DE2818432C2 - Hybrid circuit with controlled simulation - Google Patents

Description

J-1. + Jt (2)

I L-ft (3)

I «is (1) with (2), (3) and (4) follows:

Ü

'M Zt ~ 2 ■ -.

φ Since Zr can be implemented as a transfer impedance for inductive and capacitive phase angles with active or passive RC £, circuits, the problem in the ρ principle is thus solved, with the help of this Zy for a complete λ 'fork matching.

ö In F i g. 2 is a second embodiment of the

U. inventive hybrid circuit shown. Identical • elements are provided with the same reference symbols. The circuit largely corresponds to that in FIG. 1, but here the terminating resistor R, [ ; .i is connected in parallel to the four-wire output. This; V simplifies the matching condition as follows:

35

Z _T -2-R *

40

The advantage of this embodiment is that you are free to choose the terminating impedance R.,.

for U _Ä s, - 0 must I. SL I. Currently I. . i _T. themselves j '": in order to results

1 sheet of drawings

45

60

Claims (2)

Patent claims: 1. Hybrid circuit with controlled simulation using active elements for the transition from two-wire to four-wire lines and vice versa with a two-wire connection sealed off by a differential transformer, a four-wire input and a four-wire output, the simulation being controlled as a function of the incoming four-wire voltage, characterized in that The simulation consists of a current source (It ) controlled by the incoming four-wire voltage (U, _n ) via a network (Zj) and a terminating impedance (R,) , the network (Zj) being connected between the four-wire input and the control input of the current source (It) is, the current source (h) between the center tap of the differential transformer and earth and the terminating impedance (R,) is connected in parallel with the current source (/ ^
where for the network Zj with
R * - AC input resistance of the differential transformer at the four-wire input with an open four-wire output and termination of the two-wire input with a complex resistor R,
is applicable: Zt "2 2. Hybrid circuit with controlled simulation using active elements for the transition from two-wire to four-wire lines and vice versa, with a two-wire connection sealed off by a differential transformer, a four-wire input and a four-wire output, the simulation being controlled as a function of the incoming four-wire voltage, characterized in that that the simulation consists of a current source ([τ ) controlled by the incoming four-wire voltage (U _an ) via a network (Zj) and a terminating impedance (R _a ) , the network (Zj) between the four-wire input and the control input of the current source (It ) is connected, the current source (It) is connected between the center tap of the differential transformer and earth and the terminating impedance (R,) is connected in parallel to the four-wire output,
where for the network Zj with
Ä * = AC input resistance of the differential transformer at the four-wire input with an open four-wire output and termination of the two-wire input with a complex resistor R,
is applicable: Z _T -2 R *. (Fig. 2) technology, e.g. B. used at the interface between the two-wire cable routing in the local network and four-wire cable routing in the wide area network.
From DE-OS 17 62 597 an arrangement is known in which the simulation is controlled depending on the current flowing in the two-wire line. The controlling variable is obtained via a resistor inserted in the two-wire line via a current transformer. Disadvantages of this arrangement are the in Insertion loss occurring in each transmission direction and in the case of using a current transformer the inductance to be avoided for reasons of space and the distortions caused by it. A hybrid circuit of the preamble of the patent is demanding named type, so in the case of the replica is controlled in dependence on the incoming four-wire line. is known from GB-PS 11 15 216 In addition to two differential transformers, it contains two adjustable impedances to simulate them the autocorrelation function of transmitted and reflected signal is used and thus only can be implemented in a rather complex manner The invention is based on the object of avoiding the effort for the control and for the controllable simulation and to decouple the four- wire output from the four-wire input to simulate the complex input resistance R of the two-wire line coil-free with ohmic resistors and capacitors with only small capacities. The object is achieved by the features characterized in claims 1 and 2. It is now possible to simulate the complex input resistance in a simple manner without a coil and with only one differential transformer js get along. In the embodiment of the invention according to Claim 2 is the decoupling of the four-wire output from the four-wire input in an advantageous manner independent from the resistance value of the terminating resistor of the four-wire output. The invention is explained in more detail below with reference to two exemplary embodiments shown in the drawings. According to Fig.l, there is a replica of a τ over a network Zj from the incoming four-wire voltage U, _n-controlled current source [and one of the power source / r parallel termination impedance R "The network Zj is h between the input of the secondary winding of the differential transformer and the power source switched. The current source / r and thus also the terminating impedance R ₁ are between so connected to the center tap of the differential transformer and earth. The mode of action of this in FIG. 1 results from the following consideration: When calibrating, the center tap of the differential Transformer, the voltage U is applied _to / 2 and there must be no voltage at the four-wire output. Let R * denote the resistance of one half of the transmission plus the transformed input resistance R , and R "b" denotes the terminating impedance at the four-wire output. Since the terminating impedance R, lies between the center tap of the transformer and earth, the following applies for the adjustment: The invention relates to a hybrid circuit according to the preamble of claims 1 with the same wording and 2. Such hybrid circuits are used in telecommunications (Fig. 2)