Broad-band antenna having folded dipoles with hairpin transformers
United States Patent 11 1 Kay BROAD-BAND ANTENNA HAVING FOLDED DIPOLES WITH HAIRPIN TRANSFORMERS [75] Inventor: James C. Kay, Rome, Ga. [73] Assignee: Kay-Townes lnc., Rome, Ga.  
 [22] Filed: Apr. 23, 1973 [21] Appl. No.: 353,435  
 Primary Examiner-11 Lieberman Attorney, Agent, or Firm-Freeman &amp; Taylor Apr. 1, 1975 [5 7] ABSTRACT A broad-band antenna characterized by having a folded dipole that includes first and second open center portions with a broad-band transformer element spanning one of said open center portions while transmission line feed points are located at the opposed sides of the other open center portion, with this arrangement permitting the transformer element to electrically lengthen the antenna into half-wave folded dipole antenna for the reception of low-band signals while also simultaneously electrically opening the antenna into a full-wave dipole antenna for high-band reception. By the use of a single antenna to receive two bands from a broad-band spectrum, size and weight are reduced while simultaneously achieving a greater gain in decibels than would otherwise occur absent the use of the arrangement above-described.  
 2 Claims, 13 Drawing Figures PATENTEUAPR 1 1915 sawan g 3 FIG. 7  
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 BROAD-BAND ANTENNA HAVING FOLDED DIPOLES WITH HAIRPIN TRANSFORMERS BACKGROUND OF THE INVENTION In the art of television antenna construction, it has long been known that dipoles can be employed for the purpose of receiving a television signal. with the length of the dipole being accurately established to correspond to all or part ofa wave length and with half-wave length folded dipole antennas being well known in the art.  
  Also it has been known in the art to provide straight or &#34;Yagi types of antennas that comprise a length of tubing cut to the proper length to receive a given signal.  
  At the present time in the art of television antenna reception. an antenna may be made up of an array of dipole elements so as to permit reception of all of the twelve VHF television channels. In practice the dipoles correspond in width, with the widest of the dipoles being adapted to receive the so-called low-band frequencies.  
  In this regard channels 2 through 6 are normally referred to as low-band frequencies, while channels 7 through 13 are normally referred to in the art as highband frequency VHF channels. Also in this regard the low band is generally considered to extend from 54 MHz to 108 MHz, while the high-band frequencies extend from I74 MHz to 2l6 MHz.  
 DESCRIPTION OF THE PRIOR ART The prior art has been described above to the best of Applicants knowledge, with literature and writings existing to show the state of the art and with no definite reference being made to any specific patent in this regard.  
  Applicants prior US. Pat. No. 2,701,308 is representative of the prior art above-noted.  
 SUMMARY OF THE INVENTION It has been discovered that ifa hairpin&#34; transformer element is properly interposed across certain of the terminals of each of the several folded dipoles in a multiband array, the result will be an improved antenna adapted to receive selected frequency bands from a broad range of the high and low VHF frequency bands.  
  In this regard and for the purpose of low-band reception. the transformer will electrically lengthen the dipole for the reception of a low-band signal.  
  On the other hand and as regards high-band reception, the transformer will, in effect, open the dipole to create a full-wave dipole for highfrequency recep tion.  
  By this arrangement and with each dipole when considered as an element. in effect. doing the work of at least two dipole elements of the prior art, both the number of elements and their size can be materially reduced. with the result that a more efficient and compact multi-band antenna unit will be produced. It will also be noted that in high-band operation, additional gain in terms of decibels is achieved from a single folded dipole containing the hairpin transformer element. When viewed electrically the hairpin transformer changes the characteristics of the folded dipole during operation in the high-band so that it resonates as a full-wave length antenna instead of a half-wave length antenna. As a consequence, the amplitude of the high-band VHF signal is doubled in this mode of operation.  
  Production of an improved antenna incorporating the above features accordingly becomes the principal object of this invention, with other objects of the inven tion becoming more apparent upon a reading of the following brief specification considered and interpreted in view of the accompanying drawings.  
 OF TH E DRAWINGS FIG. 1 is a perspective view of the improved antenna.  
 FIG. 2 is a schematic view ofa type ofa typical priorart antenna.  
  FIG. 3 is a schematic diagram of the improved antenna element.  
  FIG. 4 is a typical high-band VHF polar pattern of a resonant dipole for low-band VHF frequency.  
  FIG. 5 is a similar polar pattern illustrating the polar pattern of the improved antenna at high-band frequencies.  
  FIG. 6 is a schematic view of a standard prior-art folded dipole of half-wave length, low-band frequency.  
  FIG. 7 is a similar schematic view illustrating the improved antenna and showing the reduced width thereof.  
  FIG. 8 is a schematic view of a standard half-wave length folded dipole for high-band frequency.  
  FIG. 9 is a schematic view (as seen electrically although in physical size and appearance it is the same as that shown in FIG. 7) of the full length high-band frequency element of the improved antenna.  
  FIG. 9A is an electrical schematic view of the element acting as a half-wave, low-band element.  
  FIG. 9B is an electrical schematic view of the element acting as a full-wave. high-band element.  
  FIG. 10 is a graph illustratrating the frequency versus amplitude characteristics of the high-band elements of the improved antenna showing their additive effect and the increased gain of the signal received.  
  FIG. 11 is a schematic view similar to FIG. 2 and illustrating the improved antenna wherein several individual improved elements containing the hairpin transformer have been utilized.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings and in particular to FIG. I thereof. the improved antenna. generally designated by the numeral 10, includes the usual mast ll, boom 12, and transmission line 13 with a series of antenna elements I4, l5, l6, l7, and 18 being secured to the boom I2 through identical insulating clamps l9, l9, and with the transmission wires being cross-phased as shown in FIGS. 2 and II in a manner well known in the prior art and with these units being appropriately spaced from each other along the boom 12 in accordance with accepted design techniques.  
  In this regard the transmission line is preferably attached first to the element 14 and thence rearward in cross-phased relationship in a manner well known in the art and as shown in FIGS. 2 and II.  
  Directors 20, 20a, and 20b are also secured to the boom for the usual purpose and serve as parasitic elements in a manner well known in the art. UHF components 23, 24, 24 are shown positioned forwardly of the director 20 for the purpose of permitting reception of UHF signals.  
  Each element 14 through 18 is essentially constructed in the same fashion and accordingly includes a dipole portion 25 and a hairpin transformer portion 26. Each dipole portion 25 is made up of identical U- shaped portions 250 and 25b, with the center being supported on the insulating means 19 and with the space between the U-shaped dipole components being referred to as an open center&#34; portion. Mechanically each hairpin transformer 26 is secured at its ends to opposite sides of one open center portion as shown in FIG. I, while the remaining open center portion is secured to the feed points 27a and 27b for the transmission lines. In this regard there is a metal-to-metal connection between the transformer 26 and the dipole components 25a and 25b, with this usually being done by riveting or otherwise securing these components to gether in supported position on the support members 19.  
  Also in this regard the individual dipole components are generally and preferably made of tubular aluminum for cost and lightweight characteristics. Similarly the hairpin transformer components are preferably made of aluminum wire or rod again for the purpose of achieving low-cost and lightweight characteristics.  
  The insulating means l9, 19 are preferably made of plastic or other electrically non-conductive material.  
  In the prior-art structure shown in FIG. 2, a series of driven elements 30, 31, 32, 33, 34, 35, 36, and 37 are shown mounted on the boom 38 in cross-phased relationship. while directors 39, 40, 41, 42, and 43 are positioned between the antenna elements as shown in FIG. 2, with a reflector 44 also being employed in known fashion. In this instance the lead-in line would initially be attached to the element 30 and thence rearward at cross-phased relationship until connected to the longest element 37.  
  In FIG. 3 the points 50, 51 indicate the distance of one of the open center portions, with the hairpin transformer 26 spanning this open center portion in the manner shown in FIGS. I and 3.  
  Feed points 52, 53 define the distance of the remaining open center portion and serve as the point of attachment for the transmission feed line.  
  Regarding the antenna elements 14 through 18, it will be noted from the drawings that antenna element 14 is the shortest. with the elements being gradually increased in length until the maximum length is achieved in the antenna element 18.  
  Referring now to FIGS. 4 and which represent polar patterns, it will be noted that FIG. 4 is representative of a typical low-band element performing at highband frequencies. It will also be noted that a plurality of lobes 54, 54 are provided in contrast to the bidirectional lobes 55, 55 shown in FIG. 5. The presence of lobes other than bi-directional lobes is indicative of poor operational characteristics in the form of ghosts. weak reception, etc.  
  The schematic views shown in FIGS. 6 through 9 are intended to graphically illustrate the improved dimensional characteristics of the subject antenna, with FIG. 6 schematically illustrating a standard half-wave length folded dipole for low-band frequency, while FIG. 7 shows the reduced width of the improved antenna of this invention. which is electrically equivalent to that shown in FIG. 6.  
  FIG. 8 shows schematically the length of a half-wave length high frequency folded dipole, while FIG. 9 illustrates schematically the width of the full-wave length high frequency dipole that is electrically achieved by the present invention from a dipole of the same physical dimensions as shown in FIG. 7.  
  Thus it will be seen that FIG. 7 shows that the antenna element is not only narrower but does perform the function of the prior-art dipole elements shown in FIGS. 6 or 8 in a single element, thus reducing the number of dipole elements as well as their overall size.  
  FIG. 10 is intended to indicate the characteristics of the improved antenna containing the hairpin transformer that are in part achieved by the fact that the structure operates as a full-wave length high-band dipole with increased incoming signal strength of several decibels.  
  Thus in FIG. 10 the line 58 indicates the output voltage of the section 25b, while the line 59 would be indicative of the output voltage of section 250. The full line 60 represents the total output voltage of the element, and it will be noted that in terms of amplitude, a considerable decibel gain has been achieved by the improved arrangement of this invention.  
  The operation of the antenna can perhaps be best understood by reference to FIG. 3 of the drawings.  
  In operation it is, of course, understood that the entire element is a resonant element, and in instances of low-band operation the entire dipole, including the transformer 26, will be resonant so as to, in effect, have an electrically lengthened folded dipole element.  
  In instances of high-band operation only the portions represented by the components 250 and 25b are resonant, with each of these being the equivalent of a onehalf wave length so that a full wave length high-band element is achieved.  
  Thus where the term hairpin transformer&#34; is used, it is to be understood that it is used more in a physical sense than it is in a usual electrical sense in that the element 26 in FIG. 1 serves to transform&#34; the dipole from a long length low-band circuit of the type schematically illustrated electrically in FIG. 9A to a pair of high-band electrical circuits of the type shown in FIG. 9B.  
  Thus in FIG. 9A there is provided a low pass filter that consists of resistors 71, 71 and a capacitor 72 electrically arranged as shown in FIG. 9A to form a low pass filter that electrically extends the length of the element as a low-band element.  
  On the other hand, in FIG. 9B capacitors 73, 73, in effect, electrically short the element into a pair of halfwave length, high-band elements that cooperate as shown in FIG. 98 to form a full length high-band element.  
  Similarly, while the invention has been described in the preferred embodiment thereof in connection with the conventional high and low VHF bands, it is believed apparent that the principles herein stated could be employed beyond the ranges that have been set forth in the specification as parameters.  
  While a full and complete description of the invention has been set forth in accordance with the dictates of the Patent Statutes, it is to be understood that the invention is not intended to be limited to the specific embodiment herein shown.  
  Accordingly, modifications of the invention may be resorted to without departing from the spirit hereof or the scope of the appended claims.  
 What is claimed is:  
  5 6 l. A broad-band antenna adapted to be received provided between said dipoles. upon the usual mast and comprising; 3. feed means connected between the opposed tera Q minals of said dipoles on one side thereof. and  
  l&#39; of antenna elements f P E Y X 4. a hairpin transformer component of different creasing silld boom fight material and lesser length than either of said diangle relat1onship therewith, with the shortest of pole elements. lg eblemenls 3 fifl gf q i f f end E. said hairpin transformer spanning the remaining Com e es 0 Sal e open surface between the remaining terminals of being mounted ad acent the rearward portion thereof, said dipoles and C. feed means adapted to transmit a signal to said ele- Serving as a low-pass. filter for the recepnon of ments. low-band frequency signals, and  
 D. each said element including 2. serving as a capacitor for the reception of high- I. a pair of U-shaped dipole elements. band frequency g 2 Support means adapted to support i dipole 2. The antenna of claim 1 further characterized by ements in coplanar facing r lati hi h i h the fact that the hairpin transformer circuit is at right while simultaneously securing the same to said angles to the plane of said dipoles. boom whereby a pair of open center portions are