US2832956A - Tv antenna having uniform directivity pattern - Google Patents

Description

April 29, 195s 4. R. wml-:GARD 2,832,956 I Tv ANTENNA HAVING UNIFORM DIRECTIVITY PATTERN Filed July 27, 1954 naar 5, fz/fw;

TV ANTENNA HAVING UNIFGRM DIRECTWITY PATTERN John R. Winegard, Burlington, Iowa Application any 27, 1954, serial No. 446,010

6 Claims. (ci. 343-819) The present invention relates to an improved receiving or transmitting element for a high frequency antenna operable over two spaced frequency bands.

In -certain high frequency radio applications, such as television reception, it is desirable to provide in a single antenna unit a mechanism which operates etlicientlyy in two spaced frequency bands.- Preferably such operation shouldV be accomplished without the use of switching devices and in a manner which assures effective resonant operation in both bands. For example, for television receiving purposes, it is desirable to provide in a single antenna an effective unit operable over channels 2 to 6 and acts in these channels in a manner similar to a dipole cut to resonate in these channels, and at the same time is operable over channels 7 to 13 and acts in these channels in a manner similar to a dipole cut to resonate in these channels. As the rst group of channels covers the frequency range from 54 to 88 megacycles, and the second group of channels covers the frequency range from 174 to 216 megacycles, it is not practical toattempt a full coverage of the frequency spectrum in a single broad band antenna, unless itis so designed that some portions of the system operate as resonant elements in one band and other portions of the system operate as resonant elements in the other band.

In accordance with the disclosure of the present application, an antenna particularly suitable for television reception is provided. In particular the antenna consists of a pair of closely spaced co-planar dipoles' in aligned relation. The first dipoleisof a length to form a resonant element in the low frequency band and primarily serves to pick up signals'in thisband. The second dipole element i's shorter than the first and is connected to the first element by rst conductors located in the inboard ends of the elements and by second conductors located intermediate the ends ofthe elements. The length of the second dipole element and the position of the second conductors are so chosen that the ends of the first dipole outboard the seconddipoles form high impedance resonant transmission lines in the high frequency band, and, in addition, th'e portions of both dipoles inboard the second dipoles form resonant antenna elements in the high frequency band. The transmission line to the television receiver or other radio apparatus is connected to the inboard ends of the dipoles.

Y The effectiveness of operation of the antenna disclosed herein is thought to result Vprimarily from the fact that in the low frequency band the .dipoles act as a single unitary structure formingV a resonant element in the low freqnency band. In this frequency range the principal effect of the second or short dipole is to add some capacity to the'system and thus improve the frequency response. In the high frequency band, theeffectiveness of the system is thought to result from the operation of the portions of tl. e dipole outboard the second conductorsV as high im# pedance resonant transmission lines whichbecause of their high impedance-do not influence the operation of 2,832,956 Patented Apr. 29, 1958 lthe portions of thelsystem inboard the second dipoles.

It is thought that the portions of the system inboard the ends of the second dipoles accordingly act as resonant antenna elements in the high frequency band as if the other portions of the antenna were not present.

It is, therefore, a general object of the present invention to provide a high frequency antenna Isuitable for use in two spaced frequency bands.

It is a further object of the present invention to provide a high frequency antenna particularly suitable for use in receiving television signals in the 54-88 megacycle and 174-216 megacycle bands. l

Further, it is an object of the present invention to provide in a unitary antenna structure elements which in effect operate as low frequency resonant elements in the low frequency band and high frequency resonant elements in the high frequency band.

Additionally, it is an object of the present invention to provide a television antenna suitable for operation in both, the low frequency and high frequency television bands without requiring switching means of any kind.

Still another object of the present invention is to provide a televisionY antenna structure which is operable in both the low frequency and high frequency television bands and, in addition, is suitable for use with various types of antenna arrays, including directors and reflectors, and, in addition, may be applied to various television driven element constructions, such as, V antennas, conical antennas and others.

It is yet another object of the present invention to provide an improved antennaV suitable for television reception which incorporates in a single element a construction which operates as a tuned element in the high frequency band 'and a tuned element in the low frequency band Without the'use of resonant transmission lines for coupling or decoupling purposes and in which the antenna element is short in its signal-receiving direction so as to be readily accommodated to antenna arrays including various types of directors and reflectors.

Still another object of the present invention is to provide an improved antenna element in which the parts required for electrical purposes contribute to its mechanical strength.

Further it is an object of the present invention to provide an improved antenna particularly suitable for television use which embodies features of construction, cornbination and arrangement rendering it particularly flexible in application, simple in construction, inexpensive and reliable.

The novel features which I believe to be characteristie of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings:

Fig. 1 is a view in perspective and from below of a simple antenna construction in accordance with the present invention;

Fig. 2 is a diagrammatic view showing the driven element of the antenna structure of Fig. 1 as it operates in the low frequency band;

Fig. 3 is a view like Fig. 2 but showing how the antenna operates in the high frequency band;

Fig. 4 is a top plan diagrammatic view of a more complex antenna array constructed in accordance with the present invention; and

Fig. 5 is a diagrammatic view in perspective of a driven` element of modified conical design constructed in accordance with the present invention.

Referring now to Fig. 1, there is shown an antenna array comprising the driven element indicated generally at and a reflector indicated generally at 12. These are mounted on a4 commonl horizontal boom B,which'is affixed to` vertical mast M'by the U-bolt 14 which, as shown, extends about the mastM and vis drawn towards the boom B by suitable nuts (not shown). 4The reflector 12 is carried on the boom B by the saddle 16 which is shaped to embracethe boom `on its bottom face and to receive the reflector 12 on its top face. The reflector is held securely on the boom by the bolt 18 which is drawn tight by thumb nut 18a. While the reflector 12 is broken away in the view of-Fig. 1,- it extends beyond the confines Vof the drivenelernent 10 to form an effective reector over the entire frequency range.V

The driven element 10 consists of a pair of elongated U-shaped antenna portions 20`which define lengthy legs 20a, short legs 20b, andnconnecting sections 20c.,V The portions 20c of the conductors 20, and the adjacent portions of the legs 20a and 20b are sandwiched between faces of the insulating support blocks 22 and 24, these blocks having suitable grooves to receive the conductors 20. The lower supporting block 22 further has a concave cylindrical mounting portion `to seat on the top face of the boom B. Bolts 26 extend through the boom B, the support block 22, and the support block 24 and seat at their headed ends on support block 24. The bolts 26 are drawn tight by the thumb nuts 26a.

In addition to the connections formed by the connecting portions 20c of the conductors 20, the leg parts 20b and 20a are connected together by the conductors 28 which, as will be noted, are located intermediate the ends of the legs. The transmission line T is connected to the connecting portions 20c of the conductors 20 by the binding posts 30 which are c'onductively mounted on the conductors 20 and extend through the insulating block 22. The transmission line T extends to the radio apparatus, such as a television receiver `with which the antenna is to be used. i

Preferably the conductors 20 are made of thin walled tubing of aluminum or similar material. The diameter of the tubing is su'iciently great to provide a broad band antenna characteristic. v

The lengthy leg portions 20a ofthe antenna are made of sufficient length to operate efficiently as resonant antenna elements in the low frequency band. Thus, for example, these legs may be cut to a total electrical length of about 1/z wave length in television channel 2, that is, in the range of 54 to 60 megacycles. Because of the broad band characteristic associated with the distributed capacitance of the legs 20a, as well as that of the other parts of the antenna, such as legs 20b,`the antenna operates effectively over the entire low frequency television band.

The conductors 28 are located inboard the ends ofk the legs 20b by a distance Vsuflicient to forma high impedance resonant transmission line in the high frequencyband. For example, the electrical length of each leg 20b outboard the conductors28 may be 1/4 wave length at 195 megacycles, which is the mid point of the high frequency television band. Inboard the conductors 28,'the electrical length of the legs 20a and 20b is such as to give an 'effective resonant dipole antenna in the high frequency band. This length may, for example, be likewise 1A: wave length at 195 megacycles.

lt will be observed that theshort legs 20b flare somewhat in a V configuration with relationto the legs 20a which are colinear. This provides some of the action of a V type antenna and in addition contributes to the attractive appearance of the unit.. f

The top plan view of Fig. 2 illustrates in a diagrammaticfashion how the above antenna is thought to operate in the low frequency television band. In this frequency range (S4-88 megacycles) the length of the legs 20a is the dominant factor giving riseto the Vantenna characteristics. As above noted, the length of these legs is i sutlicient to give an overall length of l wave in channel 2.

' In this band, the portions of the legs 20a and 20b located outboard the conductors 28 act as an open quarter wave length resonant transmission line. This 'gives rise to a very high impedance at the outboard ends of the transmission lines formed by the portions'of the dipoles out- Y board the conductors 28, with the consequence that the portions of the low band dipole formed by arms 20a and outboard the arms 20b are in effect disconnected from the remainder of the unit. They are, accordingly, shown in `dashed form in Fig. 3. The portions of legs 20a and 20b inboard the conductors 28 act as simple dipole elements in the high frequency band, and consequently give rise to antenna operation similar to that of a dipole cut to proper resonant length for operation in the high frey quency' band.

The leg portions outboard the conductors 28 may be locked upon as a matching network which acts to decouple rather than couple the portions of the low band dipole outboard theconductors 20b, 28.

Applicant does not suggest the above description of i operation as an explanation of every aspect of the operation of the antenna. Rather, it is a practical theory of operation which has been found effective in determining the dimensions of the antenna and in predicting the effect of changes in its conformation.

In a practical antenna for television reception constructed as shown in Figs. 1-3, the following dimensions were used:

Legs 20a 47 inches long. Legs 20b 25% inches long. Connecting portions: 20c 1 inch long. Conductors 28 4% inches long. Distance between connecting portions 20c and conductors 28 13 inches.

Fig. 4 shows a somewhatmodified version of the antenna element ofthe present invention in a more refined antenna array. In this structure, the driven element is indicated generally at 110 and consists of U-shaped conductors 1,20 bentto form long legs 120a, short legs 12011 and connecting Vportions 120C. In this case the leg portions 120a and 120b are parallel to each other. The legs 120 and 120b are connected by conductors 128 as shown and the entire unit cut to a length in accordance with the above description with reference'to Figs. 1-3.

The driven element has a reflector 112 and, in addition, a series of directors indicated at 114 and 116. These are of the type described in detail and claimed in my copending application entitled TV Antenna Array and Director Therefor, Case No. 54,092, now Patent 2,700,105 issued January 18, 1955 assigned to the same assignee `as the present invention. In brief, the center directors 114 operate as simple directors in the high frequency band and the directors 116 act as simple directors in the low frequency band because the connecting sections 118 are non-resonant in this band. In the high frequency band the connecting elements 118 resonate and causethe directors 116 to operate independently of each other and as eccentrically located directors tuned to the high frequency band.

It will be noted that the driven element 110 has the advantage in the ,arrangement of Fig. 4 of having a short Thus, these legs d0 dimension in the direction transverse to its length. This gives rise to minimum complication in locating the retiector 112 and the directors 114 and 116.

lFig. 5 shows in perspective still another version of the antenna of the present invention. In this construction a modified conical design is achieved by provi-ding four U-shaped like parts 220, each defining a long leg 22011, a parallel short leg 220b, and a connecting portion 220C. These `are mounted by suitable means (not shown) to form a V-shape or modified conical shape when viewed from the horizontal direction, the connecting portions 220C of each pair of U-shaped parts being in abutting relation as shown. The conductors 228 bridge each leg 22011 and the connected leg 220b to provide high band operation as described above. The result is an antenna which operates in both the low band and the high band as a simple V-shaped or modified conical dipole.

It will be noted that the driven element 10, Fig. l, 110 Fig. 4, `and the structure of Fig. 5, may be used with all types of antenna arrays, that is, various combinations of f that band may be applied to various antenna driven element configurations. Y

While I have shown and described specific antenna constructions, it will be, of course, understood'thlat various Amodifications and alternative constructions may be made without departing from the true spirit and scope of the present invention. I therefore, `intend by the appended claims to cover all modifications and alternative constructions following within their true spirit and scope.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A television antenna for use in both the low frequency and high frequency bands including in combination; a pair of spaced conductors in Igenerally in line relationship defining a dipole having total electrical lengthv of approximately one half Wave in the low frequency band; a pair of spaced conductors generally coplanar with the first conductors and in line with each other to define a dipole having total electrical length of approximately a full wave in the high frequency band; conducting elements connecting the dipoles at their inboard ends; and conducting elements connecting the dipoles itermediate their ends and `located a distance of approximately one fourth wave length in the high frequency band inboard'from the ends of the last mentioned elements to form high impedance quarter wave vopen lines in the high frequency band.

2. An antenna operable in two spaced frequency ranges compri-sing in combination: a first dipole resonant in the low frequency range; a second dipole closed to and parallel with the first dipole; first conductors extending between the dipoles at their inboard ends; second conductors extending between the dipoles intermediate their ends; the length of the second dipole and the distance of the second conductors inboard the second dipole being such that the portions outboard the second conductors form a high impedance in the high frequency range and the portions of the dipoles inboard the second dipoles form a resonant dipole in that frequency range.

3. An antenna operable in two spaced frequency ranges comprising in combination: a first dipole tuned to the low frequency range and having colinear elements; a second dipole in closely spaced relationship to the first dipole 5 and in alignment therewith, the second dipole being coplanar with the first dipole and having its arms flaring in relation to the arms of the first dipole; first conducting elements joining the dipoles at their inboard ends; second conducting elements joining the dipoles intermediate their ends; the second conducting elements being so positioned in relationship to the outboard ends of the second dipole as to define a high impedance transmission line in the high frequency range in conjunction therewith and the second dipole being of such length inboard the second elements as t-o form a resonant antenna in the high frequency range.

4. An antenna suitable for operation in two spaced frequency bands, comprising in combination: a pair of dipole units closely spaced in relation to each other in the direction transverse to their length; conductors extending between the dipoles at their inboard ends; conductors eX- tending between the dipoles intermediate their ends, the last conductors being located with respect to the first conductors to define a resonant dipole in the high frequency band, the electrical length of one dipole outboard the last conductors -being such as to reflect a high impedance at the last conductors, and the electrical length of the other dipole being such as to form a resonant dipole in the low frequency band.

5. A television antenna suitable for use in both the low frequency and the high frequency television bands, comprising: a pair of unitary elongated U-shaped conductors positioned 'to define the respective arms of a dipole, the conductors forming rear elements of substantially onehalf wave length in the low band, forward elements of Vsubstantially one-half wave length in the high band, y and inboard connecting elements of comparatively short length in relation to the wave length of both bands; and, conductors located approximately one-fourth wave length in the high band inboard the ends of the forward elements and extending between each forward element andthe corresponding rear element.

6. A television antenna suitable for use in both the low frequency and the high frequency television bands, comprising: a pair of unitary elongated U-shaped conductors positioned to define the respective arms of a dipole, the conductors forming rear colinear elements of substantially one-half wave length in the low band, forward flaring elements of substantially one-half wave length in the high band, and inboard :connecting elements of comparatively short length in both bands; and, conductors 'located approximately one-fourth wave length in the high band inboard the ends of the forward elements and extending between each forward element and the corresponding rear element.

References Cited in the lile of this patent UNITED STATES PATENTS Scheldorf July 4, 1944 OTHER REFERENCES Carpenter: Ultra Q-Tee, Radio-Electronics, September 1952, pages 66, 68, 70.

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