July 6, 1965 R. F. H. YANG 3,193,831 LOGARTHMIC PERIODIC ANTENNA w Filed Nov. 22, 1961 3. Sheets-Sheet l FE.2 Vs 2 77zz/27a ZoZ. 37 -322/22/22//X12s2:2; agital g? 2222zzees July 6, 1965 R. F. H. YANG 3,193,831 LOGARITHMIC PERIODIC ANTENNA Filed Nov. 22, 196l 3. Sheets-Sheet 2 a /72 Z/2Zzz127. 22-262-ra a >%zzez -Zé/. azz 22e ------, 2227 weezes July 6, 1965 R. F. H. YANG 3,193,831 LOGARITHMIC PERIODIC ANTENNA Filed Nov. 22, 196 3. Sheets-Sheet 3 F.E.7 23 NNSNN 2 2 ZZzz/27zz127. 2.22%azzaz / 2 Xzzez 3,193,83 United States Patent Office Patented July 6, 1965 2 wise-identical conductor elements being placed in corre LoGARTHM diffio3,193,83 CANTENNA sponding, rather than complementary, positions. These Richard F. H. Yatag, Grand Pask, E., assignor to Andrew two mirror-image elements are fed in opposite phase, to Corporation, Orland Park, iii., a corporation of Elinois produce a pattern having a null in the usual maximum Fied Nov. 22, 1961, Ser. No. 154,269 5 direction, but having fairly sharp symmetrical lobes at 24 Cais. (C. 343-792.5) the same angle with respect to the antenna axis. Hogarithmic periodic antennas are, as is well-known, This invention relates to antennas and more specifically capable of uniform performance over a wide frequency to the wide-band type of antenna developed in many band to an extent unattainable with other approaches to forms in recent years generally known as the logarithmic 10 wide-band antenna construction. However, one serious periodic antenna. limitation heretofore existing on the widespread use of The construction of logarithmic periodic antennas in such antennas lies in the rather elaborate constructions most common use employs a pair of tapered plane radi practically required for the feeding of the antenna in ating portions, more or less triangular in shape, with the order that the feed-line will not produce electrical un apexes positioned closely adjacent to each other, these balance of the two half-portions, thus destroying the radiating portions lying in planes perpendicular to the performance of the antenna in respect to radiation pat plane of the center-lines of the two triangular portions. tern, in pedance, or other characteristics. In most equip Various designs of this general type of antenna have ment, it is desirable or required that the antenna feed be been devised, having in connmon the fact that the radiat a simple coaxial transmission line. The logarithmic pe ing portions each comprise a set of conductor elements 20 riodic antennas heretofore known have required various having a straight stem conductor extending away from more or less complicated construction to prevent the the apex or vertex of the triangle which is at the apex of causing of unbalance by the presence of the outer con the antenna, along the center-line of the triangular ele ductor of the coaxial feed. It has been necessary to ment, with conductors extending from this center-line or either use Some modified form of unbalanced-to-balanced stem conductor, alternated on either side thereof in the 25 line converter (balun) of the type used with other bal plane of the element, these extending conductors or poles anced antenna constructions, or to resort to fairly complex of the antenna being of increasing length with increasing feed arrangements, such as running the coaxial trans distance from the vertex, thus forming the generally tri mission line along the stem or center-line of the conductor angular element. Additionally, within the triangle thus element which is connected to the grounded side of the formed, the width, as well as the length, of each of the 30 line, which in itself destroys the complete balance unless poles is normally tapered. The theory of such antennas a further conductor similar to the outer conductor of the has been extensively set forth in the literature, and is now transmission line is also added to the stem of the con well-known in the art along with the selection of dimen ductor element which is fed from the center conductor Sions and similar characteristics for the covering of de of the transmission line, if the dimensions of the line are sired frequency ranges. Such antennas produce, because 35 appreciable at the frequencies involved. of their geometry, substantially uniform response over a It is the principal object of the present invention to wide band of frequencies, the pairs of poles on the two provide a form of logarithmic periodic antenna which is elements or half-portions which contribute the most to fed by a simple coaxial line in an extremely simple the radiation at any given frequency shifting with the manner which permits the coaxial line to extend along frequency of operation over the desired range, the opti 40 the axis of the antenna without impairing the directivity, mum designs, including the tapering of the width or thick impedance bandwidth, or other desirable properties of ness of the elements described above, also maintaining this type of construction. This general object is achieved Substantially constant impedance characteristics over the with a modified construction of "stacked” logarithmic entire band of operation. -. periodic antenna, in which the conducting elements are Such antennas are formed in a variety of manners, Oriented and fed in such a manner that there exists, no Such as from stampings of sheet conductors, or by for electric field flux along a substantial region of the axis mation with wires or bars, or by printing techniques. of the antenna, the coaxial transmission line being, at . The common forms of such antennas employ one of all points in the neighborhood of the antenna, in this field such conducting elements in each of the two intersecting free region where it accordingly has no effect on the planes, the teeth or poles on one of the elements being balanced condition of the two angularly related half complementary to those on the other, i.e., the teeth on portions with respect to ground, despite the fact that one one being located in opposition to the gaps between the conductor element or quarter-portion of each of the half teeth on the other, on the respective sides of the plane portions is grounded at the vertex end. Except for altera of the center-lines. In a rigore refined form, two of such tion of the connections of the conducting elements to the simple structures are "stacked,” and complementary con 55 feed line, i.e., the opposite phasing of certain elements, ductor elements are employed in both of the half-portions, the present construction may be described as the stacking a conductor element being added to each of the simple of mirro-image elements such as those shown in Patent - half-portions thus described in a closely adjacent parallel 2,977,597 in the general manner in which stacking was plane, with the inner element of one half-portion fed in previously done with complementary conducting elements phase with the outer element of the other half-portion. 60 in the stacked construction mentioned above. When Although even the simpler form produces a high degree these mirror-image elements are stacked to produce a of directivity, when properly designed, in the direction of four-element structure in which the inner conductor ele the apex of the antenna, the stacking arrangement just ments or sets are mirror images of each other and the mentioned is frequently used for the purpose of even outer elements or conductor sets are likewise mirror further improving the gain. ... " 65 images of each other, but complementary with the inner In U.S. Patent 2,977,597, there is described a variant sets as regards tooth or pole orientation, and the inner of the logarithmic periodic antenna in which the direction conductor elements or sets are both connected to the same of radiation is deliberately split into two beams or lobes side of the line (i.e., fed in phase rather than out of phase by employing mirror-image symmetry with respect to the 70 as in the aforementioned patent), both outer conductor plane bisecting the angle between the two half-portion elements being fed in the phase opposite that of the inner planes, the corresponding teeth or poles on the two other elements, the directional pattern is in the form of a single 3,193,831 3 4. sharp lobe extending in the direction of the apex of the form of assembly of the antenna of the invention; and antenna. On the axis of the region between the two FIGURE 9 is a view in section showing, more or less elements or half-portions of the generally pyramidal schematically, the construction of a parabolic antenna antenna assembly, there is no field because of the equi assembly employing as the feed thereof an antenna con potential region created everywhere along this axis by 5 Structed in accordance with FIGURE 8. the mirror-image relation of the inner and outer con Referring first to the embodiment of FIGURES 1 ducting elements, respectively. The coaxial line may thus through 4, it will be seen that the antenna generally desig be placed on this axis without upsetting the desired nated by the numeral () is mounted on a piate 2 of fiber operation. glass or other similar dielectric material. The radiating The invention is of particular advantage in connection O portion is formed of two planar half-portions 4 and 16 with small antenna assemblies used as the feed for a mounted on substantially triangular insulating plates i3 parabolic reflector, in which the radiating assembly em and 28, respectively, of material similar to that of plate 2.