RU1800392C - Automatic device for measurement of differential parameters of nonlinear elements - Google Patents

Abstract

The invention relates to a radio measuring technique, for the automatic measurement of the active component of the conductivity, capacitance and quality factor of various nonlinear and linear elements in parallel and / or serial parameter equivalent circuits with increased accuracy and speed of measurements in a wide range of operating frequencies. SUMMARY OF THE INVENTION: An automatic device for measuring the differential parameters of nonlinear elements comprises an analog-to-digital converter for the coordinates of the zero-second derivative transition, a measuring unit with a non-linear element under study, a multi-channel switch, a microcomputer, an information display unit, and a code-controlled bias voltage source. As a result of the operation of double generation of reliable digital information on the coordinates of the transition through zero of the second derivative of the amplitude-frequency characteristic of the measuring unit, respectively, with the non-linear element under study disconnected and connected and subsequent calculation of the desired parameters using a microcomputer, the accuracy and speed of measurements are improved without reducing the range of operating frequencies. 3 ill. / Yo

Description

The invention relates to a radio-measuring technique, is intended for automatic measurement of the active component of conductivity (loss resistance), capacitance and quality factor of various nonlinear and linear elements in parallel and / or in series parameter equivalent circuits with increased accuracy and speed of measurements in a wide range of operating frequencies and can be used in the subsystems of the technical diagnostics of radio engineering elements of automated control systems for various radio electronic devices parameters, as well as during technological control of the parameters of semiconductor devices and other objects.

The purpose of the invention is to improve the accuracy and speed of measurement without reducing the range of operating frequencies.

Figure 1 is a block diagram of an automatic device for measuring differential parameters of non-linear elements; Fig. 2 is a diagram illustrating the principle of operation of the proposed automatic device; Fig. 3 is a structural diagram of a microcomputer operation algorithm.

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The automatic device for measuring the differential parameters of nonlinear elements (Fig. 1) contains an analog-to-digital converter 1 of the coordinates of the transition through zero of the second derivative, a measuring unit 2 with the investigated nonlinear element 3, a multi-channel switch 4, microcomputer 5, information display unit 6 and code control bias voltage source 7.

The differential parameters of the non-linear element under study measured in the parallel equivalent circuit with the device — the capacitance Cx, the active component of the conductivity Gx, and the quality factor Qx are determined by the following mathematical relations:

L f f2 - f 1

(6)

The ratios for the desired parameters of the nonlinear element, measured in a sequential equivalent circuit, respectively, capacitance Cx, active resistance vx and quality factor dfc can

be presented as follows:

1

4 L2 L (ff52 - f§i) vx 2 T2jrL (A f2- A fi) 1

Qx

(7)

(8)

(9)

The initial state and the operating order of the automatic device (Fig. 1) are determined by the microcomputer 5, for the preparation of which it is necessary to perform a number of well-known operations. The initially edited program for calculating the parameters of the investigated nonlinear elements 3 (the program text is attached), together with the algorithmic language on which the microcomputer 5 works, for example BASIC, is written to a read-only memory (ROM), where it is to be stored.

Before each new start-up of the automatic device, the information from the ROM is copied to the random access memory (RAM), then this program is called up by the appropriate command (the START key is used) and a comment is displayed on the screen of the information displaying unit 6 indicating the order to the operator action. At the same time, the signal levels are set to zero on the first four buses of the third input / output port of the microcomputer 5. On the remaining buses of all the input / output ports of the microcomputer 5, zero potentials are also initially set, although their presence is not essential for the normal operation of the measuring device as a whole.

Subsequently, in accordance with the structural diagram (Fig. 3) of the operation algorithm of the microcomputer 5, the value of the inductance L of the measuring unit 2 is inputted sequentially in time in dialogue mode from the keyboard, followed by the calculation of the coefficient:

M

1

4l21

(10)

constituent in the relations (1) and (7) for the desired parameters. In the case of measuring block 2 with a constant inductance L, its value and coefficient M (10) are constants and their values can be entered in the ROM of the microcomputer 5 during the initial debugging of the program for calculating the desired parameters.

Then, the equivalent circuits W are introduced, and when measuring the parameters of the nonlinear elements 3 by the parallel equivalent circuit, the value of the variable W is taken to be zero (W 0), and by the sequential equivalent circuit to the unit (). In accordance with this, on the first bus Vi of the third input / output port of the microcomputer 5, zero or unit potential is generated (Fig. 2 a), which, transmitted to the second control input of the measuring unit 2, commutes the investigated non-linear element 3 in parallel or sequential equivalent circuit of its parameters.

After that, the required value of the bias voltage Uf, represented by

0 in the form of a decimal number ranging from zero to a certain maximum value, for example 32V, onto which a co-controlled bias voltage source 7 is designed, proceeding from the measurement conditions of parameters 5 of the investigated non-linear elements 3.

It should be noted that the maximum value of the bias voltage obtained at the output of the code-controlled source 7 is determined within the range of the maximum output voltage used in conjunction with the digital-to-analog converter of the operational amplifier. For domestic high voltage

5 of the K1 408UD1 type operational amplifier, the maximum output voltage is +19 V (4), which allows us to obtain, using the output level bias circuit, the maximum output voltage

0 code-controlled source 7 to 38V. Using well-known schematic solutions, the discussed voltage is obtained of arbitrary value, however, the accuracy of its installation is determined by the bit

5 of the used digital-to-analog converter, which must be at least 12. Unfortunately, it is difficult to obtain the resolution of the digital-analog converter by known means, and this determined

0 implementation of a code-controlled bias voltage source 7 as a 12-bit function block. In this regard, all the buses of the first and second input / output ports of the microcomputer 5 are connected only with the multi-channel switch 4, which is 16-bit, and only 12 buses are used with the code-controlled source 7, which does not interfere with normal operation microcomputer 5.

0 The entered numerical value of the bias voltage Uv of the microcomputer 4 is converted into a digital binary code, which appears on the corresponding buses of its first and second input / output ports, 5 is transmitted to the corresponding digital buses of the code-controlled source 7 of the bias voltage and acts on the biased voltage isolated from the input parts of the output bus of the multi-channel switch 4, which is in the initial (zero) state, so

as there is no signal from the second output of the analog-to-digital converter 1 of the coordinates of the transition through zero of the second derivative at its control input. In order to reduce the component error in setting the bias voltage due to the finite bit size of the code-controlled source 7, the bias voltage value is not input to the screen of the information displaying unit 6, but its value corresponding to the received binary code.

After inputting and converting this information on the second bus V 2. of the third input / output port of the microcomputer 5, a relatively short pulse is generated (Fig.2b), which, acting on the control input, writes information available to the registers of the code-controlled bias voltage source 7 on his digital buses. At the end of the specified pulse, the digital information is stored in the registers, and at the output of the code-controlled source 7, a bias voltage is generated that corresponds exactly to the generated binary code, which is transmitted via the second information input to the measuring unit 2 and then acts on the non-linear element 3 under study.

Soon, a relatively short rectangular pulse is generated on the third bus VJ of the third input / output port of the microcomputer 5 (Fig.2c), which, acting on the control input of the analog-to-digital converter 1, activates this converter with its leading edge to perform all operations, associated with both setting the initial operating conditions and the formation of reliable digital measurement information about the coordinates of the transition through zero of the second derivative of the amplitude-frequency characteristic of the measuring unit 2 with the investigated non-linear element 3 disabled.

Initially, the analog-to-digital converter 1 sets zero potentials at its second output and information outputs, and generates a frequency-modulated test signal with small deviation, maximum amplitude and carrier frequency corresponding to the lower boundary of the frequency range of the automatic device, which affects the first information input of the measuring unit 2. In this case, the measuring unit 2,

possessed its own resonant frequency, as a rule, different from the lower limit of the frequency range of the measuring device, the signal to

the output does not pass, and therefore, there is no signal at the information input of the analog-to-digital converter 1. In turn, the absence of a signal at the second output of the analog-to-digital converter 1 leads to the fact that the output buses of the multi-channel switch 4 remain isolated from the main part of the circuit, and the microcomputer 5 after the duration of the start pulse (Fig.2c), acting on the third bus V $ Having not received information on the fifth bus of its third input / output port, it switches to the continuous readiness mode for data on the buses of the first and second input / output ports.

After a very short time, set 1 (Fig. 2d), sufficient to establish the initial operating conditions of the analog-to-digital converter 1, on its

the first output begins to change (increase) the carrier frequency of the frequency-modulated test signal. As the carrier frequency of this signal increases and approaches the passband of the measuring unit 2, the output of the latter shows a complex, time-varying amplitude in accordance with the shape of the amplitude-frequency characteristic frequency-modulated

signal. This signal in the analog-to-digital Converter 1 is processed with the formation of a constant component proportional to the amplitude-frequency characteristic of the measuring unit 2, and

a number of harmonic components of the modulating signal, including the first and second, proportional to the first and second derivatives of the amplitude-frequency characteristic, respectively. After separate synchronous phase-sensitive selection and synchronous phase-sensitive demodulation, the first and second harmonic components turn into constant components proportional to the first and second derivatives.

The constant component formed, proportional to the second derivative, drives the analog-to-digital converter 1 to perform the operation

fast normalization of characteristics (before the first transition through zero of the second derivative), while the level of the carrier at the first output of the analog-to-digital converter 1 begins to change

(decreases) so that in the steady state, the maximum signal value proportional to the characteristic of the second derivative is set at a certain level defined inside the transducer 1, regardless of the quality factor of the measuring unit 2 with the non-linear element 3 disconnected and connected under study.

As a result of the normalization operation, the frequency-modulated test signal at the first output of the analog-to-digital converter 1 can make amplitude fluctuations, which, without exceeding the tolerance, are stopped, as a rule, no later than when the characteristic of the second derivative reaches its first extreme point (maximum). In accordance with this process, there is a change in signal levels proportional to the amplitude-frequency characteristic and the characteristic of the first derivative, inside the analog-to-digital converter 1.

Upon reaching the first extreme point (maximum) on the characteristic of the second derivative, the carrier level of the frequency-modulated test signal at the first output of the analog-to-digital converter 1 is fixed and subsequently remains unchanged throughout the entire time interval necessary for digitally determining the coordinates of the transition through zero the second derivative of the amplitude-frequency characteristic of the measuring unit 2 with the non-linear element 3 under study disconnected or connected.

With a further increase in the carrier frequency of the frequency-modulated test signal at the time when the first derivative reaches its maximum value and the second derivative through zero, the carrier frequency of this signal is fixed, and the analog-to-digital converter 1 begins to generate the frequency fi (5), ( 6), exactly corresponding to the first coordinate of the transition through zero of the second derivative of the amplitude-frequency characteristics of the measuring unit 2 with the investigated non-linear element 3 disabled. After for some time, extremely short, sufficient to synchronize the processes, the analog-to-digital converter 1 generates a single-duration synchronizing pulse exemplary in duration (the pulse shown in Fig. 2d as a vertical shading), which is filled with the frequency fi, and thus, the conversion is carried out the first coordinate of the zero transition of the second derivative into a digital code. The digital code received at the information outputs of the analog-to-digital converter 1 is stored and transmitted to the corresponding information inputs of the multi-channel switch 4. This essentially ends

measurement time tism1 (Fig. 2e) of the first coordinate of the zero transition of the second derivative.

At the end of the formation of a single synchronizing pulse (Fig.2g) on

the second output of the analog-to-digital converter 1 produces a single rectangular pulse (Fig. 2e) of a certain duration. This impulse, indicating the availability of data in the form of digital

of measuring information, acts on the control input of the multi-channel switch 4 and the fifth bus of the third input-output of the microcomputer 5. In this case, the multi-channel switch 4 transfers digital information from the information outputs of the analog-to-digital converter 1 to its output and then to the buses of the first and second input ports -output microcomputer 5. The same information is received and

to the information inputs of the code-controlled source 7 of the bias voltage, however, it is not perceived by them, since there is no signal at its control input.

Simultaneously with the formation of a single rectangular pulse (Fig. 2e), the carrier frequency of the frequency-modulated test signal at the first output of the analog-to-digital converter 1 changes stepwise (increases) to the value that it would acquire as a result of continuous tuning for the time interval between the moment the second derivative passes through zero and the end of the process of converting its coordinates into a digital code. Subsequently, the carrier frequency of a frequency-modulated test signal with a constant amplitude at the first output

analog-to-digital converter 1 continues to increase linearly.

The rectangular pulse (Fig.2d) received at the second output of the analog-to-digital converter 1 is perceived on the fifth bus of the third input-output port of the microcomputer 5, which, since the starting rectangular pulse (Fig.2c) has ceased to exist on the third bus V3

Throughout this time, its third I / O port has been continuously polling data availability on the buses of the first and second I / O ports. Microcomputer 5, having thus obtained permission to enter data, rewrites (enters information byte Ft and P3 in accordance with the block diagram of the algorithm shown in FIG. 3) stored in the analog-to-digital converter 1 and presented to the output channels of the multichannel switch 4 digital information about the value of the frequency fi of the first coordinate of the transition through zero of the second derivative to the corresponding memory cell, where it is to be stored for subsequent calculations.

After this operation is completed and the rectangular pulse (Fig.2d) ends, the second output of the analog-to-digital converter 1 of the microcomputer 5 again continuously polls the data availability until reliable information about the second coordinate of the zero transition of the second derivative is obtained from the amplitude-frequency characteristics of the measuring unit 2 with the investigated non-linear element 3 disabled. In order not to re-enter the previous information, the duration of the mentioned pulse (Fig.2 e) controls microcomputer 5 is launched, and only after its termination and subsequent resumption is it possible to enter new data (achieved by software). The termination of this pulse at the second output of the analog-to-digital converter 1 results in isolation of the output buses of the multi-channel switch 4 from the rest of the circuit.

When the first derivative reaches its minimum value, and the second derivative passes through zero again, the analog-to-digital converter 1 completely erases the old digital measurement information, stops tuning the carrier frequency of the frequency-modulated test signal at its first output, and again forms as described above exemplary in duration of the second synchronizing pulse (Fig.2d), during which the conversion into digital binary code generated frequency f2 (5), (b), exactly corresponding to the desired second coordinate of the transition through zero of the second derivative. This ends the measurement time Tism 2 (Fig. 2h) of the second coordinate of the zero transition of the second derivative of the amplitude-frequency characteristic of the measuring unit 2 with the non-linear element 3 under study disconnected.

At the time of the termination of the synchronization pulse (Fig. 2d), the frequency code f2 obtained on the digital buses of the analog-to-digital converter 1 is subsequently stored, and the carrier frequency of the frequency-modulated test signal at the first output of the analog-to-digital converter 1, decreasing exponentially , returns to its initial state in the region of the lower boundary of the frequency range of the device with a simultaneous increase to the limit value of the carrier level due to the fact that the normalization operation ceases to be performed vani characteristics.

Under the influence of the second rectangular pulse analog-to-digital converter 1 simultaneously obtained at the second output (Fig. 2e), digital measurement information is presented on the output buses of the multi-channel switch 4, and the microcomputer 5 is allowed to enter new data. The microcomputer 5 rewrites the newly presented digital measurement information (F2 and F / I data is also entered by byte) into the corresponding cell of its RAM for storage and subsequent calculations and proceeds to further program execution in accordance with the block diagram of the algorithm, depicted in Fig.Z.

During the input and processing of information G Sample 1 (Fig.2d), the microcomputer 5, using the obtained complete data FI and F2, calculates the center frequency fci (1), (2), (7) using formulas (5) and (b) and the bandwidth A fi (2), (8) on

/about

the level of the measuring unit 2 with the non-linear element 3 under study disconnected, which in the form of the values F (1) and D (1) are stored in RAM for subsequent calculations. The second rectangular pulse disappearing at this point in time (Fig.2d) at the second output of the analog-to-digital converter 1 again isolates the output buses of the multi-channel switch 4 from its rest.

Microcomputer 5 in a regular cycle of its work on the fourth bus V ceoero of the third input / output port sets the unit potential (Fig.2e), which, entering the first control input of the measuring unit 2, includes the investigated nonlinear element 3 as part of the measuring unit with implementation corresponding mode of its operation according to an initially determined parameter equivalent circuit. In this case, the center frequency and the passband of the measuring unit 2 change, taking the values fo2 (1), (2), (7) and Л f2 (2), (8), respectively, containing information about the desired parameters of the investigated nonlinear element 3.

After this, the microcomputer 5, once again forming a rectangular triggering pulse (Fig. 2 c) on the third bus V3 of its third input-output port, as described above, again drives the analog-to-digital converter 1 to perform its full functions, including setting the initial operating conditions, and the processes in it and in the measuring device as a whole are repeated in the same order as when forming and converting the measurement information about the parameters of the measuring unit 2 with the nonlinear element 3.

The analog-to-digital converter 1, repeating the above operations, after setting the initial conditions Tust.2 (Fig.2d), forms sequentially in time for the time intervals t measurement (Fig. 2 d) and t measurement 4 (Fig. 2c) reliable digital measurement information that exactly corresponds to the first and second coordinates of the transition through zero of the second derivative of the amplitude-frequency characteristics of the measuring unit 2 with the test element 3 connected, and with the help of rectangular pulses (Fig. 2e) WTO th output, it places a through multichannel switch 4 to the respective bus input-output ports of the microcomputer 5.

At the same time, the microcomputer 5 repeats the input of the received digital measuring information (first, in the form of byte data F1, F 3 converted to the full form of data F1, and then data F2, F4 converted to Fa) into the corresponding cells of its RAM subsequent calculation according to formulas (5) and (6) of the center frequency fo2 (1), (2), (7) and the passband Л h (2), (8)

a measuring unit 2 with a non-linear element 3 under study, which in the form of values F (2) and D (2) are stored in RAM for subsequent calculations.

After performing these operations, the microcomputer 5 on the fourth bus V4 of its third input / output port sets zero potential, thereby completing

the formation of a rectangular sufficiently long pulse (Fig.2E), disconnecting the investigated non-linear element 3 from the measuring unit 2, and

starts to execute a program for calculating the desired parameters in accordance with a given algorithm (Fig.Z). With the non-linear element 3 under investigation switched off, the measuring unit 2, returning to its initial state, jumps into the previous (initial) values of the parameters of the center frequency foi and bandwidth Afi, which can differ significantly from just

fixed values fo2 and Af2.

Due to the resulting detuning of the measuring unit 2 in frequency, its interconnection with the analog-to-digital converter 1 is practically lost also because

the last one, after the measurement time has been measured, ism.4 (Fig.2c) proceeded to return to its initial state with the formation on its first output, as described above, of a frequency-modulated test signal of maximum amplitude and a carrier frequency approaching the lower boundary of the frequency range operation of the measuring device. Regardless of how this process occurs, on

the subsequent operation of the measuring device is not reflected, since the necessary information has already been obtained and the microcomputer 5 is able to process it.

The processes taking place in the microcomputer 5

on the time interval for inputting and processing information m Sample 2 (Fig. 2d), then they are reduced to the direct calculation of the desired parameters according to the programmed formulas (1) - (4), (7) - (9), see text

programs) taking into account previously entered data in the form of corresponding constants and data obtained as a result of measurements. After the calculation is completed, on the screen of the information display unit 6 for indication

on the time interval ru (Fig. 2b), the microcomputer displays the form of the equivalent circuit W, the bias voltage 1) f in the form of the value of Y, as well as the value of the calculated parameters in the appropriate units of measurement: the frequency of measurement of the RF in the form of the value of F (2); capacitance C, the active component of the conductivity G or active resistance R (depending on the type of equivalent circuit) and the quality factor Q. On this cycle of measurements and

The calculations are completed, forming the total measurement time T ISM (Fig. 2b) and the microcomputer 5 goes into Stop mode.

If necessary, the measurement and calculation process can be continued.

with the same initial data, only with a new value of the bias voltage 1) f, only with a different equivalent circuit W for all new data. In accordance with the structural diagram (Fig. 3) of the operation algorithm with previous data, the microcomputer 5 generates a rectangular pulse (Fig. 2c) on the third bus V3 of its third input / output port and starts the automatic device in the manner described above with the resumption of measurement information. This mode of operation of the microcomputer and the automatic device as a whole is useful in studying the influence of various factors (temperature, moisture, pressure, etc.) on the parameters of the investigated nonlinear elements 3.

With all the new data, the operation of the automatic device begins with the input of this data, including the replacement of the investigated non-linear element 3, followed by the repetition of all the above operations. If it is necessary to obtain information only with a new value of the bias voltage 1) f or only with a different equivalent circuit W, it is enough to enter only the new values 1) f or W, and the microcomputer 5, having carried out the prescribed operations, starts the automatic device in operation and taking into account renewable measurement information and information stored in RAM on previously entered constants calculates new parameter values and displays them on the screen of the information display unit b.

The proposed automatic device in comparison with the best known technical solutions, including the prototype device, which is currently the best designed design and which in this regard is taken as the base object, is favorably characterized by increased accuracy and speed of measurement parameters of nonlinear elements. A significant increase in the accuracy and speed of measurements without reducing the operating frequency range was achieved mainly due to the introduction of a specialized measuring unit and the operation of double generation of reliable digital measurement information about the coordinates of the transition through zero of the second derivative of the amplitude-frequency characteristic of the measuring unit, respectively, with the nonlinear disconnected and connected element and the subsequent calculation of the desired parameters using a microcomputer, which made it possible to almost completely eliminate the manual operations of connecting the studied elements to the measuring circuit and calculating the values of the desired parameters from the results of two measurements of the coordinates of the transition through zero

second derivative.

The gain in the accuracy and speed of measurements can be determined tentatively, based on the following considerations. The absence of a specialized measuring unit in the prototype device determines the need to connect the investigated nonlinear element to the measuring circuit directly, while eliminating the possibility of correction

component of the error due to the inductance of the terminals of both the non-linear element under investigation and the terminals for its connection, the value of which at the operating frequencies of hundreds of megahertz is tens of percent. The use of a specialized measuring unit allows this error component to be reduced to tenths of a percent. Other component errors

inherent to the proposed device is negligible. For example, the main component of the error due to digital signal processing is associated with a finite value of the resolution of the analog-digital

transducer 1 of the zero transition of the second derivative, which for the used 16-bit transducer 1 is characterized by thousandths of a percent. In connection with this, it is really achievable

a gain in the accuracy of measurements provided by introducing into the proposed device a measuring unit 2, not less than 250 times.

Manual operations present with

measurements using the prototype device, determine the time required to obtain the desired parameters, calculated at best, tens of seconds. The proposed device allows to obtain reliable information about the desired parameters in a time not exceeding tenths of a second in the worst case. This suggests that the gain in the speed of measurements can be

at least about 100 times.

Thus, this automatic device is highly efficient and can significantly improve the accuracy and speed of measurements without reducing the range of operating frequencies. This device, capable of making measurements with precision accuracy and high speed, while maintaining a wide range of operating frequencies of the prototype device, is suitable for use in the process control of differential parameters of both non-linear elements and various linear radio-technical elements, as well as in automated technical diagnostic subsystems systems for monitoring the parameters of elements of various electronic equipment.

Claims (1)

SUMMARY OF THE INVENTION An automatic device for measuring the differential parameters of nonlinear elements, comprising an analog-to-digital converter of the coordinates of the zero transition of the second derivative of the microelectronic device M and an information display unit, the input of which is connected to the information output of the microcomputer, characterized in that, in order to improve the accuracy and speed of measurements without reducing the operating frequency range, a multichannel switch unit and a code-controlled bias voltage source are introduced into it Whose output is connected to the second information input of the measuring unit, the first information input of which is connected to the first output of the analog-to-digital converter 5 0 5 0 the zero coordinate derivative of the second derivative, the information input of which is connected to the output of the measuring unit, the non-linear element is connected to the first and second output, the buses of the first and second input / output ports of the microcomputer are connected to the corresponding output buses of the multichannel switch and the information inputs of a code-controlled source, for example of bias, the control input of which is connected to the second bus of the third input-output port of the microcomputer, the first and fourth bus of which, respectively but connected to the second and first control inputs of the measuring unit, the third bus of the third input-output port of the microcomputer is connected to the control input of the analog-to-digital converter for coordinates of the zero transition of the second derivative, the second output of which is connected to the fifth bus of the third input port the output of the microcomputer and the control input of the multichannel switch, the information inputs of which are connected to the corresponding information outputs of the analog-to-digital converter of the coordinates of the transition through zero of the second oizvodnoy. Figure 1 Editor Shie.Z Compiled by V. Chebotov Tehred M. Morgenthal Order 1162 VNIIIPI of the State Committee for Inventions and Discover at the USSR State Committee for Science and Technology 113035, Moscow, Zh-35, Rauska nab., 4/5 Production and Publishing Plant Patent, Uzhhorod, 101 Gagarin St. Fi g Proofreader M. Kul . ;