US3696437A

US3696437A - Broadside log periodic antenna

Info

Publication number: US3696437A
Application number: US69063A
Authority: US
Inventors: Ronald D Grant
Original assignee: Jfd Electronics Corp
Current assignee: Jfd Electronics Corp
Priority date: 1970-08-27
Filing date: 1970-08-27
Publication date: 1972-10-03
Anticipated expiration: 1989-10-03

Abstract

This invention teaches an antenna array of the broadside type in which dipoles of differing electrical lengths are stacked vertically above and below an imaginary plane with electrical lengths increasing with increasing distance in moving above and below the imaginary plane. The antenna has symmetry in that for each dipole of the array below the imaginary plane, for example, there is a dipole of substantially equal electrical length and spacing approximately the same distance above the imaginary plane. Transposed feeder harness means are employed for joining adjacent dipoles and common output (input) terminals are provided in a position substantially at the location of the imaginary plane. Directional characteristics are obtained by means of Veeing the dipole arms and/or providing a vertically aligned ground screen positioned behind the antenna stack array. In another embodiment a similar array may be positioned immediately behind the first array in place of the ground screen. Directional characteristics may be obtained through coupling an output (input) utilization means to one and then the other of the arrays which are coupled at their feed terminals by means of a transposed feeder section. The array may also be joined with a conventional endfire array, for example, to form a broadside VHF endfire array and an endfire UHF array or conversely, a broadside UHF array and an endfire VHF array. Omnidirectional characteristics may be introduced if such an application is either desired or required by bending or otherwise forming the dipole arms so as to provide a substantially U-shaped configuration for each dipole. As another embodiment the ground screen may be replaced by parasitic elements arranged in a vertically stacked array with the parasitic element being provided for each dipole in the broadside array and being positioned in substantially behind its associated dipole.

Description

United States Patent Grant 45 Oct. 3, 1972 v [54] BROADSIDE LOG PERIODIC ANTENNA [72] Inventor: Ronald D. Grant, Urbana, Ill.

[73] Assignee: JFD Electronics Corporation, Brook- X91 PL) [22] Filed: Aug. 27, 1970 211 Appl. No.i 69,063

Related US. Application Data [63] Continuation of Ser. No. 685,093, Nov. 22,

1967, abandoned.

[52] US. Cl. ..343/792.5, 343/797, 343/810, 343/793 [51] Int. Cl. ..H01q 11/10 [58] Field of Search...343/792.5, 793, 912, 796, 797, 343/798, 809, 810

Primary Examinerl-1erman Karl Saalbach Assistant Examiner-Saxfield Chatman, Jr. Attorney-Ostrolenk, Faber, Gerb & Soffen 5 7 ABSTRACT This invention teaches an antenna array of the broadside type in which dipoles of differing electrical g hs re taskc Win99!!! 291 239999 11)? imaginary plane with electrical lengths increasing with increasing distance in moving above and below the imaginary plane. The antenna has symmetry in that for each dipole of the array below the imaginary plane, for example, there is a dipole of substantially equal electrical length and spacing approximately the same distance above the imaginary plane.

Transposed feeder harness means are employed for joining adjacent dipoles and common output (input) terminals are provided in a position substantially at the location of the imaginary plane. Directional characteristics are obtained by means of Veeing the dipole arms and/or providing a vertically aligned ground screen positioned'behind the antenna stack array.

In another embodiment a similar array may be positioned immediately behind the first array in place of the ground screen. Directional characteristics may be obtained through coupling an output (input) utilization means to one and then the other of the arrays which are coupled at their feed terminals by means of a transposed feeder section. The array may also be joined with a conventional endfire array, for example, to form a broadside VHF endfire array and an endfire UHF array or conversely, a broadside UHF array and an endfire VHF arra Omnidirectional characteristics may be introduced if such an application is either desired or required by bending or otherwise forming the dipole arms so as to provide a substantially U-shaped configuration for each dipole.

As another embodiment the ground screen may be replaced by parasitic elements arranged in a vertically stacked array with the parasitic element being provided for each dipole in the broadside array and being positioned in substantially behind its associated dipole.

25 Claims, 15 Drawing Figures BROADSIDE LOG PERIODIC ANTENNA This application is a continuation of application Ser. No. 685,093, filed Nov. 22, 1967, now abandoned.

The instant invention relates to antennas, and more particularly to a broadside antenna of the log periodic type yielding extremely high gain and providing a superior radiation pattern through the use of a relatively small number of dipole elements.

Antennas of the log periodic type are presently gaining widespread prominence due to their inherent ability to provide high gain and superior radiation patterns over a substantially broad band of operating frequencies. For example, such log periodic antennas presently in use cover the entire VHF band; the entire UHF band; and a combination of both the UHF and VHF bands through the use of a composite log periodic antenna array. Such present-day log periodic antennas are of the endfire array category. In order to increase the gain of such antennas appreciably, a substantially appreciable number of dipoles and/or parasitic elements must be added to the array, thereby substantially increasing the weight of the array, length of the array and presenting significant problems as regards structural strength of the antenna as well as of the antenna mounting element.

The instant invention is characterized by providing a log periodic antenna of the broadside array category wherein the increase of the number of dipoles to the array has been found to be directly linearly related to the gain. Thus, if the number of active elements (i.e., dipoles) is doubled, the antenna gain is likewise doubled, thereby yielding a much more efficient antenna for the number of dipole elements employed.

The instant invention is comprised of a vertical supporting means for positioning and supporting a plurality of dipoles. Each of the dipoles mounted to the supporting means is comprised of a pair of dipole arms lying substantially within a horizontal plane being substantially equal in length and being oriented or Vd at an angle lying substantially within the range from 40 to 1 80. Moving downwardly from the topmost dipole, the succeeding dipoles are arranged at spaced intervals along the supporting means, with each of the Vd dipoles pointing substantially in the same direction as the topmost dipole. The arms of succeeding dipoles preferably differ in length from the dipole positioned immediately above by a factor 7 wherein 'y varies from 0.78 to 0.99. The spacing between the dipoles diminishes preferably by the amount 'y such that the spacing between the second and third dipoles, counting down from the top, is 'y, times the spacing between the topmost and next to the topmost dipole. It should be understood that the factors y and 7, need not be equal to one another.

The decreasing length of the dipole arms and decreasing spacing continues until the central or feed point of the antenna array is reached, at which time the succeedingly lower dipole arms positioned beneath the feed point increase in spacing and in length of dipole arms in accordance with the 7 factors mentioned above. A transposed feeder harness couples the feed point to each of the dipole arms for providing proper phasing of the dipoles. A ground plane or reflecting plane, preferably in the form of a metallic grid or metallic screen, is positioned behind the broadside array so that a vertically aligned imaginary plane which is the bisector of the angle formed between each dipole is substantially perpendicular to the surface of the ground plane.

The spacing between adjacent dipoles moving downwardly from the topmost dipole decreases in a substantially regular fashion until a center point or feed point is reached at which the spacing then increases moving downwardly from the central point to the bottom-most dipole. In a like manner, the length of dipole arms from the topmost dipole to the central feed point decreases in a substantially regular fashion, whereas dipole arm length increases in a regular fashion, moving downwardly from the central feed point to the bottom-most dipole. The preferred antenna array is substantially symmetrical to an imaginary horizontal plane passing through the central feed point such that dipole arms located at equal distances above and below the imaginary plane have equal arm length.

A feeder line is coupled from the central feed point both upwardly and downwardly along the array by means of a transposed feeder harness in order to assure that all signals fed from the feed point to each dipole, or conversely, fed from each dipole back toward the central feed point, are all in phase.

As an alternative embodiment, the ground plane may be replaced by a plurality of parasitic elements, each being arranged behind an associated dipole. Each parasitic element may be Vd, either forwardly or rearwardly, or may be straight. The spacing of each parasitic element relative to its associated dipole and the electrical length of each parasitic element is selected so as to reflect substantially all of the energy impinging on the element toward its associated dipole.

Experimentation with the antenna has proven that the array provides extremely high gain operation over a broad band of operating frequencies as well as yielding an extremely highly directive radiation pattern. Providing additional dipoles has been found to increase gain of the antenna array in a linear fashion, thereby providing very significant additional amounts of gain per dipole stacked to the array, especially when compared with endfire log periodic arrays.

By appropriate selection of dipole arm lengths and spacings, the antenna is capable of providing extremely good performance as a UHF antenna, a VHF antenna (covering both the low band and high band VHF), a combined VHF and UHF antenna, as well as being capable of being employed with endfire arrays to provide a combined UHF-VHF antenna. For example, the stacked array of the instant invention may be combined with a standard VHF endfire log periodic antenna for providing transmission or reception over the entire VHF and UHF bands. As another alternative, a stacked broadside array designed in accordance with the principles of the instant invention for operation as a VHF antenna may be combined with an endfire array covering the UHF band so as to incorporate the unique advantages of the stacked broadside array described herein with standard endfire arrays.

Modification of the above embodiment through either alternative of giving each arm of the dipoles a curved configuration, or an L-shaped configuration, and through omission of the ground plane or parasitic elements yields an antenna similar in all characteristics to the antenna described above, but with the differing feature of providing an omnidirectional radiation pattern yielding high gain over the operating frequency range.

It is, therefore, one object of the instant invention to provide a novel log periodic antenna of the broadside type for use in transmission and reception applications.

Another object of the instant invention is to provide a novel stacked broadside log periodic antenna comprised of a plurality of dipoles stacked in a vertical fashion with the dipoles being arranged in an asymmetric pattern relative to a horizontal plane passing through the central feed point of the antenna.

Yet another object of the instant invention is to provide a novel stacked broadside log periodic antenna comprised of a plurality of dipoles stacked in a vertical fashion with the dipoles being arranged in an asymmetric pattern relative to a horizontal plane passing through the central feed point of the antenna and wherein the array is further provided with a vertically aligned reflecting means arranged behind the dipoles for improving the radiation pattern and performance of the antenna array.

These and other objects of the instant invention will become apparent when reading the accompanying description and drawings in which:

FIG. 1 is a perspective view showing one preferred embodiment of the instant invention.

FIGS. la and 1b are front and top views, respectively, of the embodiment of FIG. 1.

FIGS. 2, 2b, 3, 4, 5 and 6 are perspective views showing alternative embodiments of the instant invention.

FIG. 2a is a top view of another preferred embodiment of the invention.

FIG. 4a is a schematic diagram of another feature of the invention.

FIGS. 7 and 8 are perspective views showing further alternative embodiments for the instant invention.

FIGS. 9a and 9b show H and E-plane radiation patterns for the antenna arrays of FIGS. 7 and 8.

Referring now to the drawings, and more particularly to FIGS. 1 through lb, there is shown therein an antenna array 10 designed in accordance with the principles of the instant invention and which is comprised of a vertical pole or mast ll adaptable for mounting to any suitable support, and which is, in turn, designed to have strength suitable for supporting the dipoles 12-14 through l2'l4, respectively. Each dipole is secured to mast 11 by a support bracket 15, preferably formed of a suitable insulating material and having a pair of mounting

terminals

16 and 17 secured thereto for the purpose of mechanically and electrically coupling the inboard ends of dipole arms 12a and 12b, as well as the terminals of a transposed feeder harness 18.

The dipole arms 12a and 12b are Vd (i.e., bent forward) so as to form an angle a lying in the range from 40 to a maximum of 180. Each of the dipoles, such as, for example, the dipole 12, is coupled at its inboard ends to a mounting bracket 15, preferably formed of an insulating material, and is secured by

suitable fastening members

16 and 17. These fastening members also secure the end terminals of a transposed feeder harness 18 which is provided for the purpose of maintaining phase synchronism of signals fed to and/or received from each of the dipoles.

The dipole arms of dipoles 12 through 14 are of decreasing length moving from dipole 12 to dipole 14. The length of the dipole arms is preferably determined by the equation where h2 the length of each of the dipole arms 13a and 13b;

h =the length of either the dipole arms 12a and 12b; and

7 has a value preferably in the range of from 0.78 to 0.99.

The distance d between

dipoles

13 and 14 is related to the distance between dipoles l2 and 13 by the eq uation where y, is preferably in the range from 0.80 to 0.99. However, it should be noted that it is not absolutely necessary that the y factor determining distance between adjacent dipoles be the same as the factor 'y for determining associated dipole arm lengths.

The dipole arm relationship and dipole spacing for dipoles 12 through 14' is substantially identical to the relationships existing amongst dipoles 12 through 14. Also, the dipole arm lengths of dipoles 12 through 14 are equal to those of dipoles 12' through 14', respectively. In addition, the dipoles 12 through 14 are spaced at distance from an imaginary horizontal plane 19 of the antenna array by an amount equal to the distances from the dipoles 12 through 14', respectively, to the imaginary plane 19. The feeder terminals 20 for coupling the antenna array 10 to a receiver (or transmitter) facility are located substantially in the plane 19 of the array. A transposed feeder harness arrangement is provided for electrically coupling dipoles 12' through 14 to the feeder terminals 20 in substantially the same manner as the coupling between feeder terminals 20 and dipoles 12 through 14. a

The ground plane or reflecting plane 21 of the array is preferably formed of a suitable conductive material arranged in a grid-like fashion so as to form a reflecting screen for the purpose of reflecting energy which impinges upon the ground plane substantially in the direction shown by arrow 22 in FIG. 1b. The reflecting plane 21 is arranged so as to be substantially perpendicular to imaginary vertical plane 23 which is the bisector of the angle formed by the dipole arms such as, for example, the arms 12a and 12b. It should be noted that all of the dipole arms are Vd to form substantially the same angle and are further arranged so that all of the .dipole arms 12a through 14a and 12a through 14a lie substantially within one plane and the arms l2b-l4b and l2b'14b lie substantially within a second plane which intersects the first plane forming an angle a, where a, as was previously described, lies within the range from 40 to In one exemplary embodiment, an antenna array of the type shown in FIGS. 1 through 1b, comprised of six dipoles, was designed for use in the UHF range encompassing UHF channels 14 through 83 in the frequency range from approximately 450 to 900 megacycles per second. The length of the dipole arms 12a and 1212 are such that their electrical length, when measured from tip-tottip (with the arms unbent or straight), is equal to 3M2, where )t is the wavelength for a signal of a frequency of 470 megacycles. Thus, tip-to-tip length is equal to 3M2 is equal to 20.0 inches.

Selecting a 7 equal to 0.70, the tip-to-tip developed lengths of dipoles I3 and 14 are 14.0 and 9.80 inches, respectively.

The spacing relationships again employing 7 equal to 0.70 are all based upon the spacing a which is determined by the equation:

d =tfh where For the present embodiment d, M4 where A the wavelength for the operating frequency of 470 megacycles.

Thus d, is equal to 7 inches. With a y, of 0.70, d is equal to 4.9 inches; and d;, (the distance between dipole l4 and feed point 20) is equal to 3.5 inches.

It is to be noted that the distances d through d;,' are equal, respectively, to the distances d through d as are the lengths of dipoles 12' through 14 equal, respectively, to dipoles 12 through 14.

The antenna array incorporating the above designed parameters was found to give broad band frequency response over the entire UHF range with a unilobe radiation pattern having a beam width 35. Secondary lobes were quite small and about 9 db down from the main lobe.

A second experimental model was exhaustively tested in which the spacings d and h, were substantially equal to those given in the above exemplary embodiment, with the modification being a selection of equal to 0.79. This selection resulted in the following parameters:

I1 20 inches d 7.00 inches h 15.8 inches 11 5.54 inches h;, 12.4 inches 11;, 4.37 inches h, 9.8 inches d 3.45 inches The antenna of this second embodiment can be seen to have included two additional dipoles when compared with the first experimental embodiment with the same design concepts being maintained throughout; namely, the symmetrical aspect of the antenna, the decreasing dipole lengths moving from the outer limits toward the center of the antenna, and the decreasing spacing between dipoles moving from the outer limits of the antenna toward the center thereof. The addition of two dipoles to the array was found to result in a significant increase in gain. The increase in the broadside aperture of 2 results in a doubling in power gain (i.e., 3db). These results are not obtainable with endfire arrays. Also, this broadside array gives frequency independent response and a greater bandwidth.

Further alternative embodiments of the instant invention are shown in FIGS. 2 through 6. Considering FIG. 2b, there is shown therein an antenna array substantially similar to that shown in FIGS. 1 through 1b, except that the ground or reflecting plane 21 is replaced by an array 21' of parasitic elements 25 through 27 arranged along a second vertical supporting means 28 such that the arms of each of the parasitic elements, for example, the arms 25a and 25b, are electrically coupled to one another at their inboard ends and are electrically insulated from the active elements 12-14 and 1214, as well as being electrically insulated from the transposed feeder harness 18. The lower half of the antenna array of FIG. 2b has been omitted for purposes of brevity, it being understood that the lower half of the array is substantially the mirror image of the upper half of the array depicted.

Each parasitic element is positioned substantially directly behind anassociated dipole. such that the associated dipole and parasitic elements, for example, dipole l2 and parasitic element 25, lie substantially within a horizontal plane. In the top view embodiment of FIG. 2a, the parasitic elements 25 through 27 and 25 through 27' are shown as being a single straight element. FIG. 2b differs from FIG. 2a in that the parasitic elements 25 through 27 are Vd at an angle B wherein [3 lies substantially within the same range as the angle at which the dipole arms are Vd.

The vertical supporting means 28 is positioned behind the support 11 by a distance s so as to space each of the parasitic elements from their associated dipoles by a distance where Am is the wavelength for the midband frequency of the frequency band to be covered.

The electrical lengths of the parasitic element may vary between being slightly smaller to slightly greater than their associated dipoles without causing any significant decrease in the quality of performance.

The parasitic elements decrease in length and in spacing in substantially the same manner as do the associated dipoles.

The Vd parasitic elements in the embodiment of FIG. 2b provide improved operation as compared with the straight parasitic elements such thatthe front-toback ratio is significantly improved and higher mode operation is improved.

FIG. 2 shows still another embodiment of the instant invention wherein a second broadside active element array 21' comprised of elements 25-27 and 25 27' are secured at spaced intervals along supporting means 28. Again it can be seen that the

dipole arrays

10 and 21 are substantially identical to that shown in FIGS. 1 through 2a, with each of the associated dipoles lying substantially within a horizontal plane. The feeder harnesses l8 and 18 of the arrays 10 and 21', respectively, are substantially-identical to the feeder harness 18 described with respect to FIGS. 1 and 1a. The midpoints of these harnesses are connected by an additional transposed section 18". The feed points 20 are located on array 10 as shown.

The arrangement of FIG. 3 is such as to maintain uniform spacing between the frontward driven elements or dipoles and their associated rearward elements in terms of electrical wavelengths such that the ratio of spacing between dipole 12, for example, and its associated dipole 25, when compared with the spacing between dipole 13 and its associated dipole 26, is substantially 1:1. The embodiment of FIG. 3 is identical in every other respect to the embodiment of FIG. 2. Whereas the embodiment of FIG. 3 shows the dipoles in the array 21' as being Vd forward in the same direction and at the same angle as its associated dipole elements of array 10, it should be understood that the dipoles of array 21 may be substituted by straight dipoles (i.e., a= l80) of substantially equal electrical length.

The antenna array of FIG. 3 provides optimum operation with the experimental data showing that the optimum front-to-back ratio over entire band is obtained as a result of the Ving of supporting mast 28.

In the embodiment of FIG. 2b, the mast 28 supporting the parasitic elements -27 may be Vd backwards about its mid-point (i.e., imaginary plane 19) in the same manner as the active array 21' of FIG. 3 to improve the front-to-back ratio of the composite array.

FIG. 4 shows still another embodiment wherein the dipole array 21" is comprised of a plurality of dipole elements 2527 and 25-27' secured to a vertical support means 28 which is positioned closer to support means 11 so that the spacing s therebetween is less for this embodiment than for any of the embodiments shown in previously described Figures. As a further alternative to minimizing spacing S, the vertical support means 28 may be removed altogether and the dipoles are Vd in the rearward direction forming an angle ,8 5

which lies in the range between and 180. This rearward Ving of the parasitic elements permits extremely close spacing of the supporting means 28 and 11, as well as permitting the use of a single support means 11 as a substitute for twin support means. 40

The feeder harnesses l8 and 18 are substantially identical in design and operation to those shown in FIGS. 1 and la. They are joined at their mid-points by transposed section 18". Feed points 20 are positioned at the mid-point of array 10. Transposed section 18" acts to maintain the front-to-back ratio with the direction of maximum gain being that indicated by arrow A. The composite array of FIG. 4 may be made bidirectional by providing array 21' with a pair of feed terminals 20' (shown in dotted fashion). A two-position switch may be switched between the feed terminals 20 and 20' so that when connected to terminals 20, the direction of maximum gain is designated by arrow A, and when connected to terminals 20', the direction of maximum gain is designated by arrow B.

The switch 90 may be replaced by bandpass filter means 91, shown in FIG. 4a. The bandpass filter may be designed to pass signals lying within a first band of frequencies from array 10 while attenuating the signals lying within the first band of frequencies from array 21. Alternatively, the bandpass filter may be further designed to pass all signals lying within a second band of frequencies from array 21' while attenuating those signals from array 10 which lie in the second band of frequencies. Thus, bidirectional operation may be obtained automatically without the need for operating a switch (90).

The parasitic elements 25-27 of FIG. 26, in addition to having their arms either straight or Vd forward, may also be Vd in the rearward direction in the same manner as the dipole elements 25-27 and 25'-27 of the array 21 shown in FIG. 4.

As still a further modification of the antenna design of the instant invention, the broadside array may be combined with endfire arrays to provide a composite broad band antenna structure. For example, considering the embodiment of FIG. 5, there is shown therein a standard VHF endfire array 30 combined with an array 10 designed in accordance with the principles of the instant invention, and which is provided with stacked dipole elements dimensioned and spaced for providing coverage of the entire VHF band.

The VHF array 30 is comprised of a plurality of active elements 31 and 35, each having electrical lengthsso as to resonate at discrete frequencies within the VHF band. For example, the dipole 31 which is shown Vd forward at an angle a lying between 40 and as an electrical length of M2, wherein A is the wavelength for the operating frequency of channel 2, for example. Thus, in accordance with log periodic principles, the dipole 31 will resonate at odd halfwavelength multiples and more particularly will operate at 3M2 so as to provide a resonant condition for the VHF high band substantially at a frequency equal to, or very nearly equal to the frequency for channel 8 which lies in the VHF high band. The remaining dipoles 32 through 36 are designed in a like manner. The dipoles are electrically coupled to the feed point 40 by means of a transposed feeder harness 41 to provide a good front-to-back ratio. The rearmost dipole 31 is shortened at its inboard ends by a shorting stub 42.

The spacing between dipoles and the electrical length of the dipole arms in endfire array 30 gradually decreases from the left toward the right-hand end of the array 30, preferably in accordance with the factor previously described. The design principles and operating characteristics of an endfire VHF log periodic antenna are covered in greater detail in U. S. Pats. re Nos. 25740; 3,150,376; and copending U. S. applications Ser. No. 345,691, now US. Pat. No. 3,276,028, issued Sept. 27, I966; Ser. No. 225,311, now US Pat. No. 3,228,257, and Ser. No. 523,477, now US. Pat. No. 3,466,655, issued Sept. 9, 1969.

The specific design considerations of the endfire log periodic antenna will be omitted herein for purposes of simplicity, and reference should be made to the above mentioned copending applications and U. S. patents regarding the specific design features to be employed.

The broadside array 10 is an antenna array substantially as shown in FIG. 1, for example, and having dipole elements 12-14 and l2-l4, respectively, which are dimensioned in space so as to provide operation over the entire UHF band and having a reflector array 21 comprised of reflectors such as 27 and 27 FIG. 6 shows still another manner in which a broadside array may be combined with an endfire array. In the combined UHF-VHF antenna array of FIG. 6, there is shown therein a broadside VHF array comprised of active elements 12-14 and I2'-14' and a ground or reflecting plane 21. Each of the antenna array 10 is substantially as shown in FIG. 1, the exception being that the dipole elements are so dimensioned and spaced as to provide operation over both the lower and upper VHF bands. If desired, the ground or reflecting plane 21 may be replaced by parasitic elements arranged in any one of the manners as shown in FIGS. 2-4.

The central feed point 50 which is coupled to the dipole elements 12-14 and 1214' in the same manner as shown in FIGS. 1 through 1b is further electrically coupled to an endfire array 60 comprised of a plurality of dipole arms 61 through 66 which are electrically coupled through a balanced feeder line 67 forming a transposed feeder harness to provide the 180 phase shift, as was previously described. The endfire array 60 I is preferably designed in accordance with the principles described in U. S. Pat. No. 3,210,767 mentioned previously such that the dipoles are of decreasing electrical length moving from the left to the right-hand end of array 60 and such that the spacing between dipoles decreases, moving in the same direction. The endfire array 60 is designed so as to provide operation over the entire UHF band.

It can, therefore, be seen from the foregoing description that the instant invention provides a novel broadside array yielding extremely effective operation over a broad frequency range and wherein design is such as to provide substantially linear increases in antenna gain as additional dipole elements are added so long as the symmetrical arrangement of the array is substantially adhered to in designing the antenna.

As an alternative embodiment to the highly directional broadside arrays of FIGS. 1 through 6, the embodiments of FIGS. 7 and 8 may be employed in cases where good all-channel omnidirectional radiation patterns are desired. Considering first FIG. 7, there is shown therein a frequency independent omnidirectional antenna array 70 comprised of an elongated support means 71 and a plurality of dipoles 72-74 and 7274 which are arranged so as to be symmetrical about a line of symmetry 75 passing through the location of the feed point terminals 76. As was previously the case with the embodiments of FIGS. 1 through 6, the dipoles 7274, while curved, nevertheless adhere to the general design of the previously described arrays in that, for example, each dipole arm 72a and 72b of dipole 72 has an electrical length equal to M4 where )t is the wavelength for the lowest operating frequency for the frequency range in which the array operates. Thus, the total tip-to-tip electrical length measured along the arms of the dipole 72 is equal to M2. The length of dipoles moving downwardly from dipole 72 vary in accordance with the factor 7 such that b (the length of dipole arm 73a) is equal to h, (the electrical length of arm 72a) times the factor 7 where 'y is a constant in the range from 0.78 to 0.99. The decreasing electrical lengths are controlled by the y factor until the dipole closest to and above the line of symmetry 75 is reached, at which time the remaining dipoles positioned below the line of symmetry increase in electrical length in the manner shown in FIG. 7 so as to provide a substantially symmetrical array with the line of symmetry for the array being the line 75. The inboard ends of the dipole arms are coupled by a transposed feeder harness 77 in the same manner as was previously described with reference to FIGS. 1 through 6. The dipoles may be mounted to suitable brackets 78,

each being provided with suitable mounting means (not shown) for securing each dipole to the vertical support means 71 and for electrically connecting the trans posed feeder harness to the inboard ends of the dipole arms.

It should be noted that neither a reflecting plane nor a parasitic element array is employed in the arrangement of FIG. 7 in order to provide an omnidirectional pattern for the antenna. FIG. 9b shows the horizontal E radiation pattern obtained with the antenna array 70, it being understood that the antenna, while represented by a dot in FIG. 9a, would be directed vertically upward out of the plane of the paper.

FIG. 9a shows the horizontal H radiation pattern which indicates that a substantially bidirectional H pattern is obtained.

The antenna of FIG. 7 has extremely advantageous use in both UHF and VHF reception in that it can be employed as a home receiving antenna providing excellent all-channel reception and being omnidirectional so that it is immaterial as to how the antenna is mounted insofar as its angular orientation is concerned due to its omnidirectional characteristics. Thus, it is possible through this design to provide the user with an antenna which requires no rotating mechanism in order to assure the use of good signal reception.

Insofar as spacing between dipoles is concerned, the spacing 11 between dipoles 72 and 73 (and likewise between dipoles 72 and 73) is determined by the equation with 8 being a constant lying in the range from 0.125 to 0.25. d thereby lies within the range from M8 to )t/4 wherein X is equal to the wavelength of the lowest frequency in the operating frequency range of the array. Spacings between subsequent dipoles are determined by the factor 3 such that, for example, d is equal to d times y, wherein d is the spacing between dipoles 73 and 74 (and likewise the spacing between dipoles 73 and 74' FIG. 8 shows an alternative arrangement which may be substituted for the embodiment of FIG. 7 wherein the curved or arcuate shaped dipole arms of each of the dipoles is replaced by a substantially L-shaped arm, as shown in FIG. 8, wherein the broadside array is comprised of a vertical support means 81 and dipoles 82-84 and 82'84'. The ratio of lengths of dipole arms moving from dipoles 82 toward 84 (and hence from dipoles 82 to 84, respectively) is determined by the constant 7 in the same manner as was previously described. Likewise, spacing gradually decreases between adjacent dipoles moving from the uppermost (or lowermost) end toward the center of the array in accordance with the factor 7. The dipole arms, however, for example, dipole arms 82a and 82b, are comprised of inboard sections 82a-1 and 82b-1, respectively, and outboard sections 82a-2 and 82b-2, respectively, wherein the electrical length of the inboard sections 82a-l and 82b-1 is of the order of M12 to M20 and is preferably M10 where )t is the wavelength for the lowest frequency within the operating frequency range of the antenna.

The outboard sections 820-2 and 82b-2 are preferably 1.5 to 3.0 times as long as their associated inboard sections so as to substantially be of a length within the range from 3A/2O to M4.

The angle a formed between the inboard and outboard sections such as, for example, the sections 82a-l and 82a-2 preferably is a right angle, but may lie within the range from 70 to 1 10.

The dipoles 82-84 (and hence 82' and 84') are coupled to the feeder point terminals 86 by means of a transposed feeder harness 87 in a similar fashion to that described with respect to the embodiments of FIGS. I

The antenna embodiment of FIG. 8 has also been found to provide an excellent frequency independent omnidirectional antenna yielding operating characteristics comparable to those achievable through the use of the embodiment of FIG. 7.

Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of the invention be limited not by the specific disclosure herein but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. An antenna array comprised of elongated support means;

a plurality of active elements positioned at spaced intervals along said support means;

a pair of feed terminals positioned intermediate the ends of said support means for coupling energy between said active elements and utilization means;

said active elements being comprised of a plurality of dipoles;

half of said dipoles being positioned at predetermined spaced intervals along said support means between said feed terminals and one end of said support means;

each of said dipoles being comprised of first and second arms lying on opposite sides of said support means;

a transposed feeder harness coupling the inboard ends of said dipoles to said feed terminals;

the remaining half of said dipoles being positioned along said support means between said feed terminals and the opposite end of said support means to form an antenna array which is substantially symmetrical about an imaginary horizontal plane passing through the point of connection of said feed terminals and said feeder harness;

said transposed feeder harness further coupling the remaining dipoles to said feed terminals.

2. The antenna array of claim 1 wherein the first arms and the second arms of all of said dipoles lie substantially in first and second respective planes which are parallel to said support means; and which intersect forming an angle within the range from 40 to 180.

3. The antenna array of claim 1 further comprising reflection means positioned adjacent said support means for enhancing the directional characteristics of said array.

6 4. The antenna array of claim 3 wherem sald reflection means is comprised of a substantially planar conductive screen having a grid-like pattern.

5. The array of claim 3 wherein said reflection means is comprised of second elongated support means positioned side by side with respect to said first support means;

a plurality of parasitic elements positioned at spaced intervals along said second support means and being secured to said support means at a point substantially equidistant from their outboard ends;

the spacing between adjacent parasitic elements and the electrical lengths of said parasitic elements being selected to provide a symmetrical pattern about said feed terminal point comparable to the symmetrical pattern of said dipoles.

6. The antenna array of claim 5 wherein each of said parasitic elements is positioned along said second support means so as to be substantially coplanar with an associated dipole.

7. The antenna array of claim 5 wherein each of said parasitic elements is bent at itspoint of securement to said second support means to form an angle lying in the range from 40 to 180.

8. The antenna array of claim 7 wherein the dipoles and parasitic elements are aligned so that one imaginary plane defines the common disector of the angles formed by the first and second arms of said dipoles and parasitic elements.

9. The antenna array of claim 1 wherein said electrical lengths of the longest dipoles are substantially equal to n/2 where n is any real integer and A is the wavelength of the lowest frequency for the operating frequency range of the antenna array.

10. The antenna array of claim 9 wherein the ratio of the electrical lengths of any dipole of said selected dipoles is given by the formula where 1,, is the electrical length of the larger dipole and l,,+ is the electrical length of the smaller adjacent dipole, and n is the nth arm running in an order from the dipole furthest from the feed terminals toward said feed terminals, and r is a constant in the range from 0.78 to 0.99;

the ratio of the electrical lengths of said remaining dipoles being determined in the same manner as that employed for the selected dipoles. 1 l. The antenna array of claim 9 wherein the spacing between adjacent dipoles measured along said first support means is determined by the formula where d is the spacing between the dipole having the electrical length l and the adjacent larger dipole; d is the spacing between the dipole having the electrical length 1,, and the adjacent smaller dipole and 'r is a constant lying in the range from 0.78 to 0.99.

12. The antenna array of claim 5 wherein the ratio of the electrical lengths of any parasitic element from the feed terminals to one end of said array is given by the formula where I is the electrical length of the larger parasitic element and l,, is the electrical length of the smaller adjacent parasitic element, and n is the nth arm running in an order from the parasitic element furthest from the feed terminals toward said feed terminals, and 'r is a constant in the range from 0.78 to 0.99;

the ratio of the electrical lengths of the remaining parasitic elements being determined in the same manner as that employed for the parasitic elements between said feed terminals and one end of said array. 13. The antenna array of claim 12 wherein the electrical length of the longest parasitic element 1,, at either outer end of the array is determined by the equation where L is the electrical length of the longest dipole associated with the longest parasitic element.

14. The antenna array of claim wherein said second elongated support means is bent at a point near the feed terminals of said array so that the upper and lower halves thereof form equal angles with said first support means so as to space each parasitic element a distance s away from its associated dipole determined by the equation A 3A S S where A wavelength to which the associated dipole is attuned to resonate.

15. The antenna array of claim 5 wherein said parasitic elements are Vd in a direction opposite from that of said dipoles.

16. The antenna array of claim 1 wherein the dipole first and second arms are curved so that the outboard ends thereof extend in a direction generally perpendicular to the inboard ends.

17. The antenna array of claim 16 wherein the electrical lengths of the first and second arms of the longest dipole are each in the range from 0.4 A to 0.6 A where A is the wavelength of the lowest frequency in the operating frequency range of the array.

18. The antenna array of claim 1 wherein the first and second arms of each dipole are comprised of an inboard section and an outboard section;

said inboard and outboard sections being substantially straight; integral with one another and forming an angle at their juncture point lying in the range from 40 to 180.

19. The antenna array of claim 18 wherein the ratio of lengths of each outboard section l to its associated inboard section l,-, is given by the equation out in where K is a constant lying in the range from 1.5 s Ks 3.0;

the total electrical length of the longest dipole arms each being in the range from 0.4 A to 0.6 A where A is the wavelength of the lowest frequency in the operating frequency range of the antenna array. 20. A composite antenna array comprised of first and second antenna arrays of the type described in claim 1 and being arranged so that their support means are arranged substantially in spaced parallel fashion and directions of maximum gain are coincident and point in opposite directions;

a transposed feeder section coupling their feed terminals;

the feed terminals of one of said arrays being adapted to be coupled to suitable utilization means.

21. A composite antenna array comprised of first and secondantenna arrays of the type described in claim 1 and being arranged so that their support means are arranged substantially in spaced parallel fashion and their directions of maximum gain are coincident and point in the same direction;

transposed feeder section coupling their feed terminals; I

22. A composite antenna array comprised of first and second antenna arrays of the type described in claim 1 and being arranged so that their support means are arranged substantially in spaced parallel fashion and their directions of maximum gain are coincident and point in opposite directions;

a transposed feeder section coupling their feed terminals;

means coupled between said feed terminals for altering the directional characteristic of the composite array.

23. The composite array of claim 22 wherein said switching means is comprised of two-position switch means for coupling one or the other of said feed terminals to suitable utilization means.

24. The composite array of claim 22 wherein said switching means is comprised of bandpass filter means coupled between the feed terminals of said first and second arrays for passing the signals of one of said arrays which lie in one frequency band while attenuating the signals from the remaining array which lie in said one frequency band;

said one frequency band beingsmaller than the frequency range for which said arrays are designed to operate.

25. An antenna array comprised of elongated support means;

said active elements being comprised of a plurality of dipoles;

a transposed feeder harness coupling the inboard ends of said half of said dipoles to said feed terminals;

the remaining half of said dipoles being positioned at predetermined spaced intervals along said support means between said feed terminals and the opposite end of said support means to form an antenna array which is substantially symmetrical about a from the feed terminals by equal distances; horizontal plane passing through the point of consaid transposed feeder harness further coupling the nection of said feed terminals and said feed hart f g half of Said ip t Said feed ness whereby associated dipoles positioned on opmmalsposite sides of said feed terminals are separated l

Claims

1. An antenna array comprised of elongated support means; a plurality of active elements positioned at spaced intervals along said support means; a pair of feed terminals positioned intermediate the ends of said support means for coupling energy between said active elements and utilization means; said active elements being comprised of a plurality of dipoles; half of said dipoles being positioned at predetermined spaced intervals along said support means between said feed terminals and one end of said support means; each of said dipoles being comprised of first and second arms lying on opposite sides of said support means; a transposed feeder harness coupling the inboard ends of said dipoles to said feed terminals; the remaining half of said dipoles being positioned along said support means between said feed terminals and the opposite end of said support means to form an antenna array which is substantially symmetrical about an imaginary horizontal plane passing through the point of connection of said feed terminals and said feeder harness; said transposed feeder harness further coupling the remaining dipoles to said feed terminals.

2. The antenna array of claim 1 wherein the first arms and the second arms of all of said dipoles lie substantially in first and second respective planes which are parallel to said support means; and which intersect forming an angle within the range from 40* to 180*.

4. The antenna array of claim 3 wherein said reflection means is comprised of a substAntially planar conductive screen having a grid-like pattern.

5. The array of claim 3 wherein said reflection means is comprised of second elongated support means positioned side by side with respect to said first support means; a plurality of parasitic elements positioned at spaced intervals along said second support means and being secured to said support means at a point substantially equidistant from their outboard ends; the spacing between adjacent parasitic elements and the electrical lengths of said parasitic elements being selected to provide a symmetrical pattern about said feed terminal point comparable to the symmetrical pattern of said dipoles.

7. The antenna array of claim 5 wherein each of said parasitic elements is bent at its point of securement to said second support means to form an angle lying in the range from 40* to 180*.

9. The antenna array of claim 1 wherein said electrical lengths of the longest dipoles are substantially equal to n/2 where n is any real integer and lambda is the wavelength of the lowest frequency for the operating frequency range of the antenna array.

10. The antenna array of claim 9 wherein the ratio of the electrical lengths of any dipole of said selected dipoles is given by the formula 1n 1/1n Tau where 1n is the electrical length of the larger dipole and 1n+1 is the electrical length of the smaller adjacent dipole, and n is the nth arm running in an order from the dipole furthest from the feed terminals toward said feed terminals, and Tau is a constant in the range from 0.78 to 0.99; the ratio of the electrical lengths of said remaining dipoles being determined in the same manner as that employed for the selected dipoles.

11. The antenna array of claim 9 wherein the spacing between adjacent dipoles measured along said first support means is determined by the formula dn 1/dn Tau where dn is the spacing between the dipole having the electrical length 1n and the adjacent larger dipole; dn 1 is the spacing between the dipole having the electrical length 1n and the adjacent smaller dipole and Tau is a constant lying in the range from 0.78 to 0.99.

12. The antenna array of claim 5 wherein the ratio of the electrical lengths of any parasitic element from the feed terminals to one end of said array is given by the formula 1n 1/1n Tau where 1n is the electrical length of the larger parasitic element and 1n 1 is the electrical length of the smaller adjacent parasitic element, and n is the nth arm running in an order from the parasitic element furthest from the feed terminals toward said feed terminals, and Tau is a constant in the range from 0.78 to 0.99; the ratio of the electrical lengths of the remaining parasitic elements being determined in the same manner as that employed for the parasitic elements between said feed terminals and one end of said array.

13. The antenna array of claim 12 wherein the electrical length of the longest parasitic element ln at either outer end of the array is determined by the equation l1 L(1+0.05L) where L is the electrical length of the longest dipole associated with the longest parasitic element.

14. The antenna array of claim 5 wherein said second elongated support means is bent at a point near the feed Terminals of said array so that the upper and lower halves thereof form equal angles with said first support means so as to space each parasitic element a distance s away from its associated dipole determined by the equation where lambda wavelength to which the associated dipole is attuned to resonate.

15. The antenna array of claim 5 wherein said parasitic elements are V''d in a direction opposite from that of said dipoles.

17. The antenna array of claim 16 wherein the electrical lengths of the first and second arms of the longest dipole are each in the range from 0.4 lambda to 0.6 lambda where lambda is the wavelength of the lowest frequency in the operating frequency range of the array.

18. The antenna array of claim 1 wherein the first and second arms of each dipole are comprised of an inboard section and an outboard section; said inboard and outboard sections being substantially straight; integral with one another and forming an angle at their juncture point lying in the range from 40* to 180*.

19. The antenna array of claim 18 wherein the ratio of lengths of each outboard section lout to its associated inboard section lin is given by the equation lout Klin where K is a constant lying in the range from 1.5 < or = K < or = 3.0; the total electrical length of the longest dipole arms each being in the range from 0.4 lambda to 0.6 lambda where lambda is the wavelength of the lowest frequency in the operating frequency range of the antenna array.

20. A composite antenna array comprised of first and second antenna arrays of the type described in claim 1 and being arranged so that their support means are arranged substantially in spaced parallel fashion and directions of maximum gain are coincident and point in opposite directions; a transposed feeder section coupling their feed terminals; the feed terminals of one of said arrays being adapted to be coupled to suitable utilization means.

21. A composite antenna array comprised of first and second antenna arrays of the type described in claim 1 and being arranged so that their support means are arranged substantially in spaced parallel fashion and their directions of maximum gain are coincident and point in the same direction; transposed feeder section coupling their feed terminals; the feed terminals of one of said arrays being adapted to be coupled to suitable utilization means.

22. A composite antenna array comprised of first and second antenna arrays of the type described in claim 1 and being arranged so that their support means are arranged substantially in spaced parallel fashion and their directions of maximum gain are coincident and point in opposite directions; a transposed feeder section coupling their feed terminals; means coupled between said feed terminals for altering the directional characteristic of the composite array.

24. The composite array of claim 22 wherein said switching means is comprised of bandpass filter means coupled between the feed terminals of said first and second arrays for passing the signals of one of said arrays which lie in one frequency band while attenuating the signals from the remaining array which lie in said one frequency band; said one frequency band being smaller than the frequency range for which said arrays are designed to operate.

25. An antenna array comprised of elongated support means; a plurality of active elements positioned at spaced intervals along said suPport means; a pair of feed terminals positioned intermediate the ends of said support means for coupling energy between said active elements and utilization means; said active elements being comprised of a plurality of dipoles; half of said dipoles being positioned at predetermined spaced intervals along said support means between said feed terminals and one end of said support means; each of said dipoles being comprised of first and second arms lying on opposite sides of said support means; a transposed feeder harness coupling the inboard ends of said half of said dipoles to said feed terminals; the remaining half of said dipoles being positioned at predetermined spaced intervals along said support means between said feed terminals and the opposite end of said support means to form an antenna array which is substantially symmetrical about a horizontal plane passing through the point of connection of said feed terminals and said feed harness whereby associated dipoles positioned on opposite sides of said feed terminals are separated from the feed terminals by equal distances; said transposed feeder harness further coupling the remaining half of said dipoles to said feed terminals.