Design, single calibration and measurement method of a radio frequency impedance measurement fixture

Abstract

This invention belongs to the field of electrical parameter measurement and discloses a design, single calibration and measurement method for a radio frequency impedance measurement fixture. The design method includes: adopting a symmetrical structure, using a coaxial SMA connector as the port for connection with a vector network analyzer (VNA), using a coplanar waveguide as the connection line between the SMA connector and the device under test (DUT), and setting four surface mount pads on the coplanar waveguide to realize a radio frequency impedance measurement fixture for DUTs with different packages and different impedance ranges.

Description

Technical Field

[0001] This invention relates to the field of electrical parameter measurement, specifically to the design, single calibration, and measurement method of a radio frequency impedance measurement fixture. Background Technology

[0002] At low frequencies, discrete electronic components such as resistors and capacitors, and the networks they form, can be considered ideal components. However, at high frequencies, their non-ideal characteristics begin to emerge, and their high-frequency models will be inaccurate if their parasitic parameters are not considered. It is necessary to obtain the non-ideal characteristics of these components as a reference for RF circuit design. For complex passive networks, their port impedances are difficult to calculate theoretically, so it is also necessary to measure their port impedances.

[0003] When an RF test system centered around an impedance analyzer or vector network analyzer (VNA) and the device under test (DUT) both have coaxial connectors, connecting them for measurement is straightforward. However, because RF components come in various sizes and shapes, such as surface mount and through-hole components, no single connector type can be suitable for all situations. In such cases, a measurement fixture needs to be designed to act as the electrical and mechanical interface between the RF test system and the DUT.

[0004] Existing PCB-based impedance measurement fixtures can only be used for DUTs of one package or size. Furthermore, there are multiple impedance measurement methods for different frequencies and impedance ranges. Therefore, it is necessary to design multiple fixtures to meet different measurement requirements, which complicates the selection and usage process of impedance measurement fixtures and is not conducive to the rapid acquisition of component impedance information.

[0005] When performing impedance measurements, the influence of the impedance measurement fixture itself cannot be ignored; therefore, the fixture should be calibrated to eliminate its influence. Currently used calibration methods, such as the SOLT calibration method (which requires short-circuiting, open-circuiting, and terminating load calibrations at both ports of the measurement fixture, as well as two-port pass-through calibration) and the TRL calibration method (which requires two-port pass-through calibration, port short-circuit / open-circuit calibration, and time-delay transmission line calibration), require multiple operations and the fabrication of multiple PCBs. While these methods achieve higher accuracy over a wider frequency band, they are complex to operate and calculate. It is necessary to simplify the calibration process while meeting the required accuracy. Summary of the Invention

[0006] To address the above technical problems, this invention provides a design, single-cycle calibration, and measurement method for an RF impedance measurement fixture.

[0007] This invention provides a design method for a radio frequency impedance measurement fixture, the design method comprising:

[0008] The device employs a symmetrical structure, using a coaxial SMA connector as the port for connecting to a vector network analyzer (VNA). A coplanar waveguide serves as the connection line between the SMA connector and the device under test (DUT). Four surface mount pads are set on the coplanar waveguide to realize an RF impedance measurement fixture for DUTs with different packages and impedance ranges.

[0009] The present invention also provides a radio frequency impedance measurement fixture, comprising: a left half M of the fixture. L The left half of the fixture includes the SMA connector and the coplanar waveguide connected to it, and the right half M of the fixture. R With the left half M L Symmetrical, the right half has four additional surface mount pads on the coplanar waveguide, and the middle part is M. DUT This is the network of the device under test (DUT).

[0010] The present invention also provides a single calibration method for a radio frequency impedance measurement fixture, the calibration method being used to perform a single calibration of the radio frequency impedance measurement fixture, comprising:

[0011] The two-port direct connection of the measurement calibration fixture to the S-parameter is used to calibrate the S-parameter.

[0012] Convert the calibration S-parameters to the calibration Z-parameters to obtain the equivalent circuit diagram of the Z-parameters;

[0013] The Z-parameter equivalent circuit diagram is symmetrically divided to obtain the Z-parameters of half of the calibration fixture;

[0014] The Z-parameters of half of the calibration fixture are transformed into an ABCD matrix to achieve the de-embedding of the system impedance, and finally the impedance spectrum of the device under test (DUT) is obtained.

[0015] Preferably, the two-port pass-through S-parameters of the calibration fixture are measured by soldering copper sheets of the same width as the intermediate signal line to both ends of the signal line, thereby achieving two-port pass-through and measuring the two-port S-parameters of the calibration fixture.

[0016] Preferably, converting calibration S-parameters to calibration Z-parameters includes:

[0017]

[0018] In the formula, Z C11 ~Z C22 The Z-parameters of the impedance measurement fixture are for the two-port straight-through configuration; S C11 ~S C22 Z0 represents the S-parameters of the two-port straight-through impedance measurement fixture; Z0 is the characteristic impedance, typically taken as 50Ω.

[0019] Preferably, the symmetrical segmentation of the Z-parameter equivalent circuit diagram includes:

[0020] Z-parameter matrix of the left half of the fixture:

[0021]

[0022] The designed fixture is approximately symmetrical; therefore, the right half of the fixture is simply the left half with its two ends reversed.

[0023]

[0024] Preferably, transforming the Z-parameters of half the calibration fixture into an ABCD matrix includes:

[0025]

[0026] This invention also discloses a measurement method for an RF impedance measurement fixture, wherein the measurement method utilizes a single-calibrated RF impedance measurement fixture to perform impedance measurement, comprising:

[0027] Measure the system S-parameters of the calibration fixture-DUT;

[0028] Convert the system S-parameters into an ABCD matrix;

[0029] If the impedance measurement method is the series / parallel direct-through method, the ABCD parameter matrix of half of the calibration fixture is used to obtain the ABCD matrix of the device under test (DUT), and the impedance of the DUT is obtained from the ABCD matrix of the DUT.

[0030] If the impedance measurement method is the reflection method, the system S-parameters are converted into Z-parameters. Combined with the equivalent circuit diagram of the calibration Z-parameters, circuit analysis is performed on the system to obtain the impedance of the device under test (DUT).

[0031] Preferably, the ABCD matrix of the device under test (DUT) includes:

[0032] By M DUT Obtain the impedance Z of the device under test (DUT). DUT include:

[0033] For the series through-calibration method:

[0034]

[0035] For the parallel direct calibration method:

[0036]

[0037] Among them, Y DUT The admittance of the device under test (DUT) is the impedance Z of the DUT. DUT The reciprocal of.

[0038] Preferably, if the impedance measurement method is the reflection method, the impedance of the device under test (DUT) includes:

[0039] Convert the S-parameters of the two-port straight-through fixture into Z-parameters. These Z-parameters correspond to the input impedance of port 1 of the system when port 2 is short-circuited.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] This invention employs a symmetrical structure, using a coaxial SMA connector as the port for connection with a vector network analyzer (VNA), and a coplanar waveguide as the connection line between the SMA connector and the device under test (DUT). In addition, four surface mount pads are provided on the coplanar waveguide to accommodate different electronic components and different measurement methods, thereby enabling impedance measurement of DUTs with different packages and impedance ranges on the same fixture.

[0042] This invention obtains the calibration information by measuring the S-parameters of the designed fixture's two-port pass-through network. Through conversions between S-parameters, Z-parameters, and ABCD parameters, as well as matrix operations, the system impedance is de-embedded, ultimately yielding the impedance spectrum of the device under test (DUT). This calibration method requires only a single measurement to acquire the necessary calibration data, thus simplifying the calibration process while meeting the required accuracy. Attached Figure Description

[0043] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 The present invention provides three methods for measuring impedance using a VNA, wherein (a) is the reflection method, (b) is the series direct-through method, and (c) is the parallel direct-through method.

[0045] Figure 2 This diagram illustrates the applicable impedance amplitude and frequency range for the three methods of VNA impedance measurement according to embodiments of the present invention.

[0046] Figure 3 This is a schematic diagram of the cascaded ABCD matrix of the impedance measurement fixture and the device under test according to an embodiment of the present invention;

[0047] Figure 4 This is a structural diagram of the measuring fixture according to an embodiment of the present invention;

[0048] Figure 5 This is a schematic diagram of the Z-matrix equivalent circuit of the measuring fixture according to an embodiment of the present invention;

[0049] Figure 6 The equivalent circuit diagrams for impedance measurement using the series direct-through method, reflection method, and parallel direct-through method according to embodiments of the present invention are shown below.

[0050] Figure 7 This is a flowchart illustrating the calibration and measurement process of the impedance measurement fixture according to an embodiment of the present invention.

[0051] Figure 8 This is a schematic diagram of a three-dimensional electromagnetic simulation model of the measuring fixture according to an embodiment of the present invention;

[0052] Figure 9 This is a comparison chart of the impedance measurement results before and after calibration using the series direct-through method according to an embodiment of the present invention, and the theoretical values.

[0053] Figure 10 This is a comparison chart of the results before and after calibration of the impedance measurement using the reflection method according to an embodiment of the present invention, and the theoretical values.

[0054] Figure 11 This is a comparison chart of the impedance measurement results before and after calibration using the parallel direct-through method according to an embodiment of the present invention, and the theoretical values. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this disclosure should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," and similar terms used in the embodiments of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0057] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] Example 1

[0059] This invention provides a design, single calibration, and measurement method for a radio frequency impedance measurement fixture.

[0060] This invention employs a symmetrical structure, using a coaxial SMA connector as the port for connection with a vector network analyzer (VNA), and a coplanar waveguide as the connection line between the SMA connector and the device under test (DUT). In addition, four surface mount pads are provided on the coplanar waveguide to accommodate different electronic components and different measurement methods, thereby enabling impedance measurement of DUTs with different packages and impedance ranges on the same fixture.

[0061] This invention obtains the calibration information by measuring the S-parameters of the designed fixture's two-port pass-through network. Through conversions between S-parameters, Z-parameters, and ABCD parameters, as well as matrix operations, the system impedance is de-embedded, ultimately yielding the impedance spectrum of the device under test (DUT). This calibration method requires only a single measurement to acquire the necessary calibration data, thus simplifying the calibration process while meeting the required accuracy.

[0062] VNA impedance measurement principle:

[0063] A VNA (Variable Frequency Amplifier) ​​is a high-performance measurement instrument widely used in the testing and analysis of microwave and radio frequency circuits. It accurately measures parameters such as amplitude-frequency characteristics, phase-frequency characteristics, and impedance characteristics of circuits, providing crucial test data support for circuit design, debugging, and optimization.

[0064] The measurement principle of VNA is to use the amplitude and phase information of vector signals to calculate the S-parameters of the circuit under test by measuring the reflection coefficient and transmission coefficient, thereby obtaining various characteristic parameters of the circuit, including impedance, gain, phase, etc.

[0065] There are three impedance measurement methods based on VNA: reflection method, series straight-through method, and parallel straight-through method, with corresponding connection methods as follows: Figure 1 (a)- Figure 1 As shown in (c). The three methods described above will be introduced below.

[0066] (1) Reflection method:

[0067] The reflection coefficient of the test piece is measured using the reflection method. Reflection coefficient Γ x (S 11 The relationship between the impedance and the port impedance is as follows:

[0068]

[0069] Among them, Z o It is the characteristic impedance of the measuring circuit, typically taken as 50Ω; Z xThis is the impedance of the DUT. According to the formula, the measured reflection coefficient follows the impedance (Z). x The variation ranges from -1 to 1. In Z... x Equal to Z o The highest accuracy can be obtained at this time. The further the impedance is from the characteristic impedance point, the slower the rate of change of the reflection coefficient curve, resulting in a decrease in impedance measurement accuracy. Impedance is calculated using the following formula:

[0070]

[0071] The accurate impedance measurement range of the reflection method is typically 2Ω to 1.5kΩ (depending on the required accuracy and measurement frequency).

[0072] (2) Series Straight-Through Method:

[0073] The series pass-through method measures impedance by connecting the DUTs in a "series transmission". Series pass-through is most effective when measuring high impedance values: 10% accuracy is achieved over a range of approximately 5Ω to 20kΩ, about ten times higher than the reflection method. Impedance is calculated using the following formula:

[0074]

[0075] (3) Parallel direct connection method:

[0076] The parallel through-through method measures impedance by connecting the DUTs in a "parallel through-through" configuration. This method is suitable for testing low impedances and is typically used for measurements in the milliohm range. An accuracy of 10% is achieved from 1 mΩ to 10 Ω, which is below the range achievable by typical impedance analyzers. Impedance is calculated using the following formula:

[0077]

[0078] The above three methods can roughly cover the measurement of impedance in different ranges, and the corresponding ranges are as follows: Figure 2 As shown.

[0079] However, it is important to note that impedance measurement fixtures are affected by factors such as the transition from coaxial line to coplanar waveguide and from coplanar waveguide to DUT, the distributed inductance of the traces themselves, the distributed capacitance between the traces and ground, and the machining accuracy. These factors cannot be considered insignificant, especially under high-frequency conditions. Therefore, the fixtures should be calibrated to eliminate test result errors caused by these factors.

[0080] Calibration principle: Figure 3 and Figure 4 The figures show the cascaded ABCD matrix diagram and structural diagram of the designed impedance measurement fixture. The left half of the fixture, M... L Includes the left half of the SMA connector and the coplanar waveguide connected to it, and the right half of the clamp M. RSymmetrical to the left half (the additional pads on the right half are only used for impedance measurement using the parallel through-through method and do not change the electrical performance of the coplanar waveguide). Middle part M DUT This represents the device under test (DUT) network. The ABCD matrix of the entire impedance measurement system is...

[0081] M C =M L M DUT M R

[0082] It should be added that if the parallel direct-through method is used to measure impedance, since the actual length of the test piece deviating from the center is small, the fixture is considered to be an approximately symmetrical structure. In this case, the same calibration method is still effective in the lower frequency band, and M... DUT correspond Figure 4 The weld joint of the test piece in the parallel direct-through method.

[0083] To obtain the true impedance information of the device under test, the left half of M should be excluded. L With the right half of M R Interference. Various circuit matrices are used to characterize circuit information, such as the Z matrix, Y matrix, ABCD matrix, and S-parameter matrix. Because ABCD matrices can be cascaded, they are beneficial for M... L With M R To avoid embedding, an ABCD matrix is ​​used to represent the information of the impedance measurement fixture. The ABCD matrix is ​​shown below:

[0084]

[0085] Wherein, V1 and I1 are the network input voltage and current, and their reference directions are non-associated reference directions; V2 and I2 are the network output voltage and current, and their reference directions are associated reference directions.

[0086] During calibration, copper sheets of the same width as the intermediate signal line are soldered to both ends of the signal line to achieve two-port pass-through and measure the two-port S-parameters of the entire system.

[0087] The copper sheet can be considered as a short-circuited device under test, and the corresponding ABCD matrix is ​​as follows:

[0088]

[0089] At this point, the matrix of the entire system is:

[0090] M C =M L M R

[0091] The designed fixture is symmetrical on both sides. In a two-port network, the Z-matrix has a corresponding equivalent circuit. If the Z-parameter matrix can be obtained, it is convenient to perform calculations using circuit theory. Therefore, the S-parameters of the two-port straight-through fixture are converted into Z-parameters:

[0092]

[0093]

[0094] In the formula, Z C11 ~Z C22 The Z-parameters of the impedance measurement fixture are for the two-port straight-through configuration; S C11 ~S C22 Z0 represents the S-parameters of the two-port straight-through impedance measurement fixture; Z0 is the characteristic impedance, typically taken as 50Ω.

[0095] like Figure 5 The equivalent circuit of the Z matrix of the impedance measurement fixture is obtained, and the equivalent circuit is divided into two parts to obtain the Z parameter matrix of half of the fixture (left half):

[0096]

[0097] The designed fixture is approximately symmetrical; therefore, the right half of the fixture is simply the left half with its two ends reversed.

[0098]

[0099] Convert the Z matrix to an ABCD matrix:

[0100]

[0101] From the above formula, M L and M R All of these can be determined. It should be noted that although the structures on both sides of the fixture are identical, the corresponding port configurations differ; therefore, M... L and M R If they are not equal, the ports should be swapped to convert them to each other.

[0102]

[0103] At this point, remove the shorting copper strip and replace it with the DUT. For series and parallel through-calibration methods, the ABCD matrix M of the network under test is... DUT It is easy to see that M is among them. L -1 and M R -1 For the above M L and M R Inverse matrix:

[0104]

[0105] M can be DUT Obtain the impedance Z of the DUT DUT The equivalent circuit diagrams for the three impedance measurement methods are as follows: Figure 6 As shown.

[0106] For the series through-calibration method:

[0107]

[0108] For the parallel direct calibration method:

[0109]

[0110] Y in the above formula DUT The admittance of the device under test (DUT) is the impedance Z of the DUT. DUT The reciprocal of.

[0111] Impedance calculation using the reflection method is slightly complex, but it can be derived through circuit analysis. First, the S-parameters of the two-port straight-through fixture are converted to Z-parameters. These Z-parameters correspond to the input impedance of port 1 of the system when port 2 is short-circuited. Then, from... Figure 6 The circuit shown in (b) can be used to calculate Z. DUT :

[0112]

[0113] in, Z in To measure the input impedance of the fixture-test system, S 11_ref These are the corresponding single-port reflection parameters, which are directly measured data; a = Z C11 -Z C12 b = 2·Z C12 .

[0114] The calibration and measurement flowchart for the impedance measurement fixture is shown below. Figure 7 .

[0115] The technical solution of this invention, such as Figure 8 As shown, the performance of the designed impedance measurement fixture was verified using the 3D electromagnetic simulation software HFSS. To fully verify the performance of the fixture under each function, the following test scheme was adopted, corresponding to the impedance range applicable to the three impedance measurement methods, with a test frequency band of 100kHz-200MHz:

[0116] 1. Reflection method: Test a network of 2Ω resistor in series with 1uH inductor and 0.3nF capacitor in parallel.

[0117] 2. Series through-through method: Test a network of 15kΩ resistor in series with 100uH inductor and 8pF capacitor in parallel.

[0118] 3. Parallel direct connection method: Test a series network of a 0.01Ω resistor, a 50nH inductor, and a 50nF capacitor.

[0119] The test results of the three schemes are as follows Figures 9-11 As shown in the figure. The results show that the calibration method proposed in this invention significantly improves the impedance curve of the DUT. The error between the impedance amplitude of the calibrated component and the theoretical value is within 5%, and the phase error is within 1%, which can meet the impedance testing requirements of the 100kHz-200MHz frequency band.

[0120] Example 2

[0121] This embodiment provides a method for measuring and calculating the impedance of a DUT using a radio frequency impedance measurement fixture, including:

[0122] 1) Measurement of S-parameters of the two-port straight-through fixture and the S-parameters of the fixture-DUT system

[0123] Impedance measurement system such as Figure 3 As shown, the system consists of a VNA, the designed impedance measurement fixture, a DUT, and necessary connecting cables. The VNA used is configured, calibrated, and measured on a host computer via Virtual Instruments Software Architecture (VISA).

[0124] When the VNA is operating, port 1 injects a stepped-sweep sinusoidal excitation signal into the impedance measurement system via an SMA connector. Simultaneously, ports 1 and 2 detect the received RF signal responses. The ratio of the signals received at ports 1 and 2 to the excitation signal emitted by port 1 is the reflection coefficient S. 11 With transmission coefficient S 21 Similarly, the reflection coefficient S corresponding to the excitation signal transmitted at port 2 22 With transmission coefficient S 12 The combination of the above coefficients constitutes the two-port S-parameters. The host computer controls the VNA to measure and saves the S-parameters as a .snp file for subsequent data processing.

[0125] First, perform initial setup and calibration of the VNA. Initial setup includes setting the start and end frequencies, intermediate frequency bandwidth, input power, number of scan points, etc. The VNA is calibrated using SOLT calibration, and the VNA's built-in SOLT algorithm will complete the calibration to the VNA coaxial cable end.

[0126] Solder copper sheets onto the signal lines of the impedance measurement fixture to put the fixture in a two-port pass-through state. Connect the two ports of the fixture to the two ports of the VNA respectively, and measure its S-parameters (called calibration S-parameters).

[0127] Replace the copper sheet with a DUT and repeat the above process to measure the S-parameters (referred to as system S-parameters).

[0128] 2) Calculate the DUT impedance from the measured S-parameters.

[0129] Depending on the impedance measurement method, the DUT impedance data is calculated from the measured S-parameters. The calculation process is as follows: Figure 7 The relevant calculation formulas can be found in the technical solutions. Corresponding programs can be written in Python for batch data processing.

[0130] It should be noted that the method of this disclosure embodiment can be executed by a single device, such as a computer or server. The method of this embodiment can also be applied to a distributed scenario, where multiple devices cooperate to complete the task. In such a distributed scenario, one of these devices may execute only one or more steps of the method of this disclosure embodiment, and the multiple devices will interact with each other to complete the method described.

[0131] It should be noted that the above description describes some embodiments of this disclosure. Other embodiments are within the scope of the appended claims. In some cases, it should be understood that the sequence number of each step in the above embodiments does not imply the order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention. The actions or steps recorded in the claims can be performed in a different order than that in the above embodiments and can still achieve the desired result. In addition, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0132] This disclosure is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A single calibration method for a radio frequency impedance measurement fixture, the calibration method being used to perform a single calibration of the radio frequency impedance measurement fixture, comprising: The two-port direct connection of the measurement calibration fixture to the S-parameter is used to calibrate the S-parameter. Convert the calibration S-parameters to the calibration Z-parameters to obtain the equivalent circuit diagram of the Z-parameters; The Z-parameter equivalent circuit diagram is symmetrically divided to obtain the Z-parameters of half of the calibration fixture; The Z-parameters of half of the calibration fixture are transformed into an ABCD matrix to achieve the de-embedding of the system impedance, and finally the impedance spectrum of the device under test (DUT) is obtained. Symmetrical partitioning of the Z-parameter equivalent circuit diagram includes: Z-parameter matrix of the left half of the fixture: ， The designed fixture is approximately symmetrical; therefore, the right half of the fixture is simply the left half with its two ends reversed. ； The transformation of the Z-parameters of half of the calibration fixture into an ABCD matrix includes: ； In the formula, Z-parameters for the two-port straight-through impedance measurement fixture; The radio frequency impedance measurement fixture adopts a symmetrical structure, with a coaxial SMA connector as the port for connecting to the vector network analyzer (VNA), and a coplanar waveguide as the connection line between the SMA connector and the device under test (DUT). Four surface mount pads are set on the coplanar waveguide to realize the radio frequency impedance measurement fixture for DUTs with different packages and different impedance ranges. The left half of the clamp M L The left half of the fixture includes the SMA connector and the coplanar waveguide connected to it, and the right half M of the fixture. R With the left half M L Symmetrical, the right half has four additional surface mount pads on the coplanar waveguide, and the middle part is M. DUT The device under test (DUT) network; The radio frequency impedance measurement fixture is also known as a calibration fixture or a clamp.

2. The method according to claim 1, characterized in that, The two-port pass-through S-parameters of the calibration fixture are measured by soldering copper sheets of the same width as the intermediate signal line to both ends of the signal line, thereby achieving two-port pass-through and measuring the two-port S-parameters of the calibration fixture.

3. The method according to claim 1, characterized in that, Converting calibration S-parameters to calibration Z-parameters includes: ， ， ， ， In the formula, Z-parameters for the two-port straight-through impedance measurement fixture; The S-parameters of the impedance measurement fixture are for the two-port straight-through connection. The characteristic impedance is 50Ω.

4. A measurement method for an RF impedance measuring fixture, wherein the measurement method utilizes the RF impedance measuring fixture calibrated once according to claim 1 to perform impedance measurement, characterized in that, include: Measure the system S-parameters of the calibration fixture-DUT; Convert the system S-parameters into an ABCD matrix; If the impedance measurement method is the series / parallel direct-through method, the ABCD parameter matrix of half of the calibration fixture is used to obtain the ABCD matrix of the device under test (DUT), and the impedance of the DUT is obtained from the ABCD matrix of the DUT. If the impedance measurement method is the reflection method, the system S-parameters are converted into Z-parameters. Combined with the equivalent circuit diagram of the calibration Z-parameters, circuit analysis is performed on the system to obtain the impedance of the device under test (DUT).

5. The measurement method according to claim 4, characterized in that, The ABCD matrix of the device under test (DUT) includes: ; By M DUT Obtain the impedance Z of the device under test (DUT). DUT include: For the series through-calibration method: ， For the parallel direct calibration method: ， in, Y DUT The admittance of the device under test (DUT) is denoted as , and the impedance of the DUT is deno Z DUT The reciprocal of.

6. The measurement method according to claim 4, characterized in that, If the impedance measurement method is the reflection method, the impedance of the device under test (DUT) includes: Convert the S-parameters of the two-port straight-through fixture into Z-parameters. These Z-parameters correspond to the input impedance of port 1 of the system when port 2 is short-circuited.

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