DE1078181B - Loss-free adaptation network for transmission equipment in electrical communications engineering, preferably conference calls - Google Patents

Description

The invention relates to a lossless matching network for transmission equipment for electrical communications engineering, preferably conference calls, for the reflection-free interconnection of two-pole terminals with the same or different ones Resistances.

There are already known matching elements for two-pole, which consist of a star connection of resistors exist and where the throughput loss is compensated by two-wire amplifiers. Such Circuits have the disadvantage that the effort required by the two-wire amplifier is relatively great is. So for each two-pole connection there are two amplifier elements and two fork carriers with replicas necessary. In addition, the two-wire amplifier is not permeable to direct current, · direct current dial pulses can therefore only be transferred through special measures.

It is also known in conference systems in which individual subscriber stations are connected to a common Connecting device are switched on, through a negative impedance the attenuation between to eliminate two subscriber positions. Such circuit arrangements have the disadvantage that the Subscriber stations are not switched to the connection device in a reflection-free manner. Such a mismatch especially has a detrimental effect on the back loss between the electroacoustic Converting a subscriber station.

The invention is based on the object of providing a lossless matching network for two-terminal networks Scratch with less effort than previous solutions for direct current and alternating current dial pulses is permeable. According to the invention this object is achieved in that between the Two-pole and the connection terminals provided for the two-pole of a lossy matching network, four-pole, known per se, reflection-free are connected, which consist of negative resistances and whose negative attenuation is dimensioned in such a way that that with correct termination of the matching network the transmission loss between two two-pole terminals canceled or negative, and that in each case at least one positive resistance of the lossy Matching network with at least one negative resistance of the four-terminal network connected in between summarized to a usually positive replacement resistance is.

Four-pole, which consist of negative resistances and are reflection-free in transmission lines of A given characteristic impedance can be found, for example, in German patent specification 589 521 known. Are such four poles between the interconnected Two-pole and the two-pole

Lossless adaptation network

for transmission interventions
electrical communications engineering,
Preferably conference calls

Applicant:

Siemens & Halske Aktiengesellschaft,

Berlin and Munich,
Munich 2, Wittelsbacherplatz 2

Dipl.-Ing. Herbert Ebel, Munich,
has been named as the inventor

pole connected terminals of the lossy matching network, then can the positive resistances of the lossy matching network with negative resistances of the Four poles are combined so that the overall circuit of the lossless matching network is simplified.

For two poles of the same resistance Z, a solution proves to be advantageous in which the lossy Adaptation network consisting of a symmetrical star connection and the interconnected Four poles each consist of a symmetrical T-circuit of three negative resistors. In the inventive A combination of resistances results in a negative series resistance each T-circuit and a resistor of the lossy matching network a single, usually positive equivalent resistance.

The invention will be explained in more detail with reference to FIGS. In Fig. 1, the lossy matching network A η has pairs of terminals with the input resistances Z ₁ , Z ₂ to Z _n . The two-pole terminals Z ₁ , Z, to Z _n can be connected to these terminal pairs without reflection. Then there is an operational damping between two poles, the size of which depends on the design of the matching network A. According to the invention _n and between the two poles of Z _1, Z ₂ to Z the appropriate terminals of the matching network quadrupoles Vp _1,

9Qi 767/283

Vp ₂ to Vp _{n are connected} from negative resistors whose characteristic impedances correspond to the connected two-pole resistors and which cancel or make the operating damping between two two-pole devices negative, with positive resistances of the network A with negative resistances of the four-pole devices Vp ₁ , Vp _s to Vp _n each are united in a single resistance.

Fig. 2 shows a symmetrical matching network ^ with η equal resistances R for reflection-free interconnection η equal two-pole resistors Z. The resistances R can be calculated

from the equation R = · Z. Such a circuit has the attenuation a = In (n-1) between two pairs of terminals. The four-pole terminals Vp ₁ , Vp ₂ to Vp _{n, which} are switched on to eliminate this attenuation, are advantageously made up of the T-connection of three negative resistors, the series resistance X and the transverse resistance Y of which can easily be calculated:

If the attenuation α between two two-pole terminals is to be canceled by the interposed four-pole system, then each of the four-pole systems must have negative attenuation

ο ^ _ ^ ___ ——

In (n - 1)

the. The entire network then has, however, a gain between two two-pole Z, which is greater, the greater the number η is selected. A check of the stability is therefore necessary for larger values of η.

3 shows the basic circuit diagram for a balanced-to-earth matching element according to the invention. The lossy adapter A has the terminal pairs 1 to n. The two-pole resistors Z are connected to these terminals without reflection via the four-pole Vp ₁ to Vp _n , of which only Vp _{1 is shown.} Each quadrupole Vp consists of a balanced ground (H-circuit), in which two negative series resistances are combined with

the original star resistances - of the lossy matching network A to the resistors

7? '

stands - ^ -. The two remaining negatives

Series resistances - and the negative transverse resistance Y of the Η-circuit are obtained from the (positive) resistors WX and W 2 via the resistance converters K 1 and K 2 . For reasons of stability, the resistance converter K 1 must be stable when idling on the line side and K2 must be short-circuit stable.

own. The transmission factor of a symmetrical T-circuit with longitudinal resistance X = ~ ■ Z and

a transverse resistance Y = I ~ \ · Z is known

35

1 + 4

40

This should be equal to the required negative damping s . It follows:

. ^{1 +} T -i

Yyy.

45

^x -f

With the help of this equation for ρ , the series and transverse resistances of the T-circuits can be calculated for η two-pole connections. Since for values of w> 2 the negative series resistance of the T-circuit is always smaller in magnitude than the series resistance of the passive matching network, these two resistances can be combined into a single positive resistance. In Fig. 2, this measure is shown in the quadrupole Vp ₃ ; the associated positive resistance is denoted there by R '. This considerably simplifies the overall circuit. According to the invention, it can be further simplified if an amplification is allowed between two two-pole terminals. If the negative series resistance X of the symmetrical T-circuit is made the same as the resistance R of the adapter, then the two resistors can be replaced by a short circuit

Claims (4)

PATENT CLAIMS; 1. Loss-free matching network for transmission equipment in electrical communications engineering, preferably conference calls, for the reflection-free interconnection of two-poles with the same or different resistances (Z _r ), characterized in that between the two-pole and the terminals of a lossy matching network known per se, four-pole non-reflective are connected, which consist of negative resistances and whose negative attenuation is dimensioned so that, when the matching network is correctly terminated, the through-attenuation between two two-pole terminals is canceled or negative, and that in each case at least one positive resistance of the lossy matching network with at least one negative resistance of the interposed one Four-pole is combined into a generally positive equivalent resistance. 2. Loss-free matching network according to claim 1, characterized in that the interposed four-pole terminals each consist of a bridged T-circuit of two negative resistances with the characteristic impedance (Z _r ). 3. Loss-free matching network according to claim 1, characterized in that at η two-pole with the same resistors (Z) a lossy matching network (A) is used in the manner of a symmetrical star connection with η equal resistances (R), the throughput loss between two pairs of terminals α =] χι (η— 1) is that each of the intervening four-pole network consists of a symmetrical T-circuit of three negative resistances (X, Y) with the characteristic impedance (Z), which the has negative damping J = - ~ , and that respectively a negative series resistance (X) of the T-circuit is combined with a resistor (J?) Of the lossy matching network to a single, usually positive resistance (R ' in Fig. 2). 4. Loss-free matching network according to claim 3, characterized in that the longitudinal resistances (x = -§- -z) and the transverse resistance j 1 = -j- \ Z I of the symmetrical T-circuit with the wave resistance (Z) at η two-pole can be determined from the equation Q-Z- _Considered publications: German patent specifications No. 550 857, 589 521, 1 sheet of drawings