US3321764A - Television antenna - Google Patents

Television antenna Download PDF

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US3321764A
US3321764A US593228A US59322866A US3321764A US 3321764 A US3321764 A US 3321764A US 593228 A US593228 A US 593228A US 59322866 A US59322866 A US 59322866A US 3321764 A US3321764 A US 3321764A
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elements
dipole
band
driven
unitary
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US593228A
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John R Winegard
Carey W Shelledy
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Winegard Co
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Winegard Co
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
    • H01Q5/40—Imbricated or interleaved structures; Combined or electromagnetically coupled arrangements, e.g. comprising two or more non-connected fed radiating elements
    • H01Q5/48—Combinations of two or more dipole type antennas
    • H01Q5/49—Combinations of two or more dipole type antennas with parasitic elements used for purposes other than for dual-band or multi-band, e.g. imbricated Yagi antennas

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  • the present invention relates to an improved television antenna having three or more low VHF band driven elements in which unitary high VHF band elements in close vertical spacing in relation to some or all the driven element-s impart, by coupler action, favorable high VHF band characteristics.
  • the principal television frequency bands now in use are the VHF bands. These cover 54 to 88 megacycles and 174 to 216 megacycles. Effective VHF antenna operation requires that there be efficient reception in both bands. However, the frequency range from the low end of the low VHF band to the high end of the high VHF band is four to one. This is too great for the effective use of a simple dipole arrangement. And even within the range of the low band (54 to 88 megacycles), the highest frequency is on the order of about sixty percent greater than the lowest frequency. The high band (174 to 216 megacycles), while of smaller spread on a percentage basis, also imposes problems because of the range involved. Because of these large frequency ranges both between the low band and the high band and within each band, effective antennas for all-channel reception require some means of extending the antenna frequency range beyond that of a simple dipole.
  • One technique for extending the frequency range of a television antenna is to use a plurality of driven elements.
  • a plurality of driven elements Considering the low band, for example, there are a total of five television channels (2 to 6, inclusive).
  • a series of five dipole elements, one tuned for good reception in each band, may be used in coplanar aligned relation, the channel 2 driven element in the rear and the other elements progressively in front of the same.
  • a smaller or even larger number of driven elements may be used, with their most effective frequencies spread over the 54 to 88 megacyc-le range to provide a balancing effect and generally favorable gain and directivity.
  • Antennas of the above type are, however, not nearly as effective in the high band as in the low band. This is because the driven elements themselves do not operate effectively at frequencies of the order of three times their half wave resonant frequencies. Particular techniques of driven element construction in some measure overcome this difficulty, especially with a small number of driven elements. But where three or more driven elements are used the art has generally used a simple folded dipole, V- dipole, or straight dipole configuration and has accepted the limited performance of these in the high band.
  • the present invention is based on the discovery that the benefits of a multi-driven element antenna can be obtained on the high hand through high band elements located in vertically spaced relation to the adjacent driven element and spaced therefrom for coupling action. While it has been known that unitary high band elements can influence the operation of a low band dipole in ways other than director action, it has been thought that such influence is best achieved with the dipole in front of the driven element where it also acts as a director. This has been the practice both with antennas having one or two driven elements and with antennas having a larger number of driven elements.
  • the antenna consists of three or more dipole driven elements, the elements being of length to serve most efficiently as half wave elements in (the frequency) spread over the 54 to 88 megacycle band.
  • Each is mounted above a boom and is connected to the others by an open wire transmission line having its conductors crossed between each adjacent pair of elements. The spacings are chosen to provide most effective low band operation.
  • a unitary high band element is mounted below the boom from one to four inches below each of these driven elements.
  • a director system is disposed in front of the forward dipole driven element, the same consisting of a pair of aligned coaxial high band directors straddling the boom in front of the forward driven element and a dipole director in front of the same, the dipole director being defined by a pair of insulated dipole arms straddling the boom and connected by a coupler effective to provide director action in the low band and in the high band to define a sufficient impedance in connection with other antenna elements to avoid detracting from high band gain.
  • a unitary high band director is located in front of the dipole director.
  • the antenna includes a low band reflector located behind the rear driven element and in the plane of the low band driven elements.
  • the reflector further includes a high band reflector suspended from about one to four inches below the same.
  • a high band reflector suspended from about one to four inches below the same.
  • Antennas constructed in accordance with the present invention are characterized by high gain, flat frequency response over each television channel, good impedance match, favorable directivity patterns and band width sufficient to cover the TV high and low VHF frequency bands.
  • a more particular object of the present invention is to provide an improved television antenna in which a plurality of aligned coplanar low band driven elements define an effective low band array and unitary high band elements located in vertically spaced relation to each of the driven elements impart effective high band characteristics to the same through the medium of coupling action devoid of substantial director or'reflector action.
  • Still another object of the present invention is to provide an improved television antenna in which effective low band performance is provided by a plurality of low band driven elements cut to lengths that provide relatively uniform effective action spread over the low frequency band and in which a similar number of unitary high band elements cooperate respectively with the low band driven elements and are cut to lengths that provide relatively uniform, effective action spread over the high frequency band, the high band elements being in vertically spaced relation to the respective low band elements and spaced for coupling action in relation thereto.
  • FIGURE 1 is a view in perspective of an antenna constructed in accordance with the preferred form of the present invention.
  • FIGURE 2 is a top plan view to a smaller scale of the antenna of FIGURE 1;
  • FIGURE 3 is an enlarged fragmentary cross-sectional view through axis 3-3, FIGURE 2;
  • FIGURE 4 is an enlarged fragmentary cross-sectional view through axis 4-4, FIGURE 2;
  • FIGURE 5 is an enlarged fragmentary view through axis 5-5, FIGURE 2;
  • FIGURE 6 is an enlanged fragmentary top plan view of the central portion of the antenna of FIGURES 1-5;
  • FIGURES 7 and 8 are views in perspective of alternate forms of the antenna of the present invention.
  • FIGURES 9 through 11 illustrate antenna arrays with the unitary parasitic elements in differing locations together with graphic representations of the response of the particular array on the high VHF band;
  • FIGURE 12 illustrates still another antenna array configuration together with a graphic representation of the response of the same, and which is useful in the functional description of the present invention.
  • FIG- URES 1-6 shows the antenna in a preferred form.
  • the antenna unit is supported on a vertical post P, to which a horizontal cross-arm or boom B is affixed. This may be accomplished, for example, by a U-bolt extending through the boom B, wrapped about the post P, and drawn tight by suitable nuts, all as shown generally at U, FIGURE 6.
  • the antenna includes a series of driven elements 10, 12, 14 and 16. These, in the antenna shown, are in the form of simple dipoles. They are coplanar and aligned in relation to the boom, as shown. Each of these is supported by an insulating mounting block of molded plastic or the like, these being indicated respectively as 10a, 12a, 14a and 16a. Each such block is suitably affixed to the boom B, as by a rivet 11 extending vertically through the boom and mounting block to secure the same together. Each mounting block sustains, in insulated relation to the boom and to each other, a pair of dipole arms. These arms are indicated, respectively, at 10b and 100, 12b and 120, 14b and 140, and 16b and Me, FIGS. 1-6.
  • each pair of dipole arms forms inboard dipole terminals.
  • the respective dipole arms receive the transmission line conductors 18a. and 18b, FIGURES 1-3 and 6, at these terminals, preferably by connection to the same rivet, bolt, or other mounting means 13 by which the dipole arms are held in position.
  • the conductors 18a and 18b preferably cross between adjacent dipole units 10,12, 14, and 16, thus permitting closer spacings of the driven elements.
  • the transmission line leading to the receiver or other connected device may be connected to this transmission line at an appropriate point along its length, the point being chosen to match most effectively the impedance at the connected transmission line.
  • dipole unit 10 is of length to provide effective reception at the high frequency end of the band
  • dipole unit 16 is of length to provide effective action at the low frequency end of the band
  • dipole units 12 and 14 are of intermediate lengths to provide effective action at intermediate frequencies.
  • a reflector is disposed behind the driven element 16, as shown in FIGURES 1, 2 and 5.
  • This reflector is in coplanar, parallel, aligned relation with the driven elements 10, 12, 14, and 16 and serves to reflect signals approaching from the left hand side as seen in FIGURE 1. It consists of a single arm 22b supported from the boom B by bracket 22a, which is conducting.
  • a series of director elements are mounted forwardly of the driven element 10. These units are indicated generally at 24, 26, and 28, FIGURE 1.
  • the unit 24 consists of a pair of arms 24b and 24c insulatingly supported from boom B and from each other by the insulating bracket 24a.
  • This unit is of generally the same mechanical construction as the driven elements 10, 12, 14, and 16, except that the conductors 18a and 181) are not connected and the arms 2% and 24c thus act in parasitic action.
  • the director unit 26 is located forwardly of the unit 24 and consists of a pair of arms 26b and 260 insulatingly supported in straddling relation to the boom B by the insulating bracket 26a. In general mechanical construction this unit is like director 24 and driven elements 10, 12, 14 and 16.
  • a closed transmission line 26d is attached to the inboard ends of the arms 26b and 260 and serves, as hereinafter described, to render the unit 26 effective as to high hand signals.
  • the director unit 28 is a single arm 28!; mounted on the boom B by the bracket 21in, which may be insulating, or not, as desired.
  • unitary elements 30, 32, 34 and 36 are mounted below and in aligned relation with each of the driven elements 10, 12, 14, and 16, as shown in FIGURES 1, 3 and 4.
  • These unitary elements are mounted by suitable conductive or nonconductive bracket means from the boom B.
  • An exemplary such means is shown in FIGURES 3 and 4 in the form of a stamped aluminum bracket 38.
  • bracket 38 defines a pair of cars embracing the under side of the boom B and is affixed thereby by a rivet or bolt 40 extend ing through the boom B and the bracket to sandwich the same together.
  • the bracket extends downwardly and rearwardly to form a downwardly facing groove-like indented face at 33b.
  • the unitary element 30 is affixed to face 38b by a suitable rivet or bolt 42, as shown. Similar mounting means is provided for unitary elements 32, 34 and 36. As shown, the elements 34], 32, 34 and 36, are located directly below their respective driven elements 10, 12, 14, and 16. They are also in alignment with these respective elements and centered in relation thereto.
  • a unitary element 44 is located below the reflector 22 as is shown in FIGURES 1 and 5. This unitary element is suspended from the boom by a suitable bracket which may, for example, be like the bracket 38, described above.
  • Director elements 24a and 24b- /s inch O.D. aluminum tubing each of inches length and defining a total span of 43 inches between outboard tips.
  • the effective elements are believed to be director 26, driven elements 10b-10c, 1212-120, 14b-14c, and 16b-16c, and the reflector element 22.
  • the driven elements Ill-16 are all connected to the transmission line defined by conductors 18a and 18b as above-described. Also, as above-described, the driven elements 10-16 have differing frequencies of maximum effectiveness to provide-by cooperative action-effective action over the full low band, that is channels 2 to 6.
  • the director 26 operates in the low hand through the joint action of arms 26b, and 26c and the tuned element 26d. In the low frequency band the latter contributes sufiicient inductance to provide director action in conjunction with the arms 26a and 26b, thereby enhancing the gain and provide desirable directivity.
  • the tuned coupler element 26d may, of course, be an inductance with inherent or other shunt capacity, or other structure providing similar impedance that varies with frequency.
  • the reflector 22 is of sufiicient length to operate in reflector action through the low band channels and thereby further contributes to the directivity and gain.
  • the driven elements 10 12, 14, and 16 are relatively ineffective. This is believed to be because they are of much greater length than half wave elements in these channels and define high, reactive, impedances and in other respects act unfavorably. It is for this reason that antennas employing a plurality of low band driven elements while they can be made to provide good low band operation, have not heretofore been effective in high band operation. In the antenna of the present invention good high band performance is nevertheless achieved.
  • the good high band performance is imparted to the driven elements 10, 12, 14 and 16 by the unitary elements 30, 32, 34, and 36.
  • the high band performance of the antenna is greatly improved. More specifically, it has been found that when these elements are present at a spacing of from one to four inches vertically in relation to the respective driven elements they are effective, and that a spacing of about three inches is most suitable.
  • each of the unitary elements 30, 32, 34 and 36 has the same spacing as the corresponding driven element itself.
  • the distance from driven element 12 to the driven elements 10, 14, and 16 is essentially the same as the distance from the driven element 12 to the unitary elements 30, 34 and 36, respectively.
  • the unitary elements 30, 32, 34 and 36 impart to the driven elements 10, 12, 14 and 16 characteristics that would be present if the driven elements were cut to lengths giving effective resonant action in the high band.
  • the response and directivity of the antenna system is further enhanced in the high band by the director unit 24. It has been found that with driven elements as shown and with the unitary elements 30, 32, and 34, and 36, a director unit having a pair of spaced insulated arms coacts with the driven elements to provide enhanced performance over a unitary centered director unit.
  • the director 26 acts through the medium of the coupler 26d to provide action similar to that obtained with two separate arms 26a and 26b.
  • This action due to the relatively high band impedance of coupler 26d, tends to avoid a shielding action otherwlse present by reason of the low band performance of the director 26 and, in conjunction with high band director 28, serves to impart some increased high band action.
  • the high band performance is further enhanced by the unitary element 44.
  • This element is of length to provide effective reflector action in the high band and has been found capable of contributing to the high band gain and directivity through a coaction with the elements 30, 32, 34, and 36 and the remaining elements of the antenna.
  • the unitary elements 30, 32, 34, and 36 are not located substantially in front'of or behind the driven elements with which they are associated and are not otherwise positioned to act as director or reflector elements. Efforts have been made in the past to improve the high band performance of driven elements similar to elements 10, 12, 14, and 16 by locating high band directors between them. Such efforts, so far as is known, have been unsuccessful because any impovements obtained are outweighed by spurious and undesirable reflections and other action that degrades performance. In the apparatus of the present invention, surprisingly, this action does not appear to take place, or, if present, is of unimportant amount.
  • FIG- URE 7 An alternative form of the antenna is shohwn in FIG- URE 7. Parts corresponding with those in the antenna of FIGURES 1 to 6 are indicated by like reference numerals with 100 added.
  • the driven element 16 and the unitary element 36 of FIG- URES 1-6 are omitted.
  • three driven elements 110, 112, and 114 are provided and each has an associated unitary element suspended below it as indicated at 130, 132, and 134.
  • FIGURE 8 shows a still further embodiment of the antenna of the present invention.
  • the construction is like that of FIGURES 16 except that the reflector 22 and the unitary element 44 are omitted.
  • Parts corresponding to FIGURES 1-6 are indicated by like reference numerals with 200 added.
  • FIGURES 7 and 8 illustrate variations that may be made in the antenna while retaining the general mode of operation and performance of the antenna of FIGURES l-6. Because of the lesser number of active elements, the antenna of FIGURE 7 is less effective than that of FIGURES 1-6 and because of the absence of the reflector, the antenna of FIGURE 8 is less effective than that of FIGURES 16 and 7.
  • the actual dimensions of the antennas of FIGURES 7 and 8 are, in their preferred forms and to the extent the corresponding elements are used, like the dimensions given above for the antenna of FIGURES 1-6. If desired, an increased gain over the antenna of FIGURES 1-6 may be provided by adding additional dipole directors like 26, FIGURE 2, and unitary directors like 28, FIGURE 2. These are located forwardly of the directors 26 and 28,
  • the present invention is based on the discovery that the benefits of a multi-driven element antenna may be obtained for low VHF band operation as well as realizing effective and efficient high VHF band operation through the use of parasitic element associated with each of the dipole elements.
  • the present invention contemplates mounting each of the parasitic elements in vertical alignment with its associated dipole element. With this configuration, the parasitics avoid either director or reflector action, the significance of which is set forth below.
  • the present invention is further characterized in that the front-most driven dipole serves as the main pick-up element on high VHF band operation.
  • the front driven element in most cases, to be the least effective in the antenna array, as promulgated in the so-called progressive or relative power absorption theory wherein each of the driven dipole elements is said to absorb or radiate substantially the same signal power. Consequently, it requires greater relative absorption or radiation for those dipole driven elements which are further away from the feed point.
  • FIG- URE 7 shows an embodiment of the invention using three dipole driven elements 118, 112 and 114, each having an associated parasitic element 130, 132 and 134, respectively.
  • each of the dipole elements 11%, 112 and 114 are active in low VHF band operation, thereby contributing to overall antenna gain. Directivity is effected by the transposed feed line and appropriate interelement spacing. For high VHF band operation, however, dipole element is the primary active element and elements 112 and 114 do not significantly contribute to overall antenna gain. That this is so may be verified from an analysis of the antenna structure under consideration.
  • the front dipole element 110 is seen to have a tipto-tip span of approximately 45 inches. Physically, dipole 110 exhibits a halfwave resonance in the vicinity of megacycles and, inter alia, serves to improve directivity and impedance match characteristics of the antenna array on low VHF band operation. The same dipole element 119 is also physically three-quarter wave resonant at approximately 195 megacycles, or about the center of the high VHF band. However, taking into account the capacitance end effects present, dipole 110 electrically approaches fullwave resonance at this high band reference frequency and serves as the primary pickup element in this range.
  • the phasing line 113 between dipole elements 110 and 112 is approximately a quarterwave in length with reference to the high end of the high VHF band and thus functions in the manner of a quarterwave stub.
  • a high impedance at one end causes a low impedance to be reflected back to the other end.
  • this inversion of impedance through stubbing action occurs because the lengths of the phasing lines 113 in conjunction with the lengths of the respective dipole arms 112k and 112a are electrically multiples of a quarterwave at the reference frequency.
  • the reflection of impedance at the inboard ends of the dipole 114 back to the feed point It will be appreciated that this loading down of the dipole 110 at its inboard ends feed point results in a substantial degradation in its operating efficiency.
  • the loading effect, however, on dipole 110 by dipoles 112 and 114 is effectively offset by the action of the unitary parasitics 132 and 134, when correctly dimensioned and positioned within the antenna array.
  • the parasitics are placed in a closely coupled relation to the dipoles 112 and 114, respectively, and tuned so as to substantially lower the impedances of dipoles 112 and 114. Lowering of the impedances of dipoles 112 and 114 to a value below that of the characteristic impedance of the openwire phasing line 118 will cause a high impedance to be reflected to the feed point at the inboard ends of the dipole 110.
  • the parasitics 132 and 134 are cut to resonate at or slightly above the upper limit of the high VHF band. In the structure shown, the parasitics 132 and 134 are approximately 25 inches in length so as to provide a halfwave resonance at about 230 megacycles.
  • dipole 110 With the dipoles 112 and 114 effectively decoupled from the phasing line 118 feed points for high VHF band operation, only the dipole 110 remains as an effective active element. However, the action of its associated parasitic element 130 is needed if optimum performance is to be realized. This is because dipole 111], standing alone, exhibits a somewhat higher impedance than that of the phasing lines 118 or conventional transmission feed line. This results in a very substantial antenna and line mismatch, and effects a reduction in overall antenna efliciency.
  • the impedance of the dipole 119 is depressed to a value approaching that of the 300 ohms of the feed line and thereby optimizes power transfer between antenna and line by proper impedance matching.
  • the associated parasitics 130, 132 and 134 serve as impedance transformation or decoupling means with respect to dipoles 110, 112 and 114. Since dipole is the main pick-up element, either director or reflector action for the parasitics 130, 132 and 134 should be avoided to eliminate, as much as possible, the undesirable effects, such as suck'outs or peaks in the overall response of the antenna on high VHF band operation, resulting from shielding or reflection of signal energy when the parasitics are in horizontal alignment, but phase-displaced from, the driven dipole elements. Consequently, for optimum performance, the conclusion is that the parasitics be placed in vertical alignment with their associated driven dipole elements and not in the same horizontal plane therewith. With this configuration, the parasitics are at the same lineal location as their associated dipole elements with respect to a signal wave traveling down the antenna array and undesirable reflection or shielding of signal energy is substantially reduced.
  • the parasitics are all cut to one particular frequency, i.e., at or above the upper limit of the high VHF band, rather to any particular harmonic of the fundamental frequency of the dipole element. All of the parasitics 130, 132 and 134 are cut to approximately 25 inches.
  • the parasitics 130, 132 and 134 were placed in different locations with respect to the dipole elements 110, 112 and 114 and the effect, if any, noted in the performance of the antenna array.
  • Observation of antenna performance was accomplished through the use of a dual-trace oscilloscope connected by suitable transmission line to the feed point at the inboard ends of the dipole 110 and set to sweep the high VHF band.
  • a crystal marker generator was employed to provide visual indication on the sweep traces of the megacycle and 215 megacycle points.
  • One trace (curve X) provided an indication of the response characteristics of the antenna array on the high VHF band and the second trace (curve Y) the VSWR as an indication of the impedance match between antenna and feed line.
  • FIGURE 9a illustrates the antenna. array with the parasitics positioned below and in vertical alignment with the associated dipole elements and corresponds to the exact structure as shown in FIGURE 7.
  • FIGURE 9b is a graphic representation of the oscilloscope traces obtained.
  • FIGURE 10a illustrates the antenna array with the parasitics positioned behind and in the same horizontal plane as the dipole elements with FIGURE 10b being a graphic representation of the oscilloscope traces obtained for this configuration.
  • FIGURE 11a illustrates the antenna array tested with the parasitics positioned in front of and in the same horizontal plane as the dipole elements with FIGURE 11b being a graphic representation of the oscilloscope traces as obtained in this configuration.
  • the gain of the antenna array on high VHF band operation is superior when the parasitics are placed beneath the dipole elements but in vertical alignment therewith. Likewise, it will be observed that this configuration provides the best impedance match between line and antenna array. With the parasitics behind the dipole elements, the gain is significantly reduced across the range of the high VHF band. With the parasitics placed in front of the associated dipole elements, the gain is improved somewhat at the lower portion of the high band due to the director action now being provided by the parasitics, but still not as good as that obtained in the configuration as represented in FIGURE 9.
  • FIGURE 12 an antenna configuration as shown in FIGURE 12 was assembled and the results noted in the same manner as the antenna arrays of FIGURES 9 through 11.
  • a fullwave dipole driven element D resonating near the center of the high VHF band was positioned on a boom B.
  • a reflector element R cut to resonate below the high VHF band was appropriately positioned behind the driven element D to provide reflector action.
  • the director parasitic element P was placed in front of instead of below the driven element D to obtain the director action as provided by the director elements 124, 126 and 128 in the antenna configuration of FIGURE 7.
  • the response characteristics parallels those obtained for the antenna configuration as shown in FIG- URE 9. Somewhat more of a mismatch between line and antenna is exhibited, however, particularly at the low end of the high VHF band. This is because of the high impedance presented by the fullwave resonant dipole driven element D.
  • the antenna configuration of FIGURE 7 approaches that of FIGURE 12 in terms of electrical equivalency and the performance characteristics obtained.
  • At least three low band dipole driven elements located in substantially parallel relation to each other, in substantial alignment, defining connecting terminals located along substantially a common line normal to the elements, and having progressively increasing lengths when said common line is traced in one direction providing differing frequencies of most effective operation and coverage of the low frequency band;
  • each unitary element being located in substantially parallel aligned relation to its associated driven element and in a plane through the driven element substantially normal to the plane defined by the driven elements, each unitary element having substantially the same number of wave lengths in the high band as the associated driven element has in the low band, each unitary element being spaced from the associated driven element by a distance that is short in relation to the length of the unitary element;
  • dipole director located in coplanar parallel aligned relation with the driven elements outboard the same on the side of the shortest element and in the plane defined thereby, said director including a pair of insulatingly supported dipole elements and a coupler connecting the same, the coupler having a substantial impedance in the high frequency band in conjunction with the other elements and the dipole director as a whole being effective in director action in the low band;
  • the reflector located in coplanar parallel aligned relation with the driven elements, outboard the same on the side of the longest element, the reflector comprising a main arm of unitary construction of length for reflector action in the low frequency band, said director further having a unitary element in parallel aligned relation with said main arm and in a plane through said main arm substantially normal to the plane defined by the driven elements, said last unitary element having substantially the same number of wave lengths length in the high band as said main arm has in the low band, said last unitary element being spaced from the main arm by a distance that is short in relation to the length of the unitary element.
  • a television antenna effective in both the high and low VHF frequency bands comprising in combination:
  • At least three dipole driven elements located in substantially parallel relation to each other, in substantial alignment, defining connecting terminals located along substantially a common line normal to the elements, said driven elements having differing lengths to provide effective operation and coverage of the low VHF band, with one of said dipoles exhibiting substantially fullwave resonance at approximately the center of the high VHF band and operating as the primary pickup element in the high VHF band;
  • unitary elements associated with said dipole driven elements respectively, each unitary element being located in substantially parallel aligned relation to an associated driven element and in a plane through the driven element substantially normal to the plane defined by the driven elements, said unitary element associated with said one dipole exhibiting fullwave resonance in the high VHF band being effective to sufficiently depress the impedance of said one dipole on high VHF band operation to a value which substantially matches the impedance of the interconnect ing transmission line, said unitary elements associated with the dipoles other than said one dipole being effective to provide an electrical decoupling action for said other dipoles from the interconnecting transmission line on high VHF band operation; and
  • director means located in parallel aligned relation with the driven elements and in the plane defined thereby, said director means including at least a unitary director element and a pair of insulatingly supported dipole arms with a coupler interconnecting the same, the coupler having a substantial impedance in the high VHF band and said director means as a whole lgeing effective in director action in the low VHF and.
  • each of said unitary elements associated with each of the'dipole driven elements are of lengths to provide halfwave resonance at a frequency above the high end of the high VHF band and wherein each of said unitary elements is spaced from the associated driven dipole by a distance that is short in relation to its length.
  • each of the unitary elements associated with the dipole driven elements has a length of approximately 25 inches and is spaced from its associated dipole driven element by a distance which is between one and four inches.
  • a reflector element is located in parallel aligned relation with the dipole driven elements and in the plane defined thereby, said reflector element having a length to provide effective reflector action in the low VHF band, and an associated parasitic element located in substantially parallel aligned relation therein in a plane through the reflector element substantially normal to the plane defined by the dipole driven elements, said unitary parasitic element having substantially the same number of wavelengths in the high VHF band as the reflector element has in the low low VHF band with the dipole driven element positioned frontmost in the dipole array having a length to provide approximately halfwave resonance at a reference frequency above the high end of the low VHF band. VHF band but below the low end of the high VHF 7.
  • a television antenna effective in both the high and band and substantially fullwave resonance at approxilow VHF frequency bands comprising in combination: mately the center of the high VHF band, the conat least three dipole driven elements located in subnecting terminals of said frontmost dipole element stantially parallel relation to each other, in substanforming the feed point for the antenna array; tial alignment, defining connecting terminals located a transmission line connecting said terminals to provide along substantially a common line normal to the elesignal elfects due to their combined action, said transments, said driven elements having differing lengths mission line being transposed between adjacent driven to provide effective operation and coverage of the dipole elements; low VHF band with the dipole driven element posiunitary elements associated with said dipole driven eletioned frontmost in the dipole array having a length 15 ments, respectively, each unitary element being 10- to provide approximately halfwave resonance at a cated in substantially parallel aligned relation to an reference frequency above the high end of the low associated driven element and in a plane normal to VHF band
  • the coupler having a substantial impedance in the high VHF band and said director means as a whole References Clltefl y the Examiner being efiective in director action in the low VHF UN STATES PATENTS band.

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Description

y 23, 1967 J. R. WINEGARD ETAL 3,321,764
TELEVI S ION ANTENNA 3 Sheets-Sheet 1 Filed Aug. 26, 1966 Inventors John .wirzegard Care a y 611 Km y 23, 1967 J. R. WINEGARD ETAL 3,321,764
TELEVISION ANTENNA Filed Aug. 26, 1966 3 Sheets-Sheet 2 Inventors John R.Wine5cnrd Care% 110. Shelledg/ May 23, 1967 J. R. WINEGARD ETAL. 3,321,764
TELEVISION ANTENNA Filed Aug. 26, 1966 3 Sheets-Sheet 3 SIGNAL VSIASR RESPONSE-b REQUENCY VSWR RESPONSE REQUENCY Vswn Rssmnse FREQUENCY V$WR RESPONSE-*- ''FREQUENCY Inventors John. R.winegard Care% W, S@Rled% United States Patent Ofi Fice 3,321,764 Patented May 23, 1967 3,321,764 TELEVISION ANTENNA John R. Winegard and Carey W. Shelledy, both of Burlington, Iowa, assignors to The Winegard Company, Burlington, Iowa, a corporation of Iowa Filed Aug. 26, 1966, Ser. No. 593,228 8 Claims. Cl. 343815) This application is -a continuation in part of our pending application, Ser. No. 320,074, filed on Oct. 30, 1963, now abandoned, entitled Television Antenna, and assigned to the same assignee as the present invention.
The present invention relates to an improved television antenna having three or more low VHF band driven elements in which unitary high VHF band elements in close vertical spacing in relation to some or all the driven element-s impart, by coupler action, favorable high VHF band characteristics.
The principal television frequency bands now in use are the VHF bands. These cover 54 to 88 megacycles and 174 to 216 megacycles. Effective VHF antenna operation requires that there be efficient reception in both bands. However, the frequency range from the low end of the low VHF band to the high end of the high VHF band is four to one. This is too great for the effective use of a simple dipole arrangement. And even within the range of the low band (54 to 88 megacycles), the highest frequency is on the order of about sixty percent greater than the lowest frequency. The high band (174 to 216 megacycles), while of smaller spread on a percentage basis, also imposes problems because of the range involved. Because of these large frequency ranges both between the low band and the high band and within each band, effective antennas for all-channel reception require some means of extending the antenna frequency range beyond that of a simple dipole.
One technique for extending the frequency range of a television antenna is to use a plurality of driven elements. Considering the low band, for example, there are a total of five television channels (2 to 6, inclusive). A series of five dipole elements, one tuned for good reception in each band, may be used in coplanar aligned relation, the channel 2 driven element in the rear and the other elements progressively in front of the same. Alternatively, a smaller or even larger number of driven elements may be used, with their most effective frequencies spread over the 54 to 88 megacyc-le range to provide a balancing effect and generally favorable gain and directivity. As to low band reception, it is possible to mount such driven elements at appropriate spacings and connect the same by a transmission line (preferably with the leads crossing between each adjacent pair of driven elements) to provide relatively good reinforcing effects between the separate elements and a relatively good antenna for the low band.
Antennas of the above type are, however, not nearly as effective in the high band as in the low band. This is because the driven elements themselves do not operate effectively at frequencies of the order of three times their half wave resonant frequencies. Particular techniques of driven element construction in some measure overcome this difficulty, especially with a small number of driven elements. But where three or more driven elements are used the art has generally used a simple folded dipole, V- dipole, or straight dipole configuration and has accepted the limited performance of these in the high band.
Efforts have been made to increase the high band response of antennas of the foregoing type by the use of high band directors located in horizontal alignment with and between successive driven elements. Such directors, in theory, increase the high band response of each of the elements and thereby the performance of the whole array in the high band. This gain is, however, somewhat illusory, for the high band directors behind each driven element influence its gain and directivity and at the various frequencies of operation the high band directors act sometimes as directors and sometimes as reflectors. The net result is that the high band directors improve performance to a limited extent, if at all, and in some frequencies of operation they tend to degrade antenna performance. J
The present invention is based on the discovery that the benefits of a multi-driven element antenna can be obtained on the high hand through high band elements located in vertically spaced relation to the adjacent driven element and spaced therefrom for coupling action. While it has been known that unitary high band elements can influence the operation of a low band dipole in ways other than director action, it has been thought that such influence is best achieved with the dipole in front of the driven element where it also acts as a director. This has been the practice both with antennas having one or two driven elements and with antennas having a larger number of driven elements. Contrary to this teaching, we have found that in a system having three or more driven elements, director apparatus should be avoided and that the unitary high band elements should be located above or below the associated driven element at spacings providing coupling action but relatively little or no director or reflector action. Surprisingly, it has been found that unitary elements so located have the property of imparting favorable high band performance to the antenna without giving rise to undesirable spurious action as reflectors or directors.
In the preferred form of the present invention, herein described in detail, the antenna consists of three or more dipole driven elements, the elements being of length to serve most efficiently as half wave elements in (the frequency) spread over the 54 to 88 megacycle band. Each is mounted above a boom and is connected to the others by an open wire transmission line having its conductors crossed between each adjacent pair of elements. The spacings are chosen to provide most effective low band operation. A unitary high band element is mounted below the boom from one to four inches below each of these driven elements. Preferably, a director system is disposed in front of the forward dipole driven element, the same consisting of a pair of aligned coaxial high band directors straddling the boom in front of the forward driven element and a dipole director in front of the same, the dipole director being defined by a pair of insulated dipole arms straddling the boom and connected by a coupler effective to provide director action in the low band and in the high band to define a sufficient impedance in connection with other antenna elements to avoid detracting from high band gain. A unitary high band director is located in front of the dipole director. Further in accordance with the preferred form of the present invention, the antenna includes a low band reflector located behind the rear driven element and in the plane of the low band driven elements. The reflector further includes a high band reflector suspended from about one to four inches below the same. With this type of array, the dis tance between each of the high band elements and each of the elements other than its adjacent low band element is the same as the distance between each of the low band elements and the other low band elements. It has been found that with this construction the respective high band elements tend to impart to the low band elements the same characteristics as would be present if the high band elements were in place and phased in end fire relation without the low band elements.
Antennas constructed in accordance with the present invention are characterized by high gain, flat frequency response over each television channel, good impedance match, favorable directivity patterns and band width sufficient to cover the TV high and low VHF frequency bands.
It is therefore a general object of the present invention to provide an improved television antenna having a plurality of low band driven elements and in which unitary high band elements impart effective high band characteristics without otherwise degrading the antenna performance.
A more particular object of the present invention is to provide an improved television antenna in which a plurality of aligned coplanar low band driven elements define an effective low band array and unitary high band elements located in vertically spaced relation to each of the driven elements impart effective high band characteristics to the same through the medium of coupling action devoid of substantial director or'reflector action.
Still another object of the present invention is to provide an improved television antenna in which effective low band performance is provided by a plurality of low band driven elements cut to lengths that provide relatively uniform effective action spread over the low frequency band and in which a similar number of unitary high band elements cooperate respectively with the low band driven elements and are cut to lengths that provide relatively uniform, effective action spread over the high frequency band, the high band elements being in vertically spaced relation to the respective low band elements and spaced for coupling action in relation thereto.
It is yet another object of the present invention to provide an improved television antenna in which effective low band performance is provided by a plurality of driven elements cut for effective operation over the low frequency band and in which high band performance is imparted to the same through the medium of one or more vertically spaced unitary high band elements of lengths providing effective high band operation, and the performance of the entire array is improved in director action through the medium of a pair of spaced high band directors.
It is still another object of the present invention to provide an improved television antenna in which effective low band performance is provided by a plurality of driven elements cut for effective operation over the low frequency band and in which high band performance is imparted to the same through the medium of one or more vertically spaced unitary high band elements of lengths providing effective high band operation, and the performance of the entire array ,is improved in reflector action through the medium of a low band reflector in coplanar ali-gned relation to the low frequency elements andhaving a unitary high band reflector in vertical closelyspaced relation thereto.
The novel features which we believe to be characteristics of our invention are set forth with particularity in the appended claims. Our invention itself, however, together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings in which:
FIGURE 1 is a view in perspective of an antenna constructed in accordance with the preferred form of the present invention;
FIGURE 2 is a top plan view to a smaller scale of the antenna of FIGURE 1;
FIGURE 3 is an enlarged fragmentary cross-sectional view through axis 3-3, FIGURE 2;
FIGURE 4 is an enlarged fragmentary cross-sectional view through axis 4-4, FIGURE 2;
FIGURE 5 is an enlarged fragmentary view through axis 5-5, FIGURE 2;
FIGURE 6 is an enlanged fragmentary top plan view of the central portion of the antenna of FIGURES 1-5;
FIGURES 7 and 8 are views in perspective of alternate forms of the antenna of the present invention;
FIGURES 9 through 11 illustrate antenna arrays with the unitary parasitic elements in differing locations together with graphic representations of the response of the particular array on the high VHF band; and
FIGURE 12 illustrates still another antenna array configuration together with a graphic representation of the response of the same, and which is useful in the functional description of the present invention.
The antenna construction contemplated by the present invention will best be understood by reference to FIG- URES 1-6, which shows the antenna in a preferred form. As shown, the antenna unit is supported on a vertical post P, to which a horizontal cross-arm or boom B is affixed. This may be accomplished, for example, by a U-bolt extending through the boom B, wrapped about the post P, and drawn tight by suitable nuts, all as shown generally at U, FIGURE 6.
As further shown, the antenna includes a series of driven elements 10, 12, 14 and 16. These, in the antenna shown, are in the form of simple dipoles. They are coplanar and aligned in relation to the boom, as shown. Each of these is supported by an insulating mounting block of molded plastic or the like, these being indicated respectively as 10a, 12a, 14a and 16a. Each such block is suitably affixed to the boom B, as by a rivet 11 extending vertically through the boom and mounting block to secure the same together. Each mounting block sustains, in insulated relation to the boom and to each other, a pair of dipole arms. These arms are indicated, respectively, at 10b and 100, 12b and 120, 14b and 140, and 16b and Me, FIGS. 1-6. The respective dipole arms preferably rest in a shallow channel or groove formed on the top side of the corresponding mounting block and are secured therein by a rivet, bolt or other mounting means extending through the respective dipole arm and the mounting block as indicated at 13, FIGURE 6. At their inboard ends, in the regions where the rivet, bolt, or other mounting means 13 affixes dipole arm to the mounting block, each pair of dipole arms forms inboard dipole terminals. The respective dipole arms receive the transmission line conductors 18a. and 18b, FIGURES 1-3 and 6, at these terminals, preferably by connection to the same rivet, bolt, or other mounting means 13 by which the dipole arms are held in position.
As shown in FIGURES 1, 2 and 6, the conductors 18a and 18b preferably cross between adjacent dipole units 10,12, 14, and 16, thus permitting closer spacings of the driven elements. The transmission line leading to the receiver or other connected device may be connected to this transmission line at an appropriate point along its length, the point being chosen to match most effectively the impedance at the connected transmission line.
The four dipole units 10, 12, 14, 16 are intended to provide effective action over the low frequency television band, that is channels 26, inclusive. To this end, dipole unit 10 is of length to provide effective reception at the high frequency end of the band, dipole unit 16 is of length to provide effective action at the low frequency end of the band, and dipole units 12 and 14 are of intermediate lengths to provide effective action at intermediate frequencies. As is well known in the art, by a proper adjustment of the lengths and spacings of .dipole units of this type it is possible to provide a relatively good low band operation with relatively favorable gain, impedance, and directivity characteristics and thereby achieve reception of any low band channel in effective fashion.
A reflector is disposed behind the driven element 16, as shown in FIGURES 1, 2 and 5. This reflector is in coplanar, parallel, aligned relation with the driven elements 10, 12, 14, and 16 and serves to reflect signals approaching from the left hand side as seen in FIGURE 1. It consists of a single arm 22b supported from the boom B by bracket 22a, which is conducting.
A series of director elements are mounted forwardly of the driven element 10. These units are indicated generally at 24, 26, and 28, FIGURE 1. The unit 24 consists of a pair of arms 24b and 24c insulatingly supported from boom B and from each other by the insulating bracket 24a. This unit is of generally the same mechanical construction as the driven elements 10, 12, 14, and 16, except that the conductors 18a and 181) are not connected and the arms 2% and 24c thus act in parasitic action.
The director unit 26 is located forwardly of the unit 24 and consists of a pair of arms 26b and 260 insulatingly supported in straddling relation to the boom B by the insulating bracket 26a. In general mechanical construction this unit is like director 24 and driven elements 10, 12, 14 and 16. A closed transmission line 26d is attached to the inboard ends of the arms 26b and 260 and serves, as hereinafter described, to render the unit 26 effective as to high hand signals.
The director unit 28 is a single arm 28!; mounted on the boom B by the bracket 21in, which may be insulating, or not, as desired.
In addition to the foregoing, unitary elements 30, 32, 34 and 36 are mounted below and in aligned relation with each of the driven elements 10, 12, 14, and 16, as shown in FIGURES 1, 3 and 4. These unitary elements are mounted by suitable conductive or nonconductive bracket means from the boom B. An exemplary such means is shown in FIGURES 3 and 4 in the form of a stamped aluminum bracket 38. At its forward end 38a bracket 38 defines a pair of cars embracing the under side of the boom B and is affixed thereby by a rivet or bolt 40 extend ing through the boom B and the bracket to sandwich the same together. The bracket extends downwardly and rearwardly to form a downwardly facing groove-like indented face at 33b. The unitary element 30 is affixed to face 38b by a suitable rivet or bolt 42, as shown. Similar mounting means is provided for unitary elements 32, 34 and 36. As shown, the elements 34], 32, 34 and 36, are located directly below their respective driven elements 10, 12, 14, and 16. They are also in alignment with these respective elements and centered in relation thereto.
A unitary element 44 is located below the reflector 22 as is shown in FIGURES 1 and 5. This unitary element is suspended from the boom by a suitable bracket which may, for example, be like the bracket 38, described above.
The above description gives the general organization of the antenna of FIGURES 1-6. Its more specific construction will be better understood by reference to the following dimensions which were used in an antenna that was found highly effective in both the low band and the high band:
Director 28-% inch O.D. aluminum tubing and of 24 inches length.
Director elements 260 and 26b% inch O.D. aluminum tubing each of 25% inches length and defining a total span of 5 3 inches between outboard tips.
Director element 26d inch O.D. aluminum rod having a total length of 18 /2 inches.
Director elements 24a and 24b- /s inch O.D. aluminum tubing each of inches length and defining a total span of 43 inches between outboard tips.
Driven element arms 10b and 1llc% inch O.D. aluminum tubing of 21 /8 inches length and having a total span of 45 inches between the outboard tips.
Unitary element Bil-Vs inch OD. aluminum tubing of inches length mounted 2% inches directly below driven element arms 10b and 10c.
Driven element arms 12b and 12c-% inch O.D. aluminum tubing of 29% inches length and having a total span of 61 inches between outboard tips.
Unitary element 32% inch O.D. aluminum tubing of 25 inches length mounted 2% inches directly below driven element arms 12b and 120.
Driven element arms 14b and 14c- V inch O.D. aluminum tubing 38% inches length and having a total span of 79 inches between outboard tips.
Unitary element 34% inch O.D. aluminum tubing of 25 inches length mounted 2% inches directly below driven element arms 14b and 140.
Driven element arms 16b and 16c% inch O.D. aluminum tubing with 48% inches length. and having a total span of 98 inches between outboard tips.
Unitary element 36--% inch O.D. aluminum tubing of 29 inches length mounted 2% inches directly below driven element arms 16b and 160.
Reflector arm 22ainch O.D. aluminum tubing with a total span of inches.
Unitary element 44% inch O.D. aluminum tubing of 35 inches lengths mounted 2% inches directly below reflector arm 22a.
Distances along the boom B between the respective elements in the antenna above described were as follows:
Between elements 28 and 26--9 inches. Between elements 26 and 248 /z inches. Between elements 24 and 1tl8 inches. Between elements 10 and 12-11 inches. Between elements 12 and 14-l1 inches. Between elements 14 and 16-13 inches. Between elements 16 and 22-17 inches.
Practical operation In the low frequency bands (channels 2-6), the effective elements are believed to be director 26, driven elements 10b-10c, 1212-120, 14b-14c, and 16b-16c, and the reflector element 22. The driven elements Ill-16 are all connected to the transmission line defined by conductors 18a and 18b as above-described. Also, as above-described, the driven elements 10-16 have differing frequencies of maximum effectiveness to provide-by cooperative action-effective action over the full low band, that is channels 2 to 6.
The director 26 operates in the low hand through the joint action of arms 26b, and 26c and the tuned element 26d. In the low frequency band the latter contributes sufiicient inductance to provide director action in conjunction with the arms 26a and 26b, thereby enhancing the gain and provide desirable directivity. The tuned coupler element 26d may, of course, be an inductance with inherent or other shunt capacity, or other structure providing similar impedance that varies with frequency. The reflector 22 is of sufiicient length to operate in reflector action through the low band channels and thereby further contributes to the directivity and gain.
In the high frequency band (channels 7-13), the driven elements 10 12, 14, and 16 are relatively ineffective. This is believed to be because they are of much greater length than half wave elements in these channels and define high, reactive, impedances and in other respects act unfavorably. It is for this reason that antennas employing a plurality of low band driven elements while they can be made to provide good low band operation, have not heretofore been effective in high band operation. In the antenna of the present invention good high band performance is nevertheless achieved.
The good high band performance is imparted to the driven elements 10, 12, 14 and 16 by the unitary elements 30, 32, 34, and 36. When these elements are located sub stantially in the vertical planes of the respective driven elements at a relatively close spacing in relation to the respective driven elements, the high band performance of the antenna is greatly improved. More specifically, it has been found that when these elements are present at a spacing of from one to four inches vertically in relation to the respective driven elements they are effective, and that a spacing of about three inches is most suitable.
One important reason why the unitary elements 30, 32, 34 and 36 are effective is believed to be their coupled relationship to the respective driven elements in conjunction with their location substantially in the vertical plane of the driven elements. As to each driven element other than the corresponding driven element, each of the unitary elements 30, 32, 34 and 36 has the same spacing as the corresponding driven element itself. Thus the distance from driven element 12 to the driven elements 10, 14, and 16, is essentially the same as the distance from the driven element 12 to the unitary elements 30, 34 and 36, respectively. Whatever the mode of action, however, the unitary elements 30, 32, 34 and 36 impart to the driven elements 10, 12, 14 and 16 characteristics that would be present if the driven elements were cut to lengths giving effective resonant action in the high band.
The response and directivity of the antenna system is further enhanced in the high band by the director unit 24. It has been found that with driven elements as shown and with the unitary elements 30, 32, and 34, and 36, a director unit having a pair of spaced insulated arms coacts with the driven elements to provide enhanced performance over a unitary centered director unit.
Also in the high band, the director 26 acts through the medium of the coupler 26d to provide action similar to that obtained with two separate arms 26a and 26b. This action, due to the relatively high band impedance of coupler 26d, tends to avoid a shielding action otherwlse present by reason of the low band performance of the director 26 and, in conjunction with high band director 28, serves to impart some increased high band action.
The high band performance is further enhanced by the unitary element 44. This element is of length to provide effective reflector action in the high band and has been found capable of contributing to the high band gain and directivity through a coaction with the elements 30, 32, 34, and 36 and the remaining elements of the antenna.
It should be noted that the unitary elements 30, 32, 34, and 36 are not located substantially in front'of or behind the driven elements with which they are associated and are not otherwise positioned to act as director or reflector elements. Efforts have been made in the past to improve the high band performance of driven elements similar to elements 10, 12, 14, and 16 by locating high band directors between them. Such efforts, so far as is known, have been unsuccessful because any impovements obtained are outweighed by spurious and undesirable reflections and other action that degrades performance. In the apparatus of the present invention, surprisingly, this action does not appear to take place, or, if present, is of unimportant amount.
Alternative embodiments An alternative form of the antenna is shohwn in FIG- URE 7. Parts corresponding with those in the antenna of FIGURES 1 to 6 are indicated by like reference numerals with 100 added. In the antenna of FIGURE 7, the driven element 16 and the unitary element 36 of FIG- URES 1-6 are omitted. Thus only three driven elements 110, 112, and 114 are provided and each has an associated unitary element suspended below it as indicated at 130, 132, and 134.
FIGURE 8 shows a still further embodiment of the antenna of the present invention. In this instance the construction is like that of FIGURES 16 except that the reflector 22 and the unitary element 44 are omitted. Parts corresponding to FIGURES 1-6 are indicated by like reference numerals with 200 added.
The alternative constructions of FIGURES 7 and 8 illustrate variations that may be made in the antenna while retaining the general mode of operation and performance of the antenna of FIGURES l-6. Because of the lesser number of active elements, the antenna of FIGURE 7 is less effective than that of FIGURES 1-6 and because of the absence of the reflector, the antenna of FIGURE 8 is less effective than that of FIGURES 16 and 7. Other variations that may be used, if desired, include the omission of some or all of the director elements 24, 26, and 28, FIGURES 16, the use of folded dipole, V-dipole, or other variations of the simple dipole driven element constructions shown, a number of driven elements greater than four, and the like. While in the present application we have shown and described a specific preferred antenna construction in accordance with the present invention and some variations of the same, it will be understood that other modifications and alternative constructions may be made without departing from the true spirit and scope of the present invention. We therefore intend by the appended claims to cover all such modifications and alternative constructions as fall within their true spirit and scope.
The actual dimensions of the antennas of FIGURES 7 and 8 are, in their preferred forms and to the extent the corresponding elements are used, like the dimensions given above for the antenna of FIGURES 1-6. If desired, an increased gain over the antenna of FIGURES 1-6 may be provided by adding additional dipole directors like 26, FIGURE 2, and unitary directors like 28, FIGURE 2. These are located forwardly of the directors 26 and 28,
in fashion similar to that shown and described in Winegard Patent 2,700,105.
Functional considerations As stated previously, the present invention is based on the discovery that the benefits of a multi-driven element antenna may be obtained for low VHF band operation as well as realizing effective and efficient high VHF band operation through the use of parasitic element associated with each of the dipole elements. However, instead of conforming to the prior art teaching commonly requiring the parasitic elements to be located in front of and in the same horizontal plane as the associated driven elements, the present invention contemplates mounting each of the parasitic elements in vertical alignment with its associated dipole element. With this configuration, the parasitics avoid either director or reflector action, the significance of which is set forth below.
The present invention is further characterized in that the front-most driven dipole serves as the main pick-up element on high VHF band operation. This is contrary to prior art teaching which requires the front driven element, in most cases, to be the least effective in the antenna array, as promulgated in the so-called progressive or relative power absorption theory wherein each of the driven dipole elements is said to absorb or radiate substantially the same signal power. Consequently, it requires greater relative absorption or radiation for those dipole driven elements which are further away from the feed point.
For convenience, the structure of the antenna array as shown in FIGURE 7 will be considered for illustrative purposes' It is to be understood, however, that the same characteristics apply to the other embodiments of the invention, as shown in FIGURES 1 and 8, as well. FIG- URE 7 shows an embodiment of the invention using three dipole driven elements 118, 112 and 114, each having an associated parasitic element 130, 132 and 134, respectively.
As previously stated, each of the dipole elements 11%, 112 and 114 are active in low VHF band operation, thereby contributing to overall antenna gain. Directivity is effected by the transposed feed line and appropriate interelement spacing. For high VHF band operation, however, dipole element is the primary active element and elements 112 and 114 do not significantly contribute to overall antenna gain. That this is so may be verified from an analysis of the antenna structure under consideration.
The front dipole element 110 is seen to have a tipto-tip span of approximately 45 inches. Physically, dipole 110 exhibits a halfwave resonance in the vicinity of megacycles and, inter alia, serves to improve directivity and impedance match characteristics of the antenna array on low VHF band operation. The same dipole element 119 is also physically three-quarter wave resonant at approximately 195 megacycles, or about the center of the high VHF band. However, taking into account the capacitance end effects present, dipole 110 electrically approaches fullwave resonance at this high band reference frequency and serves as the primary pickup element in this range. With spans of 61 and 79 inches for the dipoles 112 and 114, respectively, fullwave resonance for dipoles 112 and 114 are seen to be somewhat lower than the range of the high VHF band. However, since dipole elements 112 and 114 are electrically connected to the feed point of the antenna array at the inboard ends of dipole 110, they do have an effect on overall antenna operation in the high VHF band-a rather substantial effect. It will be realized that the impedance of a fullwave dipole is substantially higher than that of a conventional transmission line-in actual figures, around 3 to 4 times higher. Moreover, a high impedance at the inboard ends of the dipole 112 results in a relatively low impedance being reflected back to the feed point at the inboard ends of the dipole 110. This occurs because the phasing line 113 between dipole elements 110 and 112 is approximately a quarterwave in length with reference to the high end of the high VHF band and thus functions in the manner of a quarterwave stub. A high impedance at one end causes a low impedance to be reflected back to the other end. To be more accurate, this inversion of impedance through stubbing action occurs because the lengths of the phasing lines 113 in conjunction with the lengths of the respective dipole arms 112k and 112a are electrically multiples of a quarterwave at the reference frequency. The same of course is true of the reflection of impedance at the inboard ends of the dipole 114 back to the feed point. It will be appreciated that this loading down of the dipole 110 at its inboard ends feed point results in a substantial degradation in its operating efficiency.
The loading effect, however, on dipole 110 by dipoles 112 and 114 is effectively offset by the action of the unitary parasitics 132 and 134, when correctly dimensioned and positioned within the antenna array. The parasitics are placed in a closely coupled relation to the dipoles 112 and 114, respectively, and tuned so as to substantially lower the impedances of dipoles 112 and 114. Lowering of the impedances of dipoles 112 and 114 to a value below that of the characteristic impedance of the openwire phasing line 118 will cause a high impedance to be reflected to the feed point at the inboard ends of the dipole 110. This reflection of a high impedance across the feed point at high frequencies has the effect of making the dipoles 112 and 114' look as if they are electrically detached or decoupled from the feed point on high VHF band operation. To effect the reduction in the respective impedances of the dipoles 112 and 114, the parasitics 132 and 134 are cut to resonate at or slightly above the upper limit of the high VHF band. In the structure shown, the parasitics 132 and 134 are approximately 25 inches in length so as to provide a halfwave resonance at about 230 megacycles.
With the dipoles 112 and 114 effectively decoupled from the phasing line 118 feed points for high VHF band operation, only the dipole 110 remains as an effective active element. However, the action of its associated parasitic element 130 is needed if optimum performance is to be realized. This is because dipole 111], standing alone, exhibits a somewhat higher impedance than that of the phasing lines 118 or conventional transmission feed line. This results in a very substantial antenna and line mismatch, and effects a reduction in overall antenna efliciency. However, with the parasitic element 130 placed in close proximity to the dipole 110 and having a linear dimension for resonating at or above the upper limit of the high VHF band, the impedance of the dipole 119 is depressed to a value approaching that of the 300 ohms of the feed line and thereby optimizes power transfer between antenna and line by proper impedance matching.
It can be seen therefore that the associated parasitics 130, 132 and 134 serve as impedance transformation or decoupling means with respect to dipoles 110, 112 and 114. Since dipole is the main pick-up element, either director or reflector action for the parasitics 130, 132 and 134 should be avoided to eliminate, as much as possible, the undesirable effects, such as suck'outs or peaks in the overall response of the antenna on high VHF band operation, resulting from shielding or reflection of signal energy when the parasitics are in horizontal alignment, but phase-displaced from, the driven dipole elements. Consequently, for optimum performance, the conclusion is that the parasitics be placed in vertical alignment with their associated driven dipole elements and not in the same horizontal plane therewith. With this configuration, the parasitics are at the same lineal location as their associated dipole elements with respect to a signal wave traveling down the antenna array and undesirable reflection or shielding of signal energy is substantially reduced.
In addition, it will be observed that the parasitics are all cut to one particular frequency, i.e., at or above the upper limit of the high VHF band, rather to any particular harmonic of the fundamental frequency of the dipole element. All of the parasitics 130, 132 and 134 are cut to approximately 25 inches.
As a means of testing the soundness of the conclusion that optimum operation is obtained with the unitary parasitic elements in vertical alignment with their associated dipole elements, the parasitics 130, 132 and 134 were placed in different locations with respect to the dipole elements 110, 112 and 114 and the effect, if any, noted in the performance of the antenna array. Observation of antenna performance was accomplished through the use of a dual-trace oscilloscope connected by suitable transmission line to the feed point at the inboard ends of the dipole 110 and set to sweep the high VHF band. A crystal marker generator was employed to provide visual indication on the sweep traces of the megacycle and 215 megacycle points. One trace (curve X) provided an indication of the response characteristics of the antenna array on the high VHF band and the second trace (curve Y) the VSWR as an indication of the impedance match between antenna and feed line.
FIGURE 9a illustrates the antenna. array with the parasitics positioned below and in vertical alignment with the associated dipole elements and corresponds to the exact structure as shown in FIGURE 7. FIGURE 9b is a graphic representation of the oscilloscope traces obtained. FIGURE 10a illustrates the antenna array with the parasitics positioned behind and in the same horizontal plane as the dipole elements with FIGURE 10b being a graphic representation of the oscilloscope traces obtained for this configuration. FIGURE 11a illustrates the antenna array tested with the parasitics positioned in front of and in the same horizontal plane as the dipole elements with FIGURE 11b being a graphic representation of the oscilloscope traces as obtained in this configuration.
As will be observed, the gain of the antenna array on high VHF band operation is superior when the parasitics are placed beneath the dipole elements but in vertical alignment therewith. Likewise, it will be observed that this configuration provides the best impedance match between line and antenna array. With the parasitics behind the dipole elements, the gain is significantly reduced across the range of the high VHF band. With the parasitics placed in front of the associated dipole elements, the gain is improved somewhat at the lower portion of the high band due to the director action now being provided by the parasitics, but still not as good as that obtained in the configuration as represented in FIGURE 9.
To substantiate the conclusion that it is the front-most driven element shat should form the main or active pick- 1 ll up element for optimum high VHF band operation, an antenna configuration as shown in FIGURE 12 was assembled and the results noted in the same manner as the antenna arrays of FIGURES 9 through 11. As seen, a fullwave dipole driven element D resonating near the center of the high VHF band was positioned on a boom B. A reflector element R cut to resonate below the high VHF band was appropriately positioned behind the driven element D to provide reflector action. The director parasitic element P was placed in front of instead of below the driven element D to obtain the director action as provided by the director elements 124, 126 and 128 in the antenna configuration of FIGURE 7. As seen from the graphic representation of the oscilloscope traces obtained, the response characteristics parallels those obtained for the antenna configuration as shown in FIG- URE 9. Somewhat more of a mismatch between line and antenna is exhibited, however, particularly at the low end of the high VHF band. This is because of the high impedance presented by the fullwave resonant dipole driven element D.
Thus, by employing the parasitics 130, 132 and 134 in close association with the dipole elements 110, 112 and 114 to provide a decoupling action for the elements 112 and 114 and to depress the impedance of the dipole 110 at the inboard ends feed point, the antenna configuration of FIGURE 7 approaches that of FIGURE 12 in terms of electrical equivalency and the performance characteristics obtained.
What we claim as new and desired to secure by Letters Patent of the United States is:
1. A television antenna effective in both the high frequency and low frequency bands comprising in combination:
at least three low band dipole driven elements located in substantially parallel relation to each other, in substantial alignment, defining connecting terminals located along substantially a common line normal to the elements, and having progressively increasing lengths when said common line is traced in one direction providing differing frequencies of most effective operation and coverage of the low frequency band;
a transmission line connecting said terminals to provide signal effects due to their combined action;
unitary elements associated with said driven elements, respectively, each unitary element being located in substantially parallel aligned relation to its associated driven element and in a plane through the driven element substantially normal to the plane defined by the driven elements, each unitary element having substantially the same number of wave lengths in the high band as the associated driven element has in the low band, each unitary element being spaced from the associated driven element by a distance that is short in relation to the length of the unitary element;
' and a dipole director located in coplanar parallel aligned relation with the driven elements outboard the same on the side of the shortest element and in the plane defined thereby, said director including a pair of insulatingly supported dipole elements and a coupler connecting the same, the coupler having a substantial impedance in the high frequency band in conjunction with the other elements and the dipole director as a whole being effective in director action in the low band;
a pair of coaxial unitary high band directors in parallel aligned relation with the arms of the dipole director, in the plane defined by the dipole director and the driven elements;
and a reflector located in coplanar parallel aligned relation with the driven elements, outboard the same on the side of the longest element, the reflector comprising a main arm of unitary construction of length for reflector action in the low frequency band, said director further having a unitary element in parallel aligned relation with said main arm and in a plane through said main arm substantially normal to the plane defined by the driven elements, said last unitary element having substantially the same number of wave lengths length in the high band as said main arm has in the low band, said last unitary element being spaced from the main arm by a distance that is short in relation to the length of the unitary element.
2. A television antenna effective in both the high and low VHF frequency bands, comprising in combination:
at least three dipole driven elements located in substantially parallel relation to each other, in substantial alignment, defining connecting terminals located along substantially a common line normal to the elements, said driven elements having differing lengths to provide effective operation and coverage of the low VHF band, with one of said dipoles exhibiting substantially fullwave resonance at approximately the center of the high VHF band and operating as the primary pickup element in the high VHF band;
a transmission line connecting said terminals to provide signal effects due to their combined action; unitary elements associated with said dipole driven elements, respectively, each unitary element being located in substantially parallel aligned relation to an associated driven element and in a plane through the driven element substantially normal to the plane defined by the driven elements, said unitary element associated with said one dipole exhibiting fullwave resonance in the high VHF band being effective to sufficiently depress the impedance of said one dipole on high VHF band operation to a value which substantially matches the impedance of the interconnect ing transmission line, said unitary elements associated with the dipoles other than said one dipole being effective to provide an electrical decoupling action for said other dipoles from the interconnecting transmission line on high VHF band operation; and
director means located in parallel aligned relation with the driven elements and in the plane defined thereby, said director means including at least a unitary director element and a pair of insulatingly supported dipole arms with a coupler interconnecting the same, the coupler having a substantial impedance in the high VHF band and said director means as a whole lgeing effective in director action in the low VHF and.
3. The television antenna of claim 2 wherein said one dipole driven element forming the primary pickup element for high VHF band operation is the front-most driven element in the antenna array, and wherein the feed point of the antenna is formed by the inboard ends of said one dipole driven element.
4. The television antenna of claim 2 wherein said unitary elements associated with each of the'dipole driven elements are of lengths to provide halfwave resonance at a frequency above the high end of the high VHF band and wherein each of said unitary elements is spaced from the associated driven dipole by a distance that is short in relation to its length.
5. The television antenna of claim 2 wherein each of the unitary elements associated with the dipole driven elements has a length of approximately 25 inches and is spaced from its associated dipole driven element by a distance which is between one and four inches.
6. The television antenna of claim 2 wherein a reflector element is located in parallel aligned relation with the dipole driven elements and in the plane defined thereby, said reflector element having a length to provide effective reflector action in the low VHF band, and an associated parasitic element located in substantially parallel aligned relation therein in a plane through the reflector element substantially normal to the plane defined by the dipole driven elements, said unitary parasitic element having substantially the same number of wavelengths in the high VHF band as the reflector element has in the low low VHF band with the dipole driven element positioned frontmost in the dipole array having a length to provide approximately halfwave resonance at a reference frequency above the high end of the low VHF band. VHF band but below the low end of the high VHF 7. A television antenna effective in both the high and band and substantially fullwave resonance at approxilow VHF frequency bands, comprising in combination: mately the center of the high VHF band, the conat least three dipole driven elements located in subnecting terminals of said frontmost dipole element stantially parallel relation to each other, in substanforming the feed point for the antenna array; tial alignment, defining connecting terminals located a transmission line connecting said terminals to provide along substantially a common line normal to the elesignal elfects due to their combined action, said transments, said driven elements having differing lengths mission line being transposed between adjacent driven to provide effective operation and coverage of the dipole elements; low VHF band with the dipole driven element posiunitary elements associated with said dipole driven eletioned frontmost in the dipole array having a length 15 ments, respectively, each unitary element being 10- to provide approximately halfwave resonance at a cated in substantially parallel aligned relation to an reference frequency above the high end of the low associated driven element and in a plane normal to VHF band but below the low end of the high VHF the plane defined by the driven elements, said uniband and substantially fullwave resonance at aptary element associated with said frontmost dipole proximately the center of the high VHF band; driven element having a length and spacing with rea transmission line connecting said terminals to provide spect to said frontmost dipole element so as to prosignal effects due to their combined action, said transvide an effective impedance match between said frontmission line being transposed between adjacent driven most dipole and the transmission line on high VHF dipole elements; band operation, said unitary elements associated with unitary elements associated with said dipole driven elethe dipole elements behind and to the rear of said ments, respectively, each unitary element being 10- frontmost dipole having lengths and spacings with cated in substantially parallel aligned relation to an respect to said other dipole elements effective to proassociated driven element and in a plane normal to vide an electrical decoupling action thereto on high the plane defined by the driven elements, said uni- VHF band operation by causing a high impedance tary elements having lengths to impart effectiveness to be reflected down the transmission line and across to said driven elements on high VHF band operation said antenna feed point; and with each of said unitary elements being spaced director means located in parallel aligned relation with from the associated driven element by a distance that the driven elements and in the plane defined thereby, is short in relation to its length; and said director means including at least a unitary eledirector means located in parallel aligned relation with ment and a pair of insulatingly supported dipole arms the driven elements and in the plane defined thereby, with a coupler interconnecting the same, the coupler said director means including at least a unitary dihaving a substantial impedance in the high VHF rector element and a pair of insulatingly supported band and said director means as a whole being effecdipole arms with a coupler interconnecting the same, tive in director action in the low VHF band. the coupler having a substantial impedance in the high VHF band and said director means as a whole References Clltefl y the Examiner being efiective in director action in the low VHF UN STATES PATENTS band. 8. A television antenna effective in both the low and gvmegard 343 819 chwartz et a1. 343-814 high VHF frequency bands, comprising in combination. 2 955 289 10/1960 Wineoa d 343 815 at least three dipole driven elements located in sub- 30862O6 4/1963 G 343*815 stantially parallel relation to each other, in substan- ,reen erg tial alignment, defining connecting terminals located 3 127249 1 4/1966 L1H 343*862 along substantially a common line normal to the elements, said driven elements having differing lengths to provide effective operation and coverage of the HERMAN KARL SAALBACH, Primary Examiner.
C. BARAFF, Assistant Examiner.

Claims (1)

1. A TELEVISION ANTENNA EFFECTIVE IN BOTH THE HIGH FREQUENCY AND LOW FREQUENCY BANDS COMPRISING IN COMBINATION: AT LEAST THREE LOW BAND DIPOLE DRIVEN ELEMENTS LOCATED IN SUBSTANTIALLY PARALLEL RELATION TO EACH OTHER, IN SUBSTANTIAL ALIGNMENT, DEFINING CONNECTING TERMINALS LOCATED ALONG SUBSTANTIALLY A COMMON LINE NORMAL TO THE ELEMENTS, AND HAVING PROGRESSIVELY INCREASING LENGTHS WHEN SAID COMMON LINE IS TRACED IN ONE DIRECTION PROVIDING DIFFERING FREQUENCIES OF MOST EFFECTIVE OPERATION AND COVERAGE OF THE LOW FREQUENCY BAND; A TRANSMISSION LINE CONNECTING SAID TERMINALS TO PROVIDE SIGNAL EFFECTS DUE TO THEIR COMBINED ACTION; UNITARY ELEMENTS ASSOCIATED WITH SAID DRIVEN ELEMENTS, RESPECTIVELY, EACH UNITARY ELEMENT BEING LOCATED IN SUBSTANTIALLY PARALLEL ALIGNED RELATION TO ITS ASSOCIATED DRIVEN ELEMENT AND IN A PLANE THROUGH THE DRIVEN ELEMENT SUBSTANTIALLY NORMAL TO THE PLANE DEFINED BY THE DRIVEN ELEMENTS, EACH UNITARY ELEMENT HAVING SUBSTANTIALLY THE SAME NUMBER OF WAVE LENGTHS IN THE HIGH BAND AS THE ASSOCIATED DRIVEN ELEMENT HAS IN THE LOW BAND, EACH UNITARY ELEMENT BEING SPACED FROM THE ASSOCIATED DRIVEN ELEMENT BY A DISTANCE THAT IS SHORT IN RELATION TO THE LENGTH OF THE UNITARY ELEMENT; AND A DIPOLE DIRECTOR LOCATED IN COPLANAR PARALLEL ALIGNED RELATION WITH THE DRIVEN ELEMENTS OUTBOARD THE SAME ON THE SIDE OF THE SHORTEST ELEMENT AND IN THE PLANE DEFINED THEREBY, SAID DIRECTOR INCLUDING A PAIR OF INSULATINGLY SUPPORTED DIPOLE ELEMENTS AND A COUPLER CONNECTING THE SAME, THE COUPLER HAVING A SUBSTANTIAL IMPEDANCE IN THE HIGH FREQUENCY BAND IN CONJUNCTION WITH THE OTHER ELEMENTS AND THE DIPOLE DIRECTOR AS A WHOLE BEING EFFECTIVE IN DIRECTOR ACTION IN THE LOW BAND;
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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3530484A (en) * 1968-05-06 1970-09-22 Sylvania Electric Prod Broadband log periodic antenna with phase reversing parasitic elements
US3550143A (en) * 1967-03-21 1970-12-22 Jfd Electronics Corp Multiple tooth log-periodic trapezoidal array
US3683391A (en) * 1970-10-19 1972-08-08 Rca Corp Antenna system for television reception within both the uhf and vhf television band of frequencies
US4293861A (en) * 1980-01-08 1981-10-06 Winegard Company Compact television antenna system
US4739336A (en) * 1986-08-28 1988-04-19 The United States Of America As Represented By The Secretary Of The Army Log - periodic HF antenna system
US20130043885A1 (en) * 2011-08-15 2013-02-21 Fluid Motion, Inc. Antenna system for electromagnetic compatibility testing
GB2568280A (en) * 2017-11-10 2019-05-15 Univ Of Huddersfield Log-periodic antenna with a passband and a stopband

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Publication number Priority date Publication date Assignee Title
US2700105A (en) * 1954-07-26 1955-01-18 Winegard Co Tv antenna array
US2817085A (en) * 1956-11-14 1957-12-17 Channel Master Corp Broad-band end-fire television antenna
US2955289A (en) * 1957-04-15 1960-10-04 Winegard Co Tv antenna for color reception
US3086206A (en) * 1960-10-19 1963-04-16 Channel Master Corp End fire planar dipole array with line transposition between dipoles and impedance increase towards feed
US3277491A (en) * 1963-10-11 1966-10-04 Channel Master Corp Multiband television antenna with multiband parasites

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2700105A (en) * 1954-07-26 1955-01-18 Winegard Co Tv antenna array
US2817085A (en) * 1956-11-14 1957-12-17 Channel Master Corp Broad-band end-fire television antenna
US2955289A (en) * 1957-04-15 1960-10-04 Winegard Co Tv antenna for color reception
US3086206A (en) * 1960-10-19 1963-04-16 Channel Master Corp End fire planar dipole array with line transposition between dipoles and impedance increase towards feed
US3277491A (en) * 1963-10-11 1966-10-04 Channel Master Corp Multiband television antenna with multiband parasites

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3550143A (en) * 1967-03-21 1970-12-22 Jfd Electronics Corp Multiple tooth log-periodic trapezoidal array
US3530484A (en) * 1968-05-06 1970-09-22 Sylvania Electric Prod Broadband log periodic antenna with phase reversing parasitic elements
US3683391A (en) * 1970-10-19 1972-08-08 Rca Corp Antenna system for television reception within both the uhf and vhf television band of frequencies
US4293861A (en) * 1980-01-08 1981-10-06 Winegard Company Compact television antenna system
US4739336A (en) * 1986-08-28 1988-04-19 The United States Of America As Represented By The Secretary Of The Army Log - periodic HF antenna system
US20130043885A1 (en) * 2011-08-15 2013-02-21 Fluid Motion, Inc. Antenna system for electromagnetic compatibility testing
US8963560B2 (en) * 2011-08-15 2015-02-24 Steppir Antenna Systems Antenna system for electromagnetic compatibility testing
GB2568280A (en) * 2017-11-10 2019-05-15 Univ Of Huddersfield Log-periodic antenna with a passband and a stopband
GB2570038A (en) * 2017-11-10 2019-07-10 Univ Of Huddersfield Long-periodic antenna with a passband and a stopband

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