RU2317636C1 - Filter with discontinuously adjustable characteristics - Google Patents

Abstract

FIELD: automatics, possible use in signal filtration systems for automation of technological processes.

SUBSTANCE: device contains input signal source (1), filter (2) with structure which is discontinuously changeable in electric signal level function, which filter has information and control inputs, serially connected first adder (3) and integrator (4), output of which is connected to inputs of n number of relay elements (5-8), where n≥3...... - odd number, outputs of which are connected to inputs of second adder (9), output of which is connected to first input of first adder (3), second input of which is connected to source (1), decoder (10) with n-1 inputs, which are connected to outputs of corresponding relay elements (6-8), and outputs of decoder (10) are connected to control inputs of filter (2), output of which is connected to output clamp (11) of device. In accordance to the invention, input of filter (2) is connected to second input of first adder (3).

EFFECT: increased precision and interference resistance during realization of adjustable filters with differentiating characteristics.

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Description

The device relates to the field of automation and can be used in signal filtering systems for the automation of technological processes.

An active filter is known, the characteristics of which change due to switching capacitors (Gausi M., Laker K. Active filters with switched capacitors: Transl. From English. - M.: Radio and communications, 1986. - 168 p.).

This filter consists of capacitors, resistors, transistor switches and operational amplifiers.

A disadvantage of the known device is its low noise immunity, since the determination of the input signal level at which the filter must change its characteristics is carried out using comparators that are sensitive to external noise signals.

Closest to the proposed device is a filter based on a multi-zone deployment converter (MCI) (AS 1381545 USSR, G06G 7/12. Deployment converter / Tsytovich LI (USSR). - No. 41003521/24; Declared 12/17/86 ; Publish. 07.05.88, Bull. No. 10), which includes a multi-zone scanning converter (MCI), consisting of two adders, an integrator and a group of an odd number of relay elements, as well as a decoder and filter with a tunable transfer function, input and output terminal.

The change in the transfer function of the filter occurs under the action of the output signals of the decoder, which determines the code state of the relay elements, which strictly corresponds to the signal level at the input of the MCI.

The disadvantage of this device is that the filter cannot be implemented with the transfer function of the differentiating link, since in this case the high-frequency spectrum of the output pulses of the MCI is amplified, and the signal at the filter output is strongly distorted. Moreover, in most cases, such a structure is generally inoperative for differentiating regulation laws due to the saturation of the operational amplifier, on the basis of which the filter is implemented, by the output pulses of the second MCI adder. Therefore, the prototype device, as a rule, is used for n-order aperiodic filters with tunable parameters, when the link-filter implements not only the required regulation law, but also suppresses high-frequency harmonics of the output MCI signal.

Thus, the known technical solution has low accuracy and noise immunity when implementing differentiating regulators based on it.

The invention is based on a technical problem, which consists in increasing the accuracy and noise immunity of the operation of a filter that is selectively tunable as a filter input signal based on MCI.

The problem is achieved due to the fact that in the proposed device containing an input signal source, a filter with a structure discretely changed as a function of the level of the electric signal, having information and control inputs, a first adder and an integrator in series, the output of which is connected to the inputs of the nth number relay elements, and n≥3 ...... is an odd number, the outputs of which are connected to the inputs of the second adder, the output of which is connected to the first input of the first adder, the second input of which is connected to the input signal source, a decoder with n-1 inputs that are connected to the outputs of the corresponding relay elements, and the decoder outputs are connected to the control inputs of the filter with a discretely variable structure, the output of which is connected to the output terminal of the device, according to the invention, the filter input with a discretely variable structure is connected to the second input of the first adder.

In the study of the proposed device according to patent and scientific and technical literature, no technical solutions were found containing signs equivalent to those of the claimed device and, therefore, this technical solution meets the criterion of "inventive step".

The stated technical problem is achieved due to the fact that the input of the filter with a discretely variable structure is connected to the second input of the first adder. In this case, the output pulses of the MCI do not affect the information input of the filter with a discretely variable structure, which excludes the possibility of penetration of high-frequency harmonics to the output of the device due to the pulsed nature of the voltage at the output of the second MCI adder.

The invention is illustrated by drawings:

Figure 1 - structural diagram of the proposed device and the characteristic "input-output" of the relay element;

Figure 2 - timing diagrams of the signals of the proposed device;

Figure 3 - amplitude characteristic (a) and a code table of relay elements (b);

Figure 4 is an example implementation of a proportionally differentiating link with a discretely variable characteristic (a) and its frequency characteristics (b).

The device includes (Fig. 1) an input signal source 1, a filter 2 with a discretely variable structure, a first adder 3, an integrator 4, relay elements 5-8, a second adder 9, a binary code decoder 10, and an output terminal 11.

The device blocks have the following characteristics.

The filter 2, the information input of which is connected to the second input of the adder 3, is made with a discretely variable structure, which occurs under the influence of the output signal of the decoder 10.

Adders 3, 9 have a linear non-inverting characteristic "input-output" and a single gear ratio for each of the inputs.

, где Т_и - постоянная времени. При скачке входного сигнала, например положительной полярности, выходной сигнал звена 3 изменяется линейно со знаком, противоположным знаку входного воздействия.Integrator 4 has a transfer function

where T _and is the time constant. When a jump in the input signal, for example of positive polarity, the output signal of link 3 changes linearly with a sign opposite to the sign of the input action.

где индекс при «b» соответствует порядковому номеру РЭ. При рассмотрении принципа действия устройства ограничимся числом n=3Relay elements (RE) 5-8 have a non-inverting hysteresis loop symmetrical with respect to zero (Fig. 1, b) with switching thresholds ± b _i . In this case, the output signal of RE 5-8 varies discretely within ± A / n, where n≥3 is an odd number. Switching thresholds RE satisfy the condition

where the index at "b" corresponds to the serial number of RE. When considering the principle of operation of the device, we restrict ourselves to the number n = 3

The decoder 10 converts the binary code combination from the output of RE6-RE8 into a decimal code, in accordance with which the transfer function of the filter 2 is changed.

In figure 2, 3 introduced the following notation:

X _I - the signal at the output of source 1;

Y _and (t) is the output signal of the integrator 4;

_{Y p1 (t), Y p2} (t), Y p3 (t) - the output signals of relay elements 5, 6, 7, respectively;

± b ₁ , ± b ₂ , ± b ₃ - switching thresholds of relay elements 5, 6, 7, respectively;

± A / 3 - the amplitude of the output pulses of the relay links 5, 6, 7 and the adder 9;

± A - the maximum amplitude of the output signal of the adder 9;

Y _o (t) is the output pulse signal of the adder 9;

Y ₀ - the average value of the pulses at the output of the adder 9.

The device operates as follows.

When you turn on MCI and a zero input signal X _I relay elements 5, 6, 7 are set arbitrarily, for example, in the state + A / 3 (figure 2, e). Under the action of the scan signal Y _AND (t) from the output of the integrator 4 (FIG. 2, b), the blocks 5, 6 are sequentially switched to the position -A / 3 (FIG. 2 c, d, time instants t ₀₁ , t ₀₂ ), after which the direction of the sweeping transformation changes, and the signal Y _AND (t) increases in the positive direction. Starting from the moment the condition Y _И (t) = b ₁ is met, the MCI enters the stable self-oscillation mode when the amplitude of the scan signal Y _И (t) is limited by the ambiguity zone of the relay element 5 with the minimum switching thresholds, and RE6, RE7 are in static and opposite in sign of the output signals Y _p2 (t), Y _p3 (t) states (fig.2g, d). The output coordinate Y _o (t) MCI is formed due to the switching of RE5 (figv) in the first modulation zone, limited by ± A / 3 (fig.2e). In the absence of X _I (Fig. 2a, t <t ₀ ), the average value Y _{0 of the} pulses Y _o (t) is zero.

The presence of the input coordinate X _I 〈(A / 3) (Fig. 2a, t ₀ <t <t ₀ *) entails a change in the frequency and duty cycle of the pulses Y _o (t), since in the interval t ₁ (Fig. 2c) the scan Y _and (t) (fig.2b) changes under the influence of the difference of the signals supplied to the adder 3 (figa, e), and in the interval t ₂ -dY _And (t) / dt depends on the sum of these effects. As a result, Y ₀ ≡X _in (Fig.2, e).

Suppose that at time t ₀ * the signal X _I increased discretely to a value of (A / 3) <X _I <A (Fig.2A). This violates the conditions for the existence of a mode of self-oscillations in the first modulation zone, and the MCI goes to the stage of reorientation of the states of RE6, RE7, which ends at time t ₀₃ , when RE7 switches to the identical position -A / 3 (Fig.2d). The coordinate Y _o (t) reaches level -A (Fig. 3e), and the MCI goes into the second modulation zone, where in the intervals t ₁ , t ₂ (Fig. 3c) the speed of generation of the Y _and t scan signal (t) (Fig. 2b) ) is also determined by the difference or the sum of the signals acting on the adder 3. In this case, the signal Y ₀ includes a constant component -A / 3 and the average value of the pulse flow Y _o (t) of the second modulation zone (Fig.2e). MCI transition from one zone to another modulation for smaller increments of the coordinates X _Rin accompanied by a transition of the system through the characteristic points with zero frequency carrier waves (zero-frequency modulation zones interfacing mode).

Modulation and amplitude characteristics (figure 3) MCI for any i-th modulation zone are determined by the relations:

Y _{0, i} = (- _{1) A [(2Z i -3)} + 2γ] n -1 = -X _Rin,

- нормированное значение порога переключения b₁;

- нормированная величина входного сигнала МРП, причем

n - количество релейных элементов, причем n≥3 - нечетное число; Z_i=1, 2, 3... - порядковый номер модуляционной зоны; γ=t₁/(t₁+t₂) - скважность выходных импульсов МРП; ±А - максимальная амплитуда выходного сигнала МРП; Т_И - постоянная времени интегратора.Where

- the normalized value of the switching threshold b ₁ ;

is the normalized value of the input signal MCI, and

n is the number of relay elements, and n≥3 is an odd number; Z _i = 1, 2, 3 ... - serial number of the modulation zone; γ = t ₁ / (t ₁ + t ₂ ) - duty cycle of the output pulses of the MCI; ± A is the maximum amplitude of the output signal of the MCI; _And T - time constant of the integrator.

The states of all REs, with the exception of RE5, can be considered as a binary code combination, with each modulation zone of the MCI output signal corresponding to its own code combination or group thereof.

We believe that a positive “sign” of the signal at the output of the relay element corresponds to a logical “1”, and a negative sign corresponds to a logical “0”. In addition, we believe that RE6 generates the value of the least significant bit of the binary code, and the state of RE7 determines the value of the most significant bit of the binary code.

(фиг.3а) и таблице кодового состояния релейных элементов РЭ6, РЭ7 (фиг.3б). Учитывая, что при включении МРП релейные элементы 6, 7 ориентируются произвольным образом, первая модуляционная зона может быть охарактеризована двоичными кодовыми комбинациями 01 или 10, т.е. десятичными числами 1 или 2.We turn to the amplitude characteristic of the MCI

(figa) and the table of the code state of the relay elements RE6, RE7 (fig.3b). Given that when the MCI is turned on, the relay elements 6, 7 are oriented arbitrarily, the first modulation zone can be characterized by binary code combinations 01 or 10, i.e. decimal numbers 1 or 2.

число кодовых комбинаций ограничивается одной: 11 или 00 соответственно.When the system moves to the higher modulation zone of the second (+ M2) or fourth (-M2) quadrant of the characteristic

the number of code combinations is limited to one: 11 or 00, respectively.

As a result, the unambiguous relationship of the code state of RE6-RE7 with the value of the signal from source 1 allows, using the key elements included in the filter 2, to change its configuration in the function of the input signal X _I.

The latter is implemented using a DC 10 decoder, on the output buses of which logical “1” command signals are generated that change the transfer function of filter 2. For the first modulation zone M31, buses 0 and 1 of decoder 10 are usually combined using the “OR” function. As a result, each modulation zone of MCI has its own type W ₁ (p), W ₂ (p), W ₃ (p) of the transfer function W _i (p) of the filter Ф (Fig.3b).

Consider an example implementation of filter 2 (Fig. 4a). It includes resistors 12, 13, 14, an operational amplifier 15, capacitors 16, 17, keys 18, 19, an OR gate 20, control inputs 21, 22, 23, information input 24, output 11.

When MCI in the zone "-M32" filter 2 is a proportional link (figb), since the keys 18, 19 are closed. In the modulation zone “+ M31” (FIG. 3a), “1” is formed at the output of block 20, under the action of which the key 18 opens, and link 2 has a transfer function of the form W ₁ (p) = T ₁ p + 1 (FIG. 4b ) In the case of the transition of the MCI into the “+ M32” zone (Fig. 3a, b), “1” is supplied to the input 23 from the output of the decoder 10, and the key 19 opens, and the key 18 returns to its original state. In this case, the time constant T ₁ , for example, decreases (Fig.4b).

A similar algorithm for changing the dynamic characteristics of unit 2 in the prototype device is impossible, since with its differentiating properties, the high-frequency spectrum of pulses will increase from the output of the MCI, which, as a rule, will cause the saturation mode of the operational amplifier of unit 15 (Fig. 4a) and its inoperability.

In addition, the determination using the MCI of the input signal level at which the filter 2 must change its characteristics provides increased temperature and time stability of the device as a whole, since the MCI is a closed control system, where its transition from one modulation zone to another is practically independent of drift of switching thresholds of relay elements.

Thus, the proposed technical solution has higher accuracy and noise immunity compared to the prototype.

Claims (1)

A filter with discretely tunable characteristics, containing a source of an input signal, a filter with a structure discretely variable as a function of the level of an electric signal, having information and control inputs, a first adder and an integrator connected in series, the output of which is connected to the inputs of an nth number of relay elements, with n≥ 3 ... is an odd number, the outputs of which are connected to the inputs of the second adder, the output of which is connected to the first input of the first adder, the second input of which is connected to the source of the input signal a decoder with n-1 inputs that are connected to the outputs of the corresponding relay elements, and the decoder outputs are connected to the control inputs of the filter with a discretely variable structure, the output of which is connected to the output terminal of the device, characterized in that the information input of the filter with a discretely variable structure is connected to the second input of the first adder.

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