RU2582557C1 - Function generator - Google Patents

Abstract

FIELD: electronics.

SUBSTANCE: invention relates to electronics and can be used in measurement techniques and automation. Function generator comprises first 1 and second 2 adders, relay element 3, first 4 and second 5 multipliers, integrator 6, first 7 and second 8 squaring devices, phase filter 9, made from first 10 and second 11 operational amplifiers, third multiplier 12, capacitor 13, two-electrode stabilitron 14, first 15, second 16, third 17, fourth 18 and fifth 19 resistors.

EFFECT: technical result is broader functional capabilities of device by producing at its outputs quadrature harmonic signals and signals of bipolar rectangular and triangular shapes with high metrological characteristics when frequency is varied over a wide range.

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Description

The invention relates to the field of electronics and can be used in measuring equipment and automation.

A device is known [Shustov M. Functional generator. - The radio world. 2010, No. 7, p. 26-27], containing a source of quadrature signals, two half-wave rectifiers, an adder and a shaper of bipolar rectangular pulses, the first and second outputs of the source of quadrature signals are connected, respectively, to the inputs of the first and second half-wave rectifiers, the outputs of which are connected to the inputs of the adder, to the output which is connected to the shaper of bipolar rectangular pulses, while the first, second and third outputs of the functional generator are connected, respectively, with the first output of the source and quadrature signals output from the adder and the output of the bipolar rectangular pulses.

The synthesized signal of a triangular shape has S-shaped characteristics both in the forward stroke section (linearly increasing voltage) and in the reverse stroke section (linearly decreasing voltage) and has a very low linearity [Lozitsky S. Circuit CAD systems: possibilities and problems of efficient use . Circuitry, 2007, No. 3, p. 38-40], which significantly narrows the scope of the practical application of the scheme. In addition, the frequency of a triangular waveform and a rectangular bipolar waveform is twice the frequency of the original harmonic signal, which makes it impossible to obtain the same frequency values at all generator outputs with a fixed tuning of the generator. It should also be borne in mind that the formation of a “quasilinear” signal of a triangular shape requires quadrature harmonic signals, which, under conditions of frequency tuning over a wide range, also causes certain difficulties.

A device is known [Titz U., Schenk K. Semiconductor circuitry: a reference guide. - M .: Mir, 1982, p. 307, fig. 18.25], containing a triangular waveform generator, the first output of which is connected to the output terminal of the relay function, and the second output is connected to the output terminal of the linear function and to the input of the functional converter, the output of which is connected to the output terminal of the sinusoidal function. In modern functional generators for generating a harmonic signal from a triangular waveform, the most widely used are diode functional converters, as well as converters using the I – V characteristics of field-effect transistors, which are based on the principle of piecewise-linear or piecewise-nonlinear approximation of voltage of a sinusoidal shape. However, the whole range of basic requirements (low harmonic coefficient, the absence of a constant component in the sine wave signal, a wide range of operating frequencies, low accuracy of reproduction of the sine function when the temperature and supply voltages change, etc.) is quite difficult to ensure when using such functional converters [Dubrovin V.S., Nikulin V.V. A method of constructing controlled functional generators. T-comm, 2013, p. 22].

The closest device to the claimed invention for the combination of essential features is taken as a prototype controlled generator [US Pat. No. 2506692, Russian Federation, IPC ⁷ Н03В 27/00. Managed Generator / Dubrovin BC, Applicant and Patent Holder Dubrovin Viktor Stepanovich. - No. 2012137334/08; declared 08/31/12; publ. 02/10/14, bull. No. 4], which contains two multipliers, two integrators, a relay element, an adder and a control unit, while the output of the first integrator is connected to the first input of the second multiplier, the input of the relay element, the first input of the control unit and the first output of the controlled generator, the output of the second integrator is connected with the second output of the controlled generator, the second input of the control unit and the second input of the adder, the output of which is connected to the first input of the first multiplier, the second input of which is connected to the control bus the inventive generator and the second input of the second multiplier, the outputs of the first and second multipliers being connected respectively to the inputs of the first and second integrators, the third and fourth inputs of the control unit are connected, respectively, to the output of the relay element and the reference voltage bus, and the output of the control unit is connected to the first input of the adder.

The control unit is made of three quadrators, an adder, a multiplier, a limiter and an inverter, while the first, second and third inputs of the adder are connected, respectively, to the outputs of the first, second quadrators and to the inverter output, the input of which is connected to the output of the third quadrator, the first one the second and third inputs of the control unit are connected, respectively, with the inputs of the first, second and third quadrators, the fourth input of the control unit is connected to the second input of the multiplier, the first input of which is connected to the output of the adder, between the output of which and the output of the control unit a limiter is connected.

The device is designed to generate quadrature harmonic signals.

The problem to which the invention is directed is to expand the functionality of the device and to obtain quadrature harmonic signals, as well as rectangular and triangular bipolar signals with high metrological characteristics when the frequency changes over a wide range, at its outputs.

The technical result achieved by the implementation of the invention is to expand the functionality of the proposed device by introducing a phase filter and organizing new connections between the elements, which made it possible to obtain quadrature harmonic signals at its outputs, as well as rectangular and triangular bipolar signals with high metrological characteristics at change in frequency over a wide range.

The specified technical result during the implementation of the invention is achieved by the fact that in a functional generator containing the first and second adders, a relay element, the first and second multipliers, an integrator, the first and second quadrators, the output of the integrator is connected to the first input of the first adder and the input of the first quadrator, the output of which is connected to the first input of the second adder, the output of which is connected to the first input of the second multiplier, the second input of which is connected to the output of the relay element, the output of the first the multiplier is connected to the input of the integrator, the output of the second quadrator is connected to the second input of the second adder, the third input of which is connected to the reference voltage bus, the control bus of the functional generator is connected to the second input of the first multiplier, and the first, second and third outputs of the functional generator are connected to the outputs, respectively , an integrator, a relay element and a second multiplier, an additional phase filter is introduced, made of the first and second operational amplifiers, the third multiply spruce, capacitor, two-anode zener diode, first, second, third, fourth and fifth resistors, the capacitor being connected between the inverting input and the output of the first operational amplifier, the non-inverting input of which is connected to a common bus, the two-anode zener diode and the first resistor are connected in parallel between the inverting input and the output of the second operational amplifier, the non-inverting input of which is connected to a common bus, a second resistor is connected between the inverting input of the first operational amplifier the first input of the phase filter, the second input of which is connected to the second input of the third multiplier, between the output of which and the inverting input of the first operational amplifier, the third resistor is turned on, the fourth resistor is connected between the first input of the phase filter and the inverting input of the second operational amplifier, the fifth resistor is connected between the inverting the input of the second operational amplifier and the output of the third multiplier, the first input of which is connected to the output of the first operational amplifier, and the control bus The connection is connected to the second input of the phase filter, the output of which is connected to the output of the second operational amplifier and the fourth output of the functional generator, the third output of which is connected to the first input of the phase filter, and the relay element is connected between the output of the first adder and the first input of the first multiplier, the input of which is connected to the second input of the first adder, and the input of the second quadrator is connected to the output of the first quad.

The analysis of the prior art by the applicant, including a search by patent and scientific and technical sources of information, allowed to establish that the applicant did not find an analogue characterized by features identical to all the essential features of the claimed invention. Therefore, the claimed invention meets the condition of "novelty."

The introduction of the phase filter into the proposed device, as well as the organization of new connections between the elements, made it possible to obtain quadrature harmonic signals at its outputs, as well as rectangular and triangular bipolar signals with high metrological characteristics when the frequency changes over a wide range.

The invention is illustrated by the structural diagram of the functional generator (Fig. 1) and graphs (Fig. 2 - Fig. 4), explaining the principle of operation of the functional generator.

The functional generator (Fig. 1) contains two adders (1, 2), a relay element 3, two multipliers (4, 5), an integrator 6, two quadrators (7, 8) and a phase filter 9, the first and second inputs of which are connected, respectively, with the output of the second multiplier 5 and the input bus of the functional generator, while the relay element 3 is connected between the output of the first adder 1 and the first input of the first multiplier 2, the output of which is connected to the input of the integrator 6, the output of which is connected to the first input of the first adder 1 and the input first squad 7, between you the course of which and the second input of the second adder 2 includes a second quadrator 8, the input of which is connected to the first input of the second adder 2, the third input of which is connected to the voltage reference bus, and the output to the first input of the second multiplier 5, the second input of which is connected to the output of the relay element 3, the output of which is connected to the second input of the first adder 1, and the first, second, third and fourth outputs of the functional generator are connected to the outputs, respectively, of the integrator 6, relay element 3, the second multiplier 2 and phase filter 9, and the second input of the first multiplier 2 is connected to the input bus of the functional generator.

The phase filter 9 is made of the first 10 and second 11 operational amplifiers, the third multiplier 12, the capacitor 13, the two-anode zener diode 14, the first 15, the second 16, the third 17, the fourth 18 and the fifth 19 resistors, with a capacitor 13 connected between the inverting input and output the first operational amplifier 10, the non-inverting input of which is connected to the common bus, parallel connected two-anode zener diode 14 and the first resistor 15 are connected between the inverting input and the output of the second operational amplifier 11, non-inverting in One of which is connected to a common bus, the second resistor 16 is connected between the inverting input of the first operational amplifier 10 and the first input of the phase filter 9, the second input of which is connected to the second input of the third multiplier 12, between the output of which and the inverting input of the first operational amplifier 10 a third resistor 17 is connected the fourth resistor 18 is connected between the first input of the phase filter 9 and the inverting input of the second operational amplifier 11, the fifth resistor 19 is connected between the inverting input of the second operational amplifier 11 and the output of the third multiplier 12, the first input of which is connected to the output of the first operational amplifier 10, and the control bus is connected to the second input of the phase filter 9, the output of which is connected to the output of the second operational amplifier 11 and the fourth output of the functional generator, the third output of which is connected to the first input of the phase filter 9, and the relay element 3 is connected between the output of the first adder 1 and the first input of the first multiplier 2, the input of which is connected to the second input of the first adder 1, and to the output of the first quadrator 7 is connected to the input of the second quadrator 8.

Functional generator operates as follows.

The adder 1, the relay element 3, the multiplier 4 and the integrator 6, closed in a ring, form a relaxation controlled generator (Fig. 1).

The multiplier 4 and the inverting integrator 6 form a controlled integrator whose transfer function (in Laplace images)

where s is a complex variable; E _U - control voltage; τ is the time constant of the integrator 6; m ₁ - scale factor multiplier 1; τ _U = τ / Е _У - controlled time constant.

In the steady state (Fig. 2), the output of the inverting relay element generates (Fig. 2a) a rectangular bipolar signal D (t), which is fed to the input of a controlled integrator, the output of which (Fig. 2b) forms a triangular signal L (t )

As a result of summing the two signals D (t) and L (t) at the output of the inverting adder 1, a signal is generated (Fig. 2c)

where k ₁₁ and k ₁₂ are the transfer coefficients of the adder 1 at the corresponding inputs.

When k ₁₁ = k ₁₂ = 1, the output signal input to the relay element 3 will be equal to S ₁ (t) = L (t) + D (t).

The restriction levels of the relay element 3 determine (Fig. 2a) the amplitude values ± D _{m of the} generated signal D (t), which arrives at the second output of the functional generator, the first output of which is supplied with a triangular signal L (t) from the output of the integrator 6.

The frequency f of the generated signals of triangular and rectangular shape is determined by the following expression, whence it follows that the frequency f of the generated signals will linearly depend on the change in the control voltage E _U.

Squatters 7 and 8, adder 2 and multiplier 5 form (Fig. 1) a harmonic signal former, to the input of which a triangular waveform L (t) is output from the integrator 6.

To find the analytical expressions of the signal L (t), we use (Fig. 2b) the general expression for the line y = kx + b passing through two points with coordinates (x ₁ , y ₁ ) and (x ₂ , y ₂ ),

where x is the current value of the angle in radians.

Substituting in (3) the coordinates of the two boundary points [x ₁ = 0, y ₁ = 0; x ₂ = π / 2, y ₂ = -L _m ] for the first section of the signal L (t), we obtain

Substituting in (3) the coordinates of two other boundary points [x ₁ = π / 2, y ₁ = -L _m ; x ₂ = π, y ₂ = 0] for the second section of the signal L (t), we obtain

To simplify the argument, we assume that the amplitude values of the signal L (t) are equal to the normalized value L _m = A ^* = 1. In this case

Consider the operation of the harmonic signal former in the first section at x∈ [0; π / 2]. At the output of the first 7 and second 8 quadrators, corresponding signals are generated (Fig. 3d)

The adder 2 is inverting, so a signal will be generated at its output

where k ₂₁ , k ₂₂ and k ₂₃ are the transfer coefficients of the adder 2 at the corresponding inputs, E ₀ is the value of the reference voltage.

For k ₂₃ = 1, we represent expression (8) in the following form

where V _l (x) = k ₂₁ · F ₁ (x), V ₂ (x) = k ₂₂ · F ₂ (x) are virtual signals (Fig. 3b), from which the signal S ₂ (x) is generated at the output adder 2.

When E ₀ = 1 and taking into account (7) we obtain

For x = π / 2 (Fig. 3b)

From equation (11) we find the relationship between the coefficients k ₂₁ and k ₂₂

Substituting the value of the coefficient k ₂₂ from equation (12) into equation (10), we obtain

The maximum (extreme) value of S _2max will be (Fig. 3c) at x = 0

Similar results can be obtained for the second section, with S _2max = S ₂ (π) = 1.

Analysis of the curve S ₂ (x) shows that the signal is close in form to a cosine wave, therefore, to estimate the error ε (x), we find the difference between the signal S ₂ (x) and S ₀ (x) for an ideal cosine wave

and, as follows from (13), the error value will depend on the value of the coefficient k _21.

The error ε (x) is minimized when the coefficient k ₂₁ ≈1.2232, and the coefficient k ₂₂ ≈0.2232.

The formation of a harmonic signal N ₁ (t) occurs using a phase modulator made of a multiplier 5, the first input of which receives (Fig. 3c) a unipolar signal S ₂ (t), and the other (Fig. 3d) - a control signal D ( x) from the output of relay element 3.

Thus, at the output of the multiplier 5, a harmonic signal N ₁ (t) is formed, the distortion coefficient of which does not exceed 0.072% at optimal values of the coefficients k _21opt = 1.2232 and k _21opt = 0.2232.

The optimization of coefficients and the measurement of nonlinear distortion were performed using the block (THD-Total harmonic distortion) of the PSIM 9 program.

To obtain a quadrature harmonic signal N ₂ (t), a phase filter 9 is used, the input of which receives a harmonic signal N ₁ (t) from the output of the multiplier 5.

The operational amplifier 10, two resistors 16 and 17, as well as a capacitor 13 form an inverting integrator, the output signal of which

where k ₁ (s) = 1 / (R ₂ C s) = 1 / (T ₁ s) and k ₂ (s) = 1 / (R ₃ C s) = 1 / (T ₂ s) are the coefficients integrator transmission, respectively, on the first and second inputs; C is the value of the capacitor 13; R ₂ and R ₃ - resistance values of the respective resistors 16 and 17; T ₁ and T ₂ - time constants.

The signal M (s) at the output of the multiplier 12

where m ₂ is the scale factor of the multiplier 12.

When solving (15) and (16) together, we find the expression for the transfer function

_F where K = R ₃ / R ₂ - transfer coefficient of the controllable filter;

T _U = T ₂ / (m ₂ E _Y) - controlled time constant.

Thus, the transfer function (17) describes a classical first-order low-pass filter (LPF) with a controlled time constant.

The operational amplifier 11, the first 15, the fourth 18, and the fifth 19 resistors form an inverting adder, the first input of which receives a signal N ₁ (s), and the second input - a signal M (s). As a result of the summation of the signals at the output of the operational amplifier 11, a signal is generated

where k ₃₁ = R ₁ / R ₄ and k ₃₂ = R ₁ / R ₅ are the transfer coefficients of the inverting adder along the first and second inputs; R ₁ , R ₄ and R ₅ are the resistance values of the respective resistors 15, 18 and 19.

The joint solution (17) and (18) makes it possible to find the transfer function of the phase filter 9 formed by the low-pass filter and the inverting adder,

The analysis of expression (19) shows that for k ₃₁ = 1 and K _Ф · k ₃₂ = 2 the transfer function W ₂ (s) of the phase filter

takes the form of a classic all-pass (phase) filter of the first order.

To implement (20), it is convenient to take R ₂ = R ₃ , then K _Ф = 1. In this case, the transfer coefficient of the inverting adder at the first input should be equal to two, that is, k ₃₂ = 2.

Substituting the value of the complex variable s = jω into equation (20), we find the complex frequency function (CFR) of the phase filter

The KChF module does not depend on frequency and is equal to unity

and the argument

To obtain quadrature harmonic oscillations N ₁ (t) and N ₂ (t) in the entire range of operating frequencies from f _min to f _max, it is necessary to ensure a stable phase shift ψ ₂ (ω) = - 90 ° = - for the signal N ₂ (t) π / 2.

After substituting the values ψ ₂ (ω) = - π / 2 in (23) and as a result of elementary transformations, we obtain

where T _Y is the controlled time constant of the phase filter 9.

The value of tg (π / 4) = 1; therefore, we rewrite formula (24)

The frequency f of the generated signals linearly depends (formula 2) on the change in the control voltage

where K _f is the coefficient of proportionality.

Substituting the value of f from (26) into (25), we obtain

Thus, when the frequency f changes, the phase shift ψ ₂ (ω) between the signals N ₂ (t) and N ₁ (t) will remain constant and equal to 90 electrical degrees.

The value of the time constant T ₂ is selected from the condition

With an abrupt change in the control voltage E _U at the input of the functional generator, a significant short-term emission of the signal N ₂ (t) at the time of switching can occur (Fig. 4c), which is explained by the energy stored in the capacitor 13 of the phase filter. The magnitude of this surge N _2m (Fig. 4c) depends on the moment of switching, as well as on the dynamic range of the control voltage E _Umax / E _Umin and can several times exceed the amplitude value A of the signal itself.

In FIG. Figure 4 shows the transients occurring in a functional generator when the control voltage changes within one decade, which corresponds to a tenfold change in the frequency f of the generated signals.

To eliminate this effect in the feedback circuit of the operational amplifier 11, a two-anode zener diode 14 is included, which limits the burst of the signal at the time of switching at a given level (Fig. 4d). The level of limitation is selected from the condition of a slight excess of the amplitude value A of the generated signal N ₂ (t).

It should be noted that the transition process at the third output of the functional generator for the generated signal N ₁ (t) is practically absent (Fig. 2b), since the formation of signal N ₁ (t) occurs without the participation of reactive elements.

Using the present invention will expand the functionality of the device and get at its outputs quadrature harmonic signals, as well as quadrature bipolar signals of rectangular and triangular shape with high metrological characteristics when the frequency changes over a wide range.

Claims (1)

A functional generator containing the first and second adders, the relay element, the first and second multipliers, the integrator, the first and second quadrators, the output of the integrator connected to the first input of the first adder and the input of the first quadrator, the output of which is connected to the first input of the second adder, the output of which connected to the first input of the second multiplier, the second input of which is connected to the output of the relay element, the output of the first multiplier connected to the input of the integrator, the output of the second quadrator connected to the second the second input of the second adder, the third input of which is connected to the reference voltage bus, the control bus of the functional generator is connected to the second input of the first multiplier, and the first, second and third outputs of the functional generator are connected to the outputs of the integrator, relay element, and second multiplier, that it additionally introduced a phase filter made of the first and second operational amplifiers, the third multiplier, capacitor, two-anode zener diode, the first, W horn, third, fourth and fifth resistors, wherein a capacitor is connected between the inverting input and the output of the first operational amplifier, the non-inverting input of which is connected to a common bus, two-zener diode is connected in parallel and the first resistor is connected between the inverting input and the output of the second operational amplifier, whose non-inverting input connected to a common bus, a second resistor is connected between the inverting input of the first operational amplifier and the first input of the phase filter, the second input of which о is connected to the second input of the third multiplier, between the output of which and the inverting input of the first operational amplifier a third resistor is connected, the fourth resistor is connected between the first input of the phase filter and the inverting input of the second operational amplifier, the fifth resistor is connected between the inverting input of the second operational amplifier and the output of the third multiplier, the first input of which is connected to the output of the first operational amplifier, and the control bus is connected to the second input of the phase filter, the output to which is connected to the output of the second operational amplifier and the fourth output of the functional generator, the third output of which is connected to the first input of the phase filter, the relay element being connected between the output of the first adder and the first input of the first multiplier, the input of which is connected to the second input of the first adder, and to the output of the first the square of the input connected to the second quad.

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