RU2495440C2 - Measuring device of parameters of multielement passive bipoles - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: measuring device of parameters of multielement passive bipoles includes a voltage pulse generator having the shape of function of n degree of time, a differential current-voltage converter that includes two operating amplifiers. Inverting inputs of the first and the second operating amplifiers are the first and the second inputs of a differential current converter, and output of the second operating amplifier is output of the differential current converter. Besides, the device includes an n-stage differentiator on differentiating RC circuits, a null indicator, a measurement object, a potentially frequency-independent bipole, a control device, the first synchronisation output of which is connected to synchronisation input of pulse generator, and the second synchronisation output is connected to synchronisation input of the null indicator. The potentially frequency-independent bipole includes two parallel connected bipolar circuits, the first one of which includes the first capacitor and a circuit connected in series with it and consisting of parallel connected first resistor and the second capacitor; the second bipolar circuit includes the second resistor and the first inductance coil that is connected in series with it, and parallel to which there connected is the third resistor and the second inductance coil, which are connected in series.

EFFECT: improving determination accuracy of parameters of a measurement object in a measuring device with supply of voltage pulses of cubic form owing to excluding or reducing the group of components of measurement error.

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Description

The invention relates to measuring technique and, in particular, to a technique for measuring the parameters of objects in the form of passive two-terminal devices with lumped parameters having a multi-element equivalent circuit.

A known parameter meter of multi-element passive two-terminal devices (RF patent No. 2144195, G01R 17/10), made in the form of a four-armed electric bridge, in which a voltage pulse shaper of a cubic shape is used for power [1]. The inputs of the differential amplifier are included in the measuring diagonal of the bridge, and three differentiators connected in series to the output of the differential amplifier. The outputs of the differentiators, as well as the output of the differential amplifier are connected to the inputs of the zero indicator. The bridge is balanced after the end of transient processes in its circuits, sequentially leading to a zero voltage value at the outputs of the first third, then second and first differentiators and, finally, a differential amplifier. The disadvantages of this bridge meter are:

1) The influence of the input impedance of the differential amplifier on the common-mode input, which shunts the multi-element two-terminal of the measurement object and the balancing two-terminal with adjustable parameters, which is the reason for the measurement error of the parameters of the elements of the measured two-terminal.

2) The presence of common-mode voltage at the inputs of the differential amplifier, which is about half the amplitude of the supply pulse, which introduces an additional measurement error.

The closest in technical essence to the proposed one is a device for determining the parameters of multi-element passive two-terminal devices (RF patent No. 2390787, G01R 27/02), constructed according to the measuring transducer (IP) scheme on the first operational amplifier (OA), in which the measured two-terminal device is included in the inverting circuit the input of the op-amp, and in the feedback circuit - an exemplary resistor, the output of the first op-amp is connected to the input of the inverting adder on the second op-amp; the measured bipolar is affected by voltage pulses, which varies according to the law of the nth degree of time, and the output voltage is balanced by a compensating signal synthesized from current pulses in the form of power time functions with exponents from n to 0, leading to zero after the end of the transition process The voltage IP at the outputs of the n-cascade differentiator connected to the output of the inverting adder, as well as at the output of this adder, then, based on the found amplitudes of the current pulses mentioned above, compute They summarize the generalized parameters of conductivity, and then the parameters of the elements of a two-terminal network [2]. The disadvantages of this meter are measurement errors due to inaccurate scaling of the amplitudes of the compensating currents, since the two-terminal current of the measurement object is created by a voltage pulse from the output of the last integrator, and the components of the compensating current are formed from the output voltages of all integrators.

The problem to which the invention is directed, is to increase the accuracy of measuring the parameters of multi-element RLC two-terminal devices.

The technical result is achieved by the fact that in the parameter meter of multi-element passive two-terminal, containing a voltage pulse generator having the form of a function of the nth time degree, a current-voltage differential converter, which includes two operational amplifiers, in the feedback circuit of the first operational amplifier the first resistor is turned on, its output is connected to the input of an inverting repeater built on a second operational amplifier, in the input circuit of which a second resistor is connected, tance which is equal to the resistance of the first resistor, a second feedback circuit of the operational amplifier is included a third resistor, the inverting inputs of the first and second operational amplifiers are a first and second differential input currents of the converter, and the output of the second operational amplifier - the output currents of the differential converter; n-cascade differentiator on differentiating RC links, the input of the first differentiating RC link is connected to the output of the differential current transducer; a null indicator, the first input of which is connected to the output of the nth differentiating RC-link of the differentiator, the second input - with the output of the (n-1) -th differentiating RC-link, etc., ..., the nth input - with the output of the first differentiating RC link, the (n + 1) -th input of the null indicator is connected to the output of the differential current transducer; a control device, the first synchronization output of which is connected to the synchronization input of the pulse generator, and the second synchronization output - to the synchronization input of a null indicator; the output of the pulse generator is connected to the first terminal for connecting the measured multi-element two-terminal, the second terminal for connecting the measured multi-element two-terminal is connected to the first input of the differential current converter, a multi-element two-terminal with adjustable parameters, made according to the scheme of a potentially frequency-independent two-terminal and containing two parallel connected two-pole the first of which contains the first capacitor and connected in series with it s composed of parallel-connected first resistor and a second capacitor; the second two-pole circuit contains a second resistor and a first inductance connected in series with it, in parallel with which a third resistor and a second inductor are connected in series, the first pole of a multi-element bipolar with adjustable parameters is connected to the output of the pulse generator, and the second pole to the second input of the differential current converter ..

The invention is illustrated by the example of a four-element two-terminal parameter meter. The device diagram is shown in figure 1.

The meter contains a generator 1 voltage pulses cubic form

$$u_{\mathrm{one}}\left(t\right)=\frac{U_m{t}^3}{t_{\mathrm{and}}^3}.\left(\mathrm{one}\right)$$

The first pole of a multi-element two-terminal 2 (MIS) of the measurement object is connected to the output of the generator 1, the second pole of the two-terminal 2 is connected to the inverting input of the operational amplifier (OA) 3, which is the first input of the voltage-current differential converter built on the OA 3 with resistor 4 in the feedback circuit and the op-amp 5 with a resistor 6 in the input circuit and a resistor 7 in the feedback circuit, the second input of this converter is the inverting input of the op-amp 5. The operational amplifier 5 performs the functions of an output inverter voltage of the op-amp 3 and a current converter entering the circuit of its inverting input.

The output voltage of the op-amp 5 is proportional to the difference between the input currents of the op-amp 3 and op-amp 5:

$$u_{\mathrm{at}sx.\mathrm{ABOUT}\mathrm{At}5}\left(t\right)=i_{\mathrm{at}x.\mathrm{ABOUT}\mathrm{At}3}\left(t\right)\frac{R_{\mathrm{four}}{R}_7}{R_6}-i_{\mathrm{at}x.\mathrm{ABOUT}\mathrm{At}5}\left(t\right)R_7,\left(2\right)$$

where R ₄ , R ₆ and R ₇ are the resistances of resistors 4, 6 and 7, respectively. With the same resistance values of resistors 4 and 6

$$u_{\mathrm{at}sx.\mathrm{ABOUT}\mathrm{At}5}\left(t\right)=\left[i_{\mathrm{at}x.\mathrm{ABOUT}\mathrm{At}3}\left(t\right)-i_{\mathrm{at}x.\mathrm{ABOUT}\mathrm{At}5}\left(t\right)\right]R_7.\left(3\right)$$

The voltage pulse u ₁ (t) generates in the two-terminal 2 of the measurement object included in the input circuit of the op-amp 4, a current pulse that contains free and forced components. After the end of the transition process and to the end of the pulse, only the forced component of the current i _dn (t) of the two-terminal 2 remains, which consists of cubic, quadratic, linear and flat (rectangular) currents:

$$i_{dP}\left(t\right)=\frac{y_0{U}_m{t}^3}{t_{\mathrm{and}}^3}+\frac{3y_{\mathrm{one}}{U}_m{t}^2}{t_{\mathrm{and}}^3}+\frac{6y_2{U}_{m}t}{t_{\mathrm{and}}^3}+\frac{6y_3{U}_m}{t_{\mathrm{and}}^3}.\left(\mathrm{four}\right)$$

The amplitudes of these components depend on the generalized conductivity parameters y ₀ , y ₁ , y ₂ , y ₃ of the measurement object:

$$I_3={\mathrm{at}}_0{U}_m;I_2=\frac{3{\mathrm{at}}_{\mathrm{one}}{U}_m}{t_{\mathrm{and}}};I_{\mathrm{one}}=\frac{6{\mathrm{at}}_2{U}_m}{t_{\mathrm{and}}^2};I_0=\frac{6{\mathrm{at}}_3{U}_m}{t_{\mathrm{and}}^3}.\left(5\right)$$

Expression (4) is obtained by the operator method. The parameters y ₀ , y ₁ , y ₂ , y ₃ can be found from the operator image of the conductivity of the two-terminal y (p). If in general the expression y (p) is represented as

$$y\left(p\right)=\frac{b_0+b_{\mathrm{one}}p+b_2{p}^2+b_3{p}^3+...}{a_0+a_{\mathrm{one}}p+a_2{p}^2+a_3{p}^3+...},\left(6\right)$$

then for a non-zero value of a ₀ , which takes place for a large group of real two-terminal networks, the values of y ₀ , y ₁ , y ₂ , y _{3 are} determined by the values of the parameters of the elements of the two-terminal network:

$$y_0=\frac{b_0}{a_0};\left(7\right)$$

$$y_{\mathrm{one}}=\frac{b_{\mathrm{one}}-a_{\mathrm{one}}{y}_0}{a_0};\left(8\right)$$

$$y_2=\frac{b_2-a_2{y}_0-a_{\mathrm{one}}{y}_{\mathrm{one}}}{a_0};\left(9\right)$$

$$y_3=\frac{b_3-a_3{y}_0-a_2{y}_{\mathrm{one}}-a_{\mathrm{one}}{y}_2}{a_0}.\left(10\right)$$

As an example, the figure shows an RLC two-terminal device consisting of a first resistor 8, in parallel with which a capacitor 9, a second resistor 10 and an inductor 11 are connected in series, with parameters R ₈ , C ₉ , R ₁₀ and L _11, respectively. The operator image of the conductivity of this two-terminal network has the form

$$y\left(p\right)=\frac{\mathrm{one}}{R_8}+\frac{p{C}_9}{\mathrm{one}+p{R}_{10}{C}_9+p^2{L}_{\mathrm{eleven}}{C}_9}.\left(\mathrm{eleven}\right)$$

The values of y ₀ , y ₁ , y ₂ , y ₃ according to formulas (7) - (10) are equal

$$y_0=\frac{\mathrm{one}}{R_8};\left(12\right)$$

$$y_{\mathrm{one}}=C_9;\left(13\right)$$

$$y_2=-R_{10}{C}_9^2;\left(\mathrm{fourteen}\right)$$

$$y_3=C_9^2\left(R_{10}^2{C}_9-L_{\mathrm{eleven}}\right).\left(\mathrm{fifteen}\right)$$

The conductivity parameter y ₀ always has a positive sign, and other parameters, depending on the two-terminal circuit, can be both positive and negative. Moreover, as can be seen from the example of parameter y ₃ , the sign of this parameter in the two-terminal system under consideration depends on the relationship between the values of the parameters of the circuit elements.

A multi-element two-terminal 12 with adjustable parameters is designed to form a compensating current, the components of which are equal to the corresponding components of the current through the measured two-terminal 2. The current of the two-terminal 12 is supplied to the inverting input circuit of the op amp 5. To expand the functionality of the meter, the two-terminal circuit 12 must provide conditions for controlling the components of the compensating current and positive and reverse directions, including zero. Such opportunities are available for multi-element bipolar circuits, which belong to the category of “potentially frequency-independent” (PCND). They got this name because of the special property of their frequency characteristics: at certain values of the parameters of the circuit elements, the resistance (conductivity) of a two-terminal network becomes a real quantity, independent of frequency. If in the operator image of the conductance of a two-terminal 12

$$Y\left(p\right)=\frac{b_0+b_{\mathrm{one}}p+b_2{p}^2+b_3{p}^3+...}{a_0+a_{\mathrm{one}}p+a_2{p}^2+a_3{p}^3+...}\left(16\right)$$

perform the substitution p = jω, we obtain the expression of the complex frequency characteristic of conductivity:

$$Y\left(j\omega \right)=\frac{b_0+b_{\mathrm{one}}\left(j\omega \right)+b_2{\left(j\omega \right)}^2+b_3{\left(j\omega \right)}^3+...}{a_0+a_{\mathrm{one}}\left(j\omega \right)+a_2{\left(j\omega \right)}^2+a_3{\left(j\omega \right)}^3+...}.\left(17\right)$$

Conductivity becomes real and frequency independent

$$Y\left(j\omega \right)=Y_0=\frac{b_0}{a_0}\left(\mathrm{eighteen}\right)$$

under conditions:

$$\frac{b_{\mathrm{one}}}{b_0}=\frac{a_{\mathrm{one}}}{a_0},\frac{b_2}{b_0}=\frac{a_2}{a_0},\frac{b_3}{b_0}=\frac{a_3}{a_0},...\left(19\right)$$

Expressions (19) can be represented as

$$b_{\mathrm{one}}-a_{\mathrm{one}}\frac{b_0}{a_0}=0b_2-a_2\frac{b_0}{a_0}=0b_3-a_3\frac{b_0}{a_0}=0...\left(\mathrm{twenty}\right)$$

It follows from formulas (7) - (10) that under conditions (20), except for the parameter Y ₀ , all other generalized Y-parameters of the two-terminal network are equal to zero. By changing the values of a _i and b _j , you can adjust the Y-parameters, including, and changing their sign.

A multi-element bipolar 12 with adjustable parameters, made according to the scheme of a potentially frequency-independent bipolar, consists of two bipolar circuits connected in parallel, the first of which contains the first capacitor 13 and a circuit connected in series with it, consisting of the first resistor 14 and the second capacitor 15 connected in parallel; the second two-pole circuit contains a second resistor 16 and a first inductance 17 connected in series with it, parallel to which a third resistor 18 and a second inductor 19 are connected in series.

The operator image of the conductivity of the first bipolar RC-type circuit has the form

$$Y_{\mathrm{one}}\left(p\right)=\frac{p{C}_{13}+p^2{R}_{\mathrm{fourteen}}{C}_{13}{C}_{\mathrm{fifteen}}}{\mathrm{one}+p{R}_{\mathrm{fourteen}}\left(C_{13}+C_{\mathrm{fifteen}}\right)}.\left(21\right)$$

The values of Y ₁₀ , Y ₁₁ , Y ₁₂ , Y ₁₃ according to formulas (7) - (10) are equal

$$Y_{10}=0;\left(22\right)$$

$$Y_{\mathrm{eleven}}=C_{13};\left(23\right)$$

$$Y_{12}=-R_{\mathrm{fourteen}}{C}_{13}^2;\left(24\right)$$

$$Y_{13}=R_{\mathrm{fourteen}}^2{C}_{13}^2\left(C_{13}+C_{\mathrm{fifteen}}\right).\left(25\right)$$

Operator image of the conductivity of the second bipolar RL-type circuit. has the form

$$Y_2\left(p\right)=\frac{R_{\mathrm{eighteen}}+p\left(L_{17}+L_{19}\right)}{R_{16}{R}_{\mathrm{eighteen}}+p\left[\left(L_{17}+L_{19}\right)R_{16}+L_{17}{R}_{\mathrm{eighteen}}\right]+p^2{L}_{17}{L}_{19}}.\left(26\right)$$

The values of Y ₂₀ , Y ₂₁ , Y ₂₂ , Y ₂₃ according to formulas (7) - (10) are equal

$$Y_{\mathrm{twenty}}=\frac{\mathrm{one}}{R_{16}};\left(27\right)$$

$$Y_{21}=-\frac{L_{17}}{R_{16}^2};\left(28\right)$$

$$Y_{22}=\frac{L_{17}^2\left(R_{16}+R_{\mathrm{eighteen}}\right)}{R_{16}^3{R}_{\mathrm{eighteen}}};\left(\mathrm{29th}\right)$$

$$Y_{23}=-\frac{L_{17}^2}{R_{16}^2{R}_{\mathrm{eighteen}}^2}\left(\frac{L_{17}{\left(R_{16}+R_{\mathrm{eighteen}}\right)}^2}{R_{16}^2}+L_{19}\right).\left(\mathrm{thirty}\right)$$

The generalized conductivity parameters of parallel-connected bipolar circuits are summarized:

$$Y_0=\frac{\mathrm{one}}{R_{16}};$$

$$Y_{\mathrm{one}}=C_{13}-\frac{L_{17}}{R_{16}^2};$$

$$Y_2=\frac{L_{17}^2\left(R_{16}+R_{\mathrm{eighteen}}\right)}{R_{16}^3{R}_{\mathrm{eighteen}}}-R_{\mathrm{fourteen}}{C}_{13}^2;$$

$$Y_3=R_{\mathrm{fourteen}}^2{C}_{13}^2\left(C_{13}+C_{\mathrm{fifteen}}\right)-\frac{L_{17}^2}{R_{16}^2{R}_{\mathrm{eighteen}}^2}\left(\frac{L_{17}{\left(R_{16}+R_{\mathrm{eighteen}}\right)}^2}{R_{16}^2}+L_{19}\right).$$

After the end of the transient process, a signal is generated at the output of the op-amp 5 at the output of the op-amp 5, which corresponds to the difference between the current of the two-terminal 2 and the compensating current created by the two-terminal 12. By sequential approximation, such parameters of the elements of the two-terminal 12 are established that provide balancing of the currents. The balancing conditions are:

$$\frac{\mathrm{one}}{R_{16}}=y_0;\left(31\right)$$

$$C_{13}-\frac{L_{17}}{R_{16}^2}=y_{\mathrm{one}};\left(32\right)$$

$$\frac{L_{17}^2\left(R_{16}+R_{\mathrm{eighteen}}\right)}{R_{16}^2{R}_{\mathrm{eighteen}}}-R_{\mathrm{fourteen}}{C}_{13}^2=y_2;\left(33\right)$$

$$R_{\mathrm{fourteen}}^2{C}_{13}^2\left(C_{13}+C_{\mathrm{fifteen}}\right)-\frac{L_{17}^2}{R_{16}^2{R}_{\mathrm{eighteen}}^2}\left(\frac{L_{17}{\left(R_{16}+R_{\mathrm{eighteen}}\right)}^2}{R_{16}^2}+L_{19}\right)=y_3.\left(34\right)$$

In particular, for the two-terminal 2 considered as an example, these conditions are represented by expressions from which the electrical parameters of the elements can be calculated:

$$R_8=R_{16};\left(35\right)$$

$$C_9=C_{13}-\frac{L_{17}}{R_{16}^2};\left(36\right)$$

$$R_{10}{C}_9^2=R_{\mathrm{fourteen}}{C}_{13}^2-\frac{L_{17}^2\left(R_{16}+R_{\mathrm{eighteen}}\right)}{R_{16}^3{R}_{\mathrm{eighteen}}};\left(37\right)$$

$$C_9^2\left(L_{\mathrm{eleven}}-R_{10}^2{C}_9\right)=\frac{L_{17}^2}{R_{16}^2{R}_{\mathrm{eighteen}}^2}\left(\frac{L_{17}{\left(R_{16}+R_{\mathrm{eighteen}}\right)}^2}{R_{16}^2}+L_{19}\right)-R_{\mathrm{fourteen}}^2{C}_{13}^2\left(C_{13}+C_{\mathrm{fifteen}}\right).\left(38\right)$$

Balancing should be done exactly in the above sequence, since the value of Y ₀ is included in the expression for Y ₁ , the values of Y ₀ and Y ₁ are included in the formula for Y ₂ , the values of Y ₀ , Y ₁ and Y ₂ are included in the formula for Y ₃ .

In order to selectively control the amplitudes of the cubic, quadratic, linear and constant components of the compensating current, the output voltage of the op-amp 5 is supplied to a differentiator, which contains three differentiating RC-links connected in series: capacitor 20 and resistor 21, capacitor 22 and resistor 23, capacitor 24 and resistor 25. The outputs of the cascades of the differentiator and the differential current converter are connected to the inputs of the zero indicator (NI) 26. The operation of the NI and the pulse generator 1 is synchronized by the control device 27 (U ) At the output of the third stage of the differentiator, a constant voltage is generated and supplied to the first input of the null indicator 26, proportional to the difference in the amplitudes of the cubic components of the currents of the two-terminal 2 and 12. Compensation of the cubic component is carried out by reducing the output voltage of the third RC-link to zero by adjusting the resistance R _{16 of the} resistor 16.

Then analyze the voltage at the output of the second RC-link of the differentiator, proportional to the difference in the amplitudes of the quadratic components of the currents of two-terminal 2 and 12, which is fed to the second input of the NI. The quadratic component is compensated by reducing the output voltage of the second RC link to zero by adjusting the capacitance C _{13 of the} capacitor 13 with a fixed inductance L _{17 of the} coil 17, or by adjusting the inductance L _{17 of the} coil 17 with a fixed capacitance C _{13 of the} capacitor 13.

After that, analyze the voltage at the output of the first differentiating RC link, proportional to the difference between the amplitudes of the linear components of the current of the two-terminal 2 and the compensating current of the two-terminal 12, which is fed to the third input of the NI. The linear component is compensated by reducing the output voltage of the first RC link to zero by adjusting the resistance R _{14 of the} resistor 14 with a fixed resistance R _{18 of the} resistor 18 or by adjusting the resistance R _{18 of the} resistor 18 with a fixed resistance R _{14 of the} resistor 14.

And finally, to compensate for the constant component of the current pulse of the measured two-terminal 2, the output voltage of the op-amp 5 is fed to zero, which is supplied to the fourth input of the zero indicator by adjusting the capacitance C _{15 of the} capacitor 15 with a fixed inductance L _{19 of the} coil 19, or by adjusting the inductance L _{19 of the} coil 19 with a fixed capacitance C _{15 of the} capacitor 15.

After four stages of balancing the current i _dp (t) of the two-terminal 2 and the compensating current of the two-terminal 12, the elements of the measured two-terminal are determined using formulas (35) - (38): resistance R ₈ , capacitance C ₉ , resistance R ₁₀ and inductance L _11, respectively.

Since the input impedance of the operational amplifier covered by parallel negative feedback

, $$R_{\mathrm{at}x.\mathrm{ABOUT}\mathrm{At}.\mathrm{about}\mathrm{from}}=\frac{R_{\mathrm{about}\mathrm{from}}}{K_{u.\mathrm{ABOUT}\mathrm{At}}}$$

,

where R _OS - the resistance of the resistor in the feedback circuit; K _{u. ОУ} - the gain of the op-amp, is hundredths of Ohm, both two-terminal _devices are “grounded”, and their currents are determined only by the voltage of the generator 1 and the conductivity parameters of the two-terminal devices, i.e. there is no influence of the measuring circuit on the parameters of the equivalent circuit of the measurement object and the two-terminal network with adjustable elements. At the inputs of operational amplifiers 3 and 5, the differential current converter does not have a common-mode voltage, thus eliminating the second source of measurement error inherent in bridge circuits.

Claims (1)

A multi-element passive two-terminal parameter meter containing a voltage pulse generator having the form of a function of the nth time degree, a current-voltage differential converter, which includes two operational amplifiers, the first resistor is connected in the feedback circuit of the first operational amplifier, its output is connected with the input of an inverting repeater built on a second operational amplifier, in the input circuit of which a second resistor is included, the resistance of which is equal to the resistance of the first of the first resistor, a third resistor is included in the feedback circuit of the second operational amplifier, the inverting inputs of the first and second operational amplifiers are the first and second inputs of the differential current converter, and the output of the second operational amplifier is the output of the differential current converter; n-cascade differentiator on differentiating RC links, the input of the first differentiating RC link is connected to the output of the differential current transducer; a null indicator, the first input of which is connected to the output of the nth differentiating RC-link of the differentiator, the second input - with the output of the (n-1) -th differentiating RC-link, etc., ..., the nth input - with the output of the first differentiating RC link, the (n + 1) -th input of the null indicator is connected to the output of the differential current transducer; a control device, the first synchronization output of which is connected to the synchronization input of the pulse generator, and the second synchronization output - to the synchronization input of a null indicator; the output of the pulse generator is connected to the first terminal for connecting the measured multi-element two-terminal, the second terminal for connecting the measured multi-element two-terminal is connected to the first input of the differential current transducer, characterized in that a multi-element two-terminal with adjustable parameters is inserted into it, made according to the scheme of a potentially frequency-independent two-terminal containing two bipolar circuits connected in parallel, the first of which contains the first capacitor and is turned on th series with the circuit consisting of the parallel-connected first resistor and a second capacitor; the second two-pole circuit contains a second resistor and a first inductance connected in series with it, in parallel with which a third resistor and a second inductor are connected in series, the first pole of a multi-element bipolar with adjustable parameters is connected to the output of the pulse generator, and the second pole to the second input of the differential current converter .