SU1051469A1 - Varicap q-meter - Google Patents

Abstract

VARICAP VOLUME MEASUREMENT METER containing a generator, an amplifier, a linear detector, the first and second permanent capacitors, the first and second isolating elements, the third isolating element connected by the first output to the LED and the first isolating element, and the second output to the first output of the first permanent capacitor , characterized in that, in order to improve the measurement accuracy, an adjustable amplifier, a direct current amplifier, a variable resistor, a variable capacitor, a resistor, a source voltage, transformer, zero-organ, first and second synchronous detectors, the first output of the generator is connected to the first inputs of the first and second synchronous detectors, the second output is connected to the first input of an adjustable amplifier connected to the first output through a linear detector device, the second output through the primary winding of the transformer - with a common bus device, the first output of the secondary winding of the transformer is connected via a variable capacitor to the first output of the second constant condensers, to the input of the amplifier and the first terminal for coupling the controllable varicap, a second klem1.1a for connection which is connected to the second output terminal of the device, with the first conclusions. the house of the first constant capacitor connected by the second output to the second output of the transformer secondary winding, the third output of which is connected to the common bus of the device to which the second output of the first permanent capacitor and the first output are connected to the second resistor (L output connected to the second input of the first synchronous detector, connected via a null organ output to the input of the first decoupling element, directly to the third OUTPUT terminal of the device the fourth output terminal of which is connected to the first output of the variable resistor connected to the second output of the voltage source source, the third output to the common bus of the device, the first output to the 4th input of the dc amplifier, the second input of which is connected to O) the output of the second synchronous dextro torus, the output through the second decoupling element — with the second input of the adjustable amplifier; the rotor of the variable capacitor is mechanically connected to the first output of the variable resistor.

Description

The invention relates to instrumentation engineering and can be used in the manufacture of semiconductor devices for measuring the quality factor of varicaps, as well as p - /, - Shotka transitions / barriers, MIS structures and other nonlinear elements. A device for monitoring the parameters of a varicap includes a controlled transducer, an adjusting unit, a reference source, a control unit, a comparison unit, a recording unit, a switch, an offset source, a generator, capacitors, resistors, and a terminal for connecting the tested varicap f. ° This device allows you to measure the capacitance and the overlap factor of the varicap, but does not measure its Q-factor, i.e. The device has limited functionality. The closest to the proposed one is the quality factor of a Q-driver, comprising a generator, an amplifier, an extremum extraction unit that performs the functions of a linear detector, the first and second constant capacitors, the first and second an isolating element connected by the first output to the output of the first isolating element, and the second output to the first output of the first permanent capacitor 2J. The known device allows automatic measurement The quality factor of the varicap, however, has a number of disadvantages, reducing the accuracy of measurements. The presence of two varicaps in the oscillatory circuit - the test and the reference one - leads to the fact that the signal at the input of the measuring circuit at the time of resonance depends on the quality factor of both varicaps. In order to isolate the signal proportional to the quality factor of the tested varicap, a calculating device and one more standard varicap were introduced into the quality factor meter. The voltage at the output of the computing device depends on the voltage I, proportional to the voltage of the resonance in the circuit, voltage I4, the corresponding capacitance of the circuit at the time of resonance, on the voltage jig proportional to the capacity of the reference varicap in the resonance and circuit, and on the quality factor of this varicapa. The voltages U and DB / input to the inputs of the computing device depend on the stability of amplitude and frequency. In addition, the magnitude of the voltage U depends on the stability of the gain factor of the amplifier and the accuracy of the extremum extraction device, and the magnitude of the voltage Ug depends on the accuracy of conversion of the capacitance of the reference varicap, which is not in the measuring loop, to the voltage and accuracy of the maximum voltage. metering unit. The magnitude of the voltage U.f depends on the frequency stability and the amplitude of the high frequency generator. Since the voltfarad dependence of the reference varicap standing in the circuit is replaced by the dependence of the other varicap, the measurement accuracy of the quality factor is always the same as the accuracy with which the voltfarad dependences of the two varicaps are selected. The intrinsic error of the computing device also contributes to the measurement error. The purpose of the invention is to improve the measurement accuracy. The goal is achieved by that; that in the varicap quality meter, containing a generator, an amplifier, a linear detector, the first and. the second constant capacitors, the first and second isolating elements, the third isolating element connected by the first output to the output of the first isolating element, the second output to the first output of the first constant capacitor, an adjustable amplifier, a DC amplifier, a variable resistor , variable capacitor, resistor, voltage source, transformer, zero-organ, first and second synchronous detectors, the first generator output connected to the first inputs of the first and second synchronous detectors, a second output with a neisBbiM input of an adjustable amplifier connected by a first output through a linear detector to the first output terminal of the device, a second output through the transformer primary winding to a common bus of the device, the first output of the secondary transformer is connected to the first output of the second a constant capacitor, with an amplifier input and with a first terminal for connecting a controlled varicap, the second terminal for connecting which is connected to the second output terminal of the device The first terminal of the first permanent capacitor connected to the second terminal of the second terminal of the secondary winding of the transformer, the third terminal of which is connected to the common bus of the device connected to the second terminal of the first permanent capacitor and the first terminal of the resistor connected to the second terminal of the amplifier, The first output of which is connected to the second input of the first synchronous detector, which is connected via an output through a null organ to the input of the first decoupling element, directly to the third output terminal device, even the output terminal of which is connected to the first output of the variable resistor connected to the second output of the reference voltage source, the third output to the common bus of the device, the first output to the first input of the dc amplifier, the second input of which connected to the output of the second synchronous detector, output through the second decoupling element to the second input of the adjustable amplifier; the rotor of the variable capacitor is mechanically connected to the first output of the variable resistor. In the drawing, Eden block diagram of the meter. The varicap Q factor meter contains a generator 1, an amplifier 2, a linear detector 3, the first 4 and second 5 permanent capacitors, the first 6 and second 7 decoupling elements, such as RC filters, the third decoupling element 8, such as a resistor, connected first 1 1 output with the output of the first decoupling element 6, and the second output with the first output of the first permanent capacitor 4. The first output of the generator 1 is connected to the first inputs of the first 9 and second 10 synchronous detectors, the second output to the first input of the adjustable amplifier 1 1, connected by the first output through a linear detector 3 to the first output terminal of the device, and the second output through the primary winding of the transformer-12 to the common bus of the device. The first output of the secondary winding of the transformer 12 is connected via a variable capacitor 13 to the first output of the second permanent capacitor 5, to the input of the amplifier 2 and to the first terminal for connecting the controlled varicap 14, the second terminal for connecting which is connected to the second output terminal of the device, with the first output the first constant capacitor 4, connected by the second output to the second output of the secondary winding of the transformer 12, the third output of which is connected to the common bus of the device with which the second output terminal is connected capacitor 5 and the first output of a resistor 15 connected by a BTOJXJM output to the input of amplifier 2. The first output of amplifier 2 is connected to the second input of the first synchronous detector 9 connected to the output of the first dissociating element b, directly to the third output terminal of the device, the fourth output terminal of which is connected to the first terminal of the variable resistor 17, connected by the second terminal to the output of the source 18 of the reference voltage, the third terminal to the common bus of the device, and the first the output is connected to the left input of the DC amplifier 19, the second input of the amplifier 16 is connected to the output of the second synchronous detector 10, and the output through the second decoupling element 7 to the second input is adjustable. Amplifier 11. The rotor of the variable capacitor 13 is mechanically connected to the first output of the nepefvieHHoro resistor 17. Transformer 12 and conlensatel 4 and 13 form a measuring bridge 20. Disconnecting elements 6 and 7 are made in the form of RC-filters, and decoupling element 8 is a resistor . The meter operation is based on the well-known method for determining the Q-factor of nonlinear elements by measuring the capacitance and conductivity using the bridge method. This method is characterized by high accuracy in measuring capacitance and conductivity over a wide frequency range. It uses an equivalent parallel -circuit of replacing the active and reactive components of non-linear elements, according to which the quality factor Q is related to the parallel capacitance C and conductivity G by the relation Q - §- I - I. where GL) is the angular frequency. The equivalent circuit of a varicap is a pair of capacitance impedance connected in series with the resistance of the semiconductor volume P and G / R t. At low frequencies ((x), when Co «f / CQ-fRrg, the indicated equivalent circuit goes into a two-element independent circuit, while the equivalent capacitance Ce and conductivity Qg are equal to C Cg, R iQj On BucojKHX frequencies, when C«} vs / / Ci -jRrt, it also goes into a two-element scheme, but sequential (C {5 and fе, with equivalent parallel capacitance and conductivity equal, respectively, Cd C / 1 + uQg-1 / Pq (| t Qi). IF Q j 10 this condition is fulfilled for varicaps up to frequencies of 100 MHz), then Cs Cc, with an accuracy of more than 1%. In the frequency range of 60 ifCc, where it is necessary to use full This three-element scheme, the quality of the varicap is maximum in this case also with great accuracy. Thus, using a parallel replacement scheme, one can measure with great accuracy not only the quality factor, but also the capacity of the varicap Cd as equal to the measured capacitance C in the range from low frequencies up to frequencies v.ioo MHz. A sinusoidal signal with frequency i from the second output of generator 1 is fed to the first input of adjustable amplifier 11, from the second output is supplied to measuring bridge 20. We denote the amplitude of the output signal reg amplifier 11 through And per The proportional part of this signal, passing through the capacitor 13, included in one arm of the bridge 20, and through the test varicap 14, is allocated as an unbalance signal on the capacitive load — capacitor 5, which has a capacitance Sc. 5 is chosen to be significantly lower in the resistance of the resistor 15, which serves to close the circuit of the varicap 14-dc. The signal is further amplified by an amplifier 2 with a large input impedance, then a capacitive COC offset signal is extracted using a synchronous detector 9. The constant voltage i generated by the synchronous detector 9 is applied to the null organ 16 and through the connecting elements b and 8 changes the capacitance of the varicap 14 so that the DC signal at the output of the synchronous detector 9 is zero. Condition Uj. 0 means that bridge 20 is balanced in terms of capacitance and the reference capacitance of capacitor 13 {with j is the width of equivalent capacitance (s) of varicap 14, i.e.

(2)

with with

- At the same time, the variable of the variable signal arriving at varicap 14 is chosen small enough so that the measurements are carried out in a linear mode. The active unbalanced part of the signal is extracted by the synchronous detector 10 and appears at its output in the form of a constant voltage UQ. Due to the smallness of the amplitude of the variable signal on the varicap under the condition Q «CO Sc (it suffices to take Q - 0.01 C c, the voltage UQ is dependent on the conductivity of the varicap Q, as well as per and capacitive load resistance 1/60 C, i.e.

U i - ftUper ;;

where A is a constant.

The voltage UQ is supplied to the first input Vc-19 of direct current, to the second input of which comes from the source 18 the reference voltage and proportional to the reference capacitance, i.e., and isccc 1/0, where UQ COnet is the source voltage 18 OL coefficient of proportionality. The difference signal is amplified by the amplifiers 19 and through the spreading element 7 is fed to the input of the adjustable amplifier 11, changing its amplification and correspondingly (Jper so that UQ is maintained equal to

with high

reference voltage (J accuracy, i.e.

U (, and obesio.

Claims (1)

VARICAPE QUALITY METER, comprising a generator, amplifier, linear detector> first and second constant capacitors, first and second decoupling elements, a third decoupling element connected to the first terminal with the output of the first decoupling element, the second terminal to the first terminal of the first constant capacitor, characterized in that, in order to improve the accuracy of measurements, an adjustable amplifier, a DC amplifier, a variable resistor, a variable capacitor, a resistor, a reference voltage source are introduced into it voltage transformer, zero-organ, first and second synchronous detectors, the first output of the generator connected to the first inputs of the first and second synchronous detectors, the second output to the first input of an adjustable amplifier connected by the first output through a linear detector to the first output terminal of the device, the second the output through the primary winding of the transformer is with the common bus of the device, the first output of the secondary winding of the transformer is connected via an alternating capacitor to the first output of the second constant capacitor, with the amplifier amplifier and with the first terminal for connecting a controlled varicap, the second terminal for connecting it is connected to the second output terminal of the device, with the first terminal of the first constant capacitor connected to the second terminal with the second terminal of the secondary winding of the transformer, the third terminal of which is connected to the device common bus, which connects the second terminal of the first constant capacitor and the first terminal of the resistor · connected by the second terminal to the input of the amplifier, the first output of which is connected to the second input the first synchronous detector connected by the output through the nullorgan to the input of the first decoupling element, directly with the third output terminal of the device, the fourth output terminal of which is connected to the first output of the variable resistor connected by the second output to the output of the reference voltage source, and the third output to the device common bus, the first conclusion - with the first input of the DC amplifier, the second input of which is connected to the output of the second synchronous detector, the output through the second decoupling element - Further, regulation Rui second input amplifier, a variable capacitor rotor mechanically coupled to a first terminal of the variable resistor. 1051469 A