DE2322068C3 - Circuit arrangement for obtaining a direct voltage as a measure of the change in attenuation in level-regulated communication systems - Google Patents

Description

/, Ui

a Bode network is used as an attenuator, its variable resistance by a capacitor is DC-decoupled from the auxiliary quadrupole of the Bode network, and that the to the choke in Resistance lying in series, at which the direct voltage can be removed, in its size equal to the characteristic impedance of the auxiliary quadruped is chosen.

The invention, its configuration and mode of operation will be described below with reference to the figures for some Exemplary embodiments explained in more detail:

F i g. 1 shows an embodiment of the invention in the simplest form;

F i g. 2 shows a variant of the invention in which the polarity of the display current is reversed compared to the first embodiment and the display is adapted to the measuring range of the instrument in a certain way;

F i g. 3 shows another variant of the invention, in which a transformer, which is present anyway, instead of the Throttle mitvefwendci will.

In Fig. 1, the components Rt, R 2, R 3 and the auxiliary quadrupole HV represent an example of a known network according to Bode. The capacitor C I still contained in the Bodc network is used for sliding current-wise separation and is for the alternating current-wise (Jhci tragungseigcnsch ift of the network without Bcdeu-

tion. With the changeable resistance Λ3 IaDt change the attenuation of the Bode network in a known manner. It applies to Bode networks in general the equation

} a =

k.

where A a denotes the change in attenuation of the network, starting from an average attenuation; k is a constant that characterizes the dimensioning of the network; the reflection factor ο is according to the equation

= ^Λ3 " ^Λ " ρ,

'■' Ri + R ₁₁

a measure of the change in the variable resistance Λ 3, where RQ represents the real wave resistance of the quadrupole.

If equation 2 is inserted into equation 1 and solved for R 3, the result is

Ri = K ₁₁

k + Iu k-Tu '

13)

The relationship according to equation 3 is non-linear.

This gives a statement about the relationship between the size of the variable resistance R 3 and the change in attenuation of the Bode network in neper or decibel.

According to the invention, the resistor R 3, a resistor R 4 of the size KO of the wave resistance of the auxiliary four-pc-les is connected in parallel. Equation 3 gives the equation for this parallel connection

RiWR _n =

because of the condition / 7 4
over in

14)

RQ goes the equation

(4a)

45

Equation 4a shows that from an additive

Component -, - apart from a proportional relationship between the quantity R 3 || /? 4 and the change in attenuation <4 a in neper or decibel. If a constant calibrated current / 1 flows through the parallel connection of /? 3 and /? 4, a DC voltage is obtained at these resistors according to equation 4a

U = Jl

R4

+ la 71

R4

(5)

55

and thus the mentioned linear relationship with the logarithmic one for the desired DC voltage Degree of damping.

Resistor # 4 must not be connected directly in parallel to the variable resistor R 3 in terms of alternating current, in order not to change the alternating current properties of the Bode network. <s _s Therefore, in series riit R 4 a throttle Dr vorgesel.cn for decoupling. In addition, a capacitor C1 is necessary for direct current decoupling if the auxiliary quadrupole should have a direct current path to the reference point of the circuit. The direct voltage occurring at resistor R 4 can be displayed with a conventional voltage indicator or other display device A , the resistance inherent in these instruments having to be taken into account when dimensioning R 4.

In general, it is desirable that an increasing display correspond with an increasing level. In the Circuit arrangement according to FIG. 1, this is the case when the Bode network acts as an attenuator in IsL If the Bode network is used in the negative feedback path of an amplifier the polarity of the display is reversed, which is canceled by additional measures can be.

In this Figure 2, a further constant auxiliary direct current / 2 is used, which generates 6 is a voltage across a resistor R which is directed opposite to the voltage applied on the display device A. The voltage »c R 6 can be dimensioned so that the current through the display device A increases with increasing attenuation of the Bode network. The resistance R 5 in Fi %. 2 shows an additional resistance, which can also be the instrument internal resistance itself or to which the instrument internal resistance is added for the calculation. The three resistors A4 ', RS and R 6 must then be dimensioned so that the condition

R4 '

R4 '+ RS +

K 6)

16)

is satisfied.

In addition to this condition, there is still the option of dimensioning these three resistors Λ 4 ', Λ 5 and / 6 so that the display device A has half the deflection with medium attenuation of the Bode network and the limits of the control range of the Bode network displays full or zero deflection. This enables the monitoring operating personnel to be given simple instructions to initiate appropriate measures when the display limits are reached.

In Fig. 3, the display is essentially similar to the circuit according to FIG. 2, but the original resistor RS is divided into the resistors Rs and R 5 'in order to be able to insert a filter capacitor C2; this prevents AC voltages from the AC circuit in the display circuit or z. B. Störspannucgen get from the display circuit in the AC circuit. Furthermore, the throttle Dr is implemented in FIG. 3 with the aid of one winding of the transmission 0 ; the original resistor R 4 is now in the order interchanged in series with the transformer Ü. This circuit is advantageous if the auxiliary quadrupole of the Bode network is already terminated with a transformer. In this case, the otherwise necessary choke can be saved by using the transformer. The condition according to the invention for the DC resistance to be connected in parallel with the variable resistor R 3 is now:

R 4 "(« vl «5Ί R 6)
/ <4 '4 /, .., / <f. ι Κ6

- K ₁ , -

17;

In this case, the capacitor Ct must be parallel / u

/ M "in order to avoid undesirable influence on the AC behavior of the network. The resistance Rs and the AC internal resistance of the DC power source / 1 must be large compared to the largest value of the variable resistance R 3 in order not to influence the original control range.

In the exemplary embodiments, the supply of a constant auxiliary direct current is shown and explained. Of course, the circuit can also be used in a dual variant with a constant DC voltage * - infeed can be realized; it is also possible. Auxiliary voltage sources with almost any interior Resistance to be used if the corresponding internal resistances are effectively integrated into the overall circuit are included and the condition according to the invention is met again in each case, d. h "that the total resistance of the measuring arrangement is equal to the characteristic impedance /? 0clcs auxiliary quadrupole.

For this 1 Hhiil

Claims (3)

Patent claims: 1. Circuit arrangement for obtaining a DC voltage as a measure of the change in attenuation in level-regulated communication systems, with the DC voltage as a voltage drop a variable resistance of the attenuator of the attenuator through which an auxiliary current flows Level device is created and the variable resistor is a series circuit of a choke and a resistor is parallel, characterized in that to achieve a linear relationship between the DC voltage and the change in attenuation in logarithmic terms Measure (" ¹ Ui) a Bode-network is used as an attenuator, whose "eränderbarer resistor (R 3) is decoupled direct current by a capacitor (CX) from Hilfsvierpol (HV) of the Bode network, and that the resistor (lying to the choke (Dr) in series R 4), at which the direct voltage can be removed, is selected in its size equal to the characteristic impedance (R 0) of the four-pole pole (Fig. 1). 2. Circuit arrangement according to claim 1, characterized in that the direct voltage (across the resistor A4 ') is fed via a resistor (R5) to a display device (A) , the other terminal of which is connected to a / on a further auxiliary direct current (J 2) through which the resistor ( R 6) lies, and that these contradictions (R 4 ', RS, RS) satisfy the condition that their total resistance effective in terms of direct current is equal to the characteristic impedance (RQ) of the four-pole pole (FIG. 2, equation 6). 3. Circuit arrangement according to claim 1 or 2, characterized in that when using a Bode network with transformer (O), the transformer output winding is connected to the variable resistor (R3) via the parallel connection of a resistor (R 4 ") with a capacitor (Cl) is that the first auxiliary direct current (JX) is also fed to this connection point and that the display device (A) is switched on via filter means (Rs, C2) , the resistors (RA ", Rs. R5 ', R6) being dimensioned so that their total resistance effective in terms of direct current is equal to the characteristic impedance (R 0) of the four-pole pole (FIG. 3, equation 7). 55 The invention relates to a circuit arrangement for obtaining a DC voltage as a measure of the Change of attenuation in level-regulated communication systems, the DC voltage being the voltage drop across one of an auxiliary current through which variable resistance of the attenuator of the level device flows and the changeable contradiction is a series connection of a choke and a resistor in parallel. In such messaging systems it is necessary to to continuously monitor the condition of the transmission lines and amplifiers. That also includes Findings about the current setting of the regulated amplifiers contained in the transmission system or regulated attenuators. There is already a method known (DT-AS 17 62 373), in which the display of the monitoring system Pill resistance of a thermistor is used as an actuator in a regulated attenuator is used. The known method Lieiort a DC voltage, which is proportional to the ratio of the AC output voltage to AC input voltage of the attenuator. In some applications, however, it is desirable to have the display size not proportional to the ratio of the alternating voltages, but rather proportional to the logarithm of this ratio. B. with a linear display instrument for direct current or direct voltage, a statement about the gain can be obtained in a logarithmic measure. A scale on the direct current instrument, for example divided into neper or decibel, is unsatisfactory because the reading accuracy is very different over the entire range of the scale due to the non-linear division. Rather, the measured direct voltage or direct current value would have to be converted into a logarithmically changing display variable, which is complex and technically difficult. Otherwise, the known solution is only given for an attenuator in a T circuit, which cannot be transferred to a Bode network that is widely used today. The object of the invention is to use simple means to obtain a display size that corresponds to the logarithm is proportional to the voltage ratio. The object is achieved according to the invention in that in order to achieve a linear relationship between the DC voltage and the change in attenuation in a logarithmic measure