophasal, and the major and first minor lobes of the main antenna system During the dual plane lobe switching operation, the phase of the major lobe remains constant. A phasecontrol means is inserted in the line to the auxiliary antenna system for securing an auxiliary antenna maximum lobe having a phase similar to that of the major lobe and opposite that of the first minor lobes.

The invention will be more fully understood from a perusal of the following specification taken in conjunction with the drawing on which like reference characters denote elements of similar function and on which:

Fig. 1 is a perspective front view of one embodiment of the invention;

Figs. 2and 3 are, respectively, a front diagrammatic view and a side diagrammatic view of the embodimentof Fig. 1;

Figs. 4 and 5 are theoretical one-way directive patterns used for explaining the invention;

Figs. 6, '7, 8 and 9 are measured one-way dior secondary antenna member 2 and a lower cylindrical parabolic reflector or secondary antenna member 3, each having a horizontal axis 4. a horizontal focal line I, a common vertical latus rectum 6, an opening or aperture 1, and a focal distance d of a quarter wavelength. The apertures are relatively large and of equal size and, in the case of each reflector, the longitudinal dimension m is approximately equal to twice the transverse dimension n, so that the entire aperture of the main antenna comprising the two reflectors 2, 3 is substantially square. The axes 4, Fig. 3, are parallel to the on-axis or zero degree transceiving direction 8 which coincides with the equi-intensity direction for the dual plane lobe switching system or, stated differently, coincides with the axis of the scanning cone.

Reference numeral 8 denotes an auxiliary antenna system comprising a cylindrical reflector l cally related to the dimensions of reflectors 2 and 3. As explained below, in one embodiment having a design or mean operating wavelength of about 30.5 centimeters the side dimension a of the square opening i3 is two wavelengths and the side dimension m, or 2n, of the square opening for the two reflectors 2 and 3' is about six wavelengths. In other words, the dimension a is in the. order of one-third of dimension 111..

As shown in Fig. l, the main antenna system I and the auxiliary antenna system 9 are supported by a yoke assembly comprising a rotatable vertical shaft and bearing l4, a horizontal turntable member i6 attached to shaft I4 and a pair of uprights or vertical arms IS. The two reflectors 2, 3 are secured to a framework comprising two side members l1 (only one shown in Fig. 1) which are mounted on a rotatable horizontal shaft l8. Shaft I8 is supported on bearings IS in arms I6. As indicated by arrows -20, means (not shown) are provided for rotating the entire antenna system' in the horizontal or azimuthal plane and for tilting it in the vertical or elevational plane. The auxiliary antenna system is supported by struts 2| extending through reflectors 2 and 3 and attached to the framework mentioned above.

Referring to Fig. 2,

reference numerals

22 and 23 denote the primary antennas associated with the upper and lower reflectors 2, 3, respectively,

' of the main antenna system. Each primary antenna comprises eight dipoles 24 arranged in a linear array and aligned with the reflector focal line and each

array

22, 23 comprises two subarrays of four colinear dipoles. For convenience, the left upper, right upper, left lower and right 23, denotes a translation device, such as a radar transceiver, which is connected by the coaxial principal line 24 and the coaxial main line to the junction 3| of two coaxial array lines 32, one of which is connected to the junction 33 of the two subarray lines 21 associated with subarrays LU and EU and the other of which is connected to the junction 34 of the two subarray lines 21 associated with subarrays LD and RD. Each of the above-mentioned coaxial lines comprises an inner conductor 33 and an outer conductor 38.

As is apparent from the drawing, the sixteen dipole lines 23 have equal lengths, the eight branch lines "have equal lengths. the four subarray lines 21 have equal lengths and the two array lines 32 have equal lengths, so that the paths connecting device 28 to the. sixteen dipoles have equal electrical lengths. Numeral 3'! denotes an adjustable amplitude control means, such as an adjustable attenuator, included in the main line 30.

Reference numerals 33 denote four short-circuited quarter-wave coaxial lines each of which is bridged across a different subarray line 21 at a point a short distance from the junction 33 or 34, as explained inthe copending Higgins-Warren application. Numeral 33 denotes a lobe switcher having a base member 40, four stator plates 4| lower subarrays are denoted LU, RU, LD and RD,

respectively. The four dipoles 24 in each of the four subarrays are connected by four individual coaxial dipole lines 25 and two coaxial .branch lines 28 to a coaxial subarray line 21. Numeral and a rotor 42 designed for capacitive association with two stator plates. Each stator plate 4| is connected to the inner conductor 33 of a coaxial phasing line 43 through a different switch 44, and the outer conductors 38 of phasing lines 43 are connected to base member 40. The other ends of the four phasing lines 43 are each connected to the approximate midpoint of a different quarter-wave coaxial line 38 so that, as explained below, in the case of each of lines 38, the rotor 42 applies the correct capacity to the midpoint of the line. Preferably, the phasing lines 43 have negligible lengths, or lengths each equal to an odd multiple of a half wavelength. In one actual embodiment the phasing lines 43 are omitted and the capacity is successively applied directly by the rotor 42 to the midpoints of the four quarterwave lines 38 which project into the lobe switcher 39. Numerals 45 and 46 denote a motor and shaft for driving the rotor 42. The main antenna system just described is basically the same as that disclosed in the Higgins-Warren application, the primary difference between the two systems being that the phasing lines 43 in the system of the aforementioned application are each connected to the subarray line v2'I through a halfwave line instead of a portion of a short-circuited quarter-wave line 38.

Reference numeral 4! denotes the primary antenna associated with the reflector ill of the auxiliary antenna systemv 3. The primary antenna 41 comprises two spaced dipoles 24 alignedwith the focal line H of the auxiliary reflector Ill. The two dipoles 24 are connected by the dipole lines 23, the coaxial auxiliary line 48 and the principal line 29 to the translation device 28. The auxiliary line 48 includes an adjustable attenuator 31 and an adjustable phase shifter 48.

In accordance with conventional practice, adiustable impedance transformers (not shown) are inserted at the line junctions'and at the dipole junctions, for the purpose of matching the impedances throughout the system. A conventional short-clrcuited quarter-wave stub (not shown) is provided at the center of each dipole for rigidly connecting the inner coaxial line conductor 35 to the outer coaxial line conductor 38 through a auaaea' high impedance. If desired, instead of employing the two special attenuators '31, the amplitude of the current delivered to themain antenna I may be controlled by the impedance transformer at thejunction 66 of the principal line 26 and the main line 36, and the amplitude of the current supplied to the auxiliary antenna 8 maybe controlled by the impedance transformer at the junction 60 of the principal line 26 and the auxiliary line 48.

In operation, assuming device 28 is aradar transceiver, pulsed energy is conveyed through the adjustable attenuator 81, and over

lines

29, 36, 82, 21, 26 and 26, between the device 26 and the sixteen dipoles 26 of the main antenna system i. At the same time, pulses are conveyed through the adjustable attenuator 31 and adjustable phase shifter 69, and over

lines

26, 68 and 26, between device 28 and the two dipoles 24 of the auxiliary antenna system 9. As is now well understood,

the high frequency pulses emitted by the combined antenna system i, 6 are, after reflection at a target, returned thereto as echo pulses. Since only the transmitting operation of the antenna systems i, 9 is described in detail herein, it should be pointed out here that the transmitting and receiving directive patterns are, by virtue of the reciprocity theorem, substantially the same.

Considering in detail the operation of the main antenna system i taken alone, with the four switch members M open, and motor 65 inactive, the lobe switcher 39 is disconnected from the four quarter-wave lines 38 and the energies delivered to the sixteen dipoles 24 are cophasal. The quarter-wave linestfi remain bridged across lines 21 but they do not affect the phases of the currents in the subarray lines 21, since they have a high impedance. With the switches 66 closed, and with motor t6 driving the rotor 62 clockwise, the rotor becomes capacitively associated with the upper pair, right pair, lower pair, and left pair of stator plates in succession, whereby two separate capacitive impedances, each comprising the rotor 62 and one of the stator plates ll, are simultaneously connected through two phasing lines 63 and associated quarter-wave lines 36 across two of the subarray lines 21, a capacitive impedance being connected successively across the four subarray lines 21. a capacitive impedance is bridged across any of the four quarter-wave lines 66, the electrical length, and impedance, of the quarter-wave line is changed to a value which affects the phase of the current in the associated subarray line 21. Each capacitive impedance retards the phase of the current, say about sixty degrees, in the subarray line 27 to which it is momentarily connected. Hence, the lobe switcher functions to change the phase of one-half of the sixteen dipoles relative to the other half, the phases of the upper half, right half, lower half and lefthalf being changed in succession. With the lobe switcher operating, the beam or direction of maximum action for the antenna system i is positioned off-axis, that is, at an angle to the on-axis direction 8, and as rotor 62 rotates, lobe switching between the up" and down beam positions and between the "left? and "right" beam positions is obtained, as explained in the Higgins-Warren application. The cone angle is dependent upon the value of the capacitive impedance mentioned above and in one system is about three degrees. The direction of maximum action for the system may be aligned with the on-axis direction 8 by opening the four switches 44.

In other words, when Ecplanatorv directive patterns Referring to Fig. 4 and assuming switches 44 are open, curve 6! illustrates a theoretical on-axis directive pattern for the main antenna system i taken alone. The on-axis pattern 8| includes a major lobe 62, first nulls 66, first minor lobes 54, second nulls 66, second minor lobes 66, third minor lobes 51 and fourth minor lobes 66. In Fig. 5 curve 58 illustrates a theoretical oil-axis directive pattern for the main antenna system I taken alone when the switches 44 are closed. The off-axis pattern 58 includes a major lobe 66, first nulls 6i, first minor lobes 82, second nulls 63, second minor lobes 64, third minor lobes 66 and fourth minor lobes 66. Each of curves 6i and 68 represents either the electric or magnetic plane pattern, the electric or E-plane being horizontal and the magnetic or H-plane being vertical inasmuch as the dipoles 26 are horizontal.

In each of patterns 8! and 59, the first minor lobes are cophasal and have a phase opposite to that of the major lobe, as shown on the drawings by the plus and minus signs. Assuming the phase of the major lobe 62 of the on-axis pattern Si is zero, the phase of the major lobe 66 of the oilaxis pattern 69 is not zero but is --30 degrees, inasmuch as the lobe switcher introduces a lag of 60 degrees in one half the dipoles and does not affect the phase in the other half of the dipoles. It may be pointed out that if a lobeswitcher were employed which introduces a phase change of +30 degrees in one half of the dipoles and a phase change of 30 degrees in the other half of the dipoles, the

major lobes

62 and 66 of patterns iii and 69 would have the same phase. The lobing or beam direction would be the same in both cases since, in so far as directivity is concerned, it is immaterial whether the 60 degree out-of-phase relation is secured by retarding the phase of onehalf the system and leaving the phase of the other half the same, or by retarding the phase of onehalf the system 30 degrees and advancing the phase of the other half of the system 30 degrees.- In practice, it is more practical to use a simple lobe switcher, such as the switcher 39 which, as already stated, changes the phase of only onehalf the dipoles.

It will be observed that the first minor lobes 66, Fig. 4. are symmetrical on each side of the major lobe 62 and that these minor lobes are of substantially the same amplitude. As shown in Fig. 5, when the major lobe B0 is shifted to one side of the on-axis direction 8 the intensity of the first minor lobe 62 on the opposite side of the on-axis direction 6 is increased considerably,

and this first minor lobe 62 assumes a position closer to the .on-axis direction 6. On the other hand, the intensity of the first minor lobe 62 on the same side of axis 8 as the shifted major lobe is decreased, and this first minor lobe assumes a position farther away from axis 8. The first

minor lobes

56 and 62 of patterns 6i and 59 for the main antenna system I, that is, for a prior art system such as that disclosed in the Higgins- Warren application, are highly detrimental and may, in radar operation, cause false crossovers and ambiguous indications. As will now be explained in connection with Figs. 4 and 5, the

auxiliary antenna system 9 utilized in accordance with the invention, functions to eliminate or at least reduce substantially the first

minor lobes

56 and 62 which are otherwise present when switches 44 are either open or closed.

Referring first to theon-axis explanatory directive patterns, Fig. 4, reference numeral 61 decases notes ideal or theoretical maximum lobe pattern, talien in either the E-plane or the H-plane, of the auxiliary antenna system 8. The maximum lobe has an angular width, taken at the 50 per cent or half-power point. which is primarily a function of the size of the auxiliary refiector opening it, and an amplitude or height dependent upon the adjustment of the attenuator 48. By selecting an opening l8, Fig.- 3, of proper size, asby adjusting the opening in a cutand-try manner and by properly adjusting the attenuator 48, a maximum lobe may be obtained having a width and a height, that is, a shape, such as shown in Fig. 4. The maximum lobe 61, it will be observed, overlaps the major lobe 82 and the first minor lobes 84 and has. at its base, an angular width greater than. that portion of the main antenna pattern 8| which includes the two first minor lobes 84. the first nulls 88 and the major lobe 52. The phase of the maximum lobe 81 is adjusted, by means 01' phase shifter 48, so that the major lobe 52 and the maximum lobe 61 are cophasal, and the cophasal first minor lobes 84 and the maximum lobe 81 are opposite in phase or antiphasal. Since the major lobe 52 has a constant zero phase when in the onaxis position shown in Fig. 4, the phase of the maximum lobe 81 for this condition is also zero.

The two fields from themain system I and the auxiliary system 8 add together in space to produce the resultant or combined pattern 88 havin'g'a principal lobe 88, first nulls 10, first subsidiary lobes 1!, second subsidiary lobes 12, and third subsidiary lobes 18. More specifically,

' for the on-axis direction 8, the amplitude or field intensity Em of the major lobe 52 and the amplitude Ea of the maximum lobe 61 combine to produce a maximum resultant intensity Em+Ee, since in direction 8 the two lobes 52, 81 are cophasal'. On the drawing, however, the unequal maximum amplitudes of the major lobe 82 and principal lobe 68 are, for the sake of simplicity, shown equal.

Considering, for purpose of explanation, onehalf of the two patterns, for example, the pattern portions included in the angular sector at the left of axis 8, as the direction orangle increases from zero the amplitude of the major lobe 52 decreases, in accordance with the slope or shape of the lobe, to zero at the first null 53.

In the angular sector or angle included between the on-axis direction 8 and the first null 88, the amplitude of the maximum lobe 81 is fairly constant and, since lobes 52 and 61 are cophasal, the portions of lobes 52 and 61 included in this small sector add to form one-half of the central portion of the principal lobe 89 of the resultant pattern 88. Considering the angular direction coincident with the the null direction 53, the intensity of the principal lobe 88 is equal to the intensity of maximum lobe 61. In the angular sector included between the null 88 and the axis 14, that is, the direction of maximum action, of the first minor lobe 54, the amplitude of the main antenna pattern i increases, in accordance with the shape of this minor lobe. Since the first minor lobe 54 and the maximum lobe 81 are antiphasal, as previously explained, the amplitude of the resultant pattern 88 in this angular section will be equal to the diflerence between the amplitudes of the maximum lobe 81 and the first minor lobe 54. At the oil-axis direction at which the two amplitudes are equal, that is, at the point 15, at which the lobes or curves I4 and 61 intersect, the amplitude of the resultant pattern 88 iszero and the first null 18 of the reand null II, the maximum lobe 81 and the first minor lobe 84 oppose each other and the small diil'erence between their intensities forms a portion of the first subsidiary lobe 1i of the resultant pattern 88. It will be noted that the maximum lobe 81 slightly'overlaps the second minor lobe I8. Preferably, the overlapping should be kept to a minimum, by proper adjustment of the shape of the maximum lobe 81, inasmuch as the maximum lobe 81 and the second minor lobes' B8 are cophasal. Since both halves of pattern 8! and both halves of maximum lobe 81 are symmetrical about, axis 8, the pattern portions at the right of axis 8 combine to produce the right half portion of pattern 88, in the manner explained above.

Referring now to the oil-axis explanatory directive patterns, Fig. 5, reference numeral 18 designates the maximum lobe, taken ineither the E-plane or the H-plane, of auxiliary antenna pattern. The lobe 16 is the same, except as to phase, as the'lobe 81, Fig. 4. In this discussion it is assumed that the main antenna is lobe than that portion of the main antenna pattern 69, which includes the two first minor lobes 62, the first nulls 8i and the major lobe 80. As previouslyexplained, the phase of the major lobe is 30 degrees and phase shifter 49, Fig. 2, is adjusted so'that the maximum lobe 18 has a -30 degree phase, whereby themajor lobe 60 and the maximum lobe 18 are cophasal, and the maximum lobe 18 and the cophasal first minor lobes 82 are anti-phasal. In practice, if desired, after final adjustment of the phase shifter 49, the shifter may be replaced by a section of coaxial line having the proper length to effect the desired phase shift, that is, to secure cophasal maximum and major lobes. While the length of the coaxial line path connecting junction to any main antenna dipole and the length of the coaxial line path connecting junction '58 to any auxiliary antenna dipole differ by an amount necessary to secure cophasal maximum and major lobes, these lengths should nevertheless be comparable in order that the cophasal relation of the maximum and major lobes may be maintained, substantially over the frequency range of the system.

The two fields from the main system I and the auxiliary system 9 add together in space to produce the resultant pattern 11 having a principal lobe 18, a broad or flat null 18 on the left or shift" side of axis 8, a sharp null 88 and a first subsidiary lobe or pip 8| on the right side corresponding in position to the fiat null 18, the second subsidiary lobes 82, third subsidiary lobes 83 and fourth subsidiary lobes 84. More .particularly, the amplitude of the maximum lobe 18, when adjusted for optimum interaction with the pattern It. .Fig. 4, for the on-axis condition or position of the major lobe of system I, as explained above,

is also optimum for the cut-oi! axis condition resultant principal lobe 18 having an amplitude Em+Ea. As shown in Fig. 6, the particular first i minor lobe 62 the amplitude oi which is increased upon shift of major lobe 60, namely, the righthand first minor lobe 62, assumes a position closer g to the axis 8 of the maximum lobe i6 and therefore interacts, as is desired, with a portion of the maximum lobe 16 having a high amplitude. .On the other hand, the left-hand minor lobe 62 having a decreased amplitude assumes a position far- 16 ther away from axis .9 and therefore interacts, as is desired, with a portion of maximum lobe 76 having a low amplitude. Inother words, when the beam is shifted, one of first minor lobes ,62 increases in intensity and climbs cellation occurs and the firstuninor lobes 62 are eliminated or at least materially reduced. The right or high first minor lobe 62 extends above, and the left or low' first minor lobe 62 Just reaches, the maximum lobe 16. ,-In practice, the attenuator 69 is adjusted to a value at which both first minor lobes 92 are reduced to a compromise value. As shown in Fig. 5 the left or low minor lobe 92, and the maximum lobe I6 in antiphase therewith, combine to produce the fiat null 19 ofthe resultant pattern 17. The right or high first 3o minor lobe 62, and the maximum lobe 16 in antiphase therewith, combine to produce the sharp null 90 and the pip or first subsidiary lobe 6! of the resultant pattern Ti.

For both the on-axiscondition, Fig; 4, and the oil-axis condition, Fig. 5, it will be observed that the second, third and fourth minor lobes of the main antenna pattern are considerably lower in intensity than the first minor lobe. In Fig.4, the

second, third and fourth

minor lobes

56, 51 and 56' 4o correspond respectively, to the first, second and third subsidiary lobes II, 12 and 19 of the resultant pattern 69. Now, as stated before, the maximum amplitude of the major lobe 52 is Em whereas the maximum amplitude of the principal 4 4 tem, as obtained with the auxiliary antenna syslobe 69 is Em-l-Ea so that, although

minor lobes

56, 57 and 58 do not interact with the maximum lobe 67, the maximum amplitudes ofthe subsidiary lobes ll, 12 and 19 are each only a small percentage of the resultant principal lobe 69, whereas the maximum amplitude of the corresponding minor lobe is a somewhat larger percentage of the major lobe 52. Similarlyxin Fig. 5, the maximum amplitudes of the subsidiary lobes 8i, 82,

83 and 84 are each a relativel small percentage of principal lobe 18, whereas the maximumamplitudes of

minor lobes

64, 65 and 66. are each a somewhat larger percentage of the major lobe 6D. In short, as shown above, for both the on-axis condition, Fig. 4, and the off-axis condition, Fig. 60

5, the auxiliary antenna functions to reduce materially or obliterate the first minor lobes of the main antenna pattern or, in other words, to produce in cooperation with the main antenna system a resultant pattern having atthe positions of the first minor lobes very insignificant subsidiary lobes, the maximum amplitudes of which are determined primarily by the ratio of the amplitudes of the higher order minor lobes and the maximum amplitude, not of the major lobe, but

of the principal lobe. Also the auxiliary antenna produces a resultant principal lobe having a high ain, as measured along. the axisof the principallobe.

For purpose of explanation, it has been assumed 7.5

up to a high 5 system I 16 i that the main antenna patterns for the E-plane and the H-planeare the same and accordingly that the ideal auxiliary patterns are the same for that when the maximum lobe pattern is cophasal with the major lobe pattern in one plane, say the E-plane, it is also cophasal in the other plane, that is, the H-plane;

Measured oneeway directive patterns tion to that illustrated by Figs. 1, 2 and 3. More particularly, Fig. 6 illustrates the E-plane resultant pattern when the beam is" switched up (or down) or, stated difierently, when the resultant principal lobe is on-axis in the E-plane and oilaxis inthe H-plane. Fig. 7 illustrates the E-plane resultant pattern when the beam is switched left (or right) or, stated differently, when the principal lobe is off-axis in the E-plane and on-axis in the H-plane. Fig. 8 illustrates ,the H-plane resultant Dattem when thebeam is lobed left (or right), that is, when the principal lobe is on-axis in the H-plane and oiT-axisin the E- plane. Fig. 9 illustrates the H-plane resultant pattern when the beam is lobed up (or down) that is, when the principal lobe is off-axis in the Roughly,

represent the patterns for the main antenna system 9 completely removed from the structure. Hence, these curves illustrate the patterns obtained with a prior art systemsuch as that disclosed in Higgins-Warren application. The dashdot E-plane curves 69, Figs. 6 and 7, are identical and the. dash-dot'H-plane curves-90, Figs. 8 and 9, are identical; and these four-curves illustrate the directive patterns for the auxiliary antenna system taken apart from the main antenna The full line curves Si. 92. 9.3 and 94 in Figs. 6, 7, 8 and 9 respectively, illustrate the resultant patterns obtained for the combined system comprising the main and auxiliary antennas l, 9. Generally speaking, the

main antenna patterns

85, 86, 81 and 89 each include a major lobe v Considering the E-plane patterns and,

Figs. 6 and 7, for'the main antenna system I,

taken alone, it will be noted that for the on-axis condition in the E-plane, Fig. 6, the maximum amplitudes of the first minor lobes 91 are about 23 per cent-of the maximum amplitude of the 11 major lobe 88. For the off-axis condition in the l-plane. Fig. 'I, the left first minor lobe 81 which on the oppositeside of axis 8'from the beam hift, has a maximum amplitude of about 43.5 ner cent and is closer to axis 8 than the.left or :orresponding first minor lobe of Fig. 6. On the and 88, Figs."8 -and 9, for the main antenna sysforethe tern, taken alone, it-will be observed that on-axis position in the H-plane, Fig. 8, the maximum amplitudes of the first minor lobes 81 are about 28 per cent of the maximum amplitude of r the major lobe 88 and therefore slightly greater than the maximum amplitudes of the first minor lobes 81 in the E-plane pattern 88, Fig. 6. for the on-axis condition in the E-plane. For the off-' axis condition in the H-plane,'Fig. 9, the left first mindrlobe 81, which is on the side of axis 8 opposite from, the beam shift, has a maximum amplitude of 45.7 per cent and is slightly closer to the axis 8 than the left first minor lobe 81 of Fig. 8. On the contrary, 81, Fig. 9, which is on the same side of axis 8 as the beam shift, has a maximum amplitude of about 23.7 per cent and is farther from axis 8 than the right first minor lobe 81 of Fig. 8. Note that in the E-plane and H-plane the two minor lobes 81 which increase in amplitude increase about the same amount, that is, 48.5 and 45.7 per cent;

, Considering the

auxiliary antenna patterns

88 and 88, Figs. 6, 7, 8 and 9, the minimum lobes I88 have, generally speaking, a maximum amplitude of about21 per cent of the maximum amplitude of the maximum lobe 88 and about 6 per cent of the principal lobe I8I of the resultant pattern 8I. Hence; as is desired, these minimum lobes I88 are almost negligible. If desired, the minimum lobes I88 may be further reduced by using more than two, for example four, properly spaced dipoles in the primary antenna 41 of the auxiliary antenna system 8 and by tapering the intensities of the dipole currents.

The mere presence of the auxiliary. antenna system, particularly the auxiliary reflector I8, when disconnected from the translation device 28, causes a slight decrease in the width of the 1 main antenna major lobe 85 and a slight increase in the intensities of the two first minor lobes 81. Accordingly, in practice, the amplitude control means 48,'Fig. 2, associated with the auxiliary antenna system, is adjusted so that the maximum lobe and the enlarged first minor lobes mutually cancel. In the case of transmitting, in order to compensate for the change produced in the

main antenna patterns

85, 88, 81 and 88, by the blocking effect of the auxiliary reflector, a

slight increase in the power or energy supplied to the auxiliary'antenna system is required. This increase in power willnot increase the width of the resultant principal lobe -.I8J, since the tendency of this lobe to increase is compensated by the decrease in width of the major lobe 85 produced by the passive action of the auxiliary reflector I8. In one tested embodiment, it was found that the desired minor lobe suppression was achieved when energies of equal intensities assumes the right first minor lobe "i2. were supplied to, or received from, the antenna systems I and 8 by device 28. Also,

a slight increase in the higher order minor lobes T5 88 but, because of the intensity increase in the major lobe 88, that is, becauseof the large am plitude along axis 8 of the principal lobe I8 I, these higher orderminor lobes 88 are in a sense restored to normal.

Considering in detail the E-plane resultant patterns 8| and 82, Figs. 8 and 7, note that the pattern 8!, Fig. 8, includes a pair of deep nulls I82 at the angular directions corresponding to'the first minor lobes 81 which, in the main antenna pattern 88, have amplitudes of 28.7 per cent. Hence, by reason of the action of the auxiliary antenna, the first minor lobes 81 are obliterated. The subsidiary lobes I88 and I84, Fig. 6; of the resultant pattern 8! are slightly greater than the higher order minor lobes 88 of the main antenna pattern 88, because of the blocking effect of the auxiliary reflector I8 and because of the fact that in the particular embodiment tested the auxiliary pattern 88 oyerlaps-to some extent the higher order mlnor-lobes 88. The subsidiary lobes I88 and I84 are about 10 per cent of the single trip or one-way resultant principal lobe II" and about 1 per cent of the calculated round-trip or two-way principal lobe which is illustrated in Fig. 12. In Fig. 7, the left first minor lobe 81, which increased with beam shift, is in effect decreased from 48.5 per cent to 13.0 per cent in the resultant pattern, corresponding'to the value of the left first subsidiary lobe I88, Fig. 7. The right first minor lobe 81 of 9 per cent is decreased almost to zero as shown by the value of the right first null I82 of pattern 82, Fig. '7. The right; higher order minor lobe 88, Fig. '1, of 19.5 per dent is in effect reduced to 15.2 per cent which corresponds to the value of the right first subsidiary lobe I88, while the left higher order minor lobes 88 are increased somewhat, but confined to a maximum amplitude of per cent.

Referring to the H-

plane resultant patterns

88 and 84, Figs. 8 and 9, the left and right first minor lobes 81 of pattern 81, Fig. 8, which haveamplitudes of 28.5 per cent, are in effect transformed into first subsidiary lobe's I88 having amplitudes of about 12.8 per cent. In Fig.8 the left first minor lobe 81,'which increased to 45.8 per cent in amplitude with the lobing', is converted 'to the left first subsidiary lobe I88, the maximum amplitude of which is about 14.5 per cent; andthe right first minor lobe 81, which decreased to 23.8 per right first subsidiary lobe I88 having a 18.3 per cent amplitude.

Actually, the first minor lobes 81 in the H-plane patterns, Figs. 8 and 9, are each a combination of the first and second minor lobes. E-plane the first and second minor lobes have opposite phases, it has beemfound in testing one embodiment that in the H-plane the first and second' minor lobes have quadrature phases and therefore merge to form the large secondary lobes 81 which are shown in Figs. 8 and 9, and have been designated as first" minor lobes. Note that in Fig. 8 the secondary lobes 81 are, at the 70 :18 degree peak amplitude, reduced to zero or nulls I 82in the resultant pattern, but that fairly prominent first subsidiary lobes I88 are aligned with certain off-axis or off-peak directions included in the secondary lobes 81 and having minor amplitude values. The presence of the relatively the blocking action of the auxiliary antenna system 8 causes.

cent in amplitude, is in effect changed to-the* While in theprominent first subsidiary lobes I08, in each of Figs. 8 and 9, indicates that the maximum lobe 89 of the auxiliary antenna is merging with the second minor lobe 98 (not shown) which is in phase quadrature with the maximum lobe. As a result, while in the E-plane patterns, Figs. 6 and 7, substantially complete elimination of the first minor lobes 91 is efiected, in the H-plane, the reduction is not entirely complete. If only the directive operation in the H-plane is of interest, a compromise phase adjustment of the auxiliary antenna system may be made for the purpose of further decreasing the H-plane secondary lobes 91.

It should be pointed out that, in accordance with the invention, the minor lobe reduction is obtained with only a small increase in the main beam width. As shown in Figs. 6 and 7, in the.

E-plane, at the half power or 50 per cent point of the principal and major lobes, the increase is from 12 to 13.5-degrees or about 12.5 per cent. In the H-plane, Figs. 8 and 9, the increase in main beam width at the half power point is from 13.9 to 15.6 degrees or 12.5 per cent. In each plane, this increase in width is relatively small as compared to the to per cent increase in main beam width produced by the prior art method of minor lobe reduction which involves tapering the illumination of a reflector. Such an increase in the beam width is not desired, particularly because the gain of the antenna, for a given aperture, is reduced.

In addition, it should be noted that by reducing the first minor lobes, in accordance with the invention, the region close to the main beam is almost free of radiation. Hence, when the main beam is switched, false crossovers" cannot occur between'the main beam and the first minor lobes; and, as is desired, the only crossover is on axis 6 and between the two main beam positions. The true or desired crossover is the point on axis 8 at which the resultant lobe, in its up position, intersects the resultant lobe, in its down position. To illustrate, when the prior art pattern 88, Fig. 8, is reversed, the true crossover occurs on axis 6. In addition a false crossover occurs only 11 degrees from and on each side of axis 8. The false crossover is between the major lobe and the first minor lobe and its amplitude is about 38.5 per cent one way. Another false crossover occurs at i 26 degrees with an amplitude of 23 per cent one way. The false crossovers may produce, of course, false or ambiguous indications'on the train (rightleft) indicator or the elevation (up-down) indicator in the radar transceiving device 28. In the system of the invention, which has the resultant pattern 96, Fig. 9, there are no crossovers in the i 21 degree region, and, outside oi this region, the maximum false crossover amplitude is relatively low, namely, 8.2 per cent one way.

It may also be stated that the band width characteristic of the system of Figs. 1, 2 and 3 is highly satisfactory. A frequency test of the embodiment of Figs. 1, 2 and 3 mentioned above showed that, over the 920-970 megacycle band, the angular sensitivity of the system is, as is desired, substantially constant over the above band or range, and the patterns are also almost constant.

Calculated two-way patterns The two-way patterns of Figs. 10, 11 and 12 were obtained by calculating the echo amplitude received after reflection by a distant target. Figs. 10 and 11 illustrate the E-plane and H- plane resultant patterns, respectively, when the beam is lobed to the right position: and Figs. 12 and 13 illustrate the E-plane andH-plane patterns. respectively, when the beam or resultant lobe is switched to the up position. When the beam is lobed to the left position, the E-plane and H-plane patterns of Figs. 10 and 11 are eachreversed: and when the beam is lobed to the down position, the E-plane and H-lplane patterns of Figs. 12 and 13 are each reversed. In these four figures the reference numeral I05 denotes the resultant pattern for the system'oi' the invention comprising a main antenna system and an auxiliary antenna system 9 and numeral I66 denotes the patterns for the main antenna system I taken alone. Numerals I01 denote the principal lobe, numerals I08 t e first nulls and numerals I09 the subsidiary lobes of the resultant patterns I06. Numerals IIO denote the major lobes and numerals II I the first minor lobes of the main antenna patterns I06.

, Considering the two ill-plane patterns I06, Figs. 10 and 12, the maximum amplitude of the first minor lobes III for these two pattern-s is 19.2 per S0 tude from about 84-, to V42 of the maximum inmum intensity of the first minor lobes III is about 20.8 per cent and the auxiliary antenna reduces this intensity to 2.1 per cent, that is, from about V5 to about ,3 of the maximum intensity of the principal lobe III'I. In general, in Figs. 10, y

11, 12 and 13, the first minor lobes III are completely eliminated or substantially reduced.

It has thus been shown that in accordance with the invention, a satisfactory directive characteristic is secured which is of high utility, not only in the radar art but also in the radio, telephone and'telegraph arts. If desired, in radar operation, the main antenna may be disconnected from de vice 28 by suitable switching and the auxiliary antenna may be utilized as a "search" antenna for roughly locating the target direction. After the search operation is completed. the two systems may then be utilized for-accurate dual plane lobe switching.

Although the invention has been described in connection with a particular embodiment, it is not to be limited to this embodiment inasmuch as other apparatus may be successfully employed in practicing the invention.

What is claimed is:

1. A method of reducing or obliteratin at least one minor lobe in an antenna direc ive characteristic, which comprises aligning a direction of action of a lobe of another directive character-let's with the direction of, maximum action or axis of said minor lobe, substantially equal zing the two lobe intensities. and rendering said lobes antiphasal.

2. A method of materially reducing at least one minor lobe in the directive pattern of a main antenna system which comprises align ng a direction of action in the maximum lobe of. an auxiliary antenna-with the direction of maximum action of said minor lobe, substantially equalizing the intensities of said lobes in-the aligned directions, and rendering said lobes antiphasal.

3. A method of reducing the two cophasal first minor lobes flanking the major lobe in the directive characteristic of a main antenna system.

utilizing an auxiliary antenna having a maximum lobe the angular width of which is at least as great as the combined angular width of the three flrstmentioned lobes, which comprises aligning the direction of greatest action oi said maximum lobe with a direction included in said major lobe. substantially equalizing the intensities of said maximum lobe and said minor lobes, and rendering .said maximum lobe'and said minor lobes antiphasal.

4. A method of substantially reducing at least one of the first minor lobes adjoining the major lobe -in the directive pattern of a unidirective main antenna system connected to a translation device, utilizing a unidirective auxiliary antenna system having a maximum lobe the angular width of which is as great as the angular portion of the pattern including said first-mentioned lobes and the null positioned therebetween, said auxiliary antenna being connected to said device through an adjustable attenuator for regulating the intensity of said maximum lobe and through an adjustable phase shifter forcontrolling the phase of said maximum lobe, which comprises aligning the axis of said maximum lobe with a direction of action included in said major lobe, adjustingsaid attenuator so as to equalize the intensities of said maximum lobe and said minor lobe, and adjusting said phase shifter so as to secure a maximum lobe having a phase opposite to that of said minor lobe.

5. In combination, a pair of antenna systems connected through separate, lines to the same translation device, one of said antenna systems v having a minor directive lobe and the other antenna system having a maximum directive lobe. a direction of action in said maximum lobe being aligned with the axis or direction of greatest action in said minor lobe, a phase shifter included 6. In combination, a pair of antenna systems,

connected through separate lines to the same translation device, one of said antenna systems having a major directive lobe interposed between a pair of cophasal directive minor lobes and having a phase opposite that of said minor lobes, the other antenna system having a maximum directive lobe aligned with said major lobe, the width of said maximum lobe being substantially equal to the combined widths of said major lobe and-said minor lobes, and means comprising a phase shifter and an attentuator included in one of said lines (or rendering said maximum lobe and saidminor lobes antiphasal and for equalizing substantially said maximum lobe and said minor lobes.

7. In combination, a translation device, a main antenna system comprising a pair of parabolic reflectors, separate primary antennas at the fool of said reflectors, a flrst line connecting said primary antennas to said device, an auxiliary antenna system comprising a parabolic reflector, a separate primary antennaat its focus, a second line connecting said last-mentioned primary antenna to said device, said three reflectors facing the, same direction and having parallel axes included in the same plane. the aperture dimension in said plane oi each of the main antenna reflectors being greater than the aperture dimansion in said plane oi. the auxiliary antenna reflectors, the directive pattern of the'main antenna in a plane of radio action perpendicular to the first-mentioned plane including a narrow 'major lobe interposed between a pair of cophasal minor lobes having a phase opposite to that of the major lobe, and the directive pattern of the auxiliary antenna in said plane of action being the two minor lobes substantially equal to the intensities of said minor lobes. 9. A combination in accordance with claim 7, an adjustable phase'control means inserted in one of said lines for rendering the phase of the maximum lobe equal to that or the major lobe and diilerent from that or the cophasal minor lobes. i

10. A combination in accordance with claim 7,

an adjustable amplitude controlmeans inserted in one of said lines and an adjustable phase control means inserted in one oi! said lines, whereby said minor lobes may be greatly reduced and, the minor lobes of the combined directive pattern of the two antenna systems may be rendered negligible.

11. In combination, a translation device, a-

main antenna system comprising a pair of parallel linear arrays each comprising a plurality of spaced antenna elements, a first line connecting all 01' said elements to said device, an auxiliary antenna system comprising a linear array of elements, a-second line connecting the last-mentioned elements to said device, the plurality of elements in each of the two first-mentioned arrays being greater than the plurality of elements inthe last-mentioned array, said main antenna having in one plane of radio action a directive pattern including a narrow major lobe interposed between two cophasal minor lobes, the phase of the minor lobes being different from that of the major lobes, and the directive pattern of said auxiliary antenna in said plane or action being aligned substantially with the first-mentioned directive pattern and including a maximum lobe having a width substantially equal to the combined widths of said major lobe and said minor lobes.

12. A combination in accordance with claim 11, an adjustable amplitude means inserted in one of said lines.

13. A combination in accordance with claim 11, an adjustable phase control meansvinsertedin one of said lines.

14. A combination in accordance with claim 11, an adjustable amplitude control means inserted in one of said lines and an adjustable phase control means inserted in one of said lines.

15. In combination, a main antenna system and an auxiliary antenna each comprising a cylindrical parabolic reflector, said reflectors iacing in the same direction and having parallel axes, the width and length dimensions of the main reflector being greater than the corresponding dimensions of the auxiliary reflector, separate primary antennas for said reflectors each comprising a linear array of antenna elements aligned with the reflector focal line, the plurality of elements in the primary antenna of the main system being greater than the plurality of elements in the primary antenna of the auxiliary system, and means-for simultaneously connecting all of said elements to a translation device. 16. In a dual plane lobe switching system. a

' main directive antenna system comprising a large upper cylindrical parabolic reflector and a large lower cylindrical parabolic reflector, a pair of linear subarrays aligned with the focal line of each reflector and each comprising a plurality of dipoles, a translation device, separate lines connecting the four subarrays to said device, means connected to said lines for shifting the phase of the currents in two of said lines simultaneously and in all of said lines successively, an auxiliary directive antenna system positioned adjacent to said main system and comprising a small cylinattenuator, an, adjustable phase changer, said changer.

CLIFFORD A. WARREN.

REFERENGES CKTED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,821,386 Lindenblad Sept. 1, 1931 2,095,083 Renatus Oct. 5, 1937 2,342,721 Boerner Feb. 29, 1944 FOREIGN PATENTS Number Country Date 706,661 Germany Jan. 17, 1936