SU1597766A1 - Digital compensation phase meter - Google Patents

Abstract

The invention relates to a phase-measuring technique and can be used in ultrasonic and sonic ranging, where it is necessary to measure the phase shift of two radio pulses that are spaced apart in time relative to each other. The solution of the problem is to improve the accuracy of measuring the cumulative phase shift of radio pulse signals — by introducing two subtractors 3 and 4, two multiplexers 12 and 13, a comparison node 15 and a setting number 14 in a compensation phase meter, which contains two channels 1 and 2, two LPF 10 and 11, null indicator 6, synthesizer 7, calculator 8, digital indicator 9, analog switch 5. First channel 1 and LPF 11 are turned on at the first input of the zero indicator 6. Second channel 2, switch 5 and the second LPF 10 are turned on at the second input null indicator. The channels are controlled by the output signals of the frequency synthesizer 7, and the switch 5 is controlled by the output of the calculator 8. 2 Il.

Description

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The invention relates to a measurement technique and can be applied in underwater acoustics, flaw detection, ranging and other areas of science and technology. where it is necessary to measure the phase shift of two radio pulse signals (radio pulses) that are spaced apart or shifted in time relative to each other.

The purpose of the invention is to improve accuracy.

Figure 1 shows a block diagram of a digital compensation phase meter; figure 2 - transfer characteristic of the phase meter.

The digital compensating phase meter contains two identical channels 1 and 2, subtractors 3 and 4, switch 5, null indicator 6, synthesizer 7, calculator 8, and a wireless indicator 9,

10 and 11 low-pass filters (LPF), multiplexers 12 and 13, unit setter 14 codes and comparison node 15. Each channel 1 (2) has signal input 1.1 (2.1), the first 1.2 (2.2) and the second 1.3 (2.3) control inputs and output 1.4 (2.4). The synthesizer 7 frequency has three inputs 7.1-7.3 and four outputs 7.4-7.7. The calculator 8 has inputs 8.1-8.3 and outputs 8.4 and 8.5. Phase meter nodes are connected in the following way. Input 1.1 of channel 1 is connected to the input, input 2.1 - from input 7.3 and 8.2, inputs 1.3 and 2.3 - to output 7.5 of synthesizer 7, output 7.4 - to input 1.2, output 7.6 - to input 2.2, output 7.7 - to input 8.3 of the calculator 8 , output 8.5 - with the combined first inputs of the subtractor 3 and the comparison node 15, output 8.4 - with the first input of the subtractor 4, output of the subtractor 4 - with the input of the digital indicator 9, output of the subtractor

about

With control input of switch 5, switch 5 output — with LPF 10 input, output 1.4 — with LPF input 11, inputs of null indicator 6 — with outputs of LPF 10 and 11, outputs of null indicator 6 — with inputs 7.1 and 7.2, outputs 2.4 - with the inputs of the switch 5, the first output of the sensor 14 - with the first input of the multiplexer 12, the second output of the setting device 14 - with the first input of the multiplexer 13, the third output of the setting device 14 - with

45

50

Channels 1 and 2 are practically a frequency-controlled multi-tap delay line (LZ) in the form of a ruler of series-connected devices with charge coupling (CCD). The outputs of the multiple-tap LZ and its inputs are the outputs and inputs of channel 2, the control inputs 1.2 and 2.2 are for adjusting the delay, and the inputs 1.3 and 2.3 are for converting the frequency of the radio pulse filling signal supplied to the inputs 1.1 and 2.1 channels. The number N of taps (outputs) of channel 2 specifies the maximum possible measured phase shift - (/ in accordance with c / d.). The number N can be interpreted as the number of whole periods that can be written to the CCD delay line of the phase meter. The synthesizer 7, made on the basis of the multiplier and frequency dividers, forms, at outputs 7.4, 7.6 and 7.5, pulse signals of frequencies., F, f KjF, o-f ", respectively (here F is the frequency of filling of the radio pulse at the input 7.3). 3 and 4, multiplexers 12 13, master 14 and node 15 are simple. Below are arithmetic and logical functions: subtracting two numbers (subtractors 3 and 4), comparing two numbers (node 15), switching one of two numbers to one output (multiplexers 12 and 13). Setpoint 14 sets the codes for numbers 1.21Г - and N, respectively, at the first, second and third outputs (here N is the number of taps of channel 2).

Phase meter works as follows.

The main distinctive feature of the phase meter is that the full compensation of the phase shift of the input signals of the phase meter is performed at the frequency f of the clock signal of channel 1 greater than the frequency f of the clock signal of channel 2. Since the slope of the transfer input of the reference node 15 is back

master output setpoint - with the second inputs of multiplexers 12 and 13 and node 15, the outputs of multiplexers

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five

0

five

0

45

50

12 and 13 with the second inputs of the subtractors 3 and 4, respectively, the output of the comparison node 15 with the control inputs of the multiplexers 3.4.

Channels 1 and 2 practically represent a frequency-controlled multi-tap delay line (LZ) in the form of a ruler of series-connected devices with charge coupling (CCD). The outputs of the multiple-tap LZ and its inputs are the outputs and inputs of channel 2, the control inputs 1.2 and 2.2 are for adjusting the delay, and the inputs 1.3 and 2.3 are for converting the frequency of the radio pulse filling signal supplied to the inputs 1.1 and 2.1 channels. The number N of taps (outputs) of channel 2 sets the maximum possible measured phase shift - (/ in accordance with c / d.). The number N can be interpreted as the number of integer periods that can be recorded on the CCD delay line of the type forming the phase meter channel. The synthesizer 7, made on the basis of the multiplier and frequency dividers, generates pulse outputs at the outputs 7.4, 7.6 and 7.5., F, f KjF, o-f ", respectively (here F is the frequency of filling the radio pulse at input 7.3). Introduced subtractors 3 and 4, multiplexers 12 and 13, master 14 and node 15 perform the query It includes arithmetic and logical functions: subtracting two numbers (subtractors 3 and 4), comparing two numbers (node 15), switching one of two numbers to one output (multiplexers 12 and 13). Setpoint 14 sets the codes for numbers 1.21Г and N correspondingly, on the first, second and third outputs (here N is the number of taps of channel 2).

Phase meter works as follows.

The main distinctive feature of the phase meter is that the full compensation of the phase shift of the input signals of the phase meter is performed at the frequency f of the clock signal of channel 1 greater than the frequency f of the clock signal of channel 2. Since the slope of the gear is proportional to the frequency of the clock signal, then the phase meter rises by reducing the error due to the instability of the frequencies f and f.

A phase meter measures the cumulative phase shift of two radio pulses, i.e. phase shift y, 2yyyy (q-1) + s /, where F is the frequency of the oscillations filling the radio pulses; t

and

H time points that coincide with the beginning of the bend, respectively, and the second radio pulses; tp {/ i is the difference of the initial phases of the second and first radio pulses, respectively. The measurement process contains two cycles. In the first cycle, coarse compensation of the phase shift is performed, and in the second cycle (after the moment of tu) thin compensation i. The first (leading) and second radio pulses arrive at the inputs of the first and second channels, respectively, if. Under the action of the second radio pulse in the synthesizer 7, at the outputs 7.4, 7.6 and 7.5, the sequences of pulses of the frequencies f, K /,, jF and, / K, where the integers are, respectively,

K., KH

to „numbers K, 2 and tymi.

K d are

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and

TO

TO,

Kjb

for example, during the first bar for the second bar.

In the first cycle, under the action of pulses (jj-F, the first radio pulse propagating in channel 1 will be located in its first Tij its bits by the time t. Channel n corresponds, for example, to channel 2 rejection, since the channels by the number of bits identical. The number N is determined in subtractor 8 by quantizing the interval (,) pulses with the frequency of the first radio pulse. Moreover, the calculator 8 determines the difference. The number Nj from the output 8.5 of the calculator goes to the comparison node and through the emitter 3 to the control input of the switch 5. Using node 15 the number N is compared with the number N (the number N goes to the second input of the comparison node from the setting device 14.) The input logic signal of the comparison node is O if, or 1 if N is N. With the help of multiplexer 12, the output signal of the node 15 Comparison commutes to its output one of the numbers (00 or 01), constantly present at the first and fourth outputs

setter 14. We denote the output number of multiplexer 12 by C. Then, using subtractor 3, the difference, -C, is formed. Under the action of the number N, the switch is set to a position in which the output of channel 2 is connected to the input of the low-pass filter 10. Next, in the first clock cycle, starting from the moment tJ, the second radio pulse under the action of frequency pulses f from the output 7.6 of the synthesizer is recorded and advances in channel 2 from the input to its release 2.4. Thus, in the channels of the phase meter, the original radio pulses under the action of clock pulses of frequencies f and

f zader

live for times, respectively, /, and, where the number of bits in channel 1; n, P (, Ы - the number of bits in channel 2 from the input to the Nj-ro output. The phase difference of the delayed radio pulses is equal to

(2frF (,) + 2 (to -ttfJ + (((, +

(one)

21G (- - | i). K, K

 2 to

If we accept that to simplify further formulas, then, substitute for K (N, -N-C) and taking into account that, -Nj, we get

n, K, -N,

five

0

five

0

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V Vo + 2t f (- | l- - | i-) - N-C .. (2) 1 i In the first measure, the difference in parentheses is zero, since K. Therefore, when - Lf-2 1. Thus, the coarse phase shift / g compensation is performed in the first cycle. In this case, 0, which indicates the presence of overcompensation, because as a result of a larger pulse delay, the first pulse began to outpace it.

In the second cycle, compensation is made for the remaining part (f-2 by changing the frequency f ,. Since V is O, the zero indicator 6 at one of the outputs produces a pulse signal, under the action of which the frequency f increases at output 7.4 and the number K increases. output 7.7 of the synthesizer 7. The phase difference of the delayed radio pulses begins to decrease as the delay of the first pulse decreases. As soon as it becomes zero,

corresponds to full compensation, the regular arrival of the error pulses from the indicated output is stopped. In this case, the frequency f is fixed, and K on the output 7.7 of the situs 7 takes on the value, for example, K (i.e., Kp, K,).

Substituting in (2) Cd, K,, we obtain the calculated expression

 - it - -2 "

Vt-2 "c.

(3)

The transmitter 8 operates in accordance with (3), defined by {. From (3) it follows that the value of the phase shift

ABOUT

The output shift 8.4 of the calculator differs from the true one by 2 / HS. Correction (2Fc is performed using preset 14, multiplexer 13 and subtractor 4 as follows. The number 2 from the second output of the setter goes to multiplexer 13. Using the comparison node 15, a multiplexer 4 control signal is generated. Under the influence of the output signal of the comparison node 15, the multiplexer connects to the second input of the subtractor 4, or the number 21Г (if,), or O (if). The first case corresponds to the case under consideration. With the subtractor 4, the difference c is formed, equal to the measured phase shift, which is indicated by the indicator 9. On In this case, the operation of the phase meter in the first mode ends.All the change in the phase shift of the input radio pulses of the phase meter leads to a change in K and N in the manner described, and consequently, to a change in the display of digital indicator 9.

In the second mode, the phase shift compensation process is similar, but at a lower intermediate frequency. The conversion of the frequency of filling the original radio pulses is performed by the stroboscopic method under the action of short pulses of frequency F, coming from the output 7.5 of synthesizer 7.

The curves in FIG. 2 are explained by the described compensation process for specific ratios of the numbers included in (2), namely: when the cumulative phases of the radio pulses are vji, 24 °, t 76S ° (which corresponds to .t, 0,

0

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0

five

0

five

0

five

0

five

. (f, 24, “p,) 15; number of bits in channels n 45; the number of taps in channel 2. The phases of the delayed radio pulses at the end of the first cycle of the phase meter operation are displayed in FIG. 2 by point A for the first and point B for the second radio pulse, etc. Performed during the second cycle, small compensation of the phase shift of the delayed radio pulses is displayed in Fig. 2 by arrows from point A to point C along the line corresponding to the channel transfer characteristic, taking into account the dependence ((. Ordinate of the point is equal to the phase of the delayed second radio pulse, and the abscissa is equal to To

The additionally introduced subtractors, multiplexers, a comparison node, and a code setter make it possible for the phase meter to improve accuracy by increasing the values of the cumulative phase shift if N.

Claims (1)

To do this, in the setter of codes, instead of code numbers 2 and 1, the values are set to an integer number of times, but no more than (N71) times. In this case, the number N is determined from the result of the measurement of the phase shift, then the codes at the 2TG and 1 o outputs are increased (the additional measurement of the phase shift is made. In this case, in the formula (3), instead of the coefficient C, we must take the coefficient that corresponds to the accuracy of the corresponding number of times. Digital compensation phase meter containing the first and second channels, a switch, two low-pass filters and a serially connected zero indicator, synthesizer and calculator, as well as a digital indicator, the analog inputs of the switch are connected to the outputs of the second channel, the first low-pass filter is connected between the switch output and the first input of the null indicator, the second low-pass filter is connected between the output of the first channel and the second input of the null indicator, the first and second outputs of the synthesizer are connected to the first clock the inputs of the first and second channels respectively, the third output of the synthesizer is connected to the second inputs of the first and second channels, the signal inputs of which are connected respectively to the first and second signal inputs of the compute and are the phase meter inputs, which are the input of the two-input first and the second subtractors, the first and second multiplexers and the comparison node, with the first drive connected to the first output of the calculator and the output to the digital indicator input, the second subtractor connecting to the second output of the calculator, and output to code inputs to commutator, the second the inputs of the first and second subtractors are connected to the outputs of the first and second multiplexers, respectively; the first input of the comparison node is connected to the second output of the calculator, the first and second outputs of the code setter are connected to the first inputs of the first and second multiplexers, respectively; and the third output of the code generator is connected to the second input of the comparison node , the fourth output of the setting unit of the codes is connected to the combined second inputs of the multiplexers, and the output of the comparison node is connected to the combined controls. multiplexer inputs. J 5 7 11 13 15 17 19 21 23 25 27 29 Kik ig.2