SU1718144A1 - Q-meter of oscillatory systems - Google Patents

Abstract

The invention relates to radio measurements and can be used to measure the Q-factor of a cavity resonator in a microwave and oscillatory systems in the radio frequency range. The aim of the invention is to improve the accuracy of measuring the quality factor of oscillatory systems. The Q-factor of the oscillatory systems contains a tunable high-frequency oscillator 1, an oscillatory system 3, a first amplitude detector 4, a tunable low-frequency oscillator 10, a frequency ratio unit 13, a control unit 15. An introduction to the meter of the amplitude modulator 2, filter 5, low-frequency detector 6, electronic switch 7, analog-digital converter 8. digital-analog converter 9, frequency divider 11, second amplitude detector 12. Display unit 14 allows to increase accuracy by eliminating operation taking the second derivative of the measurement process, as well as eliminating errors due to non-uniformity in the range of the amplitude-frequency characteristic of the amplitude detector 4 and not avnomernostyu output level in the range of a tunable high-frequency generator 1 frequency. 5 il. t C

Description

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The invention relates to the field of radiation measurements and can be used to measure the Q-factor of the cavity resonators in the microwave range, as well as oscillatory systems in the radio frequency range.

A device for measuring the oscillation contours is equipped with a measuring circuit, an input and output matching elements, broadband amplifiers, an automatic amplitude control unit, an excitation moment recording unit, and keys.

The drawback of the device is a large measurement error due to the significant error in determining the bandwidth.

The closest technical solution to the invention is a device for measuring the quality factor of oscillatory circuits, containing tunable high and low frequency generators, the outputs of which are connected to the frequency ratio unit and the outputs of the frequency modulator, and the control inputs through memory devices and zero-organs are connected to the outputs of the first and second derivative allocation units, the output of the first derivative selection unit also being connected to. the input of the allocation unit of the second derivative, and the input of the selection unit of the first derivative through the amplitude detector and the measured circuit - with the output of the frequency modulator.

A disadvantage of the known device is the low accuracy of measuring the Q-factor due to the significant error in determining the bandwidth, especially for high-quality oscillatory systems (volume and coaxial resonators in the microwave range, quartz resonators in the radio frequency range).

In determining the resonant frequency and bandwidth, the allocation units of the first and second derivatives, respectively, are used, connected in series. Each of these blocks introduces a corresponding error. In determining the second derivative, the error in measuring the bandwidth increases substantially, since in this case the derivative is taken from the function defined with the error.

In addition, the measurement error of the resonant frequency is also significant due to the inherent non-uniformity of the output level of the tunable high-frequency generator signal and the unevenness of the amplitude-frequency

characteristics (AFC) amplitude detector.

The purpose of the invention is to improve the accuracy of measuring the quality factor.

The goal is achieved by the fact that

A second amplitude detector, an indication unit, and an analog-to-digital converter (ADC) are introduced into a device for measuring the quality factor of oscillatory circuits.

0 frequency divider, filter, low-frequency detector, electronic switch, digital-analog converter (DAC) and amplitude modulator, the first input of which is connected to the output of a tunable high-frequency generator and the input of the second amplitude detector, the output of which is connected to the second input of the electronic switch, the output of which is connected to the input of the ADC, the input-output of which is connected

0 with the corresponding inputs of a tunable high-frequency generator, a frequency ratio unit, a display unit, an electronic switch and the corresponding inputs-outputs of the control unit and a digital analog converter, the output of which is connected to the input of a tunable low-frequency generator, the output of which is connected to the input of the frequency divi whose output is connected

0 the second input of the amplitude modulator, the output of which is connected to the input of the oscillatory system, the output of the first amplitude detector through the filter is connected to the input, the low-frequency detector, the output

5 of which is connected to the first input of the electronic switch,:

A comparison of the known device with the invention shows that the claimed device exhibits new

0 technical properties expressed in increasing the accuracy of measuring the resonant frequency and bandwidth by eliminating the second derivative operation from the measurement process, correcting the unevenness of the output signal level of the tunable high frequency generator and eliminating the effect on the measurement accuracy of the amplitude detector unevenness.

0 FIG. 1 shows the structural diagram of the meter of the quality of oscillatory systems; in fig. 2 is a block diagram of a meter calibration program; in fig. 3 is a block diagram of the measurement program; in fig.

5 4 - amplitude frequency characteristic of the oscillatory system and the spectrum of the amplitude-modulated signal; in fig. 5 - timing diagrams: a, b - control voltages at the inputs of tunable high and low frequency generators; depending on the coefficient yi calculated by the algorithm; r-control voltage at the input of the electronic switch 7; e is the trigger voltage of the ADC, e is the trigger voltage of the frequency ratio block.

The meter contains connected in series tunable high-frequency generator 1, amplitude modulator 2, investigated oscillatory system 3, first amplitude detector 4, filter 5, low-frequency detector b electronic switch 7 and analog-to-digital converter (ADC) 8, connected in series to digital-to-analog converter 9, tunable low frequency generator 10 and frequency divider 11, output connected to the second (control) input of the amplitude modulator 2, second amplitude detector 12, and the input of connected to the output of the tunable high-frequency oscillator 1, and the output connected to the second input of the electronic switch 7, frequency ratio block 13, the first input connected to the output of the generator 1, and the second input connected to the generator output 10, display block 14, the control block 15 which is executed by microcomputer 16 with interface 17) connected to control and information inputs of generator 1, electronic switch 7, ADC 8, DAC 9, frequency ratio unit 13 and display unit 14.

The meter works as follows.

The measurement mode is preceded by the calibration mode, when the oscillatory system 3 under investigation is excluded, and the output of the modulator 2 is connected to the input of the amplitude detector 4.

The microcomputer 16 through the interface 17 uses its signals to set the generator 1 to the lower frequency fH of the working range of the meter, the switch 7 sets the control voltage at the output of the DAC 9 to the input of the ADC 8 signal from the output of the detector 6 generator 10, corresponding to the frequency of the signal RMin, and also starts the ADC 9.

The generator 1 generates a microwave signal with a frequency fri, which is fed to the amplitude modulator 2 and the second detector 12. Under the action of the signal from the DAC 9, the generator 10 is set to the frequency Pmin. Divided by frequency into two, the signal from the output of the divider 11 is fed to the second control input of the modulator 2. The modulator 2 performs amplitude modulation of the RF signal, which

the oscillatory system 3 is detected by the detector 4. As a result, a signal appears at its output

LM КДЕ2 (1 + М cos 2n Fat) 2, 5 where Кз is the conversion coefficient of the detector 4;

M - coefficient of amplitude modulation of the RF signal at the modulation frequency F2.1

E is the amplitude of the signal at the output of generator 0 of the 1;

Fa Pmin / 2 is the frequency of the modulating signal.

Detector 12 detects the signal coming from generator 1, and as a result, voltage appears at its 5 output.

Ui2 Ki2E2,

where Ki2 is a conversion factor of 12. Signal U4 is fed to filter 5, which selects its first harmonic, 0U5 K4KsME2cos27rF2t, (1)

where Cs is the modulus of transmission coefficient. filter 5.

From the output of filter 5, the signal Us is given

to detector b, where it is detected. As a result, a signal Ue appears at its output,

which through switch 7 enters on

ADC 8 input

si K4K5Kbme2,

where KB is the conversion coefficient of the de 0 detector 6.

A / D converter 8 converts the signal Ue to the digital equivalent of We. Microcomputer 16 through the interface 17 reads and stores the value of the code Ne.

5 In accordance with the block program,

shown in FIG. 2. The micro-computer 16 sets the switch 17 to the state when the input UI 8 from the output of the detector 12 is given a signal Uia, which is converted to 0 A / D converter 8 to the digital equivalent of N12. The microcomputer 16 reads code N12, calculates and stores the value of the coefficient acn

n -N12 .- K12

Kn Ne Ne MCBM

5 At this, the calibration at frequency f is completed and the signal from the microcomputer 16 generates generator 1 to the next frequency. The procedure for determining a? I at this and other frequencies remains the same.

0 After determining the OKB, at the upper frequency of the operating range, the calibration is completed and the text Calibration is complete appears on the screen of the display unit 14.

In the measurement mode, instead of a regular waveguide, the oscillating system 4 is switched on in the RF meter path. The operator starts the meter by pressing a button. In accordance with the measurement measurement program (Fig. 3), the microcomputer 16, via interface 17, sets generator 1 to the lower frequency fH. the switch 7, in the state when the signal from the detector b comes to the input of the ADC 8, sets at the output of the DAC 9 the control voltage of the generator 10 corresponding to the frequency Pmin resets the frequency ratio and the display unit 14 to the zero state of the registers 13, as well as launches the ADC 8.

The procedure for obtaining signals, Us, Ue, U12 and calculating the coefficients Oin at the lower and other frequencies of the operating range of generator 1 in the measurement mode is similar to that described for the Ne Ne calibration mode К4К5КбМКз (t)

N sh-to "

In accordance with the measurement program block {FIG. 3) the microcomputer 16 extracts from

the memory value of the coefficient Windows, corresponding to the frequency tn, calculates the coefficient of UN according to the algorithm

UN Windows "in), (2)

where K3 (f (0 is the modulus of the transmission coefficient of the oscillating system 3 at the frequency fH, and remembers its value.

Next, the microcomputer 16 tunes generator 1 to the frequency fH + Af, which determines the signals U4, Us, U6. Ui2, yi, where A f is the generator adjustment step 1, and checks the condition

 0. (3)

The procedure for tuning the frequency of oscillator 1, calculating yi and checking the fulfillment of condition (3) is carried out by microcomputer 16 until it is completed. In this case, the generator is tuned to the resonant frequency fpea of the oscillating system 3, and the value of yi is maximum. The microcomputer 16 calculates the coefficient

G5 s UMZKS / 2 Kz max / 2 and remembers its value.

Subsequently, generator 1 remains tuned to the frequency fpea until the end of the measuring cycle, and microcomputer 16 tunes generator 10 to the frequency of Radium + AF, where AF is the generator tuning step 10. At the same time, the signal level at the output of the filter 5 decreases in direct proportion to the change in the coefficient the modulation M (Fi) at the output of the oscillatory system 3 (Fig. 4, explaining the relationship between the level of the signal at the output of the oscillatory system 3 and the frequency FI of the modulating signal).

The signals at the output of the detector 4, filter 5, detectors 6,12, as well as the coefficients a "| iy | are defined in the former

The order and described by the following expressions

U4 KZ max (1 + .M (F |) COS 2 TlFitf

Us Kz max M (F () lOiKsE2 cos In Fit: Ue K4 max M (Fi) K4K5K6E2;

Ui2 - Ki2Ez; .- Ne. Kznax K4 Ks Kb .fc h

“And -SH - K12M (F).

yi "k1 He KM (F |),

where Kz max - the value of the modulus of the transmission coefficient of the resonator at the resonant frequency fpea.

К Кз max / М - constant coefficient;

After each restructuring step, the microcomputer 16 determines yt and checks the condition

U S oo.5. (4)

When it is executed using a signal generated by the microcomputer 16, the frequency ratio unit 13 is triggered. At its first input, a signal comes from the output of the generator 1 with the frequency -fpea. on the other - from the output of the generator 10 with the frequency FO.S. The meter 13 measures the ratio of the frequencies Q fpe3 / Fo, 5, where FO.S is the frequency of the signal at the output of the generator 10 at the moment the condition (4) is fulfilled.

The microcomputer 16 reads from the information output of the block 13 the frequency ratio the value of the quality factor Q and transmits it to the block 14 of the display.

If the meter stop signal from the button pressed by the operator has not arrived at

the microcomputer 16, then it returns to the beginning of the measuring cycle, i.e. The measurement process is repeated.

Thus, as follows from the description of the operating principle of the meter, after the introduction of new elements and connections into it, it acquires a new property, expressed in increasing the accuracy of measuring the quality factor. Achieving precision improvement is achieved by eliminating the operation.

take the second derivative of the measurement process, as well as by eliminating errors due to the unevenness in the 4aeTOf range of the amplitude-frequency characteristic of the amplitude

detector 4 and unevenness in the range of the output level of a tunable high-frequency oscillator.

Claims (1)

Invention Formula A Q-meter of oscillating systems containing a frequency ratio unit, a control unit, an oscillating system, a first amplitude detector, a tunable high frequency generator and a low-purity generator, whose outputs are connected to the first and second inputs of the frequency ratio unit, respectively, the output of the oscillating system is connected to the first amplitude input detector, characterized in that, in order to improve the measurement accuracy, a second amplitude detector, an indication unit, an analog-to-digital conversion are introduced into it Tel, a frequency divider, a filter, a low frequency detector, an electronic switch, a digital to analog converter and an amplitude modulator having a first input connected to the output of a tunable high-frequency generator and the input of the second amplitude detector, whose output is connected to a second input electronic switch, the output of which is connected to the input of the analog-digital converter, the input-output of which is connected to the corresponding inputs tunable high frequency generator frequency ratio block, display unit, electronic switch and the corresponding inputs / outputs of the control unit and digital-analog converter, the output of which is connected to the input of a tunable low frequency generator, the output of which is connected to the second input of the amplitude modulator, the output of which is connected to the input vibrational system, the output of the first amplitude detector through a filter connected to the input of the low-frequency detector, the output of which is connected to. the first input of the electronic switch. / 7Regenerator I generator for no lower frequency Block meter control x - I Definition // € one one Setting the switch off Second state 7 Determination of M2, calculation and memorization of the coefficient & n l Not Indication of the end of kalidroek G Start) x - Definition // € one mm os Yes (. The end of Rig. 2 (CHAZHG). SCONETZ) Yarig 3 {jKO M / f№yx ({If j 1 G I I JUT-TLTLnj lUwW nj-lh | J-lnj ii frequency response carrying and side components of the modulated signal -i