A scattering parameter online measurement device using a single inductive coupler and a distortion compensation method

Abstract

The present invention discloses an online scattering parameter measurement device and a distortion compensation method using a single inductive coupler, and relates to the field of inductive coupling measurement of scattering parameters of a device under test. The device comprises: a signal processing system, a vector network analyzer (VNA), an inductive coupler, a limiting insulating column, a device under test (DUT), and a power supply. The signal processing system establishes a communication connection with the vector network analyzer (VNA) via a miniUSB cable, controls the vector network analyzer (VNA) to perform measurement, and transmits and processes measured data. The vector network analyzer (VNA) is connected to the inductive coupler via an N-type connector, and a swept-frequency sinusoidal excitation signal is injected into the inductive coupler to measure the scattering parameters of the device under test (DUT). The limiting insulating column is sheathed on a power line to limit the position of the inductive coupler so that the power line passes through the center of a coupling window of the inductive coupler. The power supply is used to power the device under test (DUT).

Description

Technical Field

[0001] The present invention belongs to the field of inductive coupling measurement of scattering parameters of a device to be measured, and in particular relates to an online scattering parameter measurement device using a single inductive coupler and a distortion compensation method. Background Art

[0002] Inductively coupled contactless communication technology for broadband signals is widely used in power line communication (PLC), electromagnetic compatibility testing, contactless / online diagnosis of equipment failures, partial discharge (PD) monitoring, and other fields. Inductively coupled devices, such as inductive couplers, high current injection probes, detection probes, high-frequency current sensors (HFCTs), and Rogowski coils, are used for contactless signal communication. This avoids direct electrical connection between the measuring instrument and the device under test (DUT), protects the equipment and operators, and enables live measurement of scattering parameters of equipment and systems. However, inductively coupled devices are considered to be a type of RF transformer, and the signals transmitted through these devices are significantly distorted, which adversely affects the measurement of the scattering parameters of the DUT. Therefore, it is necessary to study the distortion formation mechanism and compensate for the distortion.

[0003] Traditional inductively coupled scattering parameter measurements primarily use a dual-coupler configuration, with one coupler for signal injection and one for signal reception. Traditional inductively coupled dual-coupler scattering parameter measurement setups suffer from high costs and electromagnetic interference between probes. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention proposes an online scattering parameter measurement device and a distortion compensation method using a single inductive coupler. The proposed online scattering parameter measurement scheme using a single coupler can reduce costs and avoid electromagnetic interference problems. The proposed signal distortion compensation scheme for a single coupler can make the scattering parameters measured online in situ equivalent to the scattering parameters measured offline.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A scattering parameter online measurement device using a single inductive coupler comprises: a signal processing system, a vector network analyzer (VNA), an inductive coupler, and a limiting insulating column;

[0007] The signal processing system establishes a communication connection with the vector network analyzer VNA via a miniUSB cable, controls the vector network analyzer VNA to perform measurements, and transmits and processes the measured data;

[0008] The vector network analyzer VNA is connected to the inductive coupler via an N-type connector, and a swept frequency sinusoidal excitation signal is injected into the inductive coupler to measure the scattering parameters of the device under test (DUT);

[0009] The limiting insulating column is sleeved on the power line to limit the position of the inductive coupler so that the power line passes through the center of the coupling window of the inductive coupler; wherein, the power line is used to connect the device under test (DUT) and the power supply.

[0010] The present invention also provides a scattering parameter distortion compensation method using a single inductive coupler, which is implemented by applying the scattering parameter online measurement device using a single inductive coupler, and includes the following steps:

[0011] Connect the lines according to the measuring device;

[0012] Characterize the measurement device as a two-port network;

[0013] Measure the scattering parameters of the coupler and the device under test as a whole;

[0014] Based on the measured scattering parameters of the coupler and the device under test as a whole and the two-port network characterization measurement device, the coupler port voltage and port current are obtained;

[0015] The measurement is based on a dedicated fixture and a vector network analyzer (VNA) to measure the scattering matrix of the coupler;

[0016] Converting the scattering matrix into a transfer matrix;

[0017] Acquire the port voltage and port current of the device under test based on the coupler port voltage and port current and the transfer matrix;

[0018] Obtaining the input impedance of the device under test based on the port voltage and port current of the device under test;

[0019] Based on the input impedance of the device under test, actual scattering parameters of the device under test are obtained to complete distortion compensation.

[0020] Preferably, the method for obtaining the coupler port voltage and port current includes:

[0021]

[0022] Among them, V s , Z0 represent the source voltage and reference impedance of the vector network analyzer respectively, S 11 is the scattering parameter of the entire system under test.

[0023] Preferably, the method of converting the scattering matrix into a transfer matrix is:

[0024]

[0025] Among them, S P11 and S P22 The return loss at both ends of the coupler, S P12 and S P21 represents the insertion loss of the coupler, and Z0 represents the 50Ω reference impedance.

[0026] Preferably, the method for obtaining the port voltage and port current of the device under test includes:

[0027]

[0028] Among them, V DUT and I DUT Respectively represent the port voltage and port current of the device under test, T P -1 Indicates T P The inverse matrix of .

[0029] Preferably, the method for obtaining the input impedance of the device under test includes:

[0030]

[0031] Preferably, the method for obtaining actual scattering parameters of the device under test based on the input impedance of the device under test and completing distortion compensation includes:

[0032]

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This invention proposes an online scattering parameter measurement scheme based on a single coupler. This reduces costs, avoids mutual electromagnetic interference between the couplers in a dual-coupler configuration, and enables in-situ online measurement of scattering parameters, rather than the limited practical utility of non-contact measurement. Furthermore, this invention proposes a scheme to compensate for the distortion caused by signal transmission through the coupler, making the scattering parameters measured online, in-situ, using the coupler, equivalent to those measured offline using a connector. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 Schematic diagram of an online scattering parameter measurement device based on a frequency domain single coupler according to an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of a coupler scattering matrix measurement configuration according to an embodiment of the present invention;

[0038] Figure 3 Schematic diagram of an equivalent circuit model of a single coupler device according to an embodiment of the present invention;

[0039] Figure 4 1 is a flow chart of a scattering parameter distortion compensation method using a single inductive coupler according to an embodiment of the present invention;

[0040] Figure 5 A schematic diagram of scattering parameters measured online using a coupler but without distortion compensation according to an embodiment of the present invention;

[0041] Figure 6 Schematic diagram of scattering parameters for online measurement and distortion compensation using a coupler according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Example 1

[0045] like Figure 1 As shown, the present invention provides an online scattering parameter measurement device using a single inductive coupler. The entire measurement device consists of a signal processing system, a vector network analyzer (VNA), an inductive coupler, a limiting insulating column, a device under test (DUT), and its power supply. The signal processing system establishes a communication connection with the VNA via a miniUSB cable, controls the VNA to perform measurements, and transmits and processes the measured data. The VNA connects to the inductive coupler via an N-type connector and injects a swept-frequency sinusoidal excitation signal into the coupler to measure the scattering parameter S. 11 A clamp-type, insulated stopper is positioned over the power cable (non-ground side). Its inner diameter is approximately equal to the outer diameter of the power cable, and its outer diameter is approximately equal to the inner diameter of the coupler. It functions to position the inductive coupler, ensuring that the power cable passes through the center of the coupler's coupling window. During measurement, the power supply normally supplies power to the DUT. Therefore, the present invention's measurement method is essentially in-situ, online, meaning it does not alter the DUT's original connection configuration or interfere with its normal operation.

[0046] Example 2

[0047] like Figure 4 As shown, the present invention also provides a scattering parameter distortion compensation method using a single inductive coupler, which is implemented by applying the scattering parameter online measurement device using a single inductive coupler, and includes the following steps:

[0048] Connect the lines according to the measuring device;

[0049] Characterize the measurement device as a two-port network;

[0050] Measure the scattering parameters of the coupler and the device under test as a whole;

[0051] Based on the measured scattering parameters of the coupler and the device under test as a whole and the two-port network characterization measurement device, the coupler port voltage and port current are obtained;

[0052] The measurement is based on a dedicated fixture and a scattering matrix of a vector network measurement coupler;

[0053] Converting the scattering matrix into a transfer matrix;

[0054] Acquire the port voltage and port current of the device under test based on the coupler port voltage and port current and the transfer matrix;

[0055] Obtaining the input impedance of the device under test based on the port voltage and port current of the device under test;

[0056] Based on the input impedance of the device under test, actual scattering parameters of the device under test are obtained to complete distortion compensation.

[0057] The measurement steps are as follows:

[0058] (1) According to Figure 1 The device shown measures the scattering parameter S of the entire system under test 11 , S 11 Measurement method: First, set the measurement frequency, output power, number of scan points, and intermediate frequency bandwidth of the vector network analyzer, and perform OSL calibration on the vector network analyzer. Then follow Figure 1 Connect the measurement system. Finally, the signal processing system controls the vector network analyzer to measure and save the overall S 11 Due to the influence of the coupler, S 11 There is a large distortion, and S 11 To make compensation, the compensation steps are as follows.

[0059] (2) Figure 2 As shown, the scattering matrix S that characterizes the transmission characteristics of the inductive coupling probe is measured P , SP Measurement process: The measurement configuration is as follows: Figure 3 As shown, first place the inductive coupler on a dedicated fixture and ensure that the inner conductor of the fixture passes through the center of the coupling window of the inductive coupler. In order to implement the measurement, the coupler is placed on the fixture, the coupler signal injection port is port 1, and the two ports of the fixture are port 2 and port 3. Here, port 1 and port 2 are connected to port 1 and port 2 of the VNA respectively, and port 3 is connected to the 50Ω load terminal. Secondly, set the measurement frequency, output power, number of sweep points, and intermediate frequency bandwidth of the vector network analyzer, and perform OSLT calibration on the vector network analyzer. Finally, connect port 1 of the vector network analyzer to the coupler signal injection port, connect port 2 of the vector network analyzer to the right port of the fixture, measure and save S P .

[0060] (3) The measured scattering matrix S P The conversion is the transfer matrix T P The conversion relationship is as follows:

[0061]

[0062] In the above formula, S P11 、S P12 、S P21 and S P22 represents the scattering parameters in the scattering matrix, where S P11 and S P22 Represent the return loss at both ends of the coupler, S P12 and S P21 represents the insertion loss of the coupler, and Z0 represents the 50Ω reference impedance.

[0063] (4) Figure 1 The device shown is characterized as Figure 2 The two-port network equivalent circuit shown is called two-port network characterization. The specific equivalent process is to firstly convert the vector network analyzer into a power supply V s The Thevenin equivalent circuit of Z0 in series, secondly, the coupler is equivalent to a two-port network, and the scattering matrix S is used p and the transfer matrix T p Characterization, the third is to use a one-port network to characterize the device under test, and then connect the various parts to complete the two-port network characterization of the entire measurement device. s , Z0 represent the source voltage and reference impedance of the vector network analyzer respectively; V P and I P Represent the voltage and port current of the coupler port respectively; V DUT and I DUT Represent the port voltage and port current of DUT respectively.

[0064] (5) Compensation coupler to S 11 To obtain the distortion caused by the DUT, we need to obtain the real scattering parameters of the DUT, which is equivalent to obtaining the DUT input impedance and then obtaining the scattering parameters based on the input impedance. To obtain the DUT input impedance, we need to obtain the DUT port signal V DUT and I DUT To obtain the port voltage of the DUT, you need to first obtain the port signal V of the coupler. P and I P , the port signal of the coupler can be obtained by formula (2).

[0065]

[0066] (6) In order to obtain the input impedance of the DUT, the port voltage V DUT and I DUT Being needed, V DUT and I DUT It can be obtained by formula (3), where T P -1 Indicates T P The inverse matrix of .

[0067]

[0068] (7) According to the obtained V DUT and I DUT , the input impedance of the DUT can be obtained by equation (4).

[0069]

[0070] (8) According to the obtained DUT input impedance Z inDUT , the actual scattering parameter S of the DUT DUT11 It can be obtained by formula (5). Through the above steps, the compensation of the distortion caused by the coupler is completed, that is, from the directly measured, distorted S 11 The actual scattering parameter S of the DUT is obtained DUT11 .

[0071]

[0072] Example 3

[0073] Taking a single coupler as an example, the technical effect of the present invention is verified through experiments. The measuring instrument used in the experiment is a vector network analyzer; an arbitrary waveform generator is used to provide power, the peak-to-peak voltage of the power supply is 10Vpp, and the frequency is 50Hz; the inductive coupler uses a laboratory-made large current injection probe and detection probe; the DUT is a 100-meter coaxial cable with an open cable terminal. In order to verify the technical effect of the present invention, the DUT is directly connected to the vector network analyzer without using a coupler, and the scattering parameters measured are used as a reference. The scattering parameters directly measured using the coupler without compensation are compared with the reference scattering parameters and are shown in Figure 1. Figure 5 As can be seen from the figure, compared with the reference value, the amplitude and phase of the scattering parameters measured online using the coupler are greatly distorted. The technical solution proposed in this invention is used to compensate for the distortion of the scattering parameters measured online. The compensated scattering parameters are shown in Figure 6 As can be seen from the figure, the scattering parameters after compensation by the proposed scheme are basically consistent with the reference scattering parameters in terms of amplitude and phase. The experimental results verify the technical effect of the present invention.

[0074] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A scattering parameter distortion compensation method using a single inductive coupler, characterized in that: The method is realized by applying an online scattering parameter measurement device using a single inductive coupler, the device comprising: a signal processing system, a vector network analyzer (VNA), an inductive coupler, and a limiting insulating column; The signal processing system establishes a communication connection with the vector network analyzer VNA via a miniUSB cable, controls the vector network analyzer VNA to perform measurements, and transmits and processes the measured data; The vector network analyzer VNA is connected to the inductive coupler via an N-type connector, and a swept frequency sinusoidal excitation signal is injected into the inductive coupler to measure the scattering parameters of the device under test (DUT); The limiting insulating column is sleeved on the power line to limit the position of the inductive coupler so that the power line passes through the center of the coupling window of the inductive coupler; wherein the power line is used to connect the device under test (DUT) and the power supply; The method comprises the following steps: Connect the lines according to the measuring device; Characterize the measurement device as a two-port network; Measure the scattering parameters of the coupler and the device under test as a whole; Based on the measured scattering parameters of the coupler and the device under test as a whole and the two-port network characterization measurement device, the coupler port voltage and port current are obtained; The measurement is based on a dedicated fixture and a vector network analyzer (VNA) to measure the scattering parameter matrix of the coupler; Converting the scattering parameter matrix into a transfer parameter matrix; Acquire the port voltage and port current of the device under test based on the coupler port voltage and port current and the transfer matrix; Obtaining the input impedance of the device under test based on the port voltage and port current of the device under test; Based on the input impedance of the device under test, actual scattering parameters of the device under test are obtained to complete distortion compensation; Measuring the scattering parameter matrix S that characterizes the transmission characteristics of the inductive coupling probe P , S P The measurement process is as follows: first, the inductive coupler is placed on a special fixture, and the inner conductor of the fixture is ensured to pass through the center of the coupling window of the inductive coupler; the coupler is placed on the fixture, the coupler signal injection port is port (1), and the two ports of the fixture are port (2) and port (3); port (1) and port (2) are connected to port (1) and port (2) of the VNA respectively, and port (3) is connected to the 50 Ω load terminal; secondly, the measurement frequency, output power, number of scanning points, and intermediate frequency bandwidth of the vector network analyzer are set, and the vector network analyzer is calibrated by OSLT; finally, port (1) of the vector network analyzer is connected to the coupler signal injection port, i.e. port (1), and port (2) of the vector network analyzer is connected to the right port of the fixture, i.e. port (2), and the scattering parameter matrix S is measured and saved. P .

2. The scattering parameter distortion compensation method using a single inductive coupler according to claim 1, wherein: Methods for obtaining coupler port voltage and port current include: Among them, V s , Z0 represent the source voltage and reference impedance of the vector network analyzer respectively, S 11 is the scattering parameter of the entire system under test.

3. The scattering parameter distortion compensation method using a single inductive coupler according to claim 2, wherein: The method to convert the scattering matrix into a transfer matrix is: Among them, S P11 and S P22 Indicates the return loss at both ends of the coupler, S P12 and S P21 is the insertion loss of the coupler, and Z0 is the 50 Ω reference impedance.

4. The scattering parameter distortion compensation method using a single inductive coupler according to claim 3, wherein: Methods for obtaining the port voltage and port current of the device under test include: Among them, V DUT and I DUT Respectively represent the port voltage and port current of the device under test, T P -1 Indicates T P The inverse matrix of .

5. The scattering parameter distortion compensation method using a single inductive coupler according to claim 4, wherein: Methods for obtaining the input impedance of the device under test include: 。 6. The scattering parameter distortion compensation method using a single inductive coupler according to claim 5, characterized in that: The method for obtaining actual scattering parameters of the device under test based on the input impedance of the device under test and completing distortion compensation includes: 。

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