An electrical impedance measurement system with DC bias application and calibration functions

Abstract

The invention discloses an electrical impedance measurement system with direct current bias application and calibration functions, which relates to the field of electronic measurement technology and comprises: an alternating current signal generator, a direct current signal generator, an alternating current and direct current coupling circuit, an output source resistor, a direct current bias integrated control system, and an impedance measurement fixture; the alternating current signal generator and the direct current signal generator are electrically connected through the alternating current and direct current coupling circuit to provide an alternating current excitation signal and a direct current bias signal to a component to be measured; the output source resistor is electrically connected to the output end of the alternating current and direct current coupling circuit and is connected to the component to be measured of the electrical impedance measurement system; the impedance measurement fixture is electrically connected to the component to be measured; the technical solution provides direct current signal excitation to the component to be measured of the electrical impedance measurement system at the same time, and performs measurement and calibration on the electrical impedance measurement system, thereby improving the accuracy of subsequent direct current bias application and impedance measurement.

Description

Technical Field

[0001] The invention relates to the technical field of electronic measurement, and in particular to an electrical impedance measurement system with direct current bias application and calibration functions. Background Art

[0002] Impedance is a physical quantity used to describe the resistance of electronic devices to electrical signals in a circuit. As one of the important technologies in the field of electronic measurement, impedance measurement technology can not only analyze the electrical properties of electronic circuits, devices and raw materials, but also measure other non-electrical physical quantities through electrical conversion sensors. Therefore, impedance analyzers are used in many disciplines closely related to electronics to perform precise measurement and analysis of impedance.

[0003] Due to the characteristics of raw materials, the impedance value of some electronic components will be affected by the amplitude of the measured excitation signal. For example, the capacitance value of ceramic capacitors will have different responses to the amplitude of the excitation signal due to the size of the material dielectric constant K, while the inductance value of iron core inductors is related to the amplitude of the excitation signal due to the hysteresis effect of the electromagnetic field. Not only is it affected by the amplitude of the AC test signal, but the DC bias signal will also affect the impedance value of some passive components. The capacitance value of ceramic capacitors with high dielectric constants will change with the amplitude of the DC bias signal applied to both sides of the capacitor. Therefore, in the impedance measurement and analysis experiment, it is necessary to measure the DC bias response characteristics of the impedance to be measured by scanning the DC bias voltage amplitude.

[0004] There are the following difficulties in adding DC bias function to the electrical impedance measurement and analysis system:

[0005] (1) When using DAC or DDS and PWM filtering as the excitation signal source for the DUT, it is very difficult to achieve a large excitation amplitude and maintain an excitation amplitude equivalent to that at low frequency at high frequency due to the influence of parameters such as power supply and parasitics in the circuit. For devices such as high-K ceramic capacitors that exhibit different impedance values ​​under DC bias, it is often necessary to be able to apply a voltage bias of several volts to tens of volts, or even hundreds of volts, within a certain measurement frequency range. It is obviously difficult to meet such DC bias requirements by simply using the above-mentioned traditional excitation signal generation scheme.

[0006] (2) Since a relatively large DC bias amplitude needs to be applied to the circuit measurement system, how can the impedance measurement system ensure its function in accordance with the implementation principle without sacrificing the accuracy and stability of the original circuit after applying such a large DC bias? Taking the self-balancing bridge method as an example, for a system implemented by the bridge balance method, how to achieve bridge balance conditions to complete the measurement when an AC signal and a large-amplitude DC excitation signal exist at the same time is an important issue.

[0007] (3) Under the action of a large-value DC excitation signal, factors such as circuit structure design and circuit component selection may lead to leakage current, DC voltage division loss, etc., resulting in the DC bias actually applied to the component under test failing to reach the target value.

[0008] (4) For signal links where AC and DC signals are superimposed and mixed, from the perspective of signal output reliability and circuit design safety, it is also important to ensure that the signal excitations of two different signal sources can be smoothly output and superimposed, while preventing the excitation output of one signal source from affecting the other signal source.

[0009] (5) In the general impedance measurement scenario, DC bias should include DC current bias and DC voltage bias. However, the generation and application methods of current and voltage are generally different, which increases the complexity of the system. Summary of the invention

[0010] In order to solve the above-mentioned problem that it is difficult to add a DC bias function to the electrical impedance measurement and analysis system to obtain the DC bias corresponding characteristics of the component to be measured, the present invention provides an electrical impedance measurement system with a DC bias application and calibration function, which can apply the required DC bias to the component to be measured while completing the AC impedance measurement, and reduce the interference of circuit parasitic parameters on DC bias application and impedance measurement through calibration, while avoiding making a lot of modifications to the original electrical impedance measurement system circuit.

[0011] The technical solution of the present invention is as follows:

[0012] An electrical impedance measurement system with DC bias application and calibration functions, comprising: an AC signal generator, a DC signal generator, an AC / DC coupling circuit, an output source resistor, a DC bias integrated control system, and an impedance measurement fixture; wherein:

[0013] The AC signal generator is electrically connected to the DC signal generator via the AC / DC coupling circuit to provide an AC excitation signal and a DC bias signal to the component under test;

[0014] The AC / DC coupling circuit causes the output signal of the DC signal generator to be superimposed on the output signal of the AC signal generator, and simultaneously provides AC / DC signal excitation to the component under test;

[0015] The output source resistor is electrically connected to the output end of the AC / DC coupling circuit and is electrically connected to the element to be measured of the electrical impedance measurement system; the output source resistor transmits the AC / DC signal excitation to the element to be measured; the output source resistor is Rs, and the element to be measured is Zx;

[0016] The DC bias integrated control system is electrically connected to the AC signal generator, the DC signal generator, the output source resistor, and the element to be measured of the electrical impedance measurement system to form a DC bias feedback adjustment link of the electrical impedance measurement system;

[0017] The impedance measurement fixture is electrically connected to the device to be measured.

[0018] Working principle of the present invention:

[0019] Compared with the prior art, the DC bias application function of the electrical impedance measurement system of the present invention can apply a DC bias to the element to be measured of the electrical impedance measurement system, and the DC bias system is simply concentrated inside the impedance measurement system without the need to design an external DC bias system; the calibration method of the electrical impedance measurement system can effectively calibrate the instrument and improve the accuracy of DC bias application and impedance measurement.

[0020] The electrical impedance measurement system with DC bias application and calibration functions also includes a calibration module, which is fixed on the impedance measurement fixture as a component to be measured for calibration measurement before formal measurement.

[0021] Preferably, the calibration module comprises: an open circuit calibration component, a short circuit calibration component and a load calibration component;

[0022] The open circuit calibration piece, short circuit calibration piece and load calibration piece are respectively fixed on the impedance measurement fixture as the elements to be measured before the formal measurement.

[0023] Preferably, the DC signal generator and the AC signal generator adjust the output AC and DC signal amplitudes and phases under the control of the DC bias integrated control system to provide AC and DC signal inputs to the device under test.

[0024] Preferably, the DC bias integrated control system includes a signal acquisition module and a signal processing module.

[0025] Furthermore, the signal acquisition module includes: an operational amplifier circuit, a filter circuit, and an analog-to-digital conversion circuit, which are used to collect the DC bias signal at both ends of the output source resistor and the component under test;

[0026] The signal processing module includes an FPGA, which is used to process the collected DC bias signal and adjust the output of the DC signal generator according to the design requirements.

[0027] The output end of the operational amplifier circuit is electrically connected to the input end of the filter circuit, and the output end of the filter circuit is electrically connected to the input end of the analog-to-digital conversion circuit; the input end of the operational amplifier circuit serves as the input end of the signal acquisition module, and the output end of the analog-to-digital conversion circuit serves as the output end of the signal acquisition module.

[0028] Furthermore, the electrical impedance measurement system also includes an external DC bias connection fixture and an external DC bias source; the output end of the external DC bias source is electrically connected to the first input end of the external DC bias connection fixture; the second input end of the external DC bias connection fixture is electrically connected to the output end of the impedance measuring instrument; the output end of the external DC bias connection fixture is electrically connected to the input end of the impedance measurement fixture.

[0029] Furthermore, the external DC bias connection fixture includes a DC bias signal mixing and protection circuit for isolation and protection, and the DC bias signal mixing and protection circuit includes: an AC / DC signal mixing circuit, a DC bias isolation circuit and a DC bias protection circuit; the output end of the AC / DC signal mixing circuit is electrically connected to the input end of the DC bias isolation circuit; the output end of the DC bias isolation circuit is electrically connected to the input end of the DC bias protection circuit; the input end of the AC / DC signal mixing circuit serves as the input end of the DC bias signal mixing and protection circuit, and the output end of the DC bias protection circuit serves as the output end of the DC bias signal mixing and protection circuit.

[0030] Furthermore, the AC / DC signal mixing circuit allows the DC signal input into the external DC bias connection fixture by the external DC bias source to be mixed with the AC signal input into the external DC bias connection fixture by the impedance measuring instrument, and both are output to the impedance measuring fixture through the connection at the impedance measuring fixture end, and then applied to the component to be measured; the DC bias isolation circuit isolates the AC / DC signals to prevent the AC / DC signals from interfering with the output of the other signal source; the DC bias protection circuit is used to avoid damage to the impedance measuring instrument when an excessive DC bias voltage is applied to the external DC bias connection fixture.

[0031] Preferably, the AC / DC coupling circuit includes a DC blocking capacitor and a mutual inductor; the DC blocking capacitor and the AC signal generator are connected in series on the signal output chain of the AC / DC signal generator, the two ends of the DC blocking capacitor are electrically connected to the mutual inductor, and the other two ends of the mutual inductor are connected to the two ends of the DC signal generator; the DC signal generator applies a DC voltage to the two ends of the DC blocking capacitor through the mutual inductor, and the DC voltage is superimposed on the AC voltage excitation generated by the AC signal generator on the link to form an AC / DC voltage excitation, which is applied to the two ends of the component to be tested.

[0032] Beneficial effects of the present invention:

[0033] 1. The DC bias application function of the impedance measurement system can apply DC bias through an external DC source without changing the circuit structure of the original impedance measurement system by using an external DC bias connection fixture between the instrument port and the measurement fixture. It can make more flexible choices for applying DC bias through the external DC source, avoid a lot of changes to the original impedance measurement system, and reduce the complexity of circuit system design.

[0034] 2. In this DC bias application function, the DC bias voltage can be applied to the component under test while the DC bias current can be applied, which simplifies the design of the hardware system and improves the utilization rate of hardware resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the electrical impedance measurement system with DC bias application and calibration functions according to the present invention.

[0036] Figure 2 This is a workflow diagram of calibration of the calibration module of the present invention by connecting with an impedance measurement fixture.

[0037] Figure 3 This is a workflow diagram of connecting the external DC bias connection fixture to the impedance measurement fixture and performing calibration through the calibration module according to the present invention.

[0038] Figure 4 The figure is a schematic diagram of the connection method between the external DC bias connection fixture and the external DC bias source according to the present invention.

[0039] Figure 5 The figure is a schematic diagram of the connection method of the external DC bias connection fixture described in the present invention.

[0040] Figure 6 The figure is a schematic diagram of the internal structure of the DC bias signal mixing and protection circuit of the present invention.

[0041] Figure 7 It is a schematic diagram of the circuit structure of the external DC bias connection fixture described in the present invention.

[0042] Figure 8 The figure is a schematic diagram of the circuit structure of the AC / DC coupling circuit of the present invention. DETAILED DESCRIPTION

[0043] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Example 1

[0045] like Figure 1 , Figure 2As shown, an electrical impedance measurement system with DC bias application and calibration functions includes: an AC signal generator, a DC signal generator, an AC / DC coupling circuit, an output source resistor, a DC bias integrated control system, and an impedance measurement fixture; wherein:

[0046] The AC signal generator is electrically connected to the DC signal generator via the AC / DC coupling circuit to provide an AC excitation signal and a DC bias signal to the component under test;

[0047] The AC / DC coupling circuit causes the output signal of the DC signal generator to be superimposed on the output signal of the AC signal generator, and simultaneously provides AC / DC signal excitation to the component under test;

[0048] The output source resistor is electrically connected to the output end of the AC / DC coupling circuit and is electrically connected to the element to be measured of the electrical impedance measurement system; the output source resistor transmits the AC / DC signal excitation to the element to be measured; the output source resistor is Rs, and the element to be measured is Zx;

[0049] The DC bias integrated control system is electrically connected to the AC signal generator, the DC signal generator, the output source resistor, and the element to be measured of the electrical impedance measurement system to form a DC bias feedback adjustment link of the electrical impedance measurement system;

[0050] The impedance measurement fixture is electrically connected to the device to be measured.

[0051] More specifically, the electrical impedance measurement system with DC bias application and calibration functions further includes a calibration module, which is fixed on the impedance measurement fixture as a component to be measured for calibration measurement before formal measurement.

[0052] More specifically, the calibration module includes: an open circuit calibration component, a short circuit calibration component and a load calibration component;

[0053] The open circuit calibration piece, short circuit calibration piece and load calibration piece are respectively fixed on the impedance measurement fixture as the elements to be measured before the formal measurement.

[0054] In a specific embodiment, the DC signal generator and the AC signal generator adjust the output AC and DC signal amplitudes and phases under the control of the DC bias integrated control system to provide AC and DC signal inputs to the DUT.

[0055] More specifically, the DC bias integrated control system includes a signal acquisition module and a signal processing module.

[0056] The signal acquisition module includes: an operational amplifier circuit, a filter circuit, and an analog-to-digital conversion circuit, which are used to collect the DC bias signal at both ends of the output source resistor and the component to be tested;

[0057] The signal processing module includes an FPGA, which is used to process the collected DC bias signal and adjust the output of the DC signal generator according to the design requirements.

[0058] The output end of the operational amplifier circuit is electrically connected to the input end of the filter circuit, and the output end of the filter circuit is electrically connected to the input end of the analog-to-digital conversion circuit; the input end of the operational amplifier circuit serves as the input end of the signal acquisition module, and the output end of the analog-to-digital conversion circuit serves as the output end of the signal acquisition module.

[0059] Example 2

[0060] In a specific embodiment, Figure 3 , Figure 4 As shown, the electrical impedance measurement system also includes an external DC bias connection fixture and an external DC bias source; the output end of the external DC bias source is electrically connected to the first input end of the external DC bias connection fixture; the second input end of the external DC bias connection fixture is electrically connected to the output end of the impedance measuring instrument; the output end of the external DC bias connection fixture is electrically connected to the input end of the impedance measuring fixture.

[0061] More specifically, Figure 5 As shown, the external DC bias connection fixture includes a DC bias signal mixing and protection circuit for isolation and protection.

[0062] More specifically, Figure 6 As shown, the DC bias signal mixing and protection circuit includes: an AC / DC signal mixing circuit, a DC bias isolation circuit and a DC bias protection circuit; the output end of the AC / DC signal mixing circuit is electrically connected to the input end of the DC bias isolation circuit; the output end of the DC bias isolation circuit is electrically connected to the input end of the DC bias protection circuit; the input end of the AC / DC signal mixing circuit serves as the input end of the DC bias signal mixing and protection circuit, and the output end of the DC bias protection circuit serves as the output end of the DC bias signal mixing and protection circuit; the DC bias signal mixing and protection circuit is an input end for AC signals and an output end for DC signals.

[0063] More specifically, the AC / DC signal mixing circuit allows the DC signal input into the external DC bias connection fixture by the external DC bias source to be mixed with the AC signal input into the external DC bias connection fixture by the impedance measuring instrument, and both are output to the impedance measuring fixture through the connection at the impedance measuring fixture end, and then applied to the component to be measured; the DC bias isolation circuit isolates the AC / DC signals to prevent the AC / DC signals from interfering with the output of the other signal source; the DC bias protection circuit is used to avoid damage to the impedance measuring instrument when an excessively large DC bias voltage is applied to the external DC bias connection fixture.

[0064] Example 3

[0065] In a specific embodiment, Figure 7 As shown, in the external DC bias connection fixture, the impedance measurement instrument end is connected to a coaxial four-port connection: Hc_i, Hp_i, Lc_i, Lc_i, the impedance measurement fixture end is connected to a coaxial four-port connection: Hc_o, Hp_o, Lc_o, Lc_o, and the external DC bias input connection is a coaxial single-port connection DCSignal. The rest is a DC bias signal mixing and protection circuit; Figure 7 As shown, the input of the external DC bias source couples the DC bias signal to the Hc_o and Hp_o ports through an inductor, a resistor or some combination structure, and at the same time isolates the interference of the AC excitation signal from the impedance measuring instrument on the external DC signal source. The outer layer of the coaxial line is directly grounded, connected to the outer layer of the four ports, or some other grounding method to construct a return path for the applied DC bias signal. The outer layer of the coaxial line is connected between the four ports Hc_i, Hp_i, Lc_i, and Lc_i of the coaxial line and the four ports Hc_o, Hp_o, Lc_o, and Lc_o to ensure good grounding and shielding of external interference. In the inner core of the coaxial line, the capacitor, resistor, and diode structure connected in series ensure that the AC excitation signal from the impedance measuring instrument passes normally, while isolating the external DC bias signal from entering the impedance measuring instrument to generate interference. The diode structure connected in series between the inner core of the coaxial line and the outer layer of the coaxial line can play a role in clamping protection. When excessive DC bias is applied to the connection at the end of the impedance measuring instrument due to improper operation or other reasons, the diode structure conducts the DC bias to the outer layer of the coaxial line to prevent damage to the impedance measuring instrument caused by excessive DC bias.

[0066] More specifically, Figure 8As shown, the AC / DC coupling circuit includes a DC blocking capacitor and a mutual inductor. The DC blocking capacitor and the AC signal generator are connected in series on the signal output chain of the AC / DC signal generator. The two ends of the DC blocking capacitor are electrically connected to the mutual inductor, and the other two ends of the mutual inductor are connected to the two ends of the DC signal generator. The DC signal generator applies a DC voltage to the two ends of the DC blocking capacitor through the mutual inductor. The DC voltage is superimposed on the AC voltage excitation generated by the AC signal generator on the link to form an AC / DC voltage excitation, which is applied to the two ends of the component to be tested.

[0067] In a specific implementation, the external DC bias connection fixture can be independent of the impedance measurement fixture, or the structure of the impedance measurement fixture can be made into it to serve as a fixture with the functions of applying DC bias and clamping the device under test.

[0068] In a specific implementation scheme, the external DC bias source can be included in the electrical impedance measuring instrument, outputting a DC bias signal in the form of a certain port output and connected to the external DC bias connection fixture, or it can be located outside the electrical impedance measuring system instrument and connected to the external DC bias connection fixture as an independent DC bias signal source.

[0069] In a specific embodiment, the impedance measurement system can be an electrical impedance measurement system based on the self-balancing bridge method, voltammetry method or bridge method, and the connection between the electrical impedance measurement system and the measurement port of the external measurement fixture can be four-port, three-port or two-port.

[0070] Obviously, the above embodiments of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. An electrical impedance measurement system with DC bias application and calibration functions, characterized in that: include: AC signal generator, DC signal generator, AC / DC coupling circuit, output source resistor, DC bias integrated control system, impedance measurement fixture; Among them: The AC signal generator is electrically connected to the DC signal generator via the AC / DC coupling circuit to provide an AC excitation signal and a DC bias signal to the component under test; The AC / DC coupling circuit causes the output signal of the DC signal generator to be superimposed on the output signal of the AC signal generator, and simultaneously provides AC / DC signal excitation to the component under test; The output source resistor is electrically connected to the output end of the AC / DC coupling circuit and is electrically connected to the element to be measured of the electrical impedance measurement system; the output source resistor transmits the AC / DC signal excitation to the element to be measured; The DC bias integrated control system is electrically connected to the AC signal generator, the DC signal generator, the output source resistor, and the element to be measured of the electrical impedance measurement system to form a DC bias feedback adjustment link of the electrical impedance measurement system; The impedance measurement fixture is electrically connected to the element to be measured; It also includes a calibration module, which is fixed on the impedance measurement fixture as a component to be measured to perform calibration measurement before formal measurement; The electrical impedance measurement system further comprises an external DC bias connection fixture and an external DC bias source; the output end of the external DC bias source is electrically connected to the first input end of the external DC bias connection fixture; the second input end of the external DC bias connection fixture is electrically connected to the output end of the impedance measuring instrument; the output end of the external DC bias connection fixture is electrically connected to the input end of the impedance measuring fixture; The external DC bias connection fixture comprises a DC bias signal mixing and protection circuit for isolation and protection; the external DC bias connection fixture has the functions of applying DC bias and clamping the component to be tested.

2. The electrical impedance measurement system with DC bias application and calibration functions according to claim 1, characterized in that: The calibration module includes: an open circuit calibration component, a short circuit calibration component and a load calibration component; The open circuit calibration piece, short circuit calibration piece and load calibration piece are respectively fixed on the impedance measurement fixture as the elements to be measured before the formal measurement.

3. The electrical impedance measurement system with DC bias application and calibration functions according to claim 1, characterized in that: The DC signal generator and the AC signal generator adjust the output AC and DC signal amplitudes and phases under the control of the DC bias integrated control system to provide AC and DC signal inputs to the device under test.

4. The electrical impedance measurement system with DC bias application and calibration functions according to claim 1, characterized in that: The DC bias integrated control system comprises a signal acquisition module and a signal processing module.

5. The electrical impedance measurement system with DC bias application and calibration functions according to claim 4, characterized in that: The signal acquisition module includes: an operational amplifier circuit, a filter circuit, and an analog-to-digital conversion circuit, which are used to collect the DC bias signal at both ends of the output source resistor and the component to be tested; The signal processing module includes an FPGA for processing the collected DC bias signal and adjusting the output of the DC signal generator according to the design requirements; The output end of the operational amplifier circuit is electrically connected to the input end of the filter circuit, and the output end of the filter circuit is electrically connected to the input end of the analog-to-digital conversion circuit; the input end of the operational amplifier circuit serves as the input end of the signal acquisition module, and the output end of the analog-to-digital conversion circuit serves as the output end of the signal acquisition module.

6. The electrical impedance measurement system with DC bias application and calibration functions according to claim 5, characterized in that: The DC bias signal mixing and protection circuit comprises: an AC / DC signal mixing circuit, a DC bias isolation circuit and a DC bias protection circuit; the output end of the AC / DC signal mixing circuit is electrically connected to the input end of the DC bias isolation circuit; the output end of the DC bias isolation circuit is electrically connected to the input end of the DC bias protection circuit; the input end of the AC / DC signal mixing circuit serves as the input end of the DC bias signal mixing and protection circuit, and the output end of the DC bias protection circuit serves as the output end of the DC bias signal mixing and protection circuit.

7. The electrical impedance measurement system with DC bias application and calibration functions according to claim 6, characterized in that: The AC / DC signal mixing circuit mixes the DC signal input into the external DC bias connection fixture by the external DC bias source and the AC signal input into the external DC bias connection fixture by the impedance measuring instrument, and outputs them to the impedance measuring fixture through the connection at the impedance measuring fixture end, and then applies them to the component to be measured; the DC bias isolation circuit isolates the AC / DC signals to prevent the AC / DC signals from interfering with the output of the other signal source; the DC bias protection circuit is used to prevent damage to the impedance measuring instrument when an excessively large DC bias voltage is applied to the external DC bias connection fixture.

8. The electrical impedance measurement system with DC bias application and calibration functions according to claim 1, characterized in that: The AC / DC coupling circuit includes a DC blocking capacitor and a mutual inductor. The DC blocking capacitor and the AC signal generator are connected in series on the signal output chain of the AC / DC signal generator. The two ends of the DC blocking capacitor are electrically connected to the mutual inductor, and the other two ends of the mutual inductor are connected to the two ends of the DC signal generator. The DC signal generator applies a DC voltage to the two ends of the DC blocking capacitor through the mutual inductor. The DC voltage is superimposed on the AC voltage excitation generated by the AC signal generator on the link to form an AC / DC voltage excitation, which is applied to the two ends of the component to be tested.

Images