Scattering parameter online measurement device using single inductive coupler and distortion compensation method

Abstract

The invention discloses a scattering parameter online measurement device using a single inductive coupler and a distortion compensation method, and relates to the field of inductive coupling measurement of scattering parameters of equipment to be measured, the device comprises a signal processing system, a vector network analyzer VNA, an inductive coupler, a limiting insulation column, equipment to be measured DUT and a power supply, the signal processing system establishes communication connection with the vector network analyzer VNA through a mini USB cable, controls the vector network analyzer VNA to implement measurement, and transmits and processes measured data; the vector network analyzer VNA is connected with the inductive coupler through an N-type connector and injects the sweep-frequency sine excitation signal into the inductive coupler to measure scattering parameters of the DUT; the limiting insulating column is sleeved on the power line and is used for limiting 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 for supplying power to the DUT.

Description

Technical Field

[0001] The 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. Among them, inductively coupled devices, such as inductive couplers, large current injection probes, detection probes, high frequency current sensors (HFCT), Rogowski coils, etc., are used for contactless signal communication, which can avoid direct electrical connection between the measuring instrument and the device under test (DUT), which is beneficial to protect the equipment and operators, and realize the live measurement of scattering parameters of equipment and systems. However, inductively coupled devices are regarded as a kind of RF transformer, and the signals transmitted through these devices are significantly distorted, which has an adverse effect on the scattering parameter measurement of the DUT. Therefore, it is necessary to study the distortion formation mechanism and compensate for the distortion.

[0003] Traditional inductively coupled scattering parameter measurement mainly uses a dual coupler configuration, where one coupler is used to inject signals and one coupler is used to receive signals. Traditional inductively coupled dual coupler scattering parameter measurement devices have problems such as high cost and electromagnetic interference between probes. Summary of the invention

[0004] In view of the shortcomings of the prior art, 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 through a miniUSB cable, controls the vector network analyzer VNA to perform measurement, 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 using 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] Based on the coupler port voltage and port current and the transfer matrix, obtaining the port voltage and port current of the device under test;

[0018] Acquire 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, the actual scattering parameters of the device under test are obtained to complete the 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 whole 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, based on the input impedance of the device under test, the actual scattering parameter of the device under test is obtained, and the method for completing distortion compensation includes:

[0032]

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

[0034] The present invention proposes an online measurement scheme of scattering parameters based on a single coupler, which can reduce costs, avoid mutual electromagnetic interference between couplers in a dual coupler configuration, and realize in-situ online measurement of scattering parameters. Instead of non-contact measurement with limited practical utility. In addition, the present invention proposes a distortion compensation scheme caused by signal transmission through a coupler, so that the scattering parameters measured online in-situ based on the coupler are equivalent to the scattering parameters measured offline through 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 creative labor.

[0036] Figure 1 It is a 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 measurement configuration of a coupler scattering matrix according to an embodiment of the present invention;

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

[0039] Figure 4 A schematic 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 It is a 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 be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work 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] Embodiment 1

[0045] like Figure 1 As shown, the present invention provides an online measurement device for scattering parameters using a single inductive coupler. The entire measurement device consists of a signal processing system, a vector network analyzer (VNA), an inductive coupler, a limit insulating column, a device under test (DUT) and its power supply. The signal processing system establishes a communication connection with the VNA through a miniUSB cable, controls the VNA to perform measurements, and transmits and processes measured data; the VNA is connected to the inductive coupler through an N-type connector, and a swept frequency sinusoidal excitation signal is injected into the coupler to measure the scattering parameter S 11 The clamp-type limiting insulating column is sleeved on the power line (non-ground side), and its inner diameter is approximately equal to the outer diameter of the power line, and its outer diameter is approximately equal to the inner diameter of the coupler. Its function is to limit the position of the inductive coupler so that the power line passes through the center of the coupling window of the coupler. During the measurement process, the power supply normally supplies power to the DUT, so the measurement method of the present invention is a substantial in-situ online measurement, that is, it does not change the original connection configuration of the DUT, nor does it interfere with the normal operation of the DUT.

[0046] Embodiment 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 vector grid measuring the scattering matrix of the coupler;

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

[0054] Based on the coupler port voltage and port current and the transfer matrix, obtaining the port voltage and port current of the device under test;

[0055] Acquire 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, the actual scattering parameters of the device under test are obtained to complete the distortion compensation.

[0057] The measurement steps are as follows:

[0058] (1) Based on 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 scanning points, and intermediate frequency bandwidth of the vector network analyzer, and perform OSL calibration on the vector network analyzer. Figure 1 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 special 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 signal injection end of the coupler 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 scanning 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 is converted into 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 They 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 overall measurement device. s , Z0 represent the source voltage and reference impedance of the vector network analyzer respectively; V P and I P Respectively represent the voltage and port current of the coupler port; V DUT and I DUT Represent the port voltage and port current of DUT respectively.

[0064] (5) Compensation coupler for S 11 The distortion caused by the DUT is obtained 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, it is necessary 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 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 DUT can be obtained by equation (4).

[0069]

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

[0071]

[0072] Embodiment 3

[0073] The following uses a single coupler as an example to verify the technical effect of the present invention 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-circuit 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 a 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 both greatly distorted. The technical solution proposed in the present invention is used to compensate for the distortion of the scattering parameters measured online, and 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 only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An online scattering parameter measurement device using a single inductive coupler, characterized in that: include: Signal processing system, vector network analyzer VNA, inductive coupler and limiting insulating column; The signal processing system establishes a communication connection with the vector network analyzer VNA through a miniUSB cable, controls the vector network analyzer VNA to perform measurement, 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.

2. A scattering parameter distortion compensation method using a single inductive coupler, characterized in that: The scattering parameter online measurement device using a single inductive coupler as claimed in claim 1 is implemented, comprising 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 matrix of the coupler; converting the scattering matrix into a transfer matrix; Based on the coupler port voltage and port current and the transfer matrix, obtaining the port voltage and port current of the device under test; Acquire 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, the actual scattering parameters of the device under test are obtained to complete the distortion compensation.

3. The scattering parameter distortion compensation method using a single inductive coupler according to claim 2, characterized in that: Methods for obtaining the 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 whole system under test.

4. The scattering parameter distortion compensation method using a single inductive coupler according to claim 3, characterized in that: The method of converting the scattering matrix into a transfer matrix is: 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.

5. The scattering parameter distortion compensation method using a single inductive coupler according to claim 4, characterized in that: 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 .

6. The scattering parameter distortion compensation method using a single inductive coupler according to claim 5, characterized in that: Methods for obtaining the input impedance of the device under test include:

7. The scattering parameter distortion compensation method using a single inductive coupler according to claim 6, characterized in that: The method of 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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