SU1257566A1 - Device for measuring complex admittance - Google Patents

Abstract

The invention relates to instrumentation technology and can be used to automatically measure and control two-port parameters. The aim of the invention is to expand the frequency range of measurements. A device containing a control unit 1, a tunable oscillator 2, a crystal oscillator 11, a low-pass filter (LPF) 12, a frequency-voltage converter 13, an output amplifier 17, conclusions 18, capacitors, measuring 19, load 20, reference 21, RC filters 35, 22, controlled phase shifter 23, wideband 24, 25 amplifiers, source with S

Description

bias 26, amplifiers 41, 27 DC, balanced 8, 29, 30 mixers, selective 34., 33 amplifiers, synchronous detectors 37, 36, 39, 40, sources of reference voltage 38, 42, to achieve the goal triggers 31 are introduced , 32, 28, frequency divider 16, synchronous detector 15,

The invention relates to instrumentation engineering and can be used to automatically measure and control two-port parameters, in particular, to measure the complex conductivity of semiconductor structures (t fjin, diodes, varicaps, Schottky barriers, photodiodes, transistors, etc.) the bridge on the magnitude of the polarizing voltage and the frequency of the test signal.

The aim of the invention is to expand the frequency range of measurements.

The drawing shows a block diagram of the proposed device,

The device contains a control unit 1, a tunable high-frequency oscillator 2, a fourth balanced mix: 3, a second low-pass filter 4, a second self-tuned oscillator 5, a fifth mixer 6, an adjustable amplifier (attenuator) 7, the first balanced mixer 8, the third RC filter 9 third selective amplifier 10, first quartz oscillator 11, first low pass filter 12, frequency-voltage converter 13, null organ 14, fifth synchronous detector 15, frequency divider 16, output amplifier 17, 18, to which ism is connected emy.y p bipole, a measuring capacitor 19, a load capacitor 20, the reference capacitor 21, the second RC -filter 22 controlled by a phase shifter 23, a first broadband amplifier 24, the second broadband amplifier 255 bias source 26, the second amplifier

27 DC, third I) -trigger 28, second balanced mixer 29, third balanced mixer 30, first 315 second 32 D triggers,

ilul-op1 ai 14, rc-filter 9, balanced mixer 3, low-pass filter 4, mixer 6, selective amplifier 10, adjustable amplifier 7, quartz auto-build oscillator 5. An external diffracted volt-eD can be connected to the output for accurate measurement. 1 il.

50

five

0

the second selective amplifier 33, the first selective amplifier 34, the first RC filter 35, the third synchronous detector 36, the first synchronous detector 37, the first reference voltage source 38, the fourth synchronous detector 39, the second synchronous detector 40, the first DC amplifier 41, the second source 42 of the reference voltage.

The input of the tunable generator 2 is connected to the output of control unit 1, the output of generator 2 is connected to the second input of the fourth balanced mixer 3 and to the first input of the first balanced mixer 8, the output of which is connected to the input of the first low-pass filter 12, the output of which is connected to the input of the output amplifier 17 The first output of which is connected to the external frequency register and the input of the frequency-voltage converter 13, the output of which is connected to an external recorder, the output of the output amplifier 17 is connected to the first meter The second capacitor 19 is connected to the input of the second wideband amplifier 25 and to the first reference capacitor 21, the second output of which is connected to the common bus, the output of the second broadband amplifier 25 is connected to the first input of the third balanced mixer 30, the second input of which is connected to the second input The second balanced mixer 29 and the output of the second low-pass filter 4, the input of which is connected to the output of the fourth balanced mixer 3, the output of the third balanced mixer 30 is connected to the input of the first projective amplifier 34 whose output is connected to

3

the first inputs of the first synchronous detector 37 and the second synchronous detector 40, the first input of the first DC amplifier 41 is connected to the output of the second synchronous detector 40, and the second input of the first RC filter 35 is connected to the output of the first DC amplifier 41, RC output filter 35 is connected to the second input of the adjustable amplifier 7, the output of which is connected to the second input of the first balanced mixer; the input is connected to the first output of the first crystal oscillator 11; the second output of which is connected to the input of a frequency divider 16, The second output of which is connected to the input D of the third trigger 28, the third output to the second input of the controlled phase rotator 23, and the first output is connected to the second input of the fifth synchronous detector 15 and the inputs of the first 31 and second 32B triggers the output of the first D-trigger 31 is connected to the second inputs of the second Synchronous detector 40 and the fourth synchronous detector 39, the output of which is connected to an external recorder; the output of the second D-Trigger 32 is connected to the second inputs of the first synchronous detector 37 and the third synchronous detector 36, out D which is connected to an external recorder, the output of the controlled phase shifter 23 is connected to input C of the third B-trigger 28, the first input of which is connected to the input C of the first D-trigger 31, and the second output - to the input C of the second B-trigger 32, the input of the second RC -filter 22 is connected to the output of the second DC amplifier 27, and the output is connected to the first input of the controlled phase shifter 23, the first input of the amplifier 27 is connected to the output of the first synchronous detector 37, and the second input is connected to the output of the second source 42 of the reference voltage wives, first vsod 18 of The dual bipolar circuit is connected to the second output of the output amplifier 17 and the first output of bias source 26, the output of which is connected to an external recorder, the input of the first wideband amplifier 24 is connected to the second output 18 of the measured bipolar and the first terminal of the load capacitor 20, the second output which is connected to ob5664

bus, the second balance / south mixer 2 input is connected to the output of amplifier 24, and the output is connected to the input of the second selective amplifier 33, the output of which is connected to the first inputs of the third synchronous detector 36 and the fourth synchronous detector 39, the output of the second automatic quartz oscillator 5 is connected to the first input of the fourth balanced mixer 3 and the first input of the fifth mixer 6, the output of which is connected to the input of the third selective amplifier 10, the output of which is connected to the first input of the fifth synchronous detector 15, the output of which is connected to the input of the null organ 14, and the output of the latter is connected to the input of the third RC filter 9, the output of which is connected to the input of the quartz oscillator 5, the second input of the fifth mixer 6 is connected to the third output of the first quartz oscillator 11 .

The device operates as follows 3 ohm.

The high-frequency signal from the output of the quartz oscillator 11 with a frequency i, and / 21Г (for example, 5 MHz) is fed to the second input of the mixer 6, the first input of which receives the voltage from the output of the second auto-amplified quartz oscillator 5, whose frequency can be adjusted in small limits by varying the voltage on the control input i 5 MHz (0-200 Hz) From the second output of the crystal oscillator 11, a signal with a frequency W is fed to frequency input 16, where frequency division Q occurs, with a factor of 2 on the first output.

(1-2)

 - on the second exit and 2 on the third exit. Thus, we have ii, / 2V at the first output, 2bi f on the second, and 4 ui | . If, for example, choose g | 18, that 19 Hz 2y 38 Hz; 4 ui 76 Hz. The signal from the first output of the divider 16 is fed to the second input of the synchronous detector 15. The signals with frequencies a and Uj are fed to the inputs of the mixer 6, the difference frequency co, - is selected by the selective amplifier 10 and then fed to the first input of the synchronous detector 15, to the second the input of which receives the reference voltage

With a frequency ωo, the signal from the output of the detector 15 through the null organ 14 and the RC-filter 9 is fed to the regulating input of an auto-adjustable quartz oscillator 5, is a negative feedback loop of the auto-adjustable frequency of the oscillator 5. The feedback works in this way that the difference frequency at the output of the mixer 6, fed to the first input of the synchronous detector 15 through the amplifier 10, is maintained equal to the reference frequency fed to the second input of the detector 15, the signal at the output of the detector 15 through the null organ and the RC filter supporting are equal to zero. This means that the difference frequency is equal to the reference frequency uw and the frequency a of generator 5 is maintained equal to O - UCO with great accuracy.

The signal with frequency b) from the crystal oscillator 11 through the adjustable amplifier 7 is fed to the second input of the balanced mixer 8, the first input of which receives a high-frequency signal from the tunable generator 2, the frequency of which can automatically (or in manual mode) change from and to 04 (e.g. from 5 to 8 MHz) 5 which is provided by control unit 1.

After mixing in the balanced mixer 8 and passing through the filter 12 at the input of output output 17, a signal whose frequency is equal to с and can automatically change from Q to CO, j-Q to W g O - CO ,. Thus, at the output of the amplifier 17 at point A, a voltage |, -e appears. e,

40

where Ufl is the amplitude of the alternating signal, which can be controlled by changing the amplitude of the signal of frequency W, supplied to the second input of the balanced mixer 8 through the adjustable amplifier 7, and H and is the phase of this signal,

The voltage of the high-frequency signal from the output of the tunable generator 2 also goes to the second 50 input of the balanced mixer 3, to the first input of which voltage is supplied with the frequency H2 0), - UU from the generator output 5, After mixing in the balanced mixer 3 and passing 55, through the low-pass filter 4 at the second inputs of balanced mixers 29 and 30, a signal appears whose frequency is U d and can vary within the following limits:

(one)

Ots-S0z g WJ-U, - UW (YO),

Og, O4 W, -i-ba) Ug "uu

wn (W4-bu1 co, The signal from the output of the output amplifier 17 is fed to the reference capacitor 21 with a high Q, while the measuring capacitor 19 is subjected to a voltage proportional to the current flowing through the capacitor 21, so that the voltage present at the input of the broadband amplifier 25 ,, at point B is equal to

and. and,. g I5M

g utgJo A

(2)

With amplifier 25, the amplified signal with frequency W (cOf,) is fed to the first input of the third balanced mixer 30, the second input of which receives the voltage from the output of the low-pass filter 4, is mixed in the balanced mixer 30, and from its output the signal goes to the input of the selective amplifier 34, where frequency selection occurs

(Q + UCO) -CJ & Q,

Thus, at the output of the selective amplifier 34, a voltage appears with a frequency yo :) equal to

 H

A (with

tucpico)

(3)

where and.

Ss

and e

 -fft

- corresponding to m

Actually, the amplitude and phase of the signal at the input of the wideband amplifier 25, and the factors A (co) and C (i) determine the amplitude-frequency and phase-frequency characteristics of the amplification and frequency conversion paths. This voltage is applied to the first inputs of the first 37 and 40 second synchronous detectors.

From the second output of the 16 frequency divider, the signal with a frequency of 2 yo) is fed to the D input of the trigger 28, where the control signals of the triggers 31 and 32 synchronize in phase, the third output and the frequency divider 16 of the frequency with the frequency 4 jy fed to the second control input phase shifter 23, from the output of which the phase-controlled signal with a frequency of 4 is fed to the C input of the trigger 28. At the outputs of the trigger 28, we have antiphase signals with a frequency of 2 ly of control of the triggers

31 and 32. At the inputs D of the flip-flops 31,

32 a sync signal is applied at the frequency of the first output of the 16 frequency divider. At the outputs of the flip-flops 31, 32, we have two meanders with a DSO frequency, the phase shift between which is 90 and remains strictly constant when the phase-locked loop is operating. Thus, at the outputs of the flip-flops 31 and 32 there are two quadrature signals with TOTO1I UCO, the signal from the output of the flip-flop 31 goes to the second inputs of the synchronous detectors 39 and 40, and the signal from the output of the flip-flop 32, shifted by 90, goes to the second inputs of the synchronous detectors 36 and

37.

The synchronous detector 40 is tuned to the reactive component of the signal, so that a constant voltage, proportional to

UdA (.5il (h At & q | (, W)). (4)

This voltage is applied to the DC amplifier 27, where it is compared with the reference voltage supplied from the reference voltage source 42. The magnitude of the reference voltage of the source 42 does not exceed +5 m and serves to compensate for the bias voltage of the amplifier 27. The error signal is amplified in the amplifier 27 and through the RC filter 22 is fed to the control input of the phase rotator 23, the feedback circuit of the phase-locked loop .

The feedback works in such a way that the voltage at the output of the synchronous detector 37 is maintained at zero, i.e. condition is met

5in (q fltiq) (): zO go qip | 4uq (u) 0 (5)

so that the phase incursion in the amplification paths of the JC (GJ) with a change in the signal frequency is automatically compensated by a change in the phase of the controlled phase shifter at a frequency of 4 i and, respectively, the phase of the reference quadrature signals with a frequency i.

12575668

The synchronous detector 40 is tuned to the reactive component of the signal, so that a voltage proportional to

Alcol p --- co5 ((ul),

with

which with

considering (5) is equal to

eleven . -

Ufs

A (u))

meas

(6)

This constant voltage enters the first input of the amplifier 41 constant current, which is compared with the reference voltage of the source 38 of the reference voltage and through the RC filter 35 enters the second regulating input of the amplifier, changing in small limits its gain and , respectively, the magnitude of the signal with frequency W ,, supplied to the second input of the balanced mixer 8 from generator 11, and closure negative feedback of the auto-tuning of the amplitude. This connection works in this way, the voltage at the output of the synchronous detector 40 is maintained equal to the reference one from the source 38 of the reference voltage with an accuracy better than

0.1%. Uft A (uV7 copgt,

or.

with,

taking into account that С ,, and meas are constant values, we have at the output of the synchronous detector 40

 J „-Atu) const.

(7)

Thus, the nonlinearity of the amplitude-frequency characteristic of the amplification and frequency conversion units, as well as the instability of the amplitude of the quartz oscillators and the tunable oscillator, as well as the imperfection of the transfer characteristic of the low-pass filters 4 and 12 are automatically compensated by a change in the amplitude of the test signal at point A due to voltage variation with frequency and , ,, arriving at the second input of the balanced mixer 8 through an adjustable amplifier 7 from a crystal oscillator 11.

At the same time, the signal from the output of the amplifier 17 is fed to the measured two-port network, with this on the measuring capacitor 19, whose capacitance is chosen depending on the capacitance C y of the two-terminal device being measured and

the required accuracy of measurement, is the voltage proportional to the current flowing through the measured two-terminal, so that the voltage at point C is equal to

., I, ICO-t CHA 1 ir

U, U "-e -e ----- IC,

ten

(eight)

From the output of the broadband amplifier 24, the amplified frequency signal is co (jg is fed to the first input of the balanced mixer 29, to the second input of which voltage is supplied from the output of the low-frequency filter 4. The signals are mixed in the balanced mixer 29 and from its output the signal goes to the selective code amplifier 33, where a frequency selection of ω s occurs. Thus, at the output of amplifier 33, a signal appears with a frequency yO equal to

U, .AM .. (c, .lG, /). E

 about

4C | (O)

(9)

This voltage from the output of the selective amplifier 33 goes to the first inputs of the synchronous detectors 36 and 39, the second inputs of which receive the reference quadrature voltage from the outputs of the flip-flops 31 and 32.

The operation and tuning of the detectors 36 and 39 are completely similar to the operation and tuning of the detectors 37 and 40, respectively. The synchronous detector 39 (similar to detector 40) is tuned to the reactive component of the signal, since its output has a constant voltage equal to

UA ftM c / co6 (cfft + uCp (cj) VCiJcj5in (cffttuqi (cjl).

(ten)

The synchronous detector 36 (similar to detector 37) is tuned to the active component of the signal, so that a constant voltage occurs at its output, equal to

Ufl-A (b1 (& qi (o) + - cos (q) d + ucf {((

Since the channels containing the amplifier 25, the mixer 30, the amplifier 34 and the amplifier 24, the mixer 29, the amplifier 33, are identical, taking into account the fulfillment of conditions (5) and (7) when the frequency of the variable test signal is 55, 1-1 the output of the synchronous detector 36 according to (11) signal.

proportional to Q, / Q, and at the output of the synchronous detector 39 according to (10) is a signal proportional to C ,,.

From the first output into the input amplifier 17, the signal is fed to the output of the frequency-voltage converter 13, where a logarithmic frequency conversion from, -, and, to the voltage takes place, which can then be fed to one of the inputs of the two-coordinate recorder for records depend

G / CO Sims

but

or cv | th

From the output of the control unit 1 to the input of the tunable high-frequency generator 2, a constant or sawtooth voltage is applied for electronic frequency tuning of the generator. In the first case are removed

Q / s from O

and

on and depend

bridges with selected fixed

frequency within (О, - со, in the second case - G / С from (J and С from CO, dependencies with fixed polarizing voltage.

From the output of the bias source 26, a constant polarizing voltage is applied to the measured two-pole, which can also be changed by a ramp to record the corresponding Q / W dependencies on and Cj (from O. Simultaneously to output I) an external digital voltmeter can be connected for accurate measurement tension

40

45

50

55

Claims (1)

Formula invented and. A device for measuring the complex conductivity, containing the first crystal oscillator, the control unit whose output is connected to the input of a tunable high-frequency generator, the output of the first balanced mixer through the first low-pass filter is connected to the input of the output amplifier, the first output of which is connected to an external frequency recorder and connected with the input of the frequency-voltage converter, the second output of the output amplifier is connected via a measuring capacitor to the input of the second broadband amplifier and the first output of the reference capacitor, the second output of which is connected to the common bus, the output of the second 1-band amplifier via a third balanced mixer connected in series, the first selective amplifier is connected to the first the inputs of the first and second synchronous detectors, the output of the second synchronous detector is connected to the first input of the first DC amplifier, the second input of which is connected to the output of the first voltage source, the input of the first RC filter is connected to the output of the first DC amplifier, the output of the first synchronous the detector is connected to the first input of the second dc amplifier, the second input of which is connected to the second reference source, the output of the second dc amplifier through the second rc filter tp is connected to the input of the controlled phase shifter, the input of the first wideband amplifier is connected to the second output for connecting the measured two-pole and the first output of the load capacitor, the second output of which is connected to the common bus, the output of the first wideband amplifier through the first input of the second balanced 25 oscillator generator, the first output is shared with the input of the second frequency selector connected to the second input of the fifth synchronous detector and the inputs D of the first and second D-trigger 35 a powerful amplifier whose output is connected to the first inputs of the third and fourth synchronous detectors, the outputs of which are connected to external, from the third D-flip-flop, the third output to the recorders, the second input of the first to the second input of the controlled phase-synchronous detector , the second input of the second synchronous detector is connected to the second input of the fourth synchronous detector, the first output of the bias source is connected to the first output to connect the measured two-pole and the output Amplifier output, the second output Q of the bias source is connected to an external recorder, which is different in that with an expansion of the frequency range and Accuracy of measurements, in it is supplemented with the second input of the fourth balanced one, but the first, second and third mixers, the output of the first RC filter D-triggers, frequency divider are entered. The fifth is connected to the second input of the regulators, the second output is connected to the input D the rotator, the inverted output of the third D-flip-flop is connected to the input C of the first D-flip-flop, and the inverted output of the third D-flip-flop is connected to the input C of the second D-flip-flop, the code of the first D-flip-flop is connected to the second inputs of the second and fourth synchronous detectors, and / stroke of the second D-trigger with the second inputs of the first and third synchronous detectors, the output of a tunable high-frequency generator is connected to the first input of the first balanced mixer my amplifier, output coupler synchronous detector, null-organ, the third YAS-filter, the fourth balanced mixer, the second filter of the low third D-trigger. Compiled by V.Stukan Editor M.Kelemesh Tekhred L.Oleinik Proofreader E.Roshko Order 4914/44 Circulation 728 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 frequency, fifth mixer, third selective amplifier, adjustable amplifier, second quartz auto-drive generator, the output of which is connected to the first inputs of the fifth mixer and the fourth balanced mixer, the output of which through the second low-pass filter is connected to the second inputs of the second and the third balanced mixers, the output of the fifth mixer through the third selective amplifier connected to the first input of the fifth synchronous detector, the output of which is through a null organ and the third The RC filter is connected to the input of a second self-regulating quartz oscillator, the third output of the first crystal oscillator is connected to the second input of the fifth mixer, the first output is connected to the input of an adjustable amplifier, the first output of which is connected to the second input of the first balanced mixer1, the frequency divider input is connected to the second output the first quarter of the D-flip-flop, the third output with the second input of the controlled phase Gerov, the second exit - with the entrance D five from the third D-flip-flop, the third output - with the second input of the controlled phase Q the rotator, the inverted output of the third D-flip-flop is connected to the input C of the first D-flip-flop, and the inverted output of the third D-flip-flop is connected to the input C of the second D-flip-flop, the code of the first D-flip-flop is connected to the second inputs of the second and fourth synchronous detectors, and / stroke of the second D-trigger with the second inputs of the first and third synchronous detectors, the output of a tunable high-frequency generator is connected to the first input of the first balanced mixer my amplifier, the output of the escaped phase shifter is connected to the input C third D flip-flop.