DE1945850A1 - Directional antenna - Google Patents

Description

it 1366

Sony Corporationj Tokyo / Japan

Directional antenna

The invention relates to a directional antenna, particularly for television receivers.

In the development of transistors, integrated semiconductor circuits and other electronic components, miniaturization has been increasing. Related to the manufacture With electronic transmitting and receiving devices, the need for miniaturized antennas also arose. Included the directivity of an antenna should be sharp, so that the punk connection through multiple reflected waves, urban Disturbances and similar phenomena are not adversely affected. Also the transmitting and receiving devices, for example Television receivers should have a sharp directivity over a wide frequency range. For this purpose a Broadband Yagi Antenna Proposed; however, it takes up a lot of space and is therefore, for example, portable Televisions not suitable. The subject of the earlier German application P 19 07 918.6-35 of 8.2.1969 of the applicant is a so-called loaded loop antenna, in which there is a loop consisting of two semicircular conductors and an artificial load is connected to a point opposite the feed point. Although this antenna has a small construction; however, their directivity is not sufficiently sharp.

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The invention is now based on the object of an antenna to develop the latter type so that it does not only small in size, but also has a sharp directivity over a wide frequency range. the The antenna according to the invention should be particularly suitable for television receivers.

The antenna according to the invention consists of curved antenna elements and a number of impedance elements, each between two adjacent ends of antenna elements are connected and determine the power distribution to the antenna elements. The values of the associated with the antenna loop Impedance elements are chosen so that when the current distribution in the loop is in each case in current distributions is decomposed, which have a non-directional radiation characteristic and directional radiation characteristics of 2, 3, JJ ... have symmetrical radiation lobes that Currents that generate the electric radiation fields that are based on these decomposed current distributions, in the phase are approximately equal and have amplitudes such that they give a desired composite directivity.

These and other features of the invention will become apparent from the following description of some illustrated in the drawings Embodiments emerge. Show it

Fig. 1 is a perspective view of a loop antenna;

Fig. 2 is a schematic representation of a erfindungsge-> MAESSEN antenna;

Fig. 3 is a diagram showing the sub-beam level in relation to the diameter of the loop;

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BAD ORIGfNAL

Flg. k is a diagram showing the antenna quality at different approximations;

5 and 6 are diagrams of an embodiment of the directional characteristic of the invention Antenna;

Flg. 7 is a schematic representation of another embodiment of the invention, in which with reactance elements are connected to the loop;

8 shows a directional characteristic of the antenna according to FIG. 7;

9 shows a diagram of a further exemplary embodiment, in which at least one negative resistance element is connected to the loop;

FIG. 10 shows a directional characteristic of the antenna according to FIG. 9;

Fig. 11 is a perspective view of a further embodiment of the invention, the covers a wide range of frequencies;

Fig. 12 is a perspective view of a further embodiment of the invention;

Fig. 13 Directional characteristics of the antenna according to Fig. 12 at different frequencies;

Figure 14 is a graphical representation of the front-to-back ratio the antenna according to FIG. 12;

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-H-

15 is a schematic representation of a further embodiment ₍ . Rungsbeispleles of the antenna according to the invention, 'which covers a wide frequency range ;.'

16 and 17 are graphs of the frequency. ■ I dependence of the sensitivity of the antenna according to FIG. 15;

18 shows further exemplary embodiments of the invention Antenna.

The antenna loop 1 illustrated in FIG. 1 has a diameter 2b and is made from a curved conductor which has a diameter 2a and to which current is supplied from the connections 3a, 3b. If the antenna loop 1 is arranged so that its plane lies in the plane formed by the x and y axes of the rectangular coordinate system (x, y, z), the center of the loop 1 is also located at the origin 0 and is along the loop 1 a certain current distribution IO) exists, the electric radiation field strength E. (R, Θ, 6) based on the current distribution can be expressed by the following equation:

here mean k =

(2) G (R, θ, ό) =

Jo (kb sin θ) +2

47CR

with γ

cos m (6-ß) Jn (kb sinQ) r

If one develops the current distribution I (ß) and the directional pattern of the loop antenna in Fourier series of cos ταέ, the following relationship results between the coefficients im and Am:

• *

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kbS _T I m-1 I » τΈΪλΤΓ

e ° \ 2 rj. ., (kb sin 6) + e 2 ^u J. "(kb sin Θ)

Here is

Since the terms of both Fourier series are equal in number, the directional pattern (D (Q, 6) and the current distribution (I (ö)) can be expressed as follows:

D (θ, «5) = * - - An cos ηέ n-0

(5) Ko) = Σ ^ i "cos no

n = 0 ⁿ

Furthermore, if a current source connected to the terminals 3a, 3b is expressed in the form of a cT function and the loop 1 is an ideal conductor, then the _{following relationship applies to the current I Q} (6) of the loop 1:

V ₁ oQ _e Jnd
⁰ " JX? Η = - * °° η

Here is

Assume a loop antenna to which impedance elements Z ₂ , Z, .... Z .... Z of the number (m-1) are connected in such a way that the impedance elements and the connections Ja, 3b are provided at approximately equal intervals (see Fig. 2). In this case the electromotive forces on the impedance elements Z ₂ , Z, .... Z .... Z _{m are} as follows:

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^V q ^S -

(8b) I _q =

where q = 1 - m. This gives:

(9) I '(rf) = "ΣΙ

(10) I = - JZ ym (P, q) IZ
^p q = l ^qq

where ^

(q-D)

_t off
(lib) ,, (Μ) 4ΣΙ

A desired current distribution and consequently a desired directional pattern can be achieved in that the impedance values of the impedance elements Z ₂ , Z ,, ... Z, ... Z _m are chosen so that the current distribution of the antenna of FIG it is obtained from the above equations (9) and (10) with which the equation (5) agrees. However, this requires ^! an unlimited number of impedance elements since equation (11) is an infinite series. A suitable approximate solution is accordingly required for practice. If the selection theorem is used, a selection is made at 29 points between 0-0-2 of the distribution of equation (5); the currents of the impedance elements at the selection points and those of the impedance elements Zp, Z ,, ... Z_ are made equal to each other. In this case the required number of impedance elements is 2 *.

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As a result, the currents I ₁ to I _m at the

Selection points indicated; at m = 2 ^ can be given by the equations (9) and (10) given current distribution can be written as below. In the case of a directional pattern that is symmetrical to the connections 3a, 3b, the following applies:

TT 7.-7 o ^^^ ro ¹ P "• Sn-P + 2 ' ^ώ Ρ" ^ώ ηι

and ot = «- _ so that

_sln

ζ _sln qqm

_cos 2P (ql) E _{= CO8} m

m m

From equation (9) results

i _q z _q cos

V ^cos

There are the following two methods of determining the impedance values of an input impedance Z ₁ and the impedance elements Z ₂ to Z _m from the equations (12) and (5). One method is to accept

¹ O ^{= 1} O ' ¹ I ^{= 11} I' ^{iv = 1} V

O ^{= 1} O ' ¹ I.

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and solve the following equation (13):

0

O I

-1

P + l

1 2

2

1 2cos £ -----

1 ■ 1

cosTl 2cos (i? -l) 1C (-1) ² '

I ^

The other method is to accept

τ - τ 'τ ( £ Jrt - τ »/ ^g *" \

¹ CO) * ^x (0) » ^II m ^J * ^I <m ^; »

and solve the following equation (I ¹ I)

0

I.

-1 f.

• y _m (i, m)

-i

Then the value of each impedance element is ^{calculated from the equation (I 1} I). If the horizontal plane radiation characteristic is expressed in the form of a linear polynomial of cos 6 , the directivity, the current distribution and the ratio between their coefficients result from equations (i) and (5) as follows:

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(15) D ((6) = A ₀ + A ₁ cos 6

(16) 1 (6) = I ₀ + I ₁ cos ό ¹ O ⁼ kbT '2J

J _o (kb) -J ₂ (kb)

Admittances are defined as follows

⁽²⁰⁾ y _u = al?

so it turns out

(21) y ₂ (l, I) = Z ^ Li, y ₂ (i, 2) =

Accordingly, if an impedance element Z _{2 is} connected to the loop at a point symmetrical to the connections 3a and 3b, its value results from equation (14) as follows:

² Vu

If the horizontal plane directivity is given in the form of a quadratic polynomial of cos 6 , it follows

(23) D (eS) = A ₀ + A ₁ COS ό + Agcos and

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Kd) = I ₀ + I ₁ COS ό + I ₂ COs 2ό If one defines

the following values of the three impedance elements Z ₂ and Zr are obtained from equation (I ¹ I):

b (27) Z ₂ = Z ₄ = 2-2 +

^{2 4} y _b ² -y _q ²

- 1 ^y b

If one calculates the values of the impedance elements Z ₁ , Z ₂ and Z, with a quadratic, binomial approximation for the directivity and the Chebishev approximation for different under-beam planes, one obtains the following solutions:

a) With ReZ <0 and ReZ,> 0 the directional effect is on Maximum in the direction of the connections 3a, 3b.

b) With ReZ ₁ > 0 and ReZ, <0, the directivity is a maximum in the connections 3a,. 3b facing away from the direction.

c) With ReZ ₁ <0 and ReZ, <0 and a negative resistance range, the directivity is a maximum in each of the two directions (a) and (b).

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In Flg. Fig. 3 illustrates one embodiment of the relationship between the above directions and the sublobe level; the ordinate represents the sub-radiation lobe level and the abscissa represents the value kb, ie the standard relationship 712WA- between the diameter 2b of the antenna loop 1 and the wavelength ; the reference numerals 4a, * lb and ^ c denote areas in which the above-mentioned solutions (a), (b) and (c) are present.

The following results for the antenna quality: (a) if ReZ ₁ = R _L1 <O and

(29) YL = 1 ♦

I ₁ ² ReZ ₁

(b) if ReZj> O and ReZ ^ ₊₁ <O

(30) ^ I ¹ Il ² ^ ² I ⁺
= 1 +

(c) if ReZ ₁ ^ O and ReZ ^ ₊₁ <0, the antenna quality can be calculated from both equations (29) and (30).

Fig. ¹ with respect to I shows the calculation results for the antenna at different quality approximate impedance values of the square direction effect. The area ¹ Ic in FIG. 3 represents the quality calculated from equation (29) for the case that the characteristic impedance CL of the antenna loop 1 is 2 ln ~ - = 9 ohms. The quality tends to increase near the boundaries of the regions in Fig. 3; however, the quality is mainly determined by the sub-beam levels.

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5 and 6 illustrate the directional radiation characteristics when the characteristic impedance C1 of the antenna loop 1 is equal to 9 ohms and when 10 dB are given for the Chebishev approximation, that is to say when the sub-radiation lobes are -10 dB. In Fig. 5 the lines marked with crosses χ and triangles / \ illustrate the directional radiation characteristics at kb = 0.1 and kb = 0.6, while in Fig. 6 the lines illustrated with crosses χ and circles ο the directional radiation characteristics at kb = 1 , 2 and kb = 1.5. Solid lines represent the ideal directional radiation characteristics. It can be seen from the drawing figures that the sub-radiation lobes, after the approximation is carried out with a limited number of impedance elements, become larger than in the ideal case; at kb - 1.2, however, no difficulties arise in practice. The impedance elements are arranged in the antenna loop at equal intervals.

FIG. 7 illustrates an embodiment in which two impedance elements are connected to an antenna element 10 instead of the impedance elements connected to the connections 3a and 3b in FIG. 1. If the characteristic impedance of the antenna element 10 is assumed to be 9 ohms, _{the value of the impedance elements is Z 2} = Z ^{for a given radiation pattern with - 1} IO dB in the Chebishev approximation and kb = 1.0 (at a frequency of 200 MHz) ₁₁ = SOO 0hm. In this case the impedance elements Z ₂ and Zu consist of reactances. Since the antenna element does not contain a resistance to cause loss, the result is a low-loss antenna. FIG. 8 shows the directional radiation characteristics of the antenna illustrated in FIG. 7; the solid line 11 illustrates a given radiation pattern and the dashed line an ex-

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experimental radiation pattern. Like Pig. 8 shows both characteristics almost coincide.

9 illustrates another embodiment of an antenna according to the invention. Three impedance elements are connected to an antenna element 13. The impedance element Ζ- consists of a negative resistance element, for example an Esaki diode 14. If the characteristic impedance of the antenna element 13 is assumed to be 9 ohms, furthermore a given radiation characteristic of -26 dB in the Chebishev approximation and kb = 1.0 ( at a frequency of 200 MHz), the directional radiation pattern illustrated in FIG. 10 is obtained. The solid line 15 illustrates a given radiation pattern and the dashed line 16 an experimental radiation pattern. Since the negative resistance element is used in this case, the power gain is 7.9 dB and the S / N sensitivity is 6.8 dB compared with a standard K / 2 dipole antenna. A unidirectional characteristic can be obtained by connecting impedance elements of the same value to the loop symmetrically to their terminals. The directional radiation characteristics at certain frequencies have been discussed above; In the following, an antenna will be described which has an excellent directional radiation characteristic and has a wide frequency band.

The shelf antenna element 17 illustrated in FIG. 11 is dimensioned so that the equivalent radii of the conductors between feed points or terminals 18 and symmetrical thereto lying points 19 are larger than at the connections 18 or in the vicinity thereof. The top edge a of the loop antenna element 17 corresponds to a period of a wave, while the lower edge c is symmetrical to the upper edge a

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is. In other words, the width of the ladder changes between their middle parts and their end parts in directions perpendicular to the direction of curvature, so that the ladder have relatively wide middle parts and relatively narrow end parts (see the drawing). The one mentioned above equivalent radius is a distance between the top and bottom edges a, c of the ladder. The loop antenna element 17 can consist of conductive plates, regardless of their thickness, through the upper and lower edge a or c are limited.

In the embodiment of Fig. 11, the conductive slats are arranged opposite one another so that the concave sides face one another and form a loop; the loop is divided into four parts 20, 21, 22 and 23 at the feed points 18, at the opposite point and at the locations of the widest central areas of the conductors, which delimit gaps 24, 25, 26 and 27 between adjacent ends. An impedance element Z- ,, serving as an artificial load and impedance elements Z ₂ and Z ^ are connected between adjacent ends of the divided conductors.

Since a current effective in the above conductors is mainly composed of current components that are in the area the upper and lower edges a and c flow, the conductors can be replaced by wire-shaped elements, for example whose shape corresponds approximately to the circumference of the conductor, as illustrated in FIG. In this case exist two upper and lower loops from the loop elements 29 to 35 · an impedance element Z, (with a resistor. stand value of 1.2 κ £ *) is an artificial load between the Points 25 of the upper loop, opposite the feed points, connected. The loop element 34 corresponds

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the lower edges of the conductors 21 and 23 (see. Pig. 11). Columns 37 to 40 remain as they are; in this case the columns 37 and 38 serve as impedance element Z ₂ with an infinitely large value and the columns 39 and 40 as impedance element Z ^ with an infinitely large value. The loop elements 29 to 35 are connected to one another in pairs in such a way that the pairs of elements 29 and 33, 32 and 35, 30 and 34 as well as 31 and 34 are held together by conductor bars Ml, 42, 43 and 44.

FIG. 13 shows the directional radiation characteristics of the antenna according to FIG. 12. As can be seen from this, the antenna has an excellent directional characteristic for different frequencies and covers a wide frequency range.

Referring to Fig. 14, for the antenna illustrated in Fig. 12, let the relationship between the front-to-back ratio and the frequency explained. In the abscissa is the frequency in MHz and in the ordinate the front-to-back ratio in dB plotted. Curve I illustrates the characteristics of an antenna whose diameter is 286 mm, in which the upper and lower loops are connected to each other at the feed point and at the opposite point, at which further the maximum distance between the elements of the upper and lower loops is 40 mm, with that between the feed point and the conductive rod 4l or 42 is a distance of 100 mm and where the distance between the point opposite to the feed point and the conductive rods 43 and 44, respectively has a value of 14o mm. Because the front-to-back ratio an antenna for television receivers should be less than -10 dB, is a frequency band that meets this requirement in curve I, around 184 to 199 MHz, which is too narrow to cover all TV channels.

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Curve II shows the characteristic of an antenna according to FIG. 12, in which the maximum distance between the elements of the upper and lower loops is 100 mm, the distances between the upper and lower loops at the feed point and at the opposite point ¹ JO mm, the distances between the feed point and the adjacent conductive rods Hl ₃ 42 have a value of 100 mm, the distances between the point opposite to the feed point and the adjacent conductive rods 43, 44 have a value of 95 mm and at which the artificial load 1, 2 kfl amounts. In curve II, the frequency range in which the front-to-back ratio is less than -10 dB extends from 177 to 212 MHz, which covers the high television channels. In this case too, the directional characteristics are excellent.

According to the invention you can widen the frequency range by the fact that the distance between the upper and lower Loop at the point opposite the feed point, choosing relatively small and by increasing the distance between of the upper and lower loops in the intermediate area between the feed point and the opposite point is greater than provides the distance mentioned above.

The antennas 17 illustrated in FIGS. 11 and 12 are sufficiently sensitive in the VHF frequency range of a high channel ; on the other hand, they show only moderate sensitivity in the frequency range of a low channel.

If the antennas are sized for use with low channels, the dimensions will be in the respective directions about twice as large as when used for a high channel; the volume dimensions are therefore about eight times as large,

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which precludes their use for practical reasons.

With reference to FIG. 15 and the other drawing figures Antennas will now be described which, despite their small size, cover a wide frequency range and are used in excellent sensitivity for all VHF television channels as well as have an excellent directional effect.

The antenna 45 shown in Fig. 15 includes an antenna element 17, which is based essentially on the basis of Flg. 12 explained antenna element corresponds. As a result, the same components are used denoted by the same reference numerals as in FIG. 12 and not explained in more detail below.

The antenna element 17 is intended to have a directional characteristic for a first frequency range, for example a VHF frequency range have a high channel; second antenna elements, for example dipole antenna elements 46, are on the the antenna element 17 forming loop arranged so that for a second frequency range, for example a VHF frequency range of a deep channel, results in increased sensitivity. The dipole antenna elements are used for this purpose 46 via wave traps (blocking circles) 47 with the ends 29a, 32a of the loop elements 29, 32 on the one opposite the feed point 18 Side connected. Each blocking circuit 47 consists of the parallel connection of a capacitor 48 and a coil 4a. The values of these two elements are chosen so that the trap circuit 47 has a high impedance in the frequency range of the high Channel, for example above 160 MHz, and that the dipole antenna elements 46 have the characteristics of the antenna element 17 does not affect. The value of. Coil 4a is also chosen so that the coil acts as the inductive load of each dipole antenna element 46 is used and thereby shortens the actual length of the dipole antenna element 46. The dipole antenna elements 46 are so-called rod antennas, which are extended and accordingly in

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Their effective length can be changed. In addition, the dipole antenna elements are rotatable on the antenna element 17 arranged.

This antenna 46 delivers in the frequency range of the high channel, the antenna element 17 produces an output signal with excellent sensitivity and directional effect (such as explained above), output signals of the dipole antenna elements are eliminated by the trap circuits 47. In the frequency domain of the low channel, on the other hand, the antenna element 17 delivers practically no output signal, while the dipole antenna elements 46 have a high sensitivity and directional effect and provide output signals to the feed point. The antenna 45 accordingly has one for all VHF television channels high sensitivity and excellent directional characteristics.

FIG. 16 shows measurement results of the sensitivity of the antenna 45 in the VHF frequency range of the lower channel, ie in the frequency range from 90 to 10 8 MHz. The frequency is plotted on the abscissa and the sensitivity is plotted on the ordinate. The length t, of the dipole antenna element 46 represents a parameter. The condition for the measurements was that the ¥ ep »gain ririUHg of the dipole antenna had the value zero at an approximate middle frequency of the frequency range of the low channel. Although not illustrated, the directionality of antenna 45 is bilateral in such a low channel frequency range. Without the dipole antenna elements 46, the output signal is greatly reduced; a measurement of the sensitivity becomes impossible.

Flg. 17 shows measurement results of the sensitivity of the antenna 45 in the frequency range of the high channel, i.e. in one frequency range from 168 to 222 MHz. The frequency is shown on the abscissa and the sensitivity is shown on the ordinate.

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gen. The distance t * between the feed point and the adjacent conductive rod is used as a parameter. The gain of the dipole antenna is again considered to be zero.

As can be seen from FIGS. 16 and 17, the antenna 45 has a in the VHF frequency range of a low channel high sensitivity. This sensitivity can be adjusted somewhat by changing the lengths of the antenna elements 46 will.

Fig. 18 illustrates further modifications of the antenna according to the invention; as far as parts of those in Flg. 15, the same reference numerals are provided; in this respect, a separate description is not necessary. In FIG. 18A, the dipole antenna elements 46 are connected to a feed point 18 of an antenna 17 via blocking circuits 47. In FIG. 18B, dipole antenna elements 46 are connected via blocking circuits 47 to conductors 41, 42 approximately in the middle thereof. In FIG. 18C, dipole antenna elements 46 are connected in pairs via blocking circuits 47 to the loop elements 33, 35 at ends which are opposite to the feed points of the antenna according to FIG. In Figs. 18D and 18E, trap circuits with distributed constants are provided. In the antenna according to FIG. 18D, the open ends of parallel lines 50 are connected to the loop elements 33 and 34 or 34 and 35, each of which is short-circuited at one end, has a length of K / 4 and the dipole antenna element 46 to the Short-circuit point is connected. A «is the wavelength of the middle frequency of the frequency range of the high channel. The parallel lines 50 are therefore non-conductive in the frequency range of the high channel and serve as feed lines in the frequency range of the low channel. Fig. 18E shows an antenna in which parallel lines 51 with a length of 1/4 are arranged so that

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lead them from the feed point to the center of the antenna 17. Parallel lines 52 extend from the open ends of lines 51 in a direction that is approximately perpendicular to the plane of antenna 17. Dipole antenna elements k6 are connected to the connection points of the parallel lines 51, 52. In such an arrangement, the free ends of the parallel lines 52 are open, so that the connection points of the lines 51, 52 are short-circuited for the frequency range of the high channel and open for the frequency range of the low channel.

In the illustrated embodiment of the invention, the output signals are at frequencies of a high channel that of can be derived from the usual antennas, with those from the dipole antennas derived signals combined at frequencies of a low channel. Even if the antenna is proportionate is small, it is excellent in sensitivity and directionality as shown in the reported measurement results emerges. The antenna is particularly suitable as an indoor antenna for VHF television reception.

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Claims (12)

Claims Directional antenna with a loop antenna element that consists of .at least three curved conductors and an output terminal between two of the adjacent ends of the curved conductors having, characterized in that between the other adjacent ends of the curved conductor impedance elements are switched on so that thereby the distribution of a flowing in the antenna element Current is determined. 2.) Directional antenna according to claim 1, characterized in that the impedance elements are reactances. 3.) Directional antenna according to claim 1, characterized in that at least one impedance element is a negative resistance element is. 4.) Directional antenna according to claim 1, characterized in that the possible value of each impedance element includes infinitely . 5.) Directional antenna according to claim 1, characterized in that the impedance elements are equidistant from the antenna element are connected. 6.) Directional antenna according to claim 1, characterized in that impedance elements of the same value symmetrically to a straight line Line are arranged which connects the output terminal of the antenna element and an opposite point. 7.) Directional antenna according to claim 1, characterized in that each conductor of the antenna element is relatively narrow end parts and has a relatively wide central portion between the end portions. 009813/1210 8 ₆ ) Directional antenna according to claim 7 _S, characterized in that the antenna element consists of wire-shaped conductors. 9.) Directional antenna according to claim 1, characterized in that a second antenna element is connected to the antenna element whose resonance frequency differs from that of the first antenna element. 10.) Directional antenna according to claim 9 »characterized in that that a blocking circuit is connected to the connection point of the antenna elements, which only occurs when the second Antenna element allows a current to flow into the second antenna element. 11.) Directional antenna according to claim 9, characterized in that that the second antenna element is a dipole antenna. 12.) Directional antenna according to claim 11, characterized in that the dipole antenna is a telescopic antenna. 0 09813/1210 Blank page