US3653056A

US3653056A - Combined vhf-uhf dipole antenna array

Info

Publication number: US3653056A
Application number: US40862A
Authority: US
Inventors: Donald William Peterson
Original assignee: RCA Corp
Current assignee: RCA Licensing Corp
Priority date: 1970-05-27
Filing date: 1970-05-27
Publication date: 1972-03-28
Anticipated expiration: 1989-03-28
Also published as: JPS5635041B1; GB1343498A; CA920242A; DE2047315A1

Abstract

A plurality of center fed dipole elements with the center portions of the dipole elements connected to each other by a transmission line feed. Each center fed dipole element has two conductive rodlike half portions which overlap near the center feed portion and extend in opposite directions from the center feed. One of the center fed dipole elements has a length determined so as to be full wave resonant at a frequency within the high VHF television frequency band. Another one of the center fed dipole element has a length determined to be half wave resonant at the low VHF television frequency band and has two conductive rodlike half portions which overlap near the center feed to provide increased performance of the combination of center fed dipoles over the entire high VHF television frequency band.

Description

United States Patent Peterson [451 Mar. 28, 1972 [54] COMBINED VHF-UHF DIPOLE ANTENNA ARRAY [72] Inventor: Donald William Peterson, Maple Shade,

[73] Assignee: RCA Corporation [22] Filed: May 27, 1970 [21] Appl. No.: 40,862

[52] U.S. Cl. ..343/795, 343/802, 343/815,

[51] int. Cl. ..ll0lq 21/12 [58] Field of Search ..343/792.5, 814, 815, 816, 817, 343/820, 795, 802, 819

[56] References Cited UNITED STATES PATENTS 2,975,423 3/1961 Wells ..343/817 2,888,678 4/1959 Weiss et al 3,362,026 1/1968 Smith et al 3,475,759 10/1969 Winegard ..343/816 Primary Examiner-Eli Lieberman Attorney-Edward J. Norton [5 7] ABSTRACT A plurality of center fed dipole elements with the center portions of the dipole elements connected to each other by a transmission line feed. Each center fed dipole element has two conductive rodlike half portions which overlap near the center feed portion and extend in opposite directions from the center feed. One of the center fed dipole elements has a length determined so as to be full wave resonant at a frequency within the high VHF television frequency band. Another one of the center fed dipole element has a length detennined to be half 7 wave resonant at the low VHF television frequency band and has two conductive rodlike half portions which overlap near the center feed to provide increased performance of the combination of center fed dipoles over the entire high VHF television frequency band.

20 Claims, 8 Drawing Figures PATENTED MR 2 8 I978 SHEET 1 [1F 5 I N VEN 'I'UR.

By Donald W Peterson m ffl ATTORNEY PATENTEnmRze I972 3, 653 O56 SHEET 2 BF 5 27! lm i I N VEN TOR.

BY Donald W Peterson ATTORNEY PMENTEU MAR 2 8 I972 SHEET 4 UF 5 INVENTOR. Donald W Peterson ATTORNEY PATENTEDMAR28 I972 v 7 3,658,056

sum 5 OF 5 I N VEN TOR. Donald W Peterson ATTORNEY COMBINED VHF-UHF DIPOLE ANTENNA ARRAY BACKGROUND OF INVENTION This invention relates to an improved multifrequency antenna system and to an antenna which is particularly suitable for reception of signals within the high VHF television frequency band and low VHF television frequency band and to reception of signals within the UHF television frequency band.

The principal television frequency bands in use in the United States at the present are the VHF television frequency bands. These bands cover the frequencies from 54 to 88 megahertz and from 174 to 216 megahertz (MI-Iz.). A satisfactory television antenna therefore must be effective in both of these VHF television frequency bands.

One technique for extending the bandwidth of a television antenna is to use a plurality of fed or driven dipole elements with the lowest frequency dipole elements located at the one end and the other elements aligned and progressing toward the opposite end. Appropriate spacing is provided between each of these dipole elements and appropriate antenna feed line arrangement is provided to obtain relatively good reinforcing effects between the separate elements and to provide a relatively good antenna for the low 54 to 88 megahertz television frequency band. Antennas of this type, while desirable at the low band, do not operate well in the higher band where the frequencies are on the order of three times the half wave length of the dipole elements.

Various arrangements are known which provide an effective antennaoperative over the entire high VHF television frequency .band'using 'the dipole elements which provide effective coverage over the low VHF television frequency band. One such arrangement provides the high VHF television frequency coverage by' placing a separate rod-like element close and parallel to and centered forward of a center fed dipole element which is one-half wavelength long at a frequency in the low VHF television frequency band.

Anothersuch arrangement provides the high VHF television band coverage by placing the separate rod-like element close and parallel to and centered either above or below the center fed dipole element which is one-half wavelength long at a frequency in the low VHF television frequency band.

In these prior arrangements several of the center fed dipole elements have the associated separate rod-like element. The use of a separate rod-like element or elements and the mounting of these elements in their desired positions relative to the fed dipole or dipoles adds significantly to the total cost of such an antenna system. Since these antenna arrangements are often mounted outdoors, it is desirable that an improved low cost sturdy structure be provided for supporting these fed dipole elements to prevent their destruction by high winds and freezing rain. One such improved structure for accomplishing this is described by Burwell et al. in copending U.S. Patent application Ser. No. 888,478, filed Dec. 29, 1969.

It is therefore an object of the present invention to provide an improved low cost antenna system for operation over two widely separated frequency bands.

It is another object of the present invention to provide an improved low cost antenna for effective operation over the entire low and high VHF television frequency bands and over the UHF television frequency band.

Briefly, these and other objects of the present invention are provided by rod-like antenna system effective over two widely separated frequency bands. The system includes two fed dipole elements in substantially aligned and parallel relation to each other. A first of the fed dipole elements has a length determined to act as a full wave resonator at a frequency within the higher frequency band of the two widely separated frequency bands. The second of the fed dipole elements has a length determined to act as a half wave resonator for a frequency within the lower of the two widely separated frequency bands. The second of the fed dipole elements includes first and second rod-like conductors extending primarily in opposite directions with the first and second conductors overlapping each other over a portion of their length. The amount of the overlap of the first and second rod-like conductors and the orientation of the rod-like conductors relative to said first fed dipole element is determined so as to provide by the combination of the first and second fed dipole elements improved performance over the higher frequency band.

This invention will best be understood by reference to the following description taken in conjunction with the accompanying drawing in which:

FIG. 1 is a perspective view of an antenna system constructed in accordance with a preferred embodiment of the present invention,

FIG. 2 is a top plan view of the antenna system illustrated in FIG. 1,

FIG. 3 is an enlarged fragmentary right side view of the UHF dipole and associated corner reflector of the antenna system including a portion of the transmission line feed illustrated in FIG. 1,

FIG. 4 is a top plan view of a portionof the feed system near the center fed UHF dipole element illustrated in FIG. 1 with the top portionof the UHF comer reflector removed,

FIG. 5 is an enlarged fragmentary cross-sectional view of one center fed VHF dipole element illustrated in FIGS. 1 and 2 as taken through axis 55 of FIG. 2,

FIG. 6 is an enlarged fragmentary cross-sectional view of another center fed dipole element illustrated in FIGS. 1 and 2 as taken through axis 6-6 of FIG. 2,

FIG. 7 is an enlarged fragmentary cross-sectional view of the VHF reflector element illustrated in FIG. I as taken through axis 77 of FIG. 2, and

FIG. 8 is an enlarged fragmentary view of the VHF director element illustrated in FIG. 1 as taken through axis 88 of FIG. 2.

Referring to FIGS. 1 and 2, a multifrequency unidirectional antenna array 1 is shown mounted horizontally to a vertical mast 2 with the front end 3 of the boom 10 pointing generally to the left in the illustrations and in the direction of maximum signal reception. The array 1 is divided into a VHF television frequency portion to the right of point 11 along the boom 10 (i.e., toward the rear of the boom) and a UHF portion to the left of point 11 along boom 10 (i.e. toward the front end 3 of the array 1).

The UHF portion includes one fed dipole element 21, four director elements 13, 15, 17 and 19 and a corner reflector element 27. The VHF portion includes four

fed dipole elements

55, 57, 59 and 61, a reflector element 63 and director elements 35 and 53. As described hereinafter in more detail some of the conductor rods that make up the reflector element 27 in addition to acting as a part of the UHF reflector are dimensioned and arranged to also act as directors for the fed dipole elements in the VHF television frequency portion of the array.

Referring to the UHF portion illustrated in FIGS. 1, 2 and 3, the first four elements from the front end 3 of the array 1 are fixedly mounted director elements l3, l5, l7 and 19, which lie generally perpendicular to boom 10 and have a total length from tip to tip of less than a half wavelength at the high end (890 megahertz) of the UHF television frequency band. The particular director elements, for example, may be 5% inches long from tip to tip with 1 inch on either end being bent so as to be parallel to the boom 10. The bending of the ends of the director near the ends enable them to be more compact without changing their response. Director elements 13, 15 and 17 are appropriately spaced to provide optimum directivity.

Referring to FIG. 1, a transmission line feed 9 including conductors 9a and 9b is connected at one end to the

respective terminals

23 and 25 of the dipole element 21 and may, in

turn, be coupled at the other end to a television receiver. Director element 19 may, for example, be placed only 2 inches from the feed point of UHF fed dipole element 21. This close spacing of director element 19 to the fed dipole element 21 provides better impedance matching of the transmission line 9 to the dipole element 21.

Rearward of these four director elements 13, 15, 17 and 19 is the fan-like UHF fed dipole element 21. Referring to FIG. 4, conductive half portions 21a and 21b of this UHF dipole element 21 are spaced from each other by an insulating spacer b located along boom 10 between the otherwise conductive portions 10a and 100 of boom 10. The insulating spacer 10b has apertures 12 therein so arranged to minimize capacitance between the

dipole terminals

23 and 25 and to provide a long leakage path for moisture which may collect on the insulating spacer 10b.

Referring to FIG. 1 the fan-like dipole element 21 is center fed by the connection of the conductors 9a and 9b of transmission line 9 to input feed terminals at

points

23 and 25 of the UHF dipole element 21. The fan-like dipole element 21 has a length about equal to 0.8 of a wavelength long at the center frequency (646 MHz.) of the UHF television frequency band.

Referring to FIGS. 1 and 4, the dipole element 21 is made up of essentially two identical fan-like half portions 21a and 21b. Each half portion 21a and 21b is a tapered sheet of conductive material double folded along the lengthwise axis of the sheet. The fan-like half portions are mounted to the boom such that the conductive sheet increases like a fan in width along the lengthwise axis as it extends away from the feed terminals and such that the apex, formed by the fold, points away from the reflector. A further discussion of a type of fan-like dipole may be found in U.S. Pat. No. 2,714,659 to E. 0. Johnson et al. The particular fan-like dipole element 21 as shown herein with the apex of the folds pointing away from the reflector rather than toward the reflector operate similarly to that of U.S. Pat. No. 2,714,659. This fan-like dipole provides effective coverage over the entire UHF television frequency band. The length of this fan-like dipole 21 between the extreme ends of the dipole halves may be, for example, 14% inches. I

Mounted to boom 10 rearward of the dipole element 21 is an associated corner reflector 27. As shown in FIG. 1, this reflector 27 includes two

rod support portions

28 and 29 which are each mounted at one end to the boom 10 and extend above and below the boom 10 respectively. This reflector 27 is constructed and operates in a manner similar to that described in the above-cited U.S. Pat. No. 2,714,659. The two

support portions

28 and 29 form an angle with each other of 110. Forming the corner reflector 27 with the

supports

28 and 29 are the

reflector rods

31, 31a, 32, 32a, 33 and 33a. Generally the lengths of the

rods

31, 31a, 32, 32a, 33 and 3311 are designed so as to be about 1.09 wavelengths long at the center frequency (646 MHz.) of the UHF television frequency band.

A further description of this form of reflector and associated dipole may be found in the above-cited U.S. Pat. No. 2,714,659.

Rods

33 and 33a are further arranged such as to act with

rods

31, 31a, 32 and 32a as director elements at the high end of the high VHF television frequency band. The specific dimensions of the elements of such a corner reflector may be, for example, as follows:

rods

28 and 29 about 12 inches;

rods

31, 31a, 32 and 32a, 20 inches; and

rods

33 and 33a, 23 inches. The fan-like dipole element 21 for this example is spaced 8% inches forward of the point where the comer reflector 27 is connected to the boom 10.

Referring to the VHF television antenna portion of the multifrequency array 1 shown in FIGS. 1 and 2, there are provided four center fed

dipole elements

55, 57, 59 and 61 which increase in length from front to rear. The spacing between the center fed

dipole elements

55 and 57 and between 57 and 59 is 1 1 inches and the spacing between the center fed

dipole elements

59 and 61 is 13 inches.

Reinforcing effects between the center fed

VHF dipole elements

55, 57, 59 and 61 are provided by the transposition of the transmission line feed between the dipole elements. A balanced transmission line feed is provided made up of conductor 75 mounted in insulated manner along and above the boom 10 and conductor 77 mounted in insulated manner along but below the boom 10. The

successive dipole elements

55, 57, 59 and 61 are each made up of a pair of conductive rods. One of the pair of rods of each dipole element is con nected to conductor 75, crosses above the boom 10 and extends primarily in one direction from boom 10. The other one of the pair of conductive rods of each dipole element is connected to conductor 77, crosses below the boom 10 and extends primarily in an opposite direction from boom 10. The transposition of the transmission line feed between the dipole elements is accomplished by arranging the rods connected to conductor 75 so that the successive conductive rods extend in opposite directions and by arranging rods connected to conductor 77 so that the successive conductive rods extend in opposite directions.

Referring to FIGS. 1 and 2, it is seen that the conductive rod 67 of dipole element 55 is connected to conductor 75 and extends to one side of the antenna array 1. The next successive conductive rod 79 connected to conductor 75 extends into an opposite side of the array 1. The next successive conductive rod connected to conductor 75 following rod 79 is a conductive rod 81 which extends to the said one side of the array 1. The next successive conductive rod connected to conductor 75 following rod 81 is the rod 83 of the dipole element 61 which extends to the said opposite side of the array 1. Similarly

conductive rods

68,87,89 and 91 are connected by transmission line 77 so that the successive

conductive rods

68,87,89 and 91 alternate in direction from right to left and left to right extending along the length of the conductor 77.

An improved form of antenna dipole element is provided by overlapping near the feed point of the conductive rods which form the fed dipole elements. Referring to FIG. 5, the

conductive rods

67, 68 of fed dipole element 55 overlap over a length L. This amount of overlap may be, for example, 6 inches, with 3 inches of overlap on either side of the center line of the boom 10. The spacing S between the

conductive rods

67 and 68 of the fed dipole element is about 2 inches in a vertical plane. The overlapping of the dipoles near the center feed point provides shunt capacitance across the dipole terminals. This additional shunt capacitance together with the changing of the length h of the rods allows for improved impedance matching of the parallel wire transmission line, made up of

conductors

75 and 77, to the dipole elements and for providing optimum power distribution. For convenience sake the

rods

67 and 68 are shown broken. These rods are continuous and take the proportions illustrated in FIGS. 1 and 2. For a further description of a single dipole element of this type, see U.S. Pat. No. 2,523,728 to Smeltzer.

The separation between the

conductive rods

67 and 68 of fed dipole element 55 and the means for supporting these dipole half portions to the boom 10 is provided by an insulating support 71. See FIG. 5. The particular support used may be like that described as support 10 in copending U.S. patent application, Ser. No. 888,478 of Neil Burwell et a1. cited above. The support 71 is made up of two sections 71a and 71b with the respective

conductive rods

67 and 68 connected thereto. When the

conductive rods

67 and 68 are in their extended condition, the two sections 71a and 71b are in interfitting relationship as illustrated in FIG. 5 to provide the support structure.

By means of an insulating support,

conductors

75 and 77 of the transmission line feed are spaced from the

conductive rods

67 and 68. The particular manner in which this may be accomplished will be more clearly understood by reference to FIGS. 3, 4 and 5 and the attendant description therewith in the above-cited application Ser. No. 888,478. Electrical connection of the feed line conductor 75 to he conductive rod 67 is provided by conductive strap 56 which may be, for example, about 3 inches long. I ..ikewise, the electrical connection of conductor 77 to conductive rod 68 is provided by another such conductive strap 56a. The distance the strap 56 or 5611 is from the overlapping end of the

conductive rods

67 or 68 may be, for example, 4 inches.

The center fed dipole element 55 is approximately one wavelength long between the extreme ends of the rods in the 192 to 198 megahertz television frequency band and is nearly one-half wavelength long between the extreme extended ends of the rods at the high end of the low VHF television frequency band. The

conductive rods

81 and 89 of center fed dipole element 59 and the conductive rods 83 and 91 of center fed dipole element 61 are similarly overlapped and arranged. The length of the overlap L, for example, may again be about 6 inches with the length h of the half portions being progressively longer so as to each be resonant at progressively lower frequencies within the low VHF television frequency band.

Referring to FIGS. 1 and 2 simple conductive director 53 is mounted on boom close to this fed VHF dipole element 55. The director element 53 is arranged to be less than one-half wavelength long at the high end of the high VHF television frequency band to therefore act as a director at the high end of the high VHF television frequency band. Also, an improved impedance match of the forwardmost VHF dipole element 55 to the feed line made up of

conductors

75 and 77 is provided by placing the director 53 close to the feed point of this dipole element 55. 7

improved performance of the antenna array 1 over the entire high VHF television frequency band is provided by the combination of the dipole element 55, full wave resonant at the high VHF band, and the type of dipole element 57 described herein, half wave resonant at the low VHF band. The dipole element 57, like that of dipole element 55, is comprised of a pair of conductive rods overlapping each other at the feed terminal ends. It has been found that by overlapping these conductive rods so as to provide a total overlap of 10 to inches, the overlapped rods together with the dipole element which is full wave resonant at the high band provide effective performance over the entire high VHF television frequency band.

Referring to FIG. 6, a partial cross-sectional view of this overlapped fed dipole element 57 is illustrated. As in the previously described dipole element 55, the

conductive rods

79 and 87 of dipole element 57 are spaced from each other by the insulative support 80 made up of two

portions

80a and 80b, which support the

rods

79 and 87 over a length of about 6 inches. When the

rod elements

79 and 81 are in their extended and operating conditions, these

support halves

80a and 80b interfit as described previously to form a support structure 80. For a further description of one specific way this may be accomplished, see above-cited application Ser. No. 888,478. The electrical connection between the

feed lines

75 and 77 and the

conductive rods

79 and 87 is provided by

flexible strap conductors

58 and 58a respectively. The

conductive rod elements

79 and 87 have an increased overlap length D on either side of the boom 10. By experimentation it has been determined that this additional amount of overlap D on either side of the boom 10 to achieve the improved high VHF television frequency band performance may vary for various arrangements from 2 to 7 inches. A particular overlap, for example, may be an additional overlap D of 6 inches on either side beyond the support 80 or a total overlap, including the 6 inch support, of l 8 inches. In the particular example illustrated, the combination of the fed dipole element 57 and the fed dipole element 55 with the director 53, provide a high level performance over the entire high VHF television frequency band.

Referring to FIGS. 1 and 2, the fed

dipole elements

59 and 61 together with the fed

dipole elements

55 and 57 and reflector 63 and director 35 provide a high level performance over the entire low VHF television frequency band (54 to 88 megahertz). The center fed dipole element 59 has a length between extreme ends of the rods such as to be about one-half a wavelength long at the low end of the low VHF television frequency band (54 to 88 megahertz). The center fed dipole element 61 is arranged to be approximately a half wavelength resonant element at the 54 megahertz (Channel 2). The element 63 has a length slightly greater than one-half wavelength at 54 megahertz and has a spacing from the fed dipole elements so as to act as a parasitic reflector. Referring to FIG. 7 there is illustrated a partial cross-sectional view of a reflector 63.

As in the case of the center fed dipole elements, the

conductive half portions

93 and 94 of the reflector element 63 are overlapped at the region near the boom. By the overlapping of the reflector halves, the reflector halves 94 and 93 are supported over the length of the support 92. This support 92 like that of the other supports may be made of two half portions which interfit together to form a support structure when the

reflector half portions

93 and 94 are in their extended and operating condition as shown. For a further description of how this may be accomplished, see U.S. patent application Ser. No. 888,478, cited above. Electrical connection between

conductors

93 and 94 is provided by

straps

95 and 95a connected between a conductive boom 10 and the respective conductive reflector halves 93 and 94.

Forward of the high VHF television frequency band director element 53 and of all the

VHF dipoles

55, 57, 59 and 61 is a low VHF television frequency band director element 35. Referring to FIG. 8 a portion of the low band director element 35 is shown in cross section. This director element 35 is made up of two director halves 37 and 39 mounted to boom 10 using an insulative support mount 38 in a manner similar to the center fed VHF dipole elements and the reflector element 63. The director halves 37 and 39, as shown, overlap each other and are mounted to the support mount 38. The director halves 37 and 39 extend generally perpendicular to the boom when in operating condition. The director half 37 crosses above the boom 10 with a major portion extending to one side of the boom 10. The director half 39 likewise crosses perpendicular to the boom, but below the boom 10 such as to be parallel aligned and in overlapping relation to the director half portion 37 with the major portion extending to the opposite side of the boom 10. The director half portion 37 is electrically connected to the conductive boom 10 by means of a flexible conductive strap 49. This strap may be, for example, about 3 inches long and may be connected to the director half portion 37 about 4 inches from the end 40. The director half 39 is connected to the conductive boom 10 by means of a similar flexible conductive strap 51. This strap may be, for example, at about the same point along the director half 39 as strap 49. With boom 10 being of conductive material, this provides a direct electrical connection between the director half portion 37 and director half portion 39. The overall length of the rod portions 37 and 39 and

conductive straps

49, 51 and the boom are such that the director 35 operates as a director at the high end of the low VHF television frequency band (bands 54 to 88 megahertz). The structural arrangement as shown with the flexible leads 49 and 51 enable folding of the director for storage or packaging of the antenna.

The director halves 37 and 39 have loops 41 and 43 respectively therealong. These loops 41 and 43 have a diameter, position and overall length along the director halves which enable the operation of the total director 35 to act as a low VHF television band director and yet provide sufficient detuning of signals within the high VHF television frequency band. The particular loop dimensions may be, for example, 4 inches long with 2 inches between the parallel overlapped portions of the loop.

Referring to FIGS. 1, 3 and 4, there is illustrated the manner in which the coupling of a receiver (not shown) to the VHF portion of the antenna array is provided and the manner in which coupling of the receiver to the UHF portion of the array is provided and the manner decoupling of the UHF portion from VHF portion of the antenna array is provided. As mentioned previously, the coupling of the feed line 9 from the receiver (not shown) to the entire UHF and the VHF antenna array is provided by connection conductors 9a and 9b of line 9 respectively at

points

23 and 25 of dipole element 21.

Parallel conductors

75a and 77a are extensions of the

respective conductors

75 and 77 which are the conductors that make up the balanced transmission line feed for the VHF television frequency portion of the array 1.

Referring to FIG. 4 between the feed points 23 and 25 of the dipole 21 and the end points 101 and 103 of

lines

77a and 75a is a high characteristic impedance line 105. This line 105 is made up of a conductor 107 coupled between feed terminal point 25 and point 103 of line 75a and a conductor 109 coupled between point 101 of line 77a and terminal point 23. The transmission line 105 may be arranged to have, for example, a characteristic impedance on the order of 500 ohms. This characteristic impedance may be provided by increased spacing between

conductors

107 and 109 as illustrated in FIG. 4 together with the diameter of the wire of the

conductors

107 and 109.

An effective short circuit is provided between points 101 and 103 at frequencies within the low and high part of the UHF television frequency band (470 to 890 megahertz) by two pairs of quarterwave stubs. Referring to FIG. 4, the first pair of stubs 110 and 111 are connected at point 101 to conductor 77a and conductor 109 of a transmission line 105. Referring to FIGS. 3 and 4, similarly the second pair of stubs 1 13 and 115 are connected at point 103 to conductor 75a and conductor 107 of transmission line 105.

Stubs 110 and 113 are each one-quarter wavelength (ll/4) long at the high end of the UHF television frequency band. The stubs 110 and 113 are arranged so as to be parallel to each other on opposite sides of the boom 10. Stubs 111 and 115 are parallel to each other and are a quarter of a wavelength long at the low end of the UHF television frequency band.

The transmission line 105 has a length on the order of one eighth of a wavelength at the low UHF television frequency band end (470 megahertz). The transmission line 105 together with the effective shorts provided by the

stubs

111, 110, 115 and 113 provide a high impedance at the points 101 and 103 in shunt with the dipole.

In the operation of the above-described arrangement, the junction of stubs 110 and 111 and the junction of

stubs

113 and 115 provide an effective short circuit at the two frequencies of the UHF television frequency band that the stubs are 1/4 resonant. This results in a reactance at the

dipole element terminals

23 and 25 that is large compared to the radiation resistance of the dipole element 21. Consequently, the received power from the dipole element 21 is applied along transmission line 9 toward the receiver (not shown) and is not coupled toward the

VHF dipole elements

55, 57, 59 and 61. The stubs 110 and 1 11, 1 13 and 115 have little effect on the VHF signals traveling along the transmission lines 750 and 77a and consequently, these signals are likewise applied along transmission line 9 toward the receiver (not shown). By making the characteristic impedance of the transmission line 105 high, compensation of the excessive capacity at the

terminals

23 and 25 for the signals in the VHF television frequency band is also provided.

The particular antenna described above and illustrated was found highly effective in both the entire low VHF television frequency band, the high VHF television frequency band and the UHF television frequency band. Its more specific construction details will be better understood by reference to the following details:

Reflector element 63 has an overall length between the extended tips of reflector half 93 and reflector half 94 of 108 inches with a 6 inch overlap between the dipole halves;

Fed dipole element 61, overall length between the outermost tip of conductive rods 83 and 91 is 97 inches with a 6 inch overlap of the conductive rods;

Fed dipole element 59, overall length from the outermost tips of the

conductive rods

81 and 89 is 82% inches with a 6 inch overlap of these conductive rods;

Fed dipole element 57, overall length between outermost tip of

conductive rods

87 and 79 is 68 inches with an 18 inch overlap of these conductive rods;

Fed dipole element 55, overall length between outermost tip of

conductive rods

67 and 68 is 50 inches with a 6 inch overlap of these conductive rods;

Director 53 has an overall length between the outermost tips of 25 inches;

Director 35 has an overall length between the outermost tip of half portion 37 and half portion 39 of 30 inches with 6 inches of overlap of the director half portion 37 and the director half portion 39;

The loops 41 and 43 are elongated loops having a length extending in the direction of the rods of 4 inches and a distance between the parallel section of the loop of 2 inches;

The spacing between elements is as follows: between director 35 and the forwardmost VHF fed dipole element 55 is twelve and one-half inches and the distance between director 53 and fed dipole element 55 is 4% inches. The distance between fed

dipole elements

55 and 57 and 57 and 59 is ll inches and the distance between fed

dipole elements

59 and 61 is 13 inches. The distance between driven element 61 and reflector element 63 is 20 inches.

Referring now to the UHF portion of the antenna described above, fan dipole 21 has a length from the outermost ends of 14% inches with a spacing between the

feed poinm

23 and 25 being 2% inches. Two inches forward of the dipole element 21 is an impedance matching and director element 19 which is 5% inches from end to end. The inner section of the

support parts

28 and 29 of the corner reflector 27 is 8% inches from the feed point of the dipole 21. The

reflector rods

33 and 33a nearest the boom are 23 inches from end to end with the

other rods

31, 31a, 32 and 32a being 20 inches. The directors 13, 15 and 17 are more widely spaced and are 5% inches from tip to tip.

In the VHF coupling and UHF decoupling systems, the shorter stubs and 113 are 4 7/16 inches long and the longer stubs 111 and 115 are 5% inches long. The

conductors

107 and 109 were 3/32 inch diameter rods about 4 inches between

conductors

107 and 109 at the widest parallel point. The length of

conductors

107 and 109 was about 5 inches.

What is claimed is:

1. An antenna effective over two widely separated frequency bands, comprising:

at least two center fed elongated dipole elements each having a pair of terminals located between the extreme elongated ends of said dipole elements, said dipole elements being located in substantially parallel relation to each other,

a transmission line feed connecting the terminals of said fed dipole elements to each other, the first of said dipole elements having a length determined so as to act as a full wave resonator at a frequency within the higher frequency band of the two widely separated frequency bands, the second of said dipole elements having a sufficient length to act as a half wave resonator at a frequency within the lower of the two widely separated frequency bands, said second dipole element including a first and a second rodlike conductor with one of said pair of terminals located along and near one end of said first rod-like conductor and the other one of said pair of terminals being located along and near one end of said second rod-like conductor, said first and second rod-like conductors being spaced from each other and overlapping each other at their feed terminal ends and extending primarily in opposite directions from said feed terminal ends, the amount of the overlap of the first and second rod-like conductors and the orientation of the rod-like conductors relative to said first fed dipole element being determined to provide by the combination of these two fed dipole elements improved higher frequency band performance and improved lower frequency band performance.

2. The combination claimed in claim 1 wherein said first fed dipole element includes a pair of overlapped conductor rods.

3. The combination claimed in claim 1 wherein the higher frequency band is the high VHF television frequency band and the lower frequency band is the low VHF television frequency band.

4. The combination claimed in claim 3 wherein the amount of overlap of the first and second conductors of said second dipole element ranges between ten and twenty inches.

5. A television antenna array effective in both the high VHF television frequency band and the low VHF television frequency band comprising in combination:

at least three center fed dipole elements, each of said fed dipole elements including a first and a second rod-like conductor with said first rod-like conductor being spaced from and overlapping a portion of said second rod-like conductor and extending in a direction primarily opposite that of said first rod-like conductor, each of said fed dipole elements having a pair of feed terminals with one of the pair of feed terminals located along the overlapped portion of said first rod-like conductor and the second terminal of the pair being located along the overlapped portion of said second rod-like conductor, said center fed dipole elements being located in substantially parallel and aligned relation to each other and having spacing and differing lengths to provide effective operation and coverage of the low VHF frequency band,

a transmission line including a pair of conductors with one of the transmission line conductors connecting a terminal of one of said pair of terminals to a terminal of each of the other pair of terminals associated with each dipole and with the second of the transmission line conductors connecting the unconnected terminals to each other,

one of said three fed dipole elements having a length determined so as to act as a full wave resonator at a frequency within the high VHF frequency band,

a second of said three fed dipole elements having a length determined so as to act as a half wave resonator at a frequency within the low VHF frequency band, the first and second rod-like conductor of said second fed dipole element having a length of overlap to provide by the combination of said first and second dipole elements improved performance for the high VHF frequency band.

6. The combination claimed in claim wherein the amount of the overlap of said first and second rod-like conductors of said second fed dipole ranges from 10 to inches.

7. The combination claimed in claim 5 wherein the pair of transmission line conductors are arranged relative to said rodlike conductors such that the successive rod-like conductors connected to each transmission line conductor extend primarily in opposite directions.

8. The combination claimed in claim 7 including an overlapped rod-like reflector having a length greater than a half wavelength at the low end of a low VHF frequency band and positioned at a point along the antenna array furtherest from said first center fed dipole element.

9. The combination claimed in claim 6 including an overlapped rod-like director having a length of less than one-half a wavelength at the high end of the high VHF frequency band positioned near said first fed dipole element.

10. A television antenna effective for signal reception in both the high VHF television frequency band, the low VHF television frequency band and the UHF television frequency band comprising, in combination:

an elongated beam of conductive material having a body of insulative material at one end of said beam,

a fan-like dipole element comprising two identical tapered sheets of conductive material with one narrow end of each of said sheets forming the terminals of said dipole element and being connected to opposed ends of said insulative material, said sheets extending generally perpendicular to said beam and having a length between extreme ends resonant at a frequency within the UHF television frequency band,

at least three center fed VHF television frequency band dipole elements mounted in insulating fashion to said elongated beam, each of said elements including a first and second rod-like conductor with said first rod-like conductor being spaced from and overlapping a portion of said second rod-like conductor and extending in a direction primarily opposite that of said first rod-like conductor, each of said fed dipole elements having a pair of feed terminals with one of the pair of feed terminals located along the overlapped portion of said first rod-like conductor and a second terminal of the pair being located along the overlapped portion of said second rod-like conductor, said center fed dipole elements being located in substantially parallel relation to each other and having spacing and differing lengths to provide effective operation and coverage over the low VHF frequency band,

a transmission line including a pair of conductors with one of the transmission line conductors connecting a terminal of one of said pair of terminals to a terminal of each of the other pair of terminals associated with each dipole element and connected to one terminal of said fan-like dipole element with the second of the transmission line conductors connecting the unconnected terminals of said center fed dipole elements and said fan-like dipole element to each other.

11. The combination claimed in claim 10 wherein said body of insulator material at one end of said beam has apertures therein so arranged to minimize capacity between the fan-like dipole element terminals for signals within the VHF television frequency bands and to provide a long leakage path for moisture which may collect on said insulative spacer.

12. The combination claimed in claim 10 wherein between said fan-like dipole element and said three VHF center fed dipole elements is a grid-like corner reflector.

13. The combination claimed in claim 12 wherein a first one of said three center fed VHF dipole elements nearest said body of insulative material has a length determined so as to act as a full wave resonator at a frequency within the high VHF television frequency band.

14. The combination claimed in claim 13 wherein a second and nearest one of said three VHF fed dipole elements to said first VHF fed dipole element has a length determined so as to act as a half wave resonator at a frequency within the low VHF frequency band and wherein the first and second conductive rods of said second fed dipole element have a length of overlap to provide by the combination of said first and second dipole elements improved performance for the high VHF television frequency band.

15. The combination claimed in claim 14 wherein the pair of transmission line conductors are arranged relative to said rod-like conductors such that the successive rod-like conductors connected to each transmission line conductor extend primarily in opposite directions.

16. The combination claimed in claim 15 including an overlapping rod-like reflector having a length greater than a half wavelength at the low end of the low VHF television frequency band positioned at a point near the end along said elongated conductive beam furtherest from said body of insulative material.

17. The combination claimed in claim 16 including a first rod-like director spaced between said corner reflector and said first of said center fed dipole elements having a length less than one-half wavelength at the high end of the high VHF frequency band, and a second rod-like director mounted to said beam between said first director and said corner reflector and extending in a generally perpendicular direction to the beam having a pair of inductive loops along said second director with one inductive loop being on either side of said beam, said inductive loops and the length of said director being arranged so that said director acts as a director at frequencies within the low VHF television frequency band and is essentially detuned as to frequencies within the high VHF television frequency band.

18. The combination claimed in claim 17 wherein said gridlike corner reflector includes a plurality of rod-like elements extending parallel to said center fed dipole elements and these rod-like elements of said corner reflector are arranged to act as director elements for signals at the high end of the high VHF television frequency band.

19. The combination claimed in claim 18 wherein a pair of shunting stubs are coupled to each one of said transmission line conductors between said fan-like dipole element and said first of said center fed VHF dipole elements with one of the pair of stubs having a length approximately equal to onequarter wavelength at a frequency at the low end of the UHF television frequency band and the other of the pair of stubs having a length approximately equal to one-quarter wavelength at a higher frequency within the UHF television frequency band.

20. A multifrequency antenna system for both the high VHF television frequency band and the low VHF television frequency band comprising:

a plurality of center fed dipole elements with the center portions of the dipole elements connected to each other by a transmission line feed, each of said center fed dipole elements having two conductive rod-like half portions which overlap near the center feed portion and extend in opposite directions from the center feed,

a first of said plurality of center fed dipole elements having a length determined so as to be full wave resonant at a frequency within the high VHF television frequency band,

a second and nearest one of said plurality of center fed dipole elements to said first center fed dipole element having a length determined to be half wave resonant at a frequency within the low VHF television frequency band, the first and second conductive rod-like portions of said second center fed dipole element having a length of overlap near the center feed to provide by the combination of said first and second center fed dipole elements increased performance of the antenna system over the entire high VHF television frequency band.

Claims

1. An antenna effective over two widely separated frequency bands, comprising: at least two center fed elongated dipole elements each having a pair of terminals located between the extreme elongated ends of said dipole elements, said dipole elements being located in substantially parallel relation to each other, a transmission line feed connecting the terminals of said fed dipole elements to each other, the first of said dipole elements having a length determined so as to act as a full wave resonator at a frequency within the higher frequency band of the two widely separated frequency bands, the second of said dipole elements having a sufficient length to act as a half wave resonator at a frequency within the lower of the two widely separated frequency bands, said second dipole element including a first and a second rod-like conductor with one of said pair of terminals located along and near one end of said first rod-like conductor and the other one of said pair of terminals being located along and near one end of said second rod-like conductor, said first and second rod-like conductors being spaced from each other and overlapping each other at their feed terminal ends and extending primarily in opposite directions from said feed terminal ends, the amount of the overlap of the first and second rod-like conductors and the orientation of the rod-like conductors relative to said first fed dipole element being determined to provide by the combination of these two fed dipole elements improved higher frequency band performance and improved lower frequency band performance.

5. A television antenna array effective in both the high VHF television frequency band and the low VHF television frequency band comprising in combination: at Least three center fed dipole elements, each of said fed dipole elements including a first and a second rod-like conductor with said first rod-like conductor being spaced from and overlapping a portion of said second rod-like conductor and extending in a direction primarily opposite that of said first rod-like conductor, each of said fed dipole elements having a pair of feed terminals with one of the pair of feed terminals located along the overlapped portion of said first rod-like conductor and the second terminal of the pair being located along the overlapped portion of said second rod-like conductor, said center fed dipole elements being located in substantially parallel and aligned relation to each other and having spacing and differing lengths to provide effective operation and coverage of the low VHF frequency band, a transmission line including a pair of conductors with one of the transmission line conductors connecting a terminal of one of said pair of terminals to a terminal of each of the other pair of terminals associated with each dipole and with the second of the transmission line conductors connecting the unconnected terminals to each other, one of said three fed dipole elements having a length determined so as to act as a full wave resonator at a frequency within the high VHF frequency band, a second of said three fed dipole elements having a length determined so as to act as a half wave resonator at a frequency within the low VHF frequency band, the first and second rod-like conductor of said second fed dipole element having a length of overlap to provide by the combination of said first and second dipole elements improved performance for the high VHF frequency band.

6. The combination claimed in claim 5 wherein the amount of the overlap of said first and second rod-like conductors of said second fed dipole ranges from 10 to 20 inches.

7. The combination claimed in claim 5 wherein the pair of transmission line conductors are arranged relative to said rod-like conductors such that the successive rod-like conductors connected to each transmission line conductor extend primarily in opposite directions.

10. A television antenna effective for signal reception in both the high VHF television frequency band, the low VHF television frequency band and the UHF television frequency band comprising, in combination: an elongated beam of conductive material having a body of insulative material at one end of said beam, a fan-like dipole element comprising two identical tapered sheets of conductive material with one narrow end of each of said sheets forming the terminals of said dipole element and being connected to opposed ends of said insulative material, said sheets extending generally perpendicular to said beam and having a length between extreme ends resonant at a frequency within the UHF television frequency band, at least three center fed VHF television frequency band dipole elements mounted in insulating fashion to said elongated beam, each of said elements including a first and second rod-like conductor with said first rod-like conductor being spaced from and overlapping a portion of said second rod-like conductor and extending in a direction primarily opposite that of said first rod-like conductor, each of said fed dipole elements having a pair of feed terminals with one of the pair of feed terminals located along the overlapped portion of said first rod-like conductor and a second terminal of the pair being located along the overlapped portion of said second rod-like conductor, said center fed dipole elements being located in substantially parallel relation to each other and having spacing and differing lengths to provide effective operation and coverage over the low VHF frequency band, a transmission line including a pair of conductors with one of the transmission line conductors connecting a terminal of one of said pair of terminals to a terminal of each of the other pair of terminals associated with each dipole element and connected to one terminal of said fan-like dipole element with the second of the transmission line conductors connecting the unconnected terminals of said center fed dipole elements and said fan-like dipole element to each other.

18. The combination claimed in claim 17 wherein said grid-like corner reflector includes a plurality of rod-like elements extending parallel to said center fed dipole elements and these rod-like elements of said corner reflector are arranged to act as director elements for signals at the high end of the high VHF television frequency band.

19. The combination claimed in claim 18 wherein a pair of shunting stubs are coupled to each one of said transmission line conductors between said fan-like dipole element and said first Of said center fed VHF dipole elements with one of the pair of stubs having a length approximately equal to one-quarter wavelength at a frequency at the low end of the UHF television frequency band and the other of the pair of stubs having a length approximately equal to one-quarter wavelength at a higher frequency within the UHF television frequency band.

20. A multifrequency antenna system for both the high VHF television frequency band and the low VHF television frequency band comprising: a plurality of center fed dipole elements with the center portions of the dipole elements connected to each other by a transmission line feed, each of said center fed dipole elements having two conductive rod-like half portions which overlap near the center feed portion and extend in opposite directions from the center feed, a first of said plurality of center fed dipole elements having a length determined so as to be full wave resonant at a frequency within the high VHF television frequency band, a second and nearest one of said plurality of center fed dipole elements to said first center fed dipole element having a length determined to be half wave resonant at a frequency within the low VHF television frequency band, the first and second conductive rod-like portions of said second center fed dipole element having a length of overlap near the center feed to provide by the combination of said first and second center fed dipole elements increased performance of the antenna system over the entire high VHF television frequency band.