US3757343A

US3757343A - Slot antenna array

Info

Publication number: US3757343A
Application number: US00079893A
Authority: US
Inventors: R Bogner
Original assignee: Ampex Corp
Current assignee: Ampex Corp
Priority date: 1970-10-12
Filing date: 1970-10-12
Publication date: 1973-09-04
Anticipated expiration: 1990-09-04
Also published as: DE2150792A1; FR2110353B1; ZA716112B; GB1311620A; FR2110353A1

Abstract

An antenna, which may be used for signal transmission, comprises conductive means defining a slot therein having a longitudinal dimension. Various means may be provided in operative relation to the slot along said longitudinal dimension for causing all radiation from the antenna to be emitted only from sections of the slot of like field polarity without significantly affecting the phase velocity of the signals as they pass from the point of transmission line connection to all other points along the slot, so that the antenna functions as a plural slot array fed with only a single line.

Description

United States Patent Bogner Sept. 4, 1973 [54] SLOT ANTENNA ARRAY FOREIGN PATENTS OR APPLICATIONS Inventor: Richard 3 Roslyn, 610,259 12/1960 Canada 343/767 Assigneez Ampex Corporation, Redwood Germany Calif.

Primary ExaminerE. J. Lieberman [22] Filed: O 1970 Att0rneyLuedeka, Fitch, Even & Tabin [21] App]. No.: 79,893

[57] ABSTRACT [52] U.S. Cl. 343/770, 343/833 An antenna, which may be used for signal transmission, [51] Int. Cl. H0lq 13/10 om rises conductive means defining a slot therein [58] Field of Search ..343/767-771, 770, 833 having a longitudinal dimension. Various means may be provided in operative relation to the slot along said longitudinal dimension for causing all radiation from References Cited the antenna to be emitted only from sections of the slot UNITED STATES PATENTS of like field polarity without significantly affecting the 2,807,019 9/1957 Darling 343/852 Phase "emity 0f signals as they Pass from 2,794,184 5/1957 et a1. 343/767 of transmission line connection to all other points along 2,632,851 3/1953 Lees et al. 343/768 the slot, so that the antenna functions as a plural slo 2,665,382 1/1954 Smith et al 343/770 array fed with only a single line. 1,874,983 8/1932 Hansel] v 343/840 2,655,599 8/1953 Finneburgh 343/722 9 Claims, 7 Drawing Flglll'es IOO ' F 110 I 103% I04 SLOT ANTENNA ARRAY The present invention relates to slot antenna arrays, and more particularly to multiple-bay broadcast antennas utilizing slot-type driven antenna elements.

As is well known, vertical slot antenna elements are useful at ultra-high frequencies for producing horizontally polarized waves. Typically, the slot in such an antenna element may vary in length from a fraction of a wavelength to several wavelengths and may generally be formed in a planar conductive sheet or in the wall of a cylinder. The use of such elementary slot antennas in various linear arrays is very often desired because of their simplicity and low cost; and thus, it is generally required that in such antenna designs, the linear row of slots be excited or driven with an electrical signal having equal amplitude and phase to each slot in the row. This has generally been accomplished by merely bringing separate transmission lines to each slot from a conventional power divider distribution system.

In constructions where the slots are cut into a metal plate, each slot is typically about one-half wavelength long, and quite narrow with respect to this given wavelength. These slots may be used to radiate in directions normal to both sides of the plate or on merely one side of the plate if the other side is backed by a suitable cavity. Such slots are typically arranged in a colinear manner or, in other words, with their respective longitudinal axes in direct alignment, and are generally spaced about one wavelength apart, center-to-center.

Where such a slot antenna is formed in the wall of a cylinder, for cylinder diameters of about 0.1x 051155 (A being the wavelength at the transmitted frequency) and for slot widths which are very small as compared to the cylinder diameter, the radiation pattern in the horizontal plane is generally omnidirectional. For cylinder diameters of from 025A to 0.5) or greater, the radiation has the greatest intensity on the slotted side of the cylinder, i.e., along the radiation axis of the slot.

In the design of UHF-TV broadcasting antennas, it is generally desired to obtain high gain with an omnidirectional azimuth plane radiation pattern at the least cost. To achieve high overall gain, it is usual to vertically stack a large number of such slot antenna elements, each one defining a bay, and a vertical array extending for to 50 feet or more is typical for UHF- TV frequencies (e.g., 470 MHz to 890 MHz). Therefore, the supporting tower or pole in which the slots may be formed, or on which suitable cavities, plates or other slot-defining members may be mounted, will generally be made with a substantially larger diameter than 0.5)\ to have the necessary strength and rigidity to mechanically support the antenna and maintain stability in the wind and weather conditions to which it may be subjected. Thus, because of the relatively large diameter of the supporting tower, which may be in the form of a pipe or open-work structural members or girders, a simple, single vertical array of slots will not ordinarily provide the desired omnidirectional pattern due to shadowing effects of the tower.

To minimize or avoid such shadowing effects, it has been a practice to employ dipole or zigzag panels on each of three or four sides of the tower, staggered arrays of many slots around and along the wall of a cylindrical support, or a long helix wrapped around such a cylindrical support. Additionally, a very simple and inexpensive, but advantageous means of achieving an omnidirectional, or other desired pattern with a single vertical linear array of elementary antennas mounted on a large diameter tower of conventional construction is disclosed and claimed in copending application Ser. No. 661,625, filed Aug. 18, 1967, now Pat. No. 3,5 87,108, of the same inventor and assigned to the assignee hereof.

Although the employment of slot type antennas as compared to other types of driven antenna elements generally leads to the most economical broadcast antenna construction, as indicated above, it has heretofore been the practice to bring a separate transmission line in the form of a coaxial cable from the transmitter power distribution system to each and every elementary slot in the array, each coaxial cable being terminated at its respective slot by electrical connection of the cable conductors across the middle of the longitudinal edges of the slot. Consequently, a relatively large amount of coaxial cable must be used in such antenna structures, at a substantially highcost.

It is an object of the present invention to provide a low cost antenna array employing slot type driven elements which may be fed with only a single transmission line at a single point along the array, but yet will provide the same radiation characteristics as produced by multi-line feed arrangements, with a considerable further savings in cost and without any sacrifice in performance.

It is another object of the invention to provide an improved broadcast antenna which may be constructed and operated at considerably less cost than prior broadcast antennas of comparable performance.

These and other objects of the invention are more particularly set forth in the following detailed description and in the accompanying drawings, of which:

FIG. 1 is a perspective view showing an antenna array in accordance with a first embodiment of the present invention;

FIG. 2 is a plan view of the antenna array of FIG. 1;

FIG. 3 is a perspective view of a portion of a broadcast antenna employing the general type of antenna array of FIGS. 1 and 2, mounted vertically on a supporting mast;

FIG. 4 is a section view taken along line 4-4 in FIG. 3 in the direction of the arrows;

FIG. 5 is an elevational view of an antenna array in accordance with a second embodiment of the present invention;

FIG. 6 is an elevational view of an antenna array in accordance with a third embodiment of the present invention; and

FIG. 7 is a perspective view of a portion of a broadcast antenna employing the general type of antenna array of FIG. 5, mounted vertically on a supporting mast.

In general, the antenna structures in accordance with the present embodiment of the invention are for transmitting signals of a given operating frequency, typically in the UHF-range, and comprise conductive means for defining a slot, or slot sections, therein having an overall longitudinal dimension approximately equal to an odd number of half-wavelengths at the operating fre quency, and a transverse dimension substantially smaller than a half-wavelength (e.g., less than about 0.1)t) at that frequency. These antenna structures further comprise a transmission line electrically connected across the transverse dimension at a predetermined point along the longitudinal dimension of the slot for exciting the entire slot with the signals from some transmitter source to which the opposite end of the line is connected. Additionally, means are provided in operative relation to the slot or slot sections for causing all radiation from the antenna to be emitted from regions of the slot, or selected slot sections, of like field polarity without significantly affecting the phase velocity of the signals as they pass from the point of transmission line connection to all other points along the slot, whereby the antenna structure functions as a plural slot array, while being fed from only a single transmission line at the one point of connection.

To enable a better understanding of the principles of the present invention, a somewhat simplified horizontal slot-type antenna array is illustrated in FIG. 1. As there shown, a planar metal sheet or plate has a single, continuous and narrow slot 12 formed therewithin. The entire length of the slot 12 along its longitudinal axis from end 14 to end 16 may be any odd number of halfwavelengths at the desired operating frequency, and is five half-wavelengths in the embodiment shown in FIG. 1. Thus, in general, where L is the length or longitudinal dimension of the slot 12 and N is any integer, L M2) (ZN-1). The width or transverse dimension of the slot 12 is substantially less than a half-wavelength in accordance with conventional practice in respect to slot antenna design.

The slot 12 will thus have a plurality of

halfwavelength regions

12a, 12b, 12c, 12d and 12e of spatially alternating field polarity in response to the application of an excitation signal at the given operating frequency through a coaxial cable 18 connected across the transverse dimension of the slot 12 at the center or mid-point 20 thereof. The plate 10 defines a radiation direction, as indicated by the arrow 22, normal to the plane of plate 10, and is taken here as being the forward direction. The plate 10 would also define a backward radiation direction 180 from that indicated by arrow 22 but for the addition of means for suppressing this backward radiation as will be described hereinafter.

Considering, first, the forward radiation from the front face of plate 10 (as shown in FIG. 1 a sinusoidal standing wave is produced along the slot 12 with a maximum or peak at the feed point 20 of the coaxial cable 18. Since the slot 12 is five half-wavelengths in length, the respective first, third and fifth half-wavelength regions 120, 12c and l2e are of one polarity, while the respective second and fourth half-wavelength regions 12b and 12d are of opposite polarity. Half-

wave chokes

24a and 24b are each connected across the front face or forward radiation side of slot 12 over the respective half-wavelength regions 12b and 12d of such opposite polarity to permit the three unchoked regions or slot sections 12a, 12c and l2e to radiate without destructive interference from the respective regions of different polarity.

The half-

wave chokes

24a and 24b suppress the radiation from regions 12b and 12d, but present an opencircuit impedance at these regions of the slot and thus do not effect any phase shift or delay of the signal as it passes through these regions from the feed point 20 to the

ends

14 and 16 of slot 12.

Although, as previously indicated, such a slot antenna would normally radiate identically in both forward and backward directions normal to the opposed sides or faces of the plate 10, radiation may be confined to only one side of the plate, such as in the direction indicated by the arrow 22, by providing a further halfwave choke 28 along the entire length L of the slot 12 on the rear or backward radiation side of the plate 10. The choke 28 then blocks all radiation from the slot in the backward direction.

The presence of the alternately positioned half-

wave chokes

24a and 24b and the presence of the continuous half-wave choke 28 does not disturb the phase velocity of the signals within the slot from the normal free-space phase velocity, and thus they permit the standing wave pattern along the slot to remain sinusoidal in one wavelength cycles. Consequently, the radiation characteristics which are produced simulate those which are produced by an array of slots separately driven by a feed system having an individual transmission line connected to each of the radiating slots.

In the use of alternately positioned half-wave chokes as described above, it is generally preferable to block the regions of the slot of like polarity of which there are the least number, so as maximize the number of radiating regions or sections of the slot having the opposite polarity, but having the same amplitude and phase distribution. Thus, in FIG. 1 there are two blocked regions and three radiating regions on the forward side of the antenna.

Each of the half-wave

forward chokes

24a and 24b are formed from sheet metal and bent into a generally block U-shape having upper and lower opposing surfaces and a closed end normal to the opposing surfaces, as shown. The respective lateral ends, indicated as 30a and 32a, and 30b and 32b, of the

chokes

24a and 24b are preferably left open.

Each of the

forward chokes

24a and 24b have identical structures, and the backward choke 28 has the same structure, except for its continuous length in the direction parallel to the slot 12 which equals the longitudinal dimension thereof. All of the chokes are attached or affixcd to the plate 10 by welding or soldering the leading edges of the respective upper and lower opposing faces of the U-shaped members to the portions of the plate just above and below the slot 12. Of course, alternatively, any suitable metal joining technique may be employed to attach the chokes to the plate.

More particularly, referring to FIG. 2, the

forward chokes

24a and 24b have a dimension a extending normal to the plate 10 of M2, and a dimension b extending parallel to the plate 10 of A/2. Each of the forward chokes 24a and 24b are respectively offset from the

ends

14 and 16 of the slot 12 by a distance 0 equal to M2, and thus the distance between the inner

transverse edges

32a and 30b of the

respective chokes

24a and 24b is also M2. The backward choke 28 has a dimension d of also )./2 extending from the plane of the slot. The length e, however, of the choke 28 is equal to the length L of the slot which is equal to 5M2 in the illustrated embodiment of FIGS. 1 and 2.

In the embodiment of FIGS. 1 and 2, all of the

chokes

24a, 24b and 28 are coplanar, and their common plane is transverse or normal to the plane of the sheet or plate 10, although this is not necessary in the practice of the principles of the present invention.

Referring now to FIG. 3, there is shown a variation of the slot antenna array of FIGS. 1 and 2 mounted on a pipe or mast 40 to form a vertically oriented multibay broadcast antenna for UHF television transmission and the like. The mast 40 is typically composed of steel or other structurally sound material generally used for this purpose, and has a mounting flange 42 disposed at the lower end. The flange 42 has a number of mounting holes, as shown, through which suitable fastening means may be employed to mount the structure to an appropriate support in the usual manner. The modified form of the slotted antenna array of FIGS. 1 and 2 is indicated generally by the reference character 44 and is mounted securely to the pipe 40 by any suitable means, such as by welding, fasteners, etc.

The antenna array 44 comprises three halfwavelength radiating

slot sections

46, 48 and 50 which are defined by the open forward edges'of a continuous half-wave choke 52. The choke 52, having a length of 5M2, functions in the general manner previously described in connection with the backward choke 28 in FIGS. 1 and 2, and may be conveniently formed from sheet metal bent into a U-channel with the rear-most edge 54 being closed. Alternate half-wave forward chokes 56a and 56b have a similar configuration and structure to

chokes

24a and 24b of FIGS. 1 and 2, and each have their respective open ends welded or otherwise suitably fastened to the opposing open end edges of the continuous choke 52 at positions spaced one-half wavelength from the respective top and bottom ends 58 and 59 thereof. The upper and lower ends 58 and 59 of the continuous choke 52 are preferably closed by respective sheet metal end portions so that these end portions short the extreme ends 60 and 62 of the

slot sections

46 and 50. This type of construction avoids the necessity of utilizing a plate like that in the embodiment of FIGS. 1 and 2 to define the slot.

As best shown in the section view of FIG. 4, the planes of the forward and backward chokes form a generally obtuse angle, and the planes of the forward chokes 56a and 56b are normal to the plane defined by the radiating

slots

46, 48 and 50 are coplanar with the principal radiation axis of the array. The continuous choke 52 is tangential to the mast pipe 40, and the antenna array formed by the respective chokes is mounted to the pipe 40 by means of a bracket 64 and the choke 52.

A coaxial cable 68 serves as a transmission line to deliver the UHF signal from the transmitter to the antenna array 44 for excitation thereof. The cable 68 is terminated at the middle of the longitudinal dimension of the center radiating slot section 48, although it could alternatively be terminated at the corresponding point of radiating

sections

46 or 50.

Parasitic end-

fire directors

70a, 70b and 700 are each mounted on one side of the mast pipe 40 and identical directors 72a, 72b and 720 are symmetrically mounted on the other side of the mast pipe 40 (the latter directors not being visible in FIG. 3). These directors are arranged to provide any particular desired antenna radiation pattern and to compensate for the shadowing effect produced by the mast pipe 40 as disclosed in the aforementioned copending application of the present inventor. These parasitic directors are preferably of the disc-on-rod type employing a plurality of discrete planar conductive members,such as plate or disc elements 74 which are mounted on a common rod or support 78 having its longitudinal axis transverse to the plane of the discrete conductive members. The individual discon-rod end-fire directors act as parasitic elements, and are not conductively connected to the elementary or driven slot antenna elements. They are merely mechanically connected to the mast pipe 40 for support in their respective appropriate positions. The axis of each director is preferably in a plane approximately normal to the longitudinal axis of the mast pipe 40, and a symmet-' rical pair of such directors (e.g., a-72a, 70b-72b, etc.) are associated with each respective

radiating slot section

46, 48 and 50, the plane containing the axes of each such pair of directors preferably intersecting the mast within N2 of the perpendicular bisecting plane .through each radiating slot section measured along the axis of the mast. Each radiating slot section in this embodiment is considered a bay, and more than one level of directors may be associated with each bay, the parasitic elements being offset from each other in the azimuth plane, as shown in FIG. 4.

More particularly, as shown in FIG. 4, the endfire parasitic directors are mounted on the mast pipe 40 by mounting brackets like those shown as 80 and 82 which may be fastened to the pipe by any suitable means. The directors extend outward from the mast at about 120 on either side of the driven antenna to produce a generally omnidirectional radiation pattern over the entire 360 azimuth. These directors, by suitable placement, fill in the null areas of the pattern around the tower to compensate for the shadow efiect of the tower. However, by changing the position and/or angle of the directors, it is possible to direct the radiation pattern with large lobes covering only certain areas, while having large nulls of various depth in other areas or angular sectors. Thus, the particular angular displacement of the parasitic directors in FIGS. 3 and 4 are merely illustrative of one example, and may be modified to produce various antenna patterns as desired and as described in the aforementioned copending application.

The planar conductive members 74 of each end-fire director have a major dimension transverse to their axis of between M4 and M2, preferably being about M3. This major dimension is that dimension of the plates or discs which is in the plane of the electric field or E vector, being the horizontal dimension 1: in the embodiment of FIG. 3. The inter-element spacing of the plates or discs of any one of the directors is preferably between )t/8 and M2, and whilethese spacing dimensions are preferred, even closer spacings are permissible. Additionally, in some circumstances it may be desirable to have the major dimensions of the discrete metallic planar members non-uniform, with members farther from the mast pipe larger than the members close to the mast pipe on any one support rod 78.

The discrete planar members 74 may be in the form of solid plates, mesh, or rods placed transversely on a support, or, for example, within a non-conductive tube.

The term plates is thus used herein in an electrical or electromagnetic-wave sense and includes mechanical structures that behave in the general manner of solid conductive plates, but which may actually have the mechanical or physical form of mesh, screen, wires, rods, etc. whose overall effect is to form generally planar configurations transverse to the axis of the director.

Another embodiment of a linear horizontal array of slot elements in accordance with principles of the present invention is illustrated in FIG. 5 wherein a slot 102 is cut within a conductive plate with a longitudinal dimension or length L of 5M2 as in the embodiment of FIG. 1; however, at each half-wavelength interval f a cross or transverse slot is also cut into the plate 100; These cross or transverse slots, illustrated as 104, have a dimension 3 of M4 extending normal from each edge of the long slot 102, as shown. Thus, the total or overall length of each transverse slot across the long slot 102 is )t/2 plus the transverse dimension or width of the long slot. A coaxial cable 106 is terminated across the middle of the center half-wavelength setion of slot 102 for excitation of the antenna from a transmitter source of signal.

In the area or region of the intersection of the long slot 102 with each of the transverse slots, direct conductive interconnections are made by suitable conductive wires or bars 108 and 110 between diagonally opposite corners of the conductive plate 100 formed by the intersection of the slots. It is believed that these provisions result in a'180 phase reversal of the standing wave at each successive half-wavelength interval along the array, and since the standing wave would normally be sinusoidal, the amplitude and phase distribution across each half-wavelength reegion is the same as that across the center region, i.e., with the same polarity. Thus, each of the half-wavelength sections of the slot 102 may be utilized for radiating energy to provide an array of slot sections only one half-wavelength (or slightly more) apart, rather than one wavelength apart as in the embodiment of FIGS. 1 through 4. Although, some radiation of a destructive type may be produced at the phase shift regions between the slots, this will be insignificant in many applications of this embodiment.

The antenna array of FIG. 5 will radiate in the backward direction as well as in the forward direction, having principal radiation axes normal or perpendicular to the opposed faces of the conductive sheet 100 which defines the plane of the radiating slot sections.

A further embodiment of a horizontal slot antenna array in accordance with principles of the invention is illustrated in FIG. 6 wherein a conductive sheet 120 has a slot 122 cut therein. The slot 122 has a longitudinal dimension or length of 9M2, or it may have any other odd number of half-wavelengths. The slot 122 comprises

colinear slot sections

124a, 124b, 1240, 124d and 124e of which each has a longitudinal dimension h of a half-wavelength, and the slot 122 further comprises intermediate folded or

U-shaped slot sections

126a, 126b, 1260 and 126d interconnecting the ends of the respective adjacent colinear slot sections. Each of the U-shaped slot sections has a longitudinal dimension i also of a halfwavelength. A coaxial cable 128 is terminated across the midpoint or center of the center colinear slot section 124c in the same manner as that shown in connection with the embodiment of FIG. 5.

The U-shaped slot sections 126a through 126d are believed to contain the opposite field polarity portions of the standing wave and function for phase reversal so that the same amplitude and phase distribution of the field is provided across each of the colinear slot sections 124a through 124e, which act as separate antenna elements to radiate energy in a constructive fashion. The particular geometry or shape of the intermediate or interconnecting U-shaped slot sections 126a through 126d is believed to provide a mutualy cancelling effect for the opposite polarity phase distributions present along these sections of the slot 122, and thus destructive radiation from these sections is minimized.

Other slot configurations may also be alternatively employed to achieve a similar end, but generally less advantageously. For example, alternate radiating and mutually cancelling slot sections may be arranged in a generally serpentine fashion, such as where the radiating slot sections are generally diagonally parallel and the interconnecting sections have a generally S-shape for providing the cancelling and phase reversing action described.

A vertical slot array employing a single feed in accordance with principles of the present invention is illustrated in FIG. 7 utilizing a modified version of the antenna array illustrated in FIG. 5. More particularly, FIG. 7 shows a portion of a vertically oriented antenna array of slot elements suitable for television broadcast use. An array 160 of slotted elements is mounted on a supporting mast 162 of identical construction to the mast 40 previously described in connection with the embodiment illustrated in FIG. 3. The antenna element 160 has the identical structure as that described in connection with the embodiment of FIG. 5, except that the sheet is preferably folded toward the mast 162 so that it has a generally V-shape, and the sheet 100 is preferably mounted to the mast 162 by any suitable means with the vertex of the fold pointing away from the mast. A coaxial cable 164 is brought up through the mast as in the embodiment of FIG. 3, but is connected at 166 across the center of the lowest half-wavelength radiating slot section of the antenna assembly. The connection of the coaxial cable to the antenna may alternatively be connected across the center of any of the half wavelength radiating slot sections, but for reasons of economy and ease of repair and maintenance, it is preferable to make the connection at the half-wavelength radiating slot section which is closest to the transmitter and/or most accessible.

With this arrangement of the folded sheet 100 mounted to the mast 162, the principal radiation axis of the array of slots will be directed away from the mast 162 radially from the slot sections. A pair of parasitic end-

fire directors

168a and 168b are symmetrically positioned on the mast 162 and oriented at about from the radiation axis of the driven slot antenna elements to provide an omnidirectional or other desired antenna pattern compensating for the shadowing effects of the mast. The parasitic directors function in a manner like that described in connection with the embodiment of FIG. 3, but the discrete conductive plates, such as 170 and 172, extend in a continuous vertical fashion to be coextensive with the longitudinal dimension of the driven antenna 160, and thus are coextensive with the combined length of all of the half wavelength radiating slot sections of the antenna.

The

plates

170 and 172 of the parasitic end-fire parasitic director 168a (as well as the plates associated with the director l68b) are maintained in fixed relation to the mast 162 by means of supporting

rods

174 and 176 which are securely mounted by any suitable means to the mast 162. The supporting

rods

174 and 176 are normal to the planes of the

plates

170 and 172 which are thus maintained in general alignment with the longitudinal axis of the mast 162. The respective dimensions of these plates in the plane of the electric field vector of the transmitted signal is preferably between )t/8 and M4, and in the embodiment of FIG. 7 this dimension is indicated as y.

The considerations regarding the interplate spacings applicable to this embodiment are the same as were discussed above in connection with the embodiment of FIG. 3, and a greater number of discrete plates than shown may be employed for each end-fire director, the

two illustrated in FIG. 7 being merely exemplary. Also, the considerations regarding the positioning and location of such end-fire parasitic directors as are disclosed in the copending patent application previously referred to are applicable to the antenna embodiment illustrated in FIG. 7 to achieve various desired antenna pattern configurations.

Thus, there has been described various embodiments of antenna arrays comprising a plurality of slot sections which are driven or excited by merely a single transmission line, and thus provide substantial reductions in cost, greater reliability, fewer required parts and connectors, greater power handling capability, easier impedance matching, and less chance for lightening or other damage to disturb the distribution of power for lightening to cause power failure, as compared to prior antenna arrays having a plurality of slot elements which are all necessarily driven by separate transmission lines connected to each of the slots.

Although the present embodiments are described in connection with their use as transmitting antennas, it is of course understood that the principles of the invention are applicable to receiving antennas as well. Further, it is understood that although several specific embodiments of the present invention are herein illustrated and described, various modifications will be apparent to those skilled in the art based on the teachings hereof; and accordingly, the scope of the present invention should be defined only by the claims, and equivalents thereof.

Various features of the invention are set forth in the following appended claims.

What is claimed is:

1. An antenna for signals of a given frequency, comprising conductive means defining a slot therein having a longitudinal dimension, a transmission line electrically connected to said slot at a predetermined point along said longitudinal dimension, and means in operative relation to said slot for causing all radiation relative to said antenna to be associated only with sections of said slot of like field polarity without significantly affecting the phase velocity of the signals as they pass from said predetermined point to all other points along said slot, said means comprising additional slots defined by said conductive means, eachadditional slot having a longitudinal dimension normal to said first mentioned slot. at half-wavelength intervals therealong and extending a quarter-wavelength therefrom on each' side thereof, the intersection of each of said additional slots with said first mentioned slot defining four comer portions in said conductive means at each respective intersection, and discrete conductors coupling together the respective diagonally opposite pairs of comer portions at each of said intersections so that a field distribution is established along said first mentioned slot having the same field polarity over each successive half-wavelength section thereof, and whereby said antenna functions as a plural slot array in operation with only a single transmission line.

2. The antenna of claim 1 wherein said transmission line is connected at the center of a half-wavelength section of said first mentioned slot.

3. The antenna of claim 1 wherein said conductive means comprises a metal plate.

4. The antenna of claim 3 wherein said metal plate is folded along the longitudinal dimension of said first mentioned slot.

5. An antenna assembly for transmitting signals of a given frequency, comprising an elongated electrically conductive supporting structure having a longitudinal axis and a major transverse dimension at least a quarter-wavelength at said given frequency, conductive means defining a continuous slot on said supporting structure, said slot having a longitudinal dimension par allel to the longitudinal axis of said supporting structure, a transmission line electrically connected to said slot at a predetermined point along said longitudinal dimension for exciting said slot with said given frequency signals from a source, means in operative relation to said slot for causing all radiation therefrom to be emitted from sections of said slot of like field polarity without significantly affecting the phase velocity of the signals as they pass from said predetermined point to all other points along said slot, said means comprising additional slots defined by said conductive means, each additional slot having a longitudinal dimension normal to said first mentioned slot at half-wavelength intervals therealong and extending a quarter wavelength therefrom on each side thereof, the intersection of each of said additional slots with said first mentioned slot defining four corner portions in said conductive means at each respective intersection, discrete conductors coupling together the respective diagonally opposite pairs of comer portions at each of said intersections so that a field distribution is established along said first mentioned slot having the same field polarity over each successive half-wavelength section thereof, at least one end-fire parasitic director comprising a plurality of discrete conductive members disposed in spaced parallel relation along an axis transverse to said conductive members, said discrete conductive members having a respective dimension in the plane of the electric field vector of the transmitted signals, and said end-fire parasitic director being so positioned relative to said first mentioned slot and supporting structure as to alter the shape of the antenna pattern produced by the combined effects of said slot and supporting structure, while not intersecting the radiation axis of the radiating slot sections, to provide a selected pattern for said antenna assembly, and said antenna assembly functioning as a plural slot array fed from only a single transmission line.

6. The antenna of claim 5 wherein said conductive means comprises a metal plate, said plate being folded along the longitudinal dimension of said first mentioned slot toward the supporting structure to define the radiation axis for the radiating slot sections directed away from the supporting structure.

7. The antenna of claim 5 wherein said predetermined point of connection of said transmission line is at the center of a half-wavelength slot section of said first mentioned slot.

8. The antenna assembly of claim 5 wherein the longitudinal axis of said supporting structure is vertical, and said predetermined point of connection of said transmission line is at the center of the lowest halfwavelength slot section of the antenna assembly.

9. An antenna for signals of a given frequency, comprising conductive means defining a slot therein having a longitudinal dimension, a transmission line electrically connected to said slot at a predetermined point along said longitudinal dimension, additional slots defined by said conductive means, each additional slot having a longitudinal dimension normal to said first at each of said intersections so that a field distribution is established along said first mentioned slot having the same field polarity over each successive halfwavelength section thereof, whereby said antenna functions as a plural slot array in operation with only a single transmission line.

i I. i I.

Claims

1. An antenna for signals of a given frequency, compriSing conductive means defining a slot therein having a longitudinal dimension, a transmission line electrically connected to said slot at a predetermined point along said longitudinal dimension, and means in operative relation to said slot for causing all radiation relative to said antenna to be associated only with sections of said slot of like field polarity without significantly affecting the phase velocity of the signals as they pass from said predetermined point to all other points along said slot, said means comprising additional slots defined by said conductive means, each additional slot having a longitudinal dimension normal to said first mentioned slot at half-wavelength intervals therealong and extending a quarter-wavelength therefrom on each side thereof, the intersection of each of said additional slots with said first mentioned slot defining four corner portions in said conductive means at each respective intersection, and discrete conductors coupling together the respective diagonally opposite pairs of corner portions at each of said intersections so that a field distribution is established along said first mentioned slot having the same field polarity over each successive half-wavelength section thereof, and whereby said antenna functions as a plural slot array in operation with only a single transmission line.

5. An antenna assembly for transmitting signals of a given frequency, comprising an elongated electrically conductive supporting structure having a longitudinal axis and a major transverse dimension at least a quarter-wavelength at said given frequency, conductive means defining a continuous slot on said supporting structure, said slot having a longitudinal dimension parallel to the longitudinal axis of said supporting structure, a transmission line electrically connected to said slot at a predetermined point along said longitudinal dimension for exciting said slot with said given frequency signals from a source, means in operative relation to said slot for causing all radiation therefrom to be emitted from sections of said slot of like field polarity without significantly affecting the phase velocity of the signals as they pass from said predetermined point to all other points along said slot, said means comprising additional slots defined by said conductive means, each additional slot having a longitudinal dimension normal to said first mentioned slot at half-wavelength intervals therealong and extending a quarter-wavelength therefrom on each side thereof, the intersection of each of said additional slots with said first mentioned slot defining four corner portions in said conductive means at each respective intersection, discrete conductors coupling together the respective diagonally opposite pairs of corner portions at each of said intersections so that a field distribution is established along said first mentioned slot having the same field polarity over each successive half-wavelength section thereof, at least one end-fire parasitic director comprising a plurality of discrete conductive members disposed in spaced parallel relation along an axis transverse to said conductive members, said discrete conductive members having a respective dimension in the plane of the electric field vector of the transmitted signals, and said end-fire parasitic director being so positioned relative to said first mentioned slot and supporting structure as to alter the shape of the antenna pattern produced by the combined effects of said slot and supporting structure, while not intersecting the radiation axis of the radiating slot sections, to provide a selected pattern for said antenna assembly, and said antenna assembly functioning as a plural slot array fed from only a single transmission line.

8. The antenna assembly of claim 5 wherein the longitudinal axis of said supporting structure is vertical, and said predetermined point of connection of said transmission line is at the center of the lowest half-wavelength slot section of the antenna assembly.

9. An antenna for signals of a given frequency, comprising conductive means defining a slot therein having a longitudinal dimension, a transmission line electrically connected to said slot at a predetermined point along said longitudinal dimension, additional slots defined by said conductive means, each additional slot having a longitudinal dimension normal to said first mentioned slot at half-wavelength intervals therealong and extending a quarter-wavelength therefrom on each side thereof, the intersection of each of said additional slots with said first mentioned slot defining four corner portions in said conductive means at each respective intersection, discrete conductors coupling together the respective diagonally opposite pairs of corner portions at each of said intersections so that a field distribution is established along said first mentioned slot having the same field polarity over each successive half-wavelength section thereof, whereby said antenna functions as a plural slot array in operation with only a single transmission line.