RU2551824C1 - Controlled quadrature signal generator - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: device comprises two multipliers, two integrators, two squaring devices, two adders, an inverter, two dividers, a square-root extracting unit, a comparator and a reference voltage source.

EFFECT: high spectral purity of generated quadrature harmonic signals.

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Description

The invention relates to radio engineering and communications and can be used in the construction of controlled generators.

A known generator [1 (p. 202 - Fig. 4-16. "Electronic generator with a limited amplitude of oscillations")], containing two integrators, an adder, a nonlinear element (with a relay characteristic) and two passive controlled divider, realigning output oscillations according to frequency. At the output of the nonlinear element, bipolar pulses of a rectangular shape with a high content of higher odd harmonics are formed. The bipolar rectangular signal is fed through the feedback circuit directly to the input of the adder, therefore, at the output of the first integrator, a signal having significant non-linear distortions will be generated.

Known controlled generator [2 (p. 17 - Fig. 1-9.)], Which contains two integrators, two multipliers, a nonlinear element and an adder, the output of which is connected to the first multiplier, the control input of which is connected to the control bus and the control input of the second a multiplier between the output of which and the first input of the adder includes a second integrator, the output of which is connected to the second output of the controlled generator, the first output of which is connected to the output of the first integrator, while a nonlinear element is connected between the first output of the control generator and the second input of the adder, and the input of the second multiplier is connected to the output of the first integrator.

To stabilize the amplitude, a nonlinear element is used, while the harmonic coefficient and amplitude stability are inversely related, that is, a decrease in the harmonic coefficient due to a decrease in the degree of nonlinearity leads to a decrease in the amplitude stability and, on the contrary, an increase in the amplitude stability leads to an increase in harmonics in the output signal. Relatively low metrological characteristics (amplitude stability of 1-2% with a harmonic coefficient of 0.5-1%) limit the use of such generators [2 (p. 19)].

The closest device to the claimed invention in terms of essential features is a controllable generator [3], adopted for the prototype, containing two integrators, three multipliers, three quadrators, a relay element, a limiter, two adders and an inverter connected between the output of the third quadrator and the third input the second adder, the output of which is connected to the second input of the third multiplier, between the output of which and the first input of the first adder a limiter is connected, while the first integrator is connected between the output m of the first multiplier and the first input of the second multiplier, the output of which is connected to the input of the second integrator, the output of which is connected to the second input of the first adder, the output of which is connected to the first input of the first multiplier, the second input of which is connected to the second input of the second multiplier and the first bus of the controlled generator, whose second bus is connected to the input of the third quadrator, the outputs of the first and second integrators being connected to the corresponding outputs of the controlled generator, the first quadrator is connected between the first output of the controlled generator and the first input of the second adder, the second quadrator is connected between the second output of the controlled generator and the second input of the second adder, and the relay element is connected between the first output of the controlled generator and the first input of the third multiplier.

At the first output of the generator, the coefficient of nonlinear distortion exceeds 0.05%, which does not allow attributing this device to precision generators by this indicator.

The problem to which the invention is directed is to increase the spectral purity of the generated quadrature harmonic signals.

The technical result achieved by the implementation of the invention is to increase the spectral purity of the generated quadrature harmonic signals by introducing additional elements and organizing new functional relationships between the elements.

The specified technical result during the implementation of the invention is achieved by the fact that in a controlled quadrature signal generator containing the first and second multipliers, the first and second integrators, the first and second quadrators, the first and second adders and the inverter, the first quadrator is connected between the output of the first integrator and the first the input of the second adder, the second quadrator 6 is connected between the output of the second integrator and the second input of the second adder, the first input of the first multiplier is connected to the output of the first adder, the output to which is connected to the input of the first integrator, the output of which is connected to the first input of the second multiplier, the output of which is connected to the input of the second integrator, the output of which is connected to the second input of the first adder, while the second inputs of the first and second multipliers are connected to the control bus, it is additionally introduced the first and second dividers, the square root extraction unit, a comparator, and a reference voltage source, the negative terminal of which is connected to the common bus, and the positive terminal is connected to the inverting input of the comparator, output to which is connected to the fourth input of the first adder and the third input of the second adder, between the output of which and the non-inverting input of the comparator, the square root extraction unit is turned on, while the inverter is connected between the output of the first integrator and the third input of the first adder, the first input of which is connected by the output of the first divider and the first output controlled quadrature signal generator, the second output of which is connected to the output of the second divider, the first input of which is connected to the output of the second integrator, and you od square root extractor is connected to second inputs of the first and second dividers and the first input of the first divider is connected to the output of the first integrator.

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."

Introduction to the proposed controlled generator of quadrature signals of two dividers, a square root extraction unit, a comparator and a reference voltage source, as well as the organization of new functional relationships between elements made it possible to increase the spectral purity of the generated quadrature harmonic signals.

The invention is illustrated by a block diagram of a controlled quadrature signal generator shown in FIG. 1, and graphs explaining the principle of operation of the controlled quadrature signal generator, FIG. 2 and FIG. 3.

The controlled quadrature signal generator contains (Fig. 1) the first 1 and second 2 multipliers, the first 3 and second integrators 4, the first 5 and second 6 quadrators, the first 7 and second 8 adders, the inverter 9, the first 10 and second 11 dividers, an extraction unit square root 12, the comparator 13 and the reference voltage source 14, the negative terminal of which is connected to the common bus, and the positive terminal is connected to the inverting input of the comparator 13, the output of which is connected to the fourth input of the first adder 7 and the third input of the second adder 8, between the output of which is non-inverting the square root extraction unit 12 is turned on by the input of the comparator 13, while the first quadrator 5 is connected between the output of the first integrator 3 and the first input of the second adder 8, the second quadrator 6 is connected between the output of the second integrator 4 and the second input of the second adder 8, and the inverter is connected between the output the first integrator 3 and the third input of the first adder 7, the output of which is connected to the first input of the first multiplier 1, between the output of which and the first input of the second multiplier 2 the first integrator 3 is connected, and the output of the extraction unit square root 12 is connected to the second inputs of the first 10 and second 11 dividers, the control bus is connected to the second input of the first multiplier 1 and the second input of the second multiplier 2, the output of which is connected to the input of the second integrator 4, the output of which is connected to the second input of the first adder 7, the first input of which is connected to the output of the first divider and the first output of the controlled quadrature oscillator, the second output of which is connected to the output of the second divider 11, the first input of which is connected to the output of the second integrat and 4, a first input of a first divider coupled to an output of the first integrator 3.

A controlled quadrature signal generator operates as follows.

The first multiplier 1 and the first integrator 3 form (Fig. 1) the first controlled integrator with a transfer function

where τ _Y1 = τ ₁ / (m ₁ · E _Y ) is the time constant of the first controlled integrator; τ ₁ is the time constant of the first integrator 3; m ₁ - scale factor of the multiplier 1; E _U - control voltage; s is a complex variable.

The second multiplier 2 and the second integrator 4 form a second controlled integrator with a transfer function

where τ _U2 = τ ₂ / (m ₂ · E _U ) is the time constant of the second controlled integrator; τ ₂ is the time constant of the second integrator 4; m ₂ - scale factor of the multiplier 2.

With the same values of the scale factors m ₁ = m ₂ = m and with the equal time constants of the integrators, τ ₁ = τ ₂ = τ ₀ will also have the same values and time constants of the first and second controlled integrators τ _U1 = τ _U2 = τ _U = τ ₀ / (m · E _Y ).

Therefore, the transfer functions of controlled integrators in this case will have the same expression

Multipliers 1 and 2, integrators 3 and 4, an adder 7 and an inverter 9 form a controlled filter (UV). When applying to the first input of the adder 7, that is, to the input of the UV signal N ₁ (t), two signals S ₁ (t) and S ₂ (t) are formed at the output of the controlled filter.

To find the amplitude-frequency and phase-frequency characteristics, as well as determine the resonant frequency of the UV, the attenuation value and the quality factor of the filter, we find the transfer functions (PF) of the controlled filter.

We find the UV transfer function by the first W ₁ (s) and second W ₂ (s) output when exposed to the input signal N ₁ (t), for which we compose the following system of equations in operator form:

where k ₁ , k ₂ and k ₃ are the coefficients of the first adder 7 at the corresponding inputs.

Using the method of eliminating variables in (4), we write the expressions for the transfer function

and for the transfer function

For k ₂ = 1, expression (6) can be reduced to the classical form for the vibrational link with the transfer function

where ξ = k _3/2 - damping coefficient determining unit selective properties.

The transfer function W ₂ (s) can be represented as a series connection of the oscillating and differentiating links

The resonance frequency ω _{0 of the} controlled filter can be found from the characteristic equation, for which the denominator in equations (7) and (8) should be set to zero and the roots of this equation should be found

To find the complex-frequency functions in expressions (8) and (9), it is necessary to replace the complex variable s → jω

From (10) and (11) it follows that the phase shift between the output signals S ₁ (t) and S ₂ (t) will be determined only by the parameters of the differentiating link with the transfer function W _D (s) = τs, since W _D (jω) = j

Phase shift

From (12) it follows that the phase shift between the output signals S ₁ (t) and S ₂ (t) is independent of the frequency and in the entire range of operating frequencies is 90 electrical degrees.

Frequency response

it is convenient to present in a normalized form (Fig. 2), for which we introduce the relative frequency detuning

where ω ₀ = 1 / τ _Y is the resonant frequency.

After substituting (15) into (13) and (14) we obtain

Graphical dependences of the transmission coefficients W ₁ (ω) and W ₂ (ω) on the relative detuning δ are shown in FIG. 2. At the resonant frequency (with δ = 1)

If the coefficients k ₁ = k ₃ are equal, the transmission coefficients will also be equal to W ₁ (1) = W ₂ (1) = 1.

The spectral purity of the generated signals S ₁ (t) and S ₂ (t) will depend both on the shape of the signal N ₁ (t) coming through the feedback circuit and on the Q factor of the resonance system (controlled filter), which, in turn, , determines (Fig. 2) the passband P _PR filter.

The passband P _{PR is} conditionally determined by the resonance curve (Fig. 2) at the level of 0.707 (-3 dB) from its maximum value corresponding to the resonant frequency.

Managed Filter Bandwidth

The quality factor of the controlled filter is related to the attenuation coefficient ξ as follows: Q = 1 / ξ = 2 / k ₃ , therefore, the quality factor Q, the attenuation coefficient ξ and the passband P _PR can be adjusted using the coefficient k ₃ , but the equality coefficients k ₁ = k ₃ .

In this case, at any values of the quality factor at the resonance frequency, the amplitude values of A ₁ and A _{2 of the} signals S ₁ (t) and S ₂ (t) will have the same values equal to unity, and the phase shift between them will be 90 electrical degrees. Thus, at the outputs of the controlled filter, quadrature signals of stable amplitude are formed.

In the proposed solution, the input of the first adder 7 is fed a quasi-harmonic signal N ₁ (t) of stable amplitude A ^* having a small number of higher harmonics in its composition.

The formation of the feedback signal N ₁ (t) is as follows.

Squatters 5 and 6, the adder 8 and the square root extraction unit 12 form an inertia-free voltage sensor (DN).

When a harmonic signal S ₁ (t) = A ₁ sin (ωt) is supplied to the input of the quadrator 5, a signal is generated at its output

where m ₃ is the scale factor of quadrator 5.

When a harmonic signal S ₂ (t) = A ₂ cos (ωt) is supplied to the input of the quadrator 6, a signal is generated at its output

where m ₄ is the scale factor of quadrator 6.

The summation of the signals L ₁ (t) and L ₂ (t) at the output of the adder 8 produces a voltage

At the output of the square root extraction unit 12, that is, at the output of the DN, a voltage is formed

Under the conditions k ₃ = k ₄ = 1, m ₃ = m ₄ = 1 and when the amplitude values are equal, A ₁ = A ₂ = A voltage

that is, the output voltage will be exactly equal to the amplitude value E _m = A.

At the output of the divider 10, that is, at the first output of the controlled quadrature signal generator, a signal is generated

where A ^* = 1 is the normalized signal amplitude N ₁ (t).

The second divider 11 works similarly, at the output of which a signal with a stable amplitude is also formed.

The amplitude-stabilized signal N ₁ (t) 10 is supplied to the first input of the adder 7, closing the feedback circuit and creating conditions for the excitation of harmonic oscillations.

The oscillation frequency Ω ₀ in the controlled generator coincides with the resonant frequency ω ₀ = 1 / τ _U and changes in direct proportion to the change in the control voltage E _U

Since the harmonic signal is supplied to the input of the controlled filter from the output of the first divider 10, in which there are practically no higher harmonic components, the spectral purity of the generated signals S ₁ (t) and S ₂ (t) is much higher than in the prototype.

The nonlinear distortion of the generator output signals was estimated using a mathematical model in the PSIM-9 program. Nonlinear distortions at the outputs of the controlled generator were measured using the block (THD - Total harmonic distortion) of the PSIM program.

At the first output, the coefficient of non-linear distortion did not exceed 0.011%, which is approximately five times less compared to the prototype.

At the second output of the controlled generator, the distortion of the signal N ₂ (t) will be even less due to the filtering properties of the second integrator 4. The low content of the higher harmonics of the output signals N ₁ (t) and N ₂ (t) is the advantage of the proposed generator.

To reduce the start-up time of the generator, a correction signal S _k (t) is supplied to the fourth input of the adder 7 from a single pulse shaper, which is made from a comparator 13 and a reference voltage source 14. A correction signal S _k (t) is also supplied to the third input of the adder 8, providing thereby, the normal operation of the dividers 10 and 11, which, in the absence of a correction signal, form a short-term voltage surge at their outputs when the generator starts, and to eliminate which the outputs of the dividers 10 and 11 will require anichiteli.

The introduction of a correction signal S _k (t) significantly improves the dynamics of the controlled oscillator both in the starting mode (Fig. 3) and when the generator is switched from one frequency to another.

The duration of the transient process at the start of the controlled quadrature signal generator is determined (Fig. 3) by the duration T _{AND of the} correction signal S _k (t) and the value of the transmission coefficient at the fourth input of the adder 7. The duration T _{AND of the} signal S _k (t) can be changed using the bias voltage E ₀ supplied to the input of the comparator 13 from the source of the reference voltage 14.

Graphic dependencies explaining the principle of transient reduction in the generator are shown in FIG. 3. In FIG. 3a and FIG. 3b shows graphs for the case when the value of the reference voltage is E ₀ = 0.1 V, and the transfer coefficient of the adder on the fourth input is k ₄ = 0.1. In FIG. 3c and FIG. 3d shows graphs for the case when the value of the reference voltage is E ₀ = 0.8 V, and the transfer coefficient of the adder on the fourth input is k ₄ = 1.0. In FIG. 3, d and FIG. 3e shows graphs for the case when the value of the reference voltage is E ₀ = 0.9 V and the transfer coefficient of the adder on the fourth input is k ₄ = 10.0.

The choice of the best combination of the duration T _{And the} correction signal S _k (t) and the transfer coefficient k _{4 of the} adder 7 at the fourth input made it possible to minimize the duration of the transient process when the controlled quadrature signal generator was started, and the presence of dividers 10 and 11 made it possible to further stabilize the amplitudes of the output signals N ₁ ( t) and N ₂ (t). It should be noted that the signal S _k (t) is generated only once at the start of the generator and does not participate in the further operation of the controlled generator.

Using the present invention will increase (compared with analogues and prototype) the spectral purity of the generated quadrature harmonic signals.

Information sources

1. Vavilov A.A., Solodovnikov A.I. Experimental determination of the frequency characteristics of automatic systems. M.-L.: Gosenergoizdat, 1963 - 252 p.

2. Vavilov A.A., Solodovnikov A.I., Schneider V.V. Low-frequency measuring generators. - L .: Energoatomizdat, Leningrad. Department, 1985 - 104 p.

3. RF patent No. 2506692, H03B 27/00. Dubrovin B.C. Managed Generator 08/31/2012, publ. 02/10/2014. Bull. Number 4.

Claims (1)

A controlled quadrature signal generator containing the first and second multipliers, the first and second integrators, the first and second quadrators, the first and second adders and the inverter, while the first quadrator is connected between the output of the first integrator and the first input of the second adder, the second quadrator is connected between the output of the second integrator and the second input of the second adder, the first input of the first multiplier is connected to the output of the first adder, the output of which is connected to the input of the first integrator, the output of which is connected to the first input the second multiplier, the output of which is connected to the input of the second integrator, the output of which is connected to the second input of the first adder, while the second inputs of the first and second multipliers are connected to the control bus, characterized in that the first and second dividers are added to it, the square root block , a comparator and a reference voltage source, the negative terminal of which is connected to the common bus, and the positive one - with the inverting input of the comparator, the output of which is connected to the fourth input of the first adder and the third input the square of the second adder, between the output of which and the non-inverting input of the comparator, the square root extraction unit is turned on, while the inverter is connected between the output of the first integrator and the third input of the first adder, the first input of which is connected to the output of the first divider and the first output of the controlled quadrature signal generator, the second output of which connected to the output of the second divider, the first input of which is connected to the output of the second integrator, and the output of the square root extraction unit is connected to the second inputs mi of the first and second dividers, and the first input of the first divider is connected to the output of the first integrator.

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