SU1620992A1 - Device for measuring transition characteristics of precision frequency systems - Google Patents

Abstract

The invention relates to radio measurements. The purpose of the invention is to improve accuracy. The meter contains two frequency dividers, a trigger, an AND element, a switch, an adder, a synchronizer, a recorder, a mixer, a controlled oscillator, a comparator, a reference oscillator, a correction driver, a frequency multiplier, a code comparison unit, two reversible counters, a control block, an input and bus output. Increased accuracy is achieved by providing higher resolution. 3 il.

Description

The invention relates to radio measurements and can be used to study and control the dynamic properties of controlled auto-oscillatory systems, which include quartz and string sensors, as well as controlled quartz oscillators and other frequency controlled devices.

The purpose of the invention is to improve the accuracy of the meter by applying a standard comparator with all of its possible multiplication factors.

This is ensured by the fact that a change in the input frequency, which causes the frequency under study to go beyond the comparator bandwidth, is compensated by rebuilding the controlled oscillator while simultaneously correcting the resulting estimates on the recorder.

FIG. 1 shows a functional diagram of the meter transient characteristics of frequency precision devices; in fig. 2 - time diagrams of his work;

in fig. 3 is a functional diagram of the formation of correction pulses.

The measuring instrument of transient characteristics of frequency precision devices contains a mixer 1, a controlled oscillator 2, a control unit 3, a comparator 4, a reference oscillator 5, a correction pulse generator 6, a first reversible counter 7, a synchronizer 8, a frequency multiplier 9, a decoder 10, a recorder 11, the first 12 and second 13 frequency dividers, switch 14, adder 15, trigger 16, element 2 and 17, second reversing counter 18 and input bus 19.

Shaper 6 correction impulses (Fig. 3) contains elements 211 20 and 21, trigger 22, resistor 23, elements LI 24 and 25, binary reversible counters 26, crossover fields 27, blocks 28 of code comparison 28 and element 29.

The meter works as follows.

OK

with her

СЈ К

Before starting work and measurements, the division ratio of the first divider 12 frequency (nx) is set to

nx txo-ff {, (1)

where tf0 is the initial value of the averaging period;

f is the center frequency of the passband of the comparator 4. The multiplication factors of the comparator 4 (K) and the multiplier 9 frequencies (t) are chosen taking into account the ratio

(p-m-1) -I. where D / p is the required resolving value

the ability of the meter in frequency;

f0 is the generation frequency of the reference generator.

The division ratio of the second division of the gel 13 frequency (n0) is set equal to the value found from the condition

t-CPP / L-n0 / (t} 0)} - io LG „/ U„ „, (2) where N0 is the nominal number of switched pulses;

D / c is the maximum allowable frequency deviation at the output of the comparator 4. The control slope of the controlled oscillator 2 (P) and the quantization step for the voltage of the control block 3 (D / y) are chosen respectively equal to: .q / kbUy l / (q-N0 ),

where q is the proportionality coefficient. The output voltage of the control unit 3 controls the frequency of the controlled oscillator 2 so that the output frequency of the mixer 1 coincides with the center frequency of the passband of the comparator 4. The codes of the lower and upper limits of the tolerance field are, for example, equal to 0.1 -N0 and 0.9 -No and enter them into the decoder 10. At the output of the first reversible counter 7, set "od, found by the formula

N pC Non-N0,

where L 0 „, D / m - the maximum change in the frequency under study in the transition section. During the measurements, the pulses of the frequency under study are fed to the mixer 1, where they are mixed with the frequency of the controlled oscillator 2. From the output of the mixer, the monitored signal goes to the comparator 4, which multiplies the frequency fluctuations of this signal by k times. After that, at the output of the first frequency divider 12, a sequence of averaging pulses (Fig. 2b) is formed, following with a period

(f ± K.Uf) i,

(3)

where D / (0 / is the average value of the studied frequency in the / -th interval of averaging.

Averaging impulses arriving at the synchronization inputs of the first 12 and second 13

0

five

0

frequency dividers synchronize their operation. The pulses of the reference generator 5 through the frequency multiplier 9 arrive at the counting input of the second frequency divider 13 {FIG. 2c), at the output of which a sequence of reference pulses is formed (Fig. 2a) delayed relative to the sequence of averaging pulses by the reference interval (mf0). The reference pulses set the trigger 16 to one state, and the averaging pulses - to zero. As a result, at its output a measuring interval (Fig. 2e) with a duration of -10 is formed, which switches the output pulses of the frequency multiplier 9 (Fig. 2k) to the output of the element 2I17. The number of switched pulses is described by the relation Nj (tXj-t0) -rn-fo, which taking into account (1) - (3) takes the form

N, N0 ± Nfh

where N ,, tm t K f0 fn ± K- ДWO; - the function of converting frequency deviation into a code.

For a more detailed explanation of the functioning of the other nodes of the meter, we will distinguish two modes of its operation: I mode - N; is in the specified tolerance field; Mode II - N, is outside the floor tolerance.

In I mode, the reference pulses are recorded in the second reversible counter 18 you0

five

0

the input code of the first reversible counter 7, after which the switched pulses in the second reversible counter 18 are summed with this code. The output code of the second reversible counter 18 ± yVf / goes to the adder 15 to convert to voltage

,,

where UH is the nominal voltage value;

ДЈ / - quantization step over voltage.

The resulting voltage is then fed to the recorder 11 for visualization. The synchronizer 8 synchronizes the start of operation of the meter with the time it takes to apply the test effect to the object under study.

Thus, in the I mode, the frequency deviation of the studied oscillations is transformed into a deviation of the quantized voltage samples relative to the nominal voltage value.

In mode II, the reference pulses the switch 0 to the zero state, and a code is written to the second reversible counter 18. Thereafter, the switched pulses in the second reversible counter 18 are summed with the code, and in the switch 14 are converted into a code that goes to the decoder 10.

If Nji, 9N0, then at the first output of the decoder 10 a single voltage level appears, arriving at the first

five

control input of the driver 6 correction pulses. With the arrival of the next averaging pulse at its synchronization input, the binary code from the output of the decoder 10 is recorded in the correction pulse shaper 6, and then the correction pulses (Fig. 2t) generated from the output pulses of the frequency multiplier 9 appear at its first control output. The number of correction pulses is described by the ratio Nkj Nj-N0 Nn. Correction pulses are fed to the summing input of the first reversible counter 7, changing the initial voltage code for subsequent averaging intervals, which can be described as z

N0 NOK-N0 + 2Nth

w

refers to the W th cycle

where is the index of reaction;

Nfj is the NH code in the last averaging interval of the z-ro cycle of the positive correction;

z W, because in this case the correction pulses always go to the summing input of the first reversing counter 7. At the same time, the correction pulses go to the summing input of control unit 3, the output voltage of which changes the frequency of the controlled generator 2 so that the output frequency of the mixer 1 is this interval of averaging coincides with the center frequency of the passband of the comparator 4. At the beginning of the formation of the next packet of correction pulses at the transfer output of the former, 6 pulses of rektsii is by transfer pulse (Fig. 2 /) by which the output of the adder 15 for a predetermined time interval generated maximum voltage level mles (Fig. 2n). The presence on the screen of the recorder 11 U {AUMC signals about the progress of the restructuring process of the controlled oscillator 2 and about the possibility of introducing errors in the process of conversion. In the next averaging interval, the switched pulses are summed in the second reversing counter 18 with the output code of the first reversing counter 7, and the output voltage of the meter is described by the relation

(Ut /), (. Ј /,

where (Ј / f. «/) w + i, (jV / fV-n is the output voltage of the meter and the code value L // on the / -th interval of averaging (w + 1) - th correction cycle.

Similarly, the meter works when, NO. However, in this case, a single voltage level appears at the second output of the decoder 10, and the correction pulses from the second control output form

0

0

five

0

five

0

0

five

where L is the globalizer of the correction pulses fed to the subtractive inputs of the control unit 3 and the first reversible counter 7. The output voltage of the meter is generally described by the function

(), + jlN + - -Tl / t ±

± (,

NJJ code on the last averaging interval of the x-th cycle of the negative correction;

W z + x.

Thus, in the meter under consideration, the deviation of the frequency under study from the initial value is converted into a sequence of quantized voltage samples following the specified averaging interval. The output of the studied frequency beyond the passband of the comparator 4 is compensated by changing the frequency of the controlled oscillator 2 with simultaneous correction of the output voltage of the meter, which makes it possible to use a standard comparator, for example, type 47-12 with all its multiplication factors and, as a result, increase the measurement accuracy .

The shaper 6 correction pulses (Fig. 3) works as follows.

On the cross-over fields x 27 dial the code / V0.

Averaging pulses are fed to the synchronization input of the imaging unit of 6 correction pulses. If there is a single level at the first or second control input, the averaging pulses pass to the transfer output through one of the open elements 2I 20 and 21, set the trigger 22 to a single state, and also write the code from the information input of the imager to binary reversible counters 26 6 correction pulses.

If, 9 / V0, then at the first control input there is a single level and pulses from the counting input through the open element ZI 24 are sent to the first control output and the subtracting input of the first one from the chain of serially connected binary reversing counters 26. The output code of the counters 26 starts after - 5 to decrease by one. When it reaches the value of / V0, at the outputs of all of the code comparison blocks 28, the unit levels appear, which opens the element 29 and the trigger 22 returns to the zero state. The switching of the pulses to the first control output of the imaging unit 6 of the correction pulses is stopped, and the number of correction pulses is N, N ,, i.

At Nj.0, h 0, the operation of the driver 6 of the correction pulses is similar, a single level from the second control input opens the element ZI 25 and the pulses arrive at the summing input of the first of a chain of serially connected binary reversing counters 26 and the second control output, the number of correction pulses which is defined by the ratio.

Thus, the proposed meter allows obtaining the minimum possible frequency resolution, which, in turn, makes it possible to determine the transient frequency setting function with high accuracy and can be used in the design and testing of controlled frequency devices and systems.

Claims (1)

Invention Formula Measuring instrument of transient characteristics of frequency precision devices, containing the first and second frequency dividers, trigger, element I, switch, adder, serially connected synchronizer and recorder, the outputs of the first and second frequency dividers are connected to the / input and 5-input trigger, respectively, the output of the adder is connected To the information input of the recorder, characterized in that, in order to improve the accuracy of the meter, a mixer, a controlled generator, a comparator, a reference generator, a pulse driver are introduced. correction, a frequency multiplier, a decoder, two reversible counters, a control unit whose output through a controlled generator is connected to the heterodyne input of the mixer, the outputs of the mixer and the reference generator are connected to the information and control inputs the comparator, respectively, the output of the reference generator is connected to the input of the frequency multiplier, the output of which is connected to the counting input of the second frequency divider by the first input of the And element, the counting input a correction pulse generator, the first and second control outputs of which are connected to the summing and subtracting inputs of the control unit and the first reversible counter, the output of the comparator is connected to the counting input of the first frequency divider, the synchronization input of which is connected to the synchronization input of the second frequency divider, to the –– trigger input and the synchronization input of the correction pulse generator, the output of the second frequency divider is connected to the synchronization input of the switch and the recording input of the second reversible counter, the account Its input is connected to the output of the element I and to the counting input of the switch, the output of which is connected to the input of the decoder and to the information input of the pulse builder, the transfer output. The latter is connected to the synchronization input of the adder, the information input of which is connected to the output of the second reversible counter, the output the first reversible counter is connected to the information input of the second reversible counter, the first and second outputs of the decoder are connected to the first and second control inputs of the formate For each of the correction pulses, respectively, the trigger output is connected to the second input of the And element, the information input of the mixer is connected to the input bus. NW OO H QjiC tf) f: s -at