Stochastic amplification coefficient meter

FIELD: radio-electric measurements.

SUBSTANCE: device has multiplexer, filtering block, analog-digital converter, square-ware generator, two accumulating adders, functional converter, performing in simplest case operations of division and square root, as well as control block and white noise generator. Device uses random process with broad range as test signal and allows to measure amplification coefficient concurrently in certain range of frequencies. Products of nonlinear distortions are taken in consideration, which accompany operation of real amplifiers and which influence shape of output signal as well as its level.

EFFECT: higher precision.

2 dwg

 

The invention relates to the field of electrogravimetry and can be used in problems of measurement amplifiers low frequency, such as audio amplifiers.

As a prototype of the selected device, allowing to measure the gain using random test signals and contains two input devices, multiplexer, limiter, detector, an output switch and a differential amplifier, the inputs of the first and second input devices are respectively the first and second information input device, the outputs of the input devices connected respectively to the first and second multiplexer input, the output of which is connected to the input of the limiter, the output of which is connected to the input of the output switch, the outputs of which are connected to the inputs of differential amplifier whose output is the output device [Goron I.E. Broadcasting. - M.: Communication, 1979, str].

The main disadvantage of the prototype as a measuring device is the low accuracy. Despite the fact that the meter single channel and thus excludes the impact of non-identical channels on the end result, measurement error is still large because of methodological differences. The reason is that the task of converting two-channel meter in a single channel in the prototype would be settled and solved simply by switching one channel processing sequentially on the input and output signals of the investigated amplifier with the accumulation of voltage signals on the output capacitors of the switch. The non-identity parameters of the circuits of the charge and discharge of capacitors, their dependence on external factors, as well as the non-identity parameters of the capacitors is one of the components of the total error. Moreover, errors will be caused more and work actively managed limiter, as well as the discretization in time of the signals, following in the path of purely analog processing.

Device features of the prototype, which was mentioned above, limit the scope of its application and effectively allow them to use more for monitoring than for measurements, for example, for continuous monitoring of deviations of the gain from a certain value.

Technical result achieved when using the present invention is to improve measurement accuracy.

The technical result is achieved by the fact that the stochastic meter gain that contains a multiplexer, according to the invention introduced block filtering, analog-to-digital Converter, Quad splitter, two accumulating adder functional unit, a control unit and a white-noise generator, the output of which is connected to the first information input of the multiplexer, which (input) is the first information input of the meter, the second information input of which assetcentral information input multiplexer, the output of which through the filtration unit connected to the information input of the analog-to-digital Converter, the output of which is connected to the information input of the Quad, the output of which is connected to the integrated information inputs of the first and second accumulative adders whose outputs are connected to respective inputs of a functional of the inverter whose output is the output of the meter, the address input of the multiplexer and clock inputs of analog-to-digital Converter and two accumulative adders connected to the corresponding outputs of the control unit.

The invention is illustrated by drawings.

Figure 1 shows the functional diagram of the stochastic meter gain, and Fig, 2 is a functional diagram of the control unit.

Functional diagram of the meter (figure 1) contains a multiplexer 1, block 2, filtering, analog-to-digital Converter (ADC) 3, a squarer 4, two accumulating adder 5 and 6, a functional Converter 7, the control unit 8, the generator 9 white noise and the amplifier 10, the gain of which measure (RL- load resistance of the amplifier). The output of the generator 9 white noise is connected to the first information input of the multiplexer 1, which (input) is the first information input of the meter, the second information is the course which is the second information input of the multiplexer 1, the output of which through the filtering unit 2 is connected with the information input ADC 3, the output of which is connected with the information input Quad 4, the output of which is connected to the integrated information inputs accumulative adders 5 and 6, the outputs are connected to corresponding inputs of functional Converter 7, the output of which is output To the meter, the address multiplexer input 1 and clock inputs of the ADC 3 and accumulative adders 5, 6 are connected to the respective outputs A1, C1, C2, C3 of the control unit 8 that controls the entrance of which is the triggering input of the meter. Between the first and second information inputs of the meter are connected analyzed amplifier 10 with the load RL. The filtering unit 2, in turn, contains a band-pass filter 11 and the multiplexer 12, the output of which is the output of the block 2, the first information input of the multiplexer 12 is combined with the input of the bandpass filter 11 and an input unit 2, and the second information input connected to the output of bandpass filter 2, the address input of the multiplexer, as managing input unit 2 simultaneously serves as input M (Mode) mode selection of measuring.

Unit 8 controls (figure 2) contains the triggers 13, 14 and 15, a counter 16, the element OR 17, elements 18, 19 and 20, the delay element 21, the one-shot 22 and the generator 23 of clock pulses. The Manager at the Odom FROM the block 8 is the S-input of the trigger 13, the output of which is connected to the D input of the trigger 14, the output of which is connected to the first input element And 18, the second input is combined with the input of the trigger 14 and is connected to the output of the generator 23 of clock pulses, the output element And 18 connected to the counting input of the counter 16, the output of the overflow which is connected with the input of the trigger 15, the R-input of which is United with the same input of the counter 16, the first input of the OR element 17 and is boleushim the input of the control unit 8, the second input of the OR element 17 is combined with R-input of the trigger 14 and connected to the output of one-shot 22, whose input is combined with the first input element And 19 and connected to the direct output of the trigger 15, the inverting output of which is connected to the first input element And 20, the D-input of the trigger 15 is also connected to its inverting output, direct output which, in turn, serves as the address output A1 of the control unit 8, the first clock C1 output which is the output element And 18, the output of which is also connected through a delay element 21 United second input elements And 19, 20, the outputs of which are respectively third C3 and the second C2 clock outputs unit 8, the output of the OR element 17 is connected to the R input of the trigger 13.

The work of the stochastic meter gain K(ω) consists of two stages. The beginning of the first stage, as the entire cycle and the measurements, is determined by the time when the output FROM the trigger pulse (figure 1). During the first phase signal from the output of the generator 9 white noise through the multiplexer 1 is supplied to the filtering unit 2, which is allocated a given narrow frequency band Δω with center in the point ω. Allocated thus the signal is subjected to analog-to-digital conversion, and then the obtained values are squared in block 4. Code u

2
I
(tn) arrives at the input of the accumulating adder 5. By the end of the first phase at the output of the adder 5 is accumulated amount

where N is the number of samples per observation time;

tn=t01+(n-1)Δt, (n=1, 2,..., N);

Δt is the sampling period (the period of the clock pulses at the outputs C1, C2, C3 block 8);

t01- the beginning of the first stage.

At the end of the first phase of the meter moves to the second stage of measurements differing from the first by the fact that the multiplexer 1 selects the mode switching its output signal output from the studied amplifier 10: ADC input 3 receives the amplified signal, after as well as before the filtering unit 2. To sum formed at this stage samples is accumulating adder 6. in what oterom to the end of the second stage will be accumulated value

where tn=t02+(n-1)Δt;

t02- the beginning of the second phase.

Amounts received (1) and (2) are sent to the function Converter 7, which performs a division operation on the input operands SD2SD1and extracting from the received result of the square root, i.e. calculates gain

Values of sD1and sD2different from the dispersions D1and D2only by a constant factor of 1/N, that is,

and

Strictly speaking, the justice of the latter statement is true only if the test signal is white noise has zero mean and, in addition, the output signal of the investigated amplifier there is no constant component (amplifier output isolated AC). Therefore, the ratio of the variances is the ratio of accumulated amount

Given that the variance of a stationary ergodic process, which is white noise, the time does not depend (in this case from the point of time t01and t02)then the relation (3) will not depend on what times were measured value of sD1(1) and sD2(2), that is, measured on the and time concurrently or sequentially.

Since white noise is a mathematical idealization, as a real generator 9, you should use the source subarraying stationary ergodic process with a uniform spectrum across the frequency meter and zero mean. Frequency ωin the neighborhood in which the band Δω measured gain K(ω), is given by block 2 filtering by selecting the parameters of the band pass filter 11. In the General case, the filter 11 may be adjustable q-factor and the center frequency ω. To measure the gain relating to the whole frequency range investigated amplifier 10, in block 2, the filter can include a multiplexer 12 to turn off the filtering unit 2 and thus to transfer the meter is in measurement mode some integral parameter K.

The duration of the observation interval T=NΔt (when synchronizing the beginning of the observation interval with the clock pulses can assume that T=(N-1)Δt), for which at each stage of the adders 5 and 6 accumulate counts, of course, affect the accuracy of measurements and, of course, the larger T is, the smaller the error of the results of statistical processing. To determine the specific values of T should be based on a priori information about the properties of random test PR the process. In particular, if known, the maximum amount of correlation τKthis process, then T can be chosen from the condition T>>τK.

Tasks assigned to functional Converter 7, are determined, in what form should be given to the measurement results. If necessary, the functional Converter 7 can lay scaling operations or taking the logarithm, it is easy to perform hardware-tabular method.

Controls the operation of the meter unit 8 (figure 2). External control signals, the output of the block 8, are produced in the following order (see also figure 1).

In the initial state block 8, that is, prior to launching a entrance WITH momentum on its outputs A1, C1, C2 and C3 are logic zeros After a start block, at the outputs S1 and S2 be sequence of clock pulses with a period of Δt required for the ADC 3 and accumulating adder 5. Moreover, for correct interaction between ADC and accumulative adders sequence S1 is always ahead of the sequence C2, C3. Through the observation time equal to the duration of the first stage, at the output of A1 is set to a logical unit - 1 multiplexer selects and starts the second phase of the measurements. At this stage in the sequence C1 changes do not occur, ADC 3 continue C erevna it, however, instead of the clock sequence C2 begins to form a sequence of C3 required for accumulating adder 6. With the end of the second stage of measurement, equal to the duration of the first unit 8 automatically returns to its original state, and the next cycle will begin only after receiving input FROM the appropriate command.

The above signals are produced as follows. Upon receipt of the input WITH (2) pulse trigger 13 enters a state high logic level, causing the first after this transition clock pulse enters the state of logic high level and the D-flip-flop 14, thus allowing the passage of clock pulses to the counting input of the counter 16. The latter counts the interval equal to the duration of each stage of the measurement. Simultaneously, clock pulses freely pass to the output of C1 and through the delay element 21 on the output element 20, that is, the output C2. The end of the first stage is determined by the appearance of a pulse overflow at the output R of the counter 16. This pulse trigger 15 state is a high logic level at its inverting the output is a logical zero and applying pulses to the output C2 stops, but starts the supply of clock pulses to the output element And 19, then e is th output C3. In addition, the switch trigger 15 changes the status of the address output A1. Thus, the control unit 8 proceeds to the second stage, the end of which is also determined by the time counter overflow 16. When the trigger 15 is transferred in its original state and voltage jump on his direct output of the one-shot 22 (only runs from the negative fronts) clears the triggers 13 and 14: unit 8 enters the state it was in before launch; the measurement cycle is completed.

This stochastic meter designed for the measurement of gain K(ω) not at a specific frequency ωand in some the band Δωwhat distinguishes it from traditional schemes of measurements. The proposed approach is based on the fact that functioning in real conditions, the amplifier amplifies random signals with a continuous spectrum, not managementcase measuring signal. This, given the nonlinearity of the real amplitude characteristics, leads to characteristic distortions that affect the level of the output signal of the amplifier. The distortions of this kind include the effect of suppression of the weak, strong, reflected in the non-linear amplification of signals with different frequencies and intermodulation distortion caused by the formation of combinational components. Therefore, to model p the press operation of the amplifier, near real-time using a sinusoidal test signal of the same frequencyΔω=0), it is impossible, and therefore it is advisable to use a random signal with the assigned spectral parameters and providing the analysis in a given frequency band.

Stochastic meter gain that contains a multiplexer, characterized in that it introduced the block filtering, analog-to-digital Converter, Quad splitter, two accumulating adder functional unit, a control unit and a white-noise generator, the output of which is connected to the first information input of the multiplexer, which (input) is the first information input of the meter, the second information input of which is the second information input of the multiplexer, the output of which through the filtration unit connected to the information input of the analog-to-digital Converter, the output of which is connected to the information input of the Quad, the output of which is connected to the integrated information inputs of the first and second accumulative adders whose outputs are connected to respective inputs of a functional of the inverter whose output is the output of the meter, the address input of the multiplexer and clock inputs of analog-to-digital Converter and two accumulative adders is attached to the s to the corresponding outputs of the control unit.



 

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