US 3369245 A
Description (OCR text may contain errors)
Feb, 13, 1968 N. J. REA 3,369,245
WING TYPE DIPOLE WITH END MOUNTED STUBS Filed Dec. 10, 1964 2 Sheets-Sheet 1 ENVENTOR A/aPA/w/v MEL-w ATTORNEY Feb, 13, 19 N. .J. REA 3,359,245
WING TYPE DIPOLE WITH END MOUNTED STUBS Filed Dec. 10, 1964 2 Sheets-Sheep United States Patent 3,369,245 WING TYPE DIPOLE WITH END MOUNTED STUBS Norman .1. Rea, Sherburne, N.Y., assignor to Technical Appliance Corporation, Sherburne, N.Y., a corporation of Delaware Filed Dec. 10, 1964, Ser. No. 417,341 13 Claims. (Cl. 343--795) ABSTRACT OF THE DISQLGSURE A 'broad band dipole antenna employing twin tapered arms which narrow toward the center conductor. The invention being the addition of a pair of spaced conductor elements to the outer broad end of the tapered dipole arms, which elements extend beyond said arms and constitute quarter wave stubs in the high-frequency range of the antennas reception band. The addition of said elements electrically lengthens the dipole only to the lower frequencies of the reception band.
This invention relates to antennas and more particularly to antennas which are to be used over a broad range-of frequencies.
A principal object of the invention is to provide a novel dipole antenna of the socalled biconical or bow-tie kind.
Another object is to provide a biconical antenna which is capable of efficient operation in the ultra-high frequency spectrum over a frequency range of 2 to 1.
Another object is to provide a more efiicient dipole driver element for dish shape reflectors and the like.
A feature of the invention relates to a biconical dipole having its outer or divergent ends provided with spaced extensions which are so dimensioned as to render the antenna capable of eflicient operation over at least a 2 to 1 frequency range.
Another feature relates to a broad band biconical dipole having integral spaced extensions whereby the antenna permits the currents to be distributed in phase throughout the entire length of the dipole at the lower frequency end of the band, Whereas at the higher frequency end the currents are confined to the main body portion of the dipole as a result of the extensions acting as quarter wave stubs at the said higher frequencies.
Another feature relates to a broad band biconical dipole having integral spaced extensions at the outer divergent ends of the dipole whereby the length of the antenna is automatically shortened electrically at the higher frequencies, thus enabling a more constant pattern of beamwidth to be maintained.
A further feature relates to the combination of a dish shaped reflector and dipole driver therefor, which enables optimum illumination of the reflector to be obtained over a greater'bandwidth than is possible with the prior known biconical dipole-driven reflectors.
A still further feature relates to the novel organization, arrangement and relative proportioning of parts which cooperate to provide an improved biconical dipole antenna.
Other features and advantages not specifically enumerated will become apparent after a consideration of the following detailed descriptions and the appended claims.
In the drawing:
FIGS. 1 and 2 are explanatory diagrams showing the electrical characteristics of the known biconical dipole;
FIG. 3 is a plan view of a biconical dipole embodying the inventive concept and showing the associated current distribution and field pattern characteristics thereof at the lower end of the frequency band for which the antenna is designed;
FIG. 4 is a right-hand end view of the antenna of FIG. 3;
3,369,245 Patented Feb. 13., 1968 FIG. 5 is a plan view of the antenna similar to that of FIG. 4 but showing the current distribution characteristics and field characteristics of the antenna when operating at the higher end of the frequency band;
FIG. 6 is a view showing the improved dipole in combination with an associated dish shaped reflector;
FIGS. 7, 8 and 9 represent respective modifications of the antenna of FIGS. 3 and 5;
FIG. 10 is a portion of a standard Smith chart used in explaining the invention.
In the present UHF television range of 470'890 mc., one of the problems is the provision of an antenna, specifically a dipole, which is capable of Working efficiency over at least a 2 to 1 range between the lowermost frequency and the uppermost frequency of the band. The wellknown biconical or bow-tie dipole has been used heretofore for that purpose because of its desirable broad band impedance characteristics. However, the impedance plot for such biconical antenna as a function of physical length with respect to electrical wavelength shows certain limitations. Thus, in FIG. 10, which is a portion of a standard Smith chart, it will be seen that in order to stay within the 2 to 1 VSWR circle 10 with the impedance (admittance) values normalized with respect to the characteristic impedance of for example a 300 ohm dissipationless line, the overall physical length L of the dipole must be cut to a length of .65 wavelength at the lower frequency, for example 470 mc. This length L, namely 16.25 inches, therefore represents 1% wavelengths at the upper end of the band, for example 890 me. Since the individual elements 11 and 12 of the biconical dipole are in excess of /2 wavelength at the upper frequencies, out-of-phase currents are set up at the said higher frequencies. Thus in FIG. 1 the current distribution throughout the length of the conventional biconical dipole at the low frequency end of the band is represented by the dotted curve 13 and the corresponding field pattern is represented by the curve 14. However, at the high frequency end of the band the current distribution as shown in FIG. 2 is represented by the dotted curve 15 and the corresponding field pattern is represented by the multi-angularly lobed curve 16. While, therefore, the conventional biconical antenna produces a satisfactory field pattern at the lower frequencies, its field pattern at the higher frequencies is unsatisfactory.
I have found that the disadvantages of the conventional biconical dipole can be avoided by proportioning the lengths of the dipole arms 11 and 12 and by providing them with spaced extensions 17, 18 and 19, 241 of a length D as shown in FIGS. 3 and 5. In FIGS. 3 and 5 the parts which are the same as those in FIGS. 1 and 2 bear the same designation numerals. Thus, in FIGS. 3 and 5 the physical overall length L is the same as the overall length -L of FIGS. 1 and 2. Under the frequency .range assumed, the length L would then be 16 /2 inches, that is 1.25 )t wherein A is the frequency at which the antenna is functioning. However, the biconical arms 11 and 12 have an overall length L which is shorter than L by the length 2D where D=2% inches.
The extensions 17, 18 and 19, 2t] constitute effective physical and electrical lengths of the antenna when operating at the lower frequency range since they are very short in terms of wavelength at that range, and the current flow as represented by the curve 13 is the same as for the antenna of FIG. 1 and likewise the field pattern 14 is the same as that of FIG. 1. However, at the upper part of the frequency range the extensions 17, 18 and 19, 20 become quarter wave in length, effectively blocking current flow and thus rendering the effective electrical length of the antenna L as shown in FIG. 5. By this effective blocking of the current flow at the higher frequency, the current distribution in the dipole arms is in phase across the length J L and the desired FIGURE 8 field pattern 14 is maintained. By this quarter wave stub action of the extensions 17, 18 and 19, 20, current flow is blocked at the points E, thus confining the current distribution to the tapered solid sections 11 and 12 of the dipole, as indicated by the arrows.
It will be understood, of course, that the dipole arms 11 and 12 of FIGS. 3 and 4 are connected to a suitable transmission line 21 which for example may be a standard 300 ohm line.
While the antenna above described has the desired advantages mentioned, it has a special advantage when used as a driver element in association with a dish shaped eflector as shown in FIG. 7 wherein the dipole of FIGS.
3 and is supported at the optimum illumination point in front of the concave surface of a dish shaped reflector 22 of any well-known design. In this combination, the driver dipole is automatically shortened at the higher fre quencies and a more constant pattern of reflected beamwidth from the reflector 22 is maintained. In other words, this permits a more optimum illumination of the reflector 12 over a greater bandwidth than is possible with the conventional biconical dipole.
While the drawing shows the extensions 17, 18 and 19, 20 in the form of parallel arms, it will be understood that the arms may be inclined away from each other as schematically represented in FIG. 8 or toward each other as schematically illustrated in FIG. 9, or if desired, they may be curved and divergent as schematically illustrated in FIG. 10.
Various other changes and modifications may be made in the disclosed embodiments without departing from the spirit and scope of the invention. Thus, while in the foregoing the dipole arms 11 and 12 have been described and illustrated in the form of non-perforated conductive plates, it will be understood that they may be in the form of wire mesh or perforated metal plates.
In one particular antenna that was found to produce the desired results, the tapered arms 11 and 12 were symmetrical, each having a taper of 55 degrees with the width of the gap between the adjacent apices inch; the length of each conical arm from apex to base was 5 /2 inches; the spacing S between the projections 17, 18 and also between the projections 19, 20 was 4 /8 inches, and the line 21 was a 300 ohm line.
What is claimed is:
1. A dipole antenna for broadband operation, comprising a pair of dipole arms each tapered from a narrow to a broad end having their narrow ends in gapped relation for connection to a feed line, the broad ends of said arms having respectively pairs of spaced extensions for automatically increasing the electrical length of the dipole arms beyond their physical length only at the lower region of said band, said extensions extending from said arms in the direction of their increasing length, each of said extensions constituting a quarter-wave stub line only at a particular frequency range.
2. A dipole antenna comprising a pair of tapered antenna arms with their apexes in gapped relation for connection to a feed line, each arm terminating at its broad end in a pair of spaced integral extensions which extend from said arms in the direction of their increasing length, each of said extensions constituting a quarter- Wave stub line only at a particular frequency range.
3. An antenna according to claim 2 in which each of said arms is in the form of a triangular metal plate.
4. A dipole antenna for broad-band operation, comprising a pair of tapered dipole arms with the narrow ends in gapped relation for connection to a feed line, the opposite ends of said arms having respective extensions each of which act to shorten the electrical length of the antenna to the combined length of said dipole arms by forming a quarter-wave stub line only at the higher region of said band, said extensions extending from said arms in the direction of their increasing length, each of said extensions constituting a quarter-wave stub line only at a particular frequency range.
5. A broad-banding dipole antenna, comprising a pair of tapered antenna arms with their tapered ends in gapped relation for connection to a feed line, each arm terminating in a respective pair of spaced extensions which extend in the direction of increased length of said arms for enabling said arms and extensions to constitute a half-Wave antenna at the lower region of said band, and which automatically enable only the tapered arms to constitute a half-wave antenna at the higher region of said band.
6. A broad-band dipole antenna according to claim 5 in which said extensions are proportioned in length and spacing to provide a short circuit stub line at the end of each arm at said high frequency region.
7. A broad-band antenna, comprising a pair of triangular antenna arms with their apexes in gapped relation for connection to a feed line, the non-gapped opposite ends of each arm having a pair of spaced integral extensions extending in the direction of increasing length of said arms of such length that the current in the arms is maintained in phase over the entire broad band.
8. In combination, a dish-shaped reflector having mounted in front thereof for illumination purposes, a dipole antenna comprised of two triangular arms with their apexes in gapped relation, the outer ends of each arm provided with a pair of spaced extensions.
9. The combination according to claim 8 in which the said extensions of each pair are parellel.
10. The combination according to claim 8 in which the said extensions of each pair are outwardly divergent.
11. The combination according to claim 8 in which the said extension of each pair are inwardly divergent.
12. The combination according to claim 8 in which the said extensions of each pair are curved.
13. A dipole antenna for broad-band operation, comprising a pair of triangular dipole arms having their narrow ends in gapped relation for connection to a feed line; each arm terminating in a pair of extensions which increase the length of said arms and with the outer edge of each such extension being a continuation of the outer tapered edge of said dipole arms.
References Cited UNITED STATES PATENTS 2,460,869 2/1949 Braden 343840 2,622,197 12/1952 Cruser 343802 2,648,768 8/1953 Woodward 343802 2,656,463 10/1953 Woodward 343795 2,683,808 7/1954 Shumacher 343-807 X 2,724,052 11/ 1955 Boyer 343-840 ELI LIEBERMAN, Primary Examiner.
HERMAN K. SAALBACH, Examiner.