DE1005146B - Broadband directional coupler - Google Patents

Description

The invention relates to a broadband directional coupler, in which an energy input or output coupling electrical Conductor (branch conductor) both inductive and capacitive with a concentric line (through line) is coupled and the electrical length of the coupling portion is about a quarter wavelength of a mean frequency to be transmitted or a multiple of this length.

Directional couplers are already known in which they are coupled inductively and capacitively with the aid of an inductive and capacitive coupling Loop, which is much shorter than the operating wavelength, coupled out energy from a concentric line will. However, these directional couplers have the property that the coupled-in and coupled-out energy is proportional grows with the square of the frequency. This strong frequency dependence is z. B. in use in community antenna systems where a broad frequency band is to be transmitted, a major disadvantage. The purpose of the invention is an embodiment of directional couplers, in such a way that their effect is largely independent of the frequency.

Directional couplers based on the principle of hole or slot coupling are already known where the electrical length of the coupling section is on the order of a quarter wavelength of the operating frequency or more. With these well-known Arrangements, however, the coupled-out energy remains only in a very narrow range around the operating wavelength fairly constant, while at twice the operating frequency there is practically no decoupling more is done. In the arrangement according to the invention, however, is achieved by a new dimension that the energy extraction over wide frequency ranges is subject to only slight fluctuations, so that a Use in community antenna systems for radio and television broadcasting large frequency ranges is possible with advantage.

According to the invention this is achieved in that the ratio of inductive coupling to capacitive Coupling at least approximately equal to the product of the characteristic impedance of the through line and the characteristic impedance of the branch line and that the interconnected parts of the through line and the Branch line has a very different degree of reproduction exhibit. The specified ratio of inductive coupling to capacitive coupling represents a simple one Dimensioning rule for achieving directional energy coupling for lines that simultaneously have a non-reflective execution. In order to be able to adhere to this condition well, it recommends the mutual distance between the parts of the through line and branch line that are coupled to one another to make it changeable in a manner known per se. The connection of the first-mentioned condition with the Broadband directional coupler

Applicant:
Siemens & Halske Aktiengesellschaft,

Berlin and Munich,
Munich 2, Wittelsbacherplatz 4

Dipl.-Ing. Walter Wild, Munich,
has been named as the inventor

Rule that the interconnected parts of the through line and the branch line have a very different degree of propagation, brings the Advantage of an extensive frequency independence of the energy extraction even with only approximate fulfillment the first condition. A largely different measure of propagation is electrical in a very simple way

as can be realized by changing the phase measure, such as will be set out later.

The coupling device according to the invention finds a preferred field of application in communal antenna systems for radio and television reception for connecting the subscriber devices to the antenna voltage leading distribution network. Since such systems are often extremely wide The new directional couplers are particularly suitable for transmitting frequency bands. They allow over a wide frequency range a good decoupling of the connected subscriber devices from each other with low Attenuation of the energy flowing in the forward direction. Furthermore, these directional couplers can be used in Community antenna systems are advantageous for connecting two or more distribution lines to a common one Use the antenna or a common output of an antenna amplifier.

The invention and related details are explained with reference to FIGS. 1 to 8, for example.

In Fig. 1, a designated as a through line 1 is shown schematically, to which the conductor 2 of the branch line is coupled. The capacitive coupling k between the parallel conductors 1 and 2 is indicated by an equivalent capacitor, the inductive coupling m by a circle surrounding both conductors. The couplings k and m evenly distributed over the parallel guide length I should be the coupling capacitance or inductance per unit length. The line 1 on which the energy is in the direction of

609 866/307

3 4

of the arrow N ₁ propagates, is at the far end by a corresponding to the inventive idea that point

Resistance Z ₁ completed, of the parts of the through-line 1 that are coupled to one another with their characteristic impedance

is equivalent to. The branch line 2, for its part, is a very different one at its and the branch line 2

End by a propagation measure γ _χ and γ ₂ corresponding to their wave resistance. By choosing the

Resistance Z ₂ completed, while at its beginning 5 propagation measures, the error can be eliminated or

at least reduce a counter that represents the consumer resistance that the directional coupler has,

stand F ₂ cherishes. . ,,,, · if the condition Z ₁ -Z ₂ = - is not exactly fulfilled.

Due to the couplings k and m , at ° ° ^{x Δ} h ^{ö arises}

The far crosstalk voltage U ₂₁ can then also be brought close to zero at least voltage U 20 and at resistor Z _{2 the far crosstalk at least voltage U 20,} even if the direction at resistor F _{2 is} a near-end crosstalk, if this condition is not met. Strongly different voice voltage U ₂₁ . It can be shown that if the reproductive measures can be increased by large

-r,,. ^ r »,. ,,, · χ r υ τ,„ „u achieve the _{difference in the attenuation Oc 1} and a _{2, whereby}

Condition Z ₁ -Z, = - = - is fulfilled, the cross-talk,,, \, ^{ö,. x} _ ..,? . '

⁶⁵¹² A * one becomes particularly broadband directional couplers relaxation U ₂ 1 zero. At the same time, the next to 15 speaking Fig. 3 is reached.

Speaking voltage JJ ₂₀ for directional coupler use- At high frequency, however, it is often more advantageous, according to Licher type, whose electrical length I is small compared to the invention of the coupled parts of an eighth wavelength, proportional to the product through line 1 and branch line 2 a strong U ₁₀ ω · K · Z ₂ · I. The decoupled voltage grows different phase measure / J ₁ or / J ₂ with lower, ie proportionally with the frequency and to give _{the decoupled 20 attenuation Ci 1} + a _2. In this case, it is useful to have power squared with frequency. the phase measure of the coupling part of the branch-This frequency dependency is greater in the invention line 2 compared to the directional coupler corresponding to the through line 1 with one or more. According to FIG. 4, this can be achieved in practice by a meandering or quarter-wave length coupling section for a zigzag configuration of the conductor 2, a relatively large frequency range. The end of the conductor 2 is removed by one. This is concluded in accordance with the wave resistance on the basis of the resistance _{Z 2 shown in FIG}

, η λ. t j -tr -Lu. · ^ 20 · Λτ, -u "· ^{ain the} beginning of the consumer, when using the

given locus of the ratio - === - in dependent-,, 9 ~. , ,,, °,,

^ss ^ 10 tungskopplers m community antenna systems that

clarity of the angular frequency ω . The receiver is to be connected to E. Assuming that the line attenuation Ct ₁ + a ₂ is small as 30 Fig. 5 shows an exemplary embodiment for sum attenuation of both parallel lines a directional coupler according to the scheme of FIG. 4 in comparison to its phase measure β _x + / J ₂ . On the local cross-section. Between the stretched inner curve, the points are plotted which form the tip of the ladder 1 and the, for example, strip-shaped

xr 1, ZT _2n , .. -τ, · · j. -u · j j- formed outer conductor 3 of the through line is located

Vector —— for frequencies at which the. ,,,,. . P ... ^ö . ^ö , _£ ,

U ₁₀ ^H 35 is the meandering or zigzag running

electrical length I of the directional coupler a certain conductor 2, which in turn is embedded between two insulating bodies 4, a certain fraction or a multiple of a quarter and a 5. The insulating body 4 corresponds to between wavelength; this resulting fictitious waveguide 2 and inner conductor 1 consists of a loss -, .., 2 λ, · X,. yy,. j ,, ,,. ,,,, poor dielectric, the insulating body 5 between conductor 2 ^lan ^ ^{e λ} = ^{XTxT is made by the means of} 40 and outer conductorS to increase the attenuation wavelength X ₁ and I ₂ on lines 1 and 2, on the other hand, is made of a dielectric with a significantly higher level. The size of the decoupled voltage JJ ₂₀ loss angle exist. The meander or zigzag initially grows at zero frequency and the shaped conductor can advantageously be used as an electrically conductive one then fluctuates periodically with increasing frequency. Be the 45. For the purpose of symmetrical design, the through voltage U ₂₀ each reaches a maximum when the outgoing line can also be on the opposite _{,, A.} , τ .. JTT-Lx 1 1 λ 3 - 5, lying side of the continuous conductor 1 symmetrical electrical length of the directional _{coupler = T>} ^ X ₁ - ^ XJ _m ^^. 3 ^ _{correspondingly} designed conductor 3 '

etc., and a minimum at frequencies for which, with the interposition of a low-loss insulating body 4 '

, λ, 3,. _A τ,, .. ", ..,, -, i · - T ₁ -U 5 °. The meandering or zigzag shaped conductor 2

I = _T , X, -X . Thus, let it also be at a Rieh- _{GMN or together with the his train ries} membered Isoliertungskoppler very low attenuation, a frequency band body 5 or 4 and 5 are functional with respect to utilize from about 1.5 octaves, namely, for example, of the inner conductor 1 in Movable transversely, as shown in τ, · 1 j λ χ 1 ^λ 3 _1ΤΛ . . ,. is indicated in Fig. 5 by a double arrow. By

Area of the locus from -... _γ λ. The decoupled ^ _{άη &} ^ yerschiebimg 4td the capacitive coupling

Voltage U ₂₀ fluctuates only slightly in this area between lines 1 and 2, while

, .. ,,. 1 jTx π ■ τ? · U- ix · λ η the inductive coupling in a relatively wide

content ^ 7 = ", the performance in the ratio 1: 2. -r,., .., _A P ₁ -a ■ _A ■ tr · λ ~"

] / 2 ^& range can be varied. At the in tig. 4 ge

If the line attenuation a _x + a _{2 is} chosen to be large, the position of the conductor 2 shown is symmetrical to the conductor 1, the locus of the voltage JJ _{20 is} approximately equal to 60 the inductive coupling has its minimum value; 3, the vector very quickly tends towards one of the conductors 1 opposite the conductor 2 in the dashed end value, which is shifted through the center point of the drawn position 1 ', then the inductive logarithmic spiral is given. The frequency coupling is stronger than the capacitive one. By this the amplitude of the voltage U ₂₀ is therefore a function ^ ₁ ^ = the condition Z ₁ Z ₂ easily adjusted

low if at least one of the lines 1 and 2 is strong 65 ° ° k ^x

is muted. When using such a Rieh-.

coupler in communal antenna systems is the Another possibility to measure the phase dimension of the branch

Branch line 2 to attenuate because the continuous conductor to increase, according to the invention is to Line 1 the lowest possible transmission losses coupling part of the branch line than the one wire of the should sit. 70 through line 1 surrounding helix to form.

An exemplary embodiment of this is shown in FIG. 6. The dielectric constant S ₁ in the space enclosed by the helix 2 should be smaller than ε ₂ in the space between the cores of the continuous line. With the latter measure, if necessary, the same wave resistances Z ₁ and Z ₂ can be obtained.

Fig. 7 shows a coupling device in longitudinal section, which is characterized by a particularly large multiple of a quarter wavelength long coupling branch conductor 2, which between the two conductors, for. B. between inner conductor 1 and outer jacket 3, the through line is arranged and is led out of the continuous line at the branch points. The length of the branch conductor can be several meters and, in the case of antenna systems, extends from one subscriber connection point to the next subscriber connection point. The conductor 2 is strongly attenuated in order to achieve high broadband with small inductive and capacitive coupling, so that a locus curve according to FIG. 3 is obtained. The transmission line can be designed as indicated in FIG. 8 in cross section. The conductor 2 is arranged as a helix with a long lay or in a serpentine shape or the like between the inner conductor 1 and the jacket 3 of the coaxial continuous line in the vicinity of its jacket. At the subscriber connection points, the outer screen 3 is interrupted for a short length in order to be able to lead out the two ends of the conductor 2, and then again, e.g. B. through a half pipe or the metallic junction box, through-connected. Since the conductor 2 is strongly attenuated, at high frequencies, e.g. B. ultra-short wave range, the terminating resistor Z ₂ at the far end of the subscriber may be omitted. A distribution system constructed by means of such a transmission line is therefore particularly simple.

In order to attenuate the branch conductor 2 in the arrangement according to FIGS. 7 ■ and 8 to the required extent, it can off Steel wire exist and / or be provided with a lossy covering. This wrapping can be made from a varnish with a large loss angle or a lossy insulating film. The isolation between Conductor 2 and inner conductor 1 should be of high electrical quality and are made of polyethylene, for example. the Insulation between the conductor 2 and the wire mesh or a closed metal jacket existing outer conductor 3 can be represented by a thin plastic film.

Claims (17)

Claims: 50 1. Broadband directional coupler, in which an electrical conductor (branch conductor) that couples energy in or out is coupled both inductively and capacitively to a concentric line (through line) and the electrical length of the coupling section is about a quarter wavelength of an average frequency to be transmitted or a multiple of this Length, characterized in that the ratio of inductive coupling (m) to capacitive coupling (k) is at least approximately equal to the product of characteristic impedance Z _{1 of} the through line and characteristic impedance (Z ₂ ) of the branch line and that the interconnected parts of the through line ( 1) and the branch line (2) have a very different degree of propagation (y _x and y ₂ ). 2. Coupling device according to claim 1, characterized in that the mutual spacing of the Coupled parts of the through line (1) and branch line (2) can be changed. 3. Coupling device according to claim 1 or 2, characterized in that the branch line has a greatly increased line attenuation (a ₂ > Ct ₁ ) compared to the through line. 4. Coupling device according to claim 1 or 2, characterized in that the mutually coupled parts of the through line (1) and branch line (2) have a very different phase dimension {ß ₁ or / J ₂ ). 5. Coupling device according to claim 4, characterized in that the phase measure of the coupling Part of the branch line (2) compared to that of the through line (1) is enlarged. 6. Coupling device according to claim 5, characterized in that the coupling part of the branch line runs as a meandering or zigzag-shaped conductor (2) along the through line (1) (Fig. 4). 7. Coupling device according to claim 6, characterized in that between the inner conductor (1) and the outer conductor (3) of the through line which in turn is embedded between two insulating bodies (4, 5) meandering or zigzag-shaped conductor (2) is arranged, with the insulating body (4) between this Conductor (2) and the inner conductor (1) made of a low-loss dielectric, the insulating body (5) between Conductor (2) and outer conductor (3) preferably made of a dielectric with a significantly higher loss angle consists (Fig. 5). 8. Coupling device according to claim 7, characterized in that the meander or zigzag Conductor (2) alone or together with its associated insulating body (5 or 4 and 5) in Transverse direction relative to the inner conductor is displaceable. 9. Coupling device according to claim 7, characterized in that the meander or zigzag Conductor (2) as an electrically conductive layer on one of the insulating bodies (4, 5), in particular on the outer body (5) is applied. 10. Coupling device according to claim 5, characterized in that the coupling part of the Branch line is designed as a helix (2) surrounding the wire of the through line (1) (Fig. 6). 11. Coupling device according to claim 10, characterized in that the dielectric constant is smaller in the space enclosed by the coil than in the space between the veins of the Through line. 12. Coupling device according to one of claims 1 to 4 or 10, characterized by a a particularly large multiple of a quarter wavelength long coupling branch conductor (2), the between the two conductors of the through line, e.g. B. between inner conductor (1) and outer sheath (3), is arranged and led out of the continuous line at the branch points. 13. Coupling device according to claim 12, characterized in that the branch conductor (2) at smaller inductive and capacitive coupling is strongly attenuated. 14. Coupling device according to claim 12 or 13, characterized in that the branch conductor (2) as Helix with a long lay or in a snake shape or the like. between inner conductor (1) and jacket (3) of the coaxial continuous line is arranged in the vicinity of the jacket (Fig. 8). 15. Coupling device according to claim 13 or 14, characterized in that the branch conductor consists of steel wire to increase the attenuation and / or provided with a lossy envelope is. 16. Coupling device according to one of claims 1 to 15, characterized by its use in community antenna systems for radio and television reception to connect subscriber devices to the distribution network that carries the antenna voltages. 17. Coupling device according to one of claims 1 to 15, characterized by its use in community antenna systems for circular radio and television reception for connecting two or more distribution lines to one common Antenna or to a common output of an antenna amplifier. Considered publications:
German Patent No. 804,334;
U.S. Patent Publication No. 2,531,438;
»ΈΊΖ«, 1952, booklet, p. 6; "The BeU System Technical Journal", Vol. 33, May 1954, P. 718. 1 sheet of drawings