DE2125964A1 - Broadband antenna - Google Patents

Description

Dr. F. Zumstein Sr. - Dr. E. Assmann Dr. R. Koenigsberger - Dlpl.-Phys. R. Holzbauer - Dr. F. Zumstein jun.

PATENT LAWYERS

TELEPHONE: COLLECTIVE NO. 225341

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BRÄUHAUSSTRASSE 4 / III

H / III 45604-3

TOKIO SHIBAURA EIECTRIC CO., LTD., Kawasalci-shi

Japan

Broadband antenna.

The invention relates to a broadband antenna, and more particularly a broadband antenna with capacitors at equidistant points from the center of a feed area as seen on the arms unites: antenna element are provided.

A variety of antennas are currently available for receiving radio and television broadcasts. The so-called Yagi antenna is widely used as a broadband antenna for receiving VID? And UHF television signals in particular. However, the usual Yagi antenna is only able to receive frequency bands with a width of about 150 mils, so that not the entire range of 470 to 770 MHz already used today for television signals, for example in Japan, can be covered. Considerable efforts have already been made to

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tenne for such broad frequency bands. Special research was put into the improvement of a radiator, which constitutes the essential salvation of the antenna and which has hitherto prevented or interfered with the reception of such broad frequency bands. For example, double-fan antennas, large-diameter dipole antennas and folding antennas have been developed. Despite a certain improvement in the Freouenabandbreite can also be with these antennas, the entire sawn today • not used UHF television range 470-770 MIZ loading W cover satisfactorily, not to mention the already taken in view and in some countries already used range from 470 to 890 Mz. For the aforementioned antennas there is the further disadvantage that relatively expensive metal plates, in particular for the dipole antenna with a large diameter, have to be used, so that the material costs are considerable. In addition, these antennas are of a relatively complex construction, so that a high proportion of labor costs is also incurred in their manufacture.

There is therefore a need for the development of a simply constructed broadband antenna with which good reception qualities can be achieved over a very broad frequency band without having to accept the disadvantages mentioned. An investigation in this direction according to a proposal by TSMMaclean in Proceedings of IEE, Vol. 115, October 10, 1968, amounts to installing a capacitor at a plurality, for example four or six points, on a dipole antenna element at equidistant points of the center of the feed area in order to achieve the desired goal of broadening the reception frequency band. Maclean concludes in the mentioned publication on the basis of experiments that a capacitor should be provided at several points on each antenna arm in a symmetrical arrangement with respect to the center point of the antenna element, since it is practically very easy to attach such a capacitor to any one

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_ 3 -

Point on the individual arm of a spring forming an antenna element Provide pairs of antenna arms. It should be noted, however, that the theoretical considerations made by Maclean and calculations only for the pail indicated that a capacitor is provided at only one point on each antenna arm is, and it also does not specify the 'conditions necessary to achieve the desirable properties such an antenna to the full extent. His further investigations made on the basis of the calculations mentioned rather show that the installation of a single capacitor on each antenna arm in the resulting antenna does not yet allow reception of such broad frequency bands. ■ In particular, Maclean failed to provide the exact Specify conditions in order to be able to cover broad frequency bands with such an antenna. The straight line mentioned symmetrical arrangement of a large number of capacitors on both antenna arms with respect to the center of the antenna element, as suggested by Maclean, inevitably leads to reduced mechanical strength of the antenna arms, and there are extraordinary difficulties in the manufacture of such an antenna device.

The invention is based on the object of a broadband antenna of the kind described with good mechanical strength for receiving the above-mentioned latitude frequency bands, at two equally spaced points from the center of a feed area on an antenna element Capacitor is provided on each arm of a pair of antenna arms. The aim should be to reduce the ripple factor or the standing wave ratio to a Keep the value below 2.5 in the entire allowable range for fit and mismatch.

J) Ie invention consists in a broadband antenna that at least a dipole antenna provided with a feed section

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element, which consists essentially of a pair of rectilinearly arranged antenna arms with capacitors formed thereon, in that in each case one of the capacitors at a point equally spaced from the center of the feed area of the antenna element ^, electrically considered in series, on each of the two antennas 'tue arranged, and that when the ratio of a distance <£> from the center of the feed area to the outer end of the antenna arm to a distance t ^^ from the center of the feed section to the location of the capacitor to 0.4 to 0.6 and if calculated values si * and .C2 _?? are selected that are equal to the double logarithm .naturalis of the ratios of the radii of the various sections of the antenna arm3 to the total length of the antenna element to be less than 12, the capacitance value of the capacitor in pico-farad results from the definition of the Ratio of capacitance value to distance- ^ ₂ ^to 0.025 to 0.3.

According to an advantageous embodiment for receiving all Frequency bands of UHF television signals, as used throughout the world, are shared equally on the two arms, straight-line distance from the center of the supply area, in electrical terms, in series, on the radiator A capacitor of 0.5 to 5 pF, for example, is attached to a Yagi antenna.

The invention and advantageous details are explained below using several exemplary embodiments with reference to the drawing. It shows:

1 shows the perspective view of a broadband antenna according to an embodiment of the invention;

FIG. 2 shows the equivalent representation of the broadband antenna according to FIG. 1; FIG.

FIGS. 3 to 5 illustrate partial sections from specific embodiments of that section of an antenna element which

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according to the invention is provided with a capacitor;

Pig. 6 shows, in a partial section, a further specific embodiment of the capacitor section in Pig. 1; 7 illustrates the structure according to FIG. 6 from above;

Pig. 8 His 10 are Smith'sehe circuit diagrams to illustrate the properties of a wide-hand antenna according to an embodiment of the invention;

11 shows the perspective view of a Yagi antenna

applying the invention to the radiator of this antenna;

Pig. 12 shows the top view of another antenna arm using the invention and FIG

Pig. 13 shows the properties of the Yagi antenna according to Pig in a curve diagram. 11.

The invention will now be described in detail with reference to the Piguren briefly explained above. Pig. 1 shows the construction of a dipole antenna according to the invention 5 ", which form an antenna element or a dipole antenna. The feed terminals 1 and 2 are connected to a feed unit, not shown. The inner ends of the antenna arms 4 and 5 are electrically connected to the feed terminals 1 and 2 in the antenna arm holder 3. At a prescribed point of each antenna arm, two capacitors 6 and 7 are arranged in a linear as well as an electrical series, equally spaced in the opposite direction from the center point, ie from the center point O of the antenna element, of the feed terminals 1 and 2. The equivalent circuit of the dipole antenna according to Pig. 1 shows Pig. 2, in which capacitors 6 and 7 are both labeled Cj. The distance between the capacitors C. is denoted by 21 ^, while 21g denotes the total length of the antenna and β ^ denotes the radius of the section of the antenna arms 4 and 5, which extends from the center point O of the feed section to each

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- "ö ■"

Capacitor G ^ extends (in Pig. 2 the diameter of this section is labeled 2J ^ "). The radius of the ATd intersected α of antenna arms 4 and 5, which _{extends from the outer end to each capacitor C 1} , is P ₂ designated (in Fig. 2, the diameter is also designated as 2 ? ρ).

The inventors now have the conditions necessary for an antenna determined in order to achieve the desired broadband properties in a simple manner with an antemic structure according to the "Pig. 1 and 2 to be achieved by arranging a capacitance on each arm of a dipole antenna in an equal abotand in such a way that • how it is explained in the further description.

First, however, with reference to FIGS. 3 to 6, various specific embodiments for the capacitors C. are explained. Since the two arms 4 and 5 of the antenna are constructed in the same way, only the corresponding part of the arm 4 will be explained. According to FIG. 3, the arm consists of a hollow conductor section which is divided into two sections 8 and 9 approximately in the middle. The opposite ends of these sections 8 and 8 are kept separated from one another by a very specific distance. A central conductor 10 is arranged coaxially to the arm 4 over a certain length, which extends into the two ends of the sections 8 and 9 and penetrates the end faces of each section at a right angle. The interior of the hollow arm sections 8 and 9 including the space between the opposing ends is filled over a certain area with a dielectric 11, for example with phenolic resin or acrylonitrile butadiene styrene terpolymer, so that the center conductor 10 and the space between the opposing end faces of the Arm sections 8 and 9 is filled. The outer peripheral surface of this part of the antenna arm 4, which is filled with the dielectric 11 , is surrounded by a further insulating material 12 of the same or different types, in such a way that both arm sections 8 and 9 are integrally connected and in

1 09850 / 1ΠΓ

fixed local relation to each other. Because of this structure is between the hollow antenna arm 4 and the Center conductor 10 as well as between the opposite ends of the array sections 8 and 9, a capacitor C, is formed. These capacitors have a total capacity of Ο., On, as in Pig. 2 registered int.

Pig. 4 shows another structure of the capacitor. Here is In a hollow conductor 13 coaxially a rod conductor 14 of smaller diameter pushed over a certain length and held and forms an antenna arm 4 or 5. The through the inserted section of the rod conductor 14 with the inner walls The space bounded by the hollow conductor 13 is filled with a dielectric material 11. The outer peripheral surface of the area of the waveguide 13, via which the rod conductor 14 is coupled, is surrounded by an insulating material 12, so that both Conductors 13 and 14 are integrally connected to one another in a mechanically stable manner. Also in this pail is between the two ladders 13 and 14 a capacitor is formed whose capacitance value through the delimited space including the areas described the opposing planes is determined. The mentioned, rod-shaped conductor 14 can through a hollow conductor piece be replaced, which - as mentioned - has a smaller diameter than the outer, hollow conductor 13.

When building the capacitor according to Pig. 5 are columnar or plate-like conductor bars 15 and 16 arranged so that certain planar areas face each other at a fixed distance, with which a capacitor C. of the desired capacity can be determined. The space between the two conductors 15 and 16 is filled by a dielectric material 11. In the overlap area of the two conductors 15 and 16 and over a certain amount The outer jacket of this capacitor area is surrounded by an insulating material 12 at a break safety distance.

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In this case, the capacitor Cj is substantially through the opposing surface areas of the "two." Conductors 15 and 16 formed.

! The capacitor C. can also - like the l ^p ig. 6 and 7 reveal - be formed in a different way. According to Fig. 6 "for example, conductors 17 and 18 are made of hollow aluminum tubing which form antenna arms 4 and 5, and the opposite ends are pressed flat and with respect to the axis of conductors 17 and 18 around bent a certain angle in the opposite direction, in such a way that the flattened end portions 19 and 20 face each other at a certain distance. In the space between the angled flat end sections 19 and 20 and on the outer circumferential area of these end sections and over a certain break safety distance, a dielectric material is inserted or applied, for example periol resin or acrylonitrile-butadiene-styrene terpolymer, in such a way that the two Head 17 and 10 are integrally and mechanically firmly connected to one another. The capacitor C ^ is essentially formed by the flat end sections 19 and 20 facing one another. The ladder 17 and. 18 can be formed by hollow cylindrical rods, possibly also of different diameters. This construction has the advantage that the flat end portions 19 and 20 act as stops or holding parts for the dielectric material 11, so that the loiter 17 and 13 cannot be axially displaced or rotated about their axis, which may cause any "external forces" act on the ladder bars.

To now the aim of the invention in the formation of a capacity at a certain one from the center of the feed area Dixjol antenna straight on each arm of an antovmon pair arm; and be equidistant to reach the point where dor Capacitor electrical companions in series connection are

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in the following now the relationships determined by the inventor in more detail explained, through which the good broadband properties of an antenna according to the invention are achieved.

The calculated input admittance or the input admittance v / ert Yin with a dipole antenna according to the Pig. 1 and 2, as seen from the feed section, results from the following relationship :

_Yin

E.g.)

In it "means:

Za = input impedance seen from point O of the feed section, when there is no load, i.e. when the capacitor C. | is shorted;

Zb = impedance, seen from the position of the two capacitors C ₁ , which are arranged at the same distance I ^ from the point O of the feed section, which is to be thought of as being removed in the event of a short circuit of the center point O, while the other capacitor remains unchanged;

Zm = core resistance or mutual open circuit resistance or coupling resistance between the point O of the feed section and one of the center O around the Distance I ^ distant point if both capacitors are removed;

CJ = angular or circular frequency.

For a better representation, the equation (1), i.e. the mentioned Input admittance Yin replaced by the input impedance Zin:

_{zin β} _ ί (2)

Jl _ 2Zb

^Za Z ² m

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Za, Zb and Zm in equations (1) and (2) are functions of the quantities KIg, Kl ^, SL ^ and XL. For reasons of a more concise representation, the derivation of the associated puncture equations is omitted here. Κ, ϋρ and and -ίΊ. can be obtained from equations (3) to (5) given below. The variable factors JX and -Qp introduced by the inventor require explanation. "Ώ.-i and -Ω-ο ^Ξ ^ ^{η <3} - functions of the ratio of the length of the antenna arm to the radius, as can be seen from the following equations (4) and (5):

K = £ 2 - (3)

Ω
1

Therein mean:

A = wavelength
/ n = natural logarithm

The factors ^, W? 2 j / \ and J ^ ₂ characterize the dimensions of the various parts of the antenna according to Pig. 2. All possible combinations of the variables are permissible to investigate the properties of the antenna according to the invention. The derivation and description of all combinations, however, would expand the number of the resulting variable combinations to such an extent that difficulties in the representation of the essential properties of the antenna could arise due to the size alone. Corresponding references are therefore only given where this appears necessary in order to explain the test results that can be achieved with the invention accordingly. For the purpose of the further description, the assumption made in the following by equation (6) on the basis of the experiments and studies is made:

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ρ-,

From equation (6) it can be seen that i "!,. Equals jfl can be chosen. The reason for this results from equation (5) taking into account the following equation:

_Ä _2 / »2 ^ 2

This results from equation (6):

If a <C 1 is introduced as a constant of proportionality, then £ ^ can be expressed as follows:

(7)

The constant of proportionality | a is chosen to be 0.5, so that the result is the Pail in which the capacitor C ₁ is arranged in the middle of the antenna arms 4 and 5, respectively.

The term j ^ C ₁ of equations (1) and (2) can be expressed as follows:

Here c is the speed of light with 3 χ 10 ^ ° cm / sec. The inventor has thus determined that the input impedance

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Zin of equation (2) al π puncture of variables a, K '^ - ,, XL.,

Π " C- ά

and expresses 1. The Pig, 0.9 and 10 show Smith's marriage

Line diagrams in which the input impedance Zin is plotted as a function of the named variables. It should be pointed out that, in the course of this description, a normalization to an impedance of 300 S2. is taken as a basis. FIGS. 8, 9 and 10 give Zin with a modification of the ratios of the value IiCp

rr- , a and S). as variables. The inventors have found that from these wiring diagrams, Zin can be set within a range of the standing wave ratio of less than 2.5 by adding a value to the variables C,, a and - ^ ₂

appropriate value is assigned. The experimental results confirm the theoretical "considerations" to a satisfactory degree.

Pig. 8 shows the Pail for which the normalized impedance was set at 3ΟΟ.Γ2, a at 0.5 and Sl ₂ at 8.65. If the variables __1_ were selected, the curves for Zin were 0.0417, 0.0625 and

0.0834 obtained. As already mentioned, ^ Xo ^e: ^ ^{n is a} particularly important factor in determining the ratio of the radius of the antenna arm to its length. In Fig. 8, the numbers 2.2 to 4> 0 denote the values for K ^ ₉ , where the capacitance value is the.

Capacitor C ₁ , contained in the variable _Ί_ int, in pP

and C2 in cm are given.

The same units are also used in the representations of the Pig. 9 and 10 is based. The relationship of size; K A for frequency is given in the following table:

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BAD OFHGINAL

1.8

1.97
2.0

2.16

2.2

2.35
2.4

2.6

2.8

3.0

3.2

3.22

3.4

3.54

3.6

3.8

3.85
4.0

Tabel

₂ --20 cm 450 47Ο 478

469 526 561 574 621 669 716

765 77Ο 812 845 859 907 918

955

(MlisO J & .r & v cm ^ = 22 cm
C. 560 392 590 429 400 435 452 470 440 478 470 511 480 521 520 565 560 610 600 653 640 696 641 700 680 740 708 770 720 785 760 826 770 856 800 890

The fourth for K ^ ₂ becomes 2.16 "to 3.54 in the table above
obtained if £ 2 ^zn 22 cm is selected, which corresponds to a frequency band width of 470 to 770 MHz. For the interest rate curve of the

Fig. 0, which _{corresponds to 1 =} 0.0834, the value for Zt 'can be determined in such a way that the standing wave ratio in the

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A satisfactory range falls below 2.5. In this case, a fourth of the condensate G ₁ can be calculated as 0.0834 x 22 = 1.8 pF. Fig. 8 also shows

that with increasing fourth for 1 the assigned curve gradually is shifted against the adjacent outer curves, which is equivalent to larger fourths for the standing wave ratio. This increase in value from 1 means one

T ₂

^ corresponding decrease in the value of the capacitor C ₁ on deca antenna arm in relation to its fixed length

As can be seen from the description given so far, the desired frequency band can be set within practically permissible limits of the value of the standing wave ratio when a capacitor of small capacitance is at a fixed point on each arm of an antenna dipole at the same distance from the center of the feed area of a dipole antenna is arranged. As explained, this results in the possibility of receiving a much wider frequency band through a simple, constructed antenna than was previously possible with conventional antennas. An inept selection of the capacitance value of the capacitor C, however, can lead to an antenna otherwise constructed in accordance with the invention not having the advantageous properties of the broad frequency band. Tests and calculations carried out on a dipole antenna according to the invention have shown that the desired goal cannot be achieved if the value K ^ ₂ >, ^which corresponds to the ratio of the frequency to the length of the antenna arm, is lowered below a fourth of 4.1, and if the fourth for ^G 1, which is the ratio of the capacitance of the capacitor

⁷ H.

Cj defines the length of the antenna arm, for practical purposes Application case does not lie in the range from 0.025 to 0.5 pF / cm. If the specified limit values are not adhered to,

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the essential effect of the considerable widening of the Einp.fangsfrenüenzbandes not achieved.

The description given with reference to Fig. 8 is in relation to the case where the constant of proportionality a, which the required position of the capacitor C. defines, too

a = _v- £ ~ "= 0.5 was chosen. In contrast, FIG. 9 shows curves for the impedance Zin with formation to a value of 300 SL with values of -P ₂ = 8.65, 1 ₌ 0.0625 and the Proportionality

"2

constant a to 0.416, 0.5 and and 0.583 This figure shows dciß with higher values of the proportionality constant the assigned Curve is gradually shifted against the adjacent outer curves, while Zin increases with decreasing values curves further inside is reproduced. It can be seen from this that even with a fixed value for

^C 1 ··

ψ ~ a suitable choice for the impedance Zin by changing the

Constant of proportionality a, i.e. the position of the capacitor C. can achieve.

Fig. 10 illustrates the curve of the impedance Zin when the normal

C.
Impedance value to 30OiL, 1 to 0.0625, a to 0.5 or

Sl ₂ can be set to 7.75, 8.65 and 9.2 ^ 2. In this case, with increasing values of Sl ρ, the impedance Zin is increasingly shifted further outwards. If, as tests show, XÜL is chosen to be 8.65, then satisfactory values result for a broadband antenna for the reception frequency range from 470 to 770 MHz. It has been found that ipl should generally be chosen to be less than 12. Likewise, the term.Q_ | can be set smaller than 12 in equation (6 ').

From the above it follows that according to the invention a Create a dipole antenna for the reception of very wide frequency bands for a value of the standing wave ratio below 2.5

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G ₁

leaves if the conditions Κ £ _ο <4.1 »0.025 <-ττ · <0.3 pF / cm

^ ^ 2

and XL ₂ <12 are complied with. If the radiator 20 is a yagi antenna according to Pig. 11 from a dipole antenna thawed in this way, very wide frequency bands can be received with such an antenna. The mentioned dipole antenna can be constructed in that a plurality of antennas 21 and 22 are arranged parallel to one another in a horizontal plane or in that those facing one another Ends of the arms are bent, as indicated by dashed connecting lines in Fig. 12. The modification according to Fig. 12 is equivalent to a single dipole antenna, the thickness of which has been increased considerably.

The description of the invention given so far can be as follows summarize as follows:

A. The ratio of the capacitor C. to the distance £ ^ from the outer end of the antenna arm to the center O of the feed outlet

Cut, i.e. the size __1_ is determined by the border 0.025 to 0.3 pF / cm. <^ 2

B. The value SX ^ is equal to twice the natural logarithm of the ratio of the radius of that part of the antenna arm which extends from the center 0 of the feed section of the antenna element to the capacitor C., to its total length, and the value JXp ^ - ^s ^ is equal to that Logarithm naturalis of the ratio of the radius of that part of the antenna arm which extends from the location of the capacitor to the outer end of the antenna arm to the total length of the antenna element. These two sizes are chosen to be smaller than 12.

C. The ratio of a distance i ^ from the center O of the feed section of the antenna element to the outer end of the antenna arm to a distance - ^ ₁ . from the center O of the feed section to the location of the capacitor, ie ^

ti ⁼

is set to 0.4 "to 0.6.

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212596 *

If a dipole antenna fulfills these conditions, it can receive much broader frequency bands than was possible with conventional antennas with a similar structure, namely with antennas which, with regard to the value of the standing wave ratio, are within the preferred range of, for example, 2.5. The reduction in the diameter of an antenna element lowers the material costs, so that it is possible with the invention to produce an extremely inexpensive broadband antenna. Application of the invention to a yagi antenna gives excellent broadband characteristics. Pig. 13 illustrates the characteristics of a Yagi antenna with eight elements; which is made up of director, reflector and radiator elements 23, 24 and 20, and wherein the invention is applied to the radiator element 20. The curve diagram of the Pig. 13 are the Pail again, in which the distance £ ₂ ^Yom center 0 of the feed section of the Yagi antenna radiator according to Pig. 11 to the outer end of the antenna arm is 20 cm. The constant of proportionality a is 0.9 »the diameters 2 Λ and 2 f ^ of the various sections of the antenna arm are both 1.27 cm» and the capacitance Q ^ has a value of 5 pP. Like Pig. 13, all frequency bands of 470 to 790 MHz customary for UHF television transmissions can be received with such an antenna, the standing wave ratio being within a range that is less than 2.5. Therefore, if the invention is applied to a Yagi antenna for receiving television signals, the image quality and the sensitivity of a former receiver can be improved.

1 098 5 0/1 23 9 OfHGiNAL INSPECTED

Claims (1)

Claim, e Broadband antenna which has at least one dipole antenna element provided with a feed section, which consists essentially of a pair of antenna arms arranged in a straight line with capacitors formed thereon, characterized in that in each case one of the capacitors (6.7 »C .) at one of the center (O) of the feed area (3) of the antenna element (Ibis 7) equally spaced ratio of a distance ^ g ^VGI1 & ^er center (0) of the supply portion to the outer end of the antenna arm (4 or 5) to a distance £ λ from the center (O) of the feed section (3) to the position of the condenser: 0.4 to 0 , 6 and if calculated values jß .. and S1 ^ which are equal to double the natural logarithm of the ratio of the radii of the various sections of the antenna arm to the total length of the dipole antenna element are less than 12 , the capacitance value of the capacitor (C.) in pico-farads results from the definition of the ratio of the capacitance value to the distance -ς _Ρ to 0.025 to 0.3. 2; Broadband antenna after. Claim 1, characterized in that the respective capacitor (6 or 7, C ^) is formed by end sections of a pair of hollow guide rods (8, 9) which essentially form the antenna arm, opposite one another at a certain distance, one coaxially in the space between the two end sections of the central conductor (10) of a certain length arranged opposite one another, an inner dielectric (11), 109850/1239 one through the inner walls of the opposite end sections, the outer sheath of the central conductor (10) and fills the space between the ends of the opposing ladder bars, and is formed by an outer insulating material (12), which is the outer peripheral surface of the area of each other opposite end sections including a certain fracture safety zone covered (Pig. 3). Broadband antenna of claim!, Characterized in that the respective capacitor 'through the end portion of a first hollow substantially the antenna arm forming the conductor bar (13), the coaxial protrudes to a certain length into the end portion of the first conductor bar end portion of a second conductor bar ( 14) smaller diameter, an inner, the first hollow conductor rod in the area of the end portion filling dielectric (11), which surrounds the end portion of the second conductor rod, and is formed by an outer insulation material (12), the end portion of the hollow conductor rod and a covers the area adjoining the end section of the second conductor bar (14), so that a mechanically stable connection (| exists (Pig. 4). Broadband antenna according to claim 1, characterized denoted that the respective capacitor by the each other at a certain distance and on certain Length of overlapping end portions of a pair of plate-shaped Conductors (15, 16), which essentially form the antenna arm, in the space between them opposite end sections filling dielectric (11) and an outer insulation material (12) is formed, which the outer periphery of the end portions over the area 109850/1239 of the dielectric as well as a certain break-proof tone covered (Piß. 5). 5 «broadband antenna according to. Addressed 1, thereby. It is determined that the respective capacitor is formed by flattened end sections (18, 19) of a pair of hollow conductor rods (17, 18), which are opposite to one another at a fixed distance and are angled opposite to the antenna axis by the same angular amount. which essentially form the antenna arm and ψ a dielectric (11) is formed between the opposite, flattened end sections and surrounding the outer circumference of these end sections including a break-proof zone. 6. Broadband antenna according to at least one of the preceding Claims, characterized in that the broadband antenna as a Yagi antenna with a number Director elements (23), at least one reflector element (24) and a radiator element (20) is constructed with a feed section, and that the radiator element (20) is essentially composed of a pair of linearly arranged antenna arms and a capacitor each, the one at one or a plurality of points on each arm according to the provision in the characterizing part of the claim 1 is formed. 109850/1239 Lee rse ι te