MD90Y - Admittance converter - Google Patents

Abstract

The invention relates to the electrical measurement engineering and radio electronics and may be used for high-accuracy reproduction of floating admittances represented in the cartesian coordonates. The admittance converter comprises two contacts (2, 3), a differential amplifier (1), the noninverting and inverting inputs of which are connected to the contacts (2, 3), correspondingly, two programmable amplifiers (4, 5) with controllable transfer constants in the interval of positive and negative values, the inputs of which are connected to the output of the differential amplifier (1), a phase shifter (6) with a phase shift of 90?, the input of which is connected to the output of the programmable amplifier (4), two voltage-to-current converters (7, 8) with equal conversion factors, the outputs of which are connected to the contacts (2, 3), correspondingly. The voltage-to-current converters (7, 8) are provided with differential inputs. The output of the programmable amplifier (5) is connected to the noninverting input of the voltage-to-current converter (7) and to the inverting input of the voltage-to-current converter (8), and the output of the phase shifter (6) is connected to the inverting input of the voltage-to-current converter (7) and to the noninverting input of the voltage-to-current converter (8).

Description

[0001] The invention relates to measurement technology and radio electronics and can be used for highly accurate reproduction of floating admittances represented in Cartesian coordinates.

[0002] An admittance converter is known, which contains two differential amplifiers with high input admittance, two programmable amplifiers, a phase shifter and two voltage to current converters [1].

The disadvantage of this converter lies in the complex construction and high cost of the device.

[0004] The problem that the invention solves is to simplify the construction and reduce the cost price.

[0005] The admittance converter overcomes the above-mentioned disadvantages by containing two contacts, a differential amplifier, the non-inverting and inverting inputs of which are connected to the respective contacts, two programmable amplifiers with transfer coefficients adjustable in the range of positive and negative values, the inputs of which are connected to the output of the differential amplifier, a phase shifter with a phase shift of 90°, the input of which is connected to the output of the programmable amplifier, two voltage-to-current converters with equal conversion coefficients, the outputs of which are connected to the respective contacts. Voltage-to-current converters are equipped with differential inputs, the output of the programmable amplifier is connected to the non-inverting input of the voltage-to-current converter and to the inverting input of the voltage-to-current converter, and the output of the phase shifter is connected to the inverting input of the voltage-to-current converter and to the non-inverting input of the voltage-to-current converter.

[0006] The result of the invention consists in creating a converter for reproducing floating simulated admittances of any character represented in Cartesian coordinates and with the possibility of independent adjustment of the active and reactive components.

[0007] The converter diagram is represented in the figure.

[0008] The admittance converter contains a differential amplifier 1, two contacts 2, 3, the non-inverting and inverting inputs are connected to contacts 2, 3 respectively, two programmable amplifiers 4, 5 with transfer coefficients adjustable in the range of positive and negative values, the inputs of which are connected to the output of the differential amplifier 1, a phase shifter 6 with a phase shift of 90°, the input of which is connected to the output of the programmable amplifier 4, two voltage-to-current converters 7, 8 with equal conversion coefficients, the outputs of which are connected to contacts 2, 3 respectively. The voltage to current converters 7, 8 are equipped with differential inputs, the output of the programmable amplifier 5 is connected to the non-inverting input of the voltage to current converter 7 and to the inverting input of the voltage to current converter 8, and the output of the phase shifter 6 is connected to the inverting input of the voltage to current converter 7 and to the non-inverting input of the voltage to current converter 8.

The device operates in the following manner.

[0010] Differential amplifier 1 creates an output voltage U1:

U1 = KDA · Ui ,

(1)

[0012] where: Ui is the input voltage of amplifier 1, KDA - the differential amplification coefficient of amplifier 1. Voltage U2 at the output of amplifier 4:

U2 = K1 · U1 = K1KDAUi ,

(2)

[0014] where K1 is the amplification coefficient of amplifier 4.

[0015] The phase shifter 6 has a unitary transfer coefficient and introduces a 90° phase shift into the signal path. The voltage U3 at its output is:

U3 = U2 ·ej9°° = j·U2 = jK1KDAUi ,

(3)

[0017] where: j is imaginary unit, e - base of natural logarithm (e = 2.7…).

[0018] The voltage U4 at the output of the programmable amplifier 5 with the transfer coefficient K2 is:

U4 = K2 · U1 = K2KDAUi .

(4)

[0020] The voltage to current converters 7 and 8 convert the difference between the voltages U3 and U4 into the currents I1, I2 of equal magnitude and opposite directions:

[0021] I1 = Yc ·(U4 - U3) = Yc(K2KDAUi - jK1KDAUi) = YcKDAUi(K2 - jK1) , (5)

I2 = Yc · (U3 - U4) = -I1 ,

(6)

[0023] where Yc is the transfer admittance of converters 7 and 8.

[0024] These currents flow through contacts 2 and 3, forming the input current of the converter Ii:

Ii = I1 = -I2 = YcKDAUi(K2 - jK1) .

(7)

[0026] The admittance Yi reproduced by the converter at contacts 2 and 3 is determined by the formula:

Yi = (Zi)-1 = Ii/Ui = YcKDA(K2 - jK1) ≡ Gi + jBi ,

(8)

[0028] where: Gi = YcKDAK2 is the active component of the reproduced admittance, Bi = -YcKDAK2 - the reactive component.

[0029] As follows from equation (8), the value of the active component Gi of the reproduced admittance depends directly proportionally on the transfer coefficient K2 of the programmable amplifier 5, and the value of the reactive component Bi - on the coefficient K1 of the amplifier 4. Adjusting the transfer coefficients K2 and K1 of the amplifiers 5 and 4 results in the independent variation of the active and, respectively, reactive components of the reproduced admittance Yi.

[0030] Since the currents I1, I2 have equal values and constitute the current Ii, which flows through the reproduced admittance Yi, it results that the common mode impedances between the input contacts 2, 3 and ground have infinite values, which ensures the floating character of the reproduced admittance.

[0031] As an example of practical implementation, the case where Yc = 1 Ω-1, K1, K2 vary in the value range -1…+1, KDA = 1 can serve. Then, according to (8), when the coefficient K2 varies, the active component Gi of the reproduced admittance Yi is adjusted in the value range Gi = (-1…+1) Ω-1, and when the coefficient K1 varies, the reactive component Bi of the reproduced admittance Yi is adjusted in the value range Bi = (+1…-1) Ω-1.

[0032] 1. MD 3461G2 2007.12.31

Claims (1)

1. Admittance converter, comprising two contacts (2, 3), a differential amplifier (1), the non-inverting and inverting inputs of which are connected to the contacts (2, 3) respectively, two programmable amplifiers (4, 5) with transfer coefficients adjustable in the range of positive and negative values, the inputs of which are connected to the output of the differential amplifier (1), a phase shifter (6) with a phase shift of 90°, the input of which is connected to the output of the programmable amplifier (4), two voltage-to-current converters (7, 8) with equal conversion coefficients, the outputs of which are connected to the contacts (2, 3), respectively characterized in that the voltage-to-current converters (7, 8) are equipped with differential inputs, the output of the programmable amplifier (5) is connected to the non-inverting input of the voltage-to-current converter (7) and to the inverting input of the converter voltage to current converter (8), and the output of the phase shifter (6) is connected to the inverting input of the voltage to current converter (7) and to the non-inverting input of the voltage to current converter (8).