Eight-error correction method based on multi-port vector network analyzer
By converting the twelve-term error model into an eight-term error model and eliminating the switching term error, the measurement error problem caused by load matching changes in the vector network analyzer under high-power testing was solved, and high-precision multi-port measurement results were achieved.
Patent Information
- Application Number
- CN202511580612.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-31
- Publication Date
- 2026-02-06
AI Technical Summary
Existing commercial vector network analyzers cannot effectively correct measurement errors caused by load matching changes during high-power testing, especially in multi-port scenarios where accuracy is difficult to guarantee.
An eight-term error correction method is adopted, which transforms the twelve-term error model into an eight-term error model to eliminate switching term errors. The true S-parameters of the test device are calculated through matrix operations to avoid the influence of load matching changes.
It achieves high-precision measurement results under varying load conditions, is applicable to multi-port devices under test, has backward compatibility, and provides more accurate measurement results.
Smart Images
Figure CN121477090A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of microwave measurement technology, specifically relating to an eight-item error correction method based on a multi-port vector network analyzer. Background Technology
[0002] With the development of integrated circuit technology, complex modules requiring multi-port RF characteristics are becoming increasingly common. Examples include balanced linear amplifiers and dual circularly polarized antennas. A large body of literature on calibration methods, error models, and multi-port test equipment measurements is readily available. Common error models include 8-term, 10-term, 12-term, and 16-term error models.
[0003] Commercial vector network analyzers, when performing high-power testing, typically include external couplers, preamplifiers, and attenuators. During calibration, preamplifiers and attenuators can be removed to avoid damaging the calibration standard and optimize signal levels. However, these components need to be reconnected after calibration. Removing these components and then adding them back to the vector network analyzer on the coupler generally causes a change in the port load matching.
[0004] Modern vector network analyzers typically use a 12-term error model by default when measuring the device under test (DUT) because this model is fast, has low noise, and the load matching of the vector network analyzer is usually quite stable. However, in test scenarios with varying load matching, the 12-term error model can introduce some errors.
[0005] Existing commercial vector network analyzers use a 12-term error model for correction calculations by default. This 12-term model is often ineffective in handling errors caused by changes in port load matching. This invention proposes an 8-term error correction model for multi-port vector network analyzers. Its main advantage is that changes in the load matching of the vector network analyzer after calibration will not lead to measurement errors. Therefore, there is an urgent need in the field for an error correction method that can maintain high accuracy even under scenarios with changing load matching. Summary of the Invention
[0006] In view of the above-mentioned technical problems in the prior art, the present invention proposes an eight-item error correction method based on a multi-port vector network analyzer. The method is reasonably designed, overcomes the shortcomings of the prior art, and has good results.
[0007] To achieve the above objectives, the present invention adopts the following technical solution: An eight-term error correction method based on a multi-port vector network analyzer includes the following steps: Step 1: Obtain the twelve error model parameters of the vector network analyzer; Step 2: Convert the twelve error model parameters into eight error model parameters; Step 3: Measure and eliminate switching term errors to obtain intermediate state S-parameters; Step 4: Calculate the true S-parameters of the test piece based on the eight error model parameters and the intermediate state S-parameters; the calculation of the true S-parameters is not affected by the change in load matching of the vector network analyzer after calibration.
[0008] Preferably, the twelve error model parameters are converted into eight error model parameters, specifically through the following relationship: ; In the formula: , , , , , , , The eight error terms required for the eight error corrections; among them Indicates the source port. Indicates the receiving port. This represents the directionality error term at the source port. This represents the source mismatch error term on the source port. This represents the reflection tracking error term at the source port. This represents the directionality error term on the receiving port. This represents the source mismatch error term on the receive port. This represents the reflection tracking error term on the receiving port. This represents the load mismatch term from the source port to the receiver port. This represents the load mismatch term from the receive port to the source port. This represents the transmission tracking error term from the receive port to the source port. This represents the transmission tracking error term from the source port to the receiver port. This represents the crosstalk error term from the source port to the receiver port. This represents the crosstalk error term from the receiving port to the source port.
[0009] Preferably, the switching term error is measured and eliminated, specifically through the following formula: The switching term error is expressed as: ; In the formula: For the source port is hour, Port switching error term; For the source port is hour, Port switching error term; Formula for eliminating switching term errors in multi-port vector network analyzers: ; In the formula: This represents the raw S-parameters measured by the receiver, i.e., the S-parameters including the switching term error; The S-parameters represent the intermediate state, i.e., the S-parameters after eliminating the switching term error; The measurement is performed in real time by the receiver while the test piece is being measured. ; In the formula, Indicates the source port is Receive port At that time, the reference receiver signal is compared with the measured receiver signal.
[0010] Preferably, in step 4, calculating the true S-parameters of the test piece specifically includes: Step 4.1: Construct an error matrix consisting of eight error model parameters, including a forward error matrix and a backward error matrix; Step 4.2: Based on the error matrix and intermediate S-parameters, solve for the true S-parameter matrix of the test piece through matrix operations.
[0011] Preferably, the true S-parameter matrix of the test component is solved by matrix operations, specifically using the following formula: ; ; Due to the error matrix , , , All are diagonal matrices. Represented as: ; In the formula: Note the above formula The conditions for its establishment are and It is a diagonal matrix; When considering ports With port When crosstalk occurs between the components, the eight error models are affected. It is no longer a diagonal matrix because it is filled with errors from other isolation terms. and They are respectively: ; ; In the formula: Indicates reference receiver Leakage to the measuring receiver The signal.
[0012] The beneficial technical effects of this invention are as follows: 1. Resistance to load matching changes: The core advantage is that changes in the load matching of the vector network analyzer port after calibration will not cause measurement errors, solving the accuracy problem in scenarios such as high-power testing and load-pulling measurement.
[0013] 2. High-precision measurement: By converting to an 8-item model and accurately eliminating switching term errors, it provides more accurate measurement results in specific scenarios than the traditional 12-item model.
[0014] 3. Wide applicability: The method is applicable to multi-port vector network analyzers and can handle complex multi-port devices under test.
[0015] 4. Backward compatibility: Based on the widely used 12 error models, it is easy to implement and integrate on existing instrument platforms. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the 12-term forward error model for two-port measurements in the prior art.
[0017] Figure 2 This is a schematic diagram of a 12-term reverse error model for two-port measurements in the prior art.
[0018] Figure 3 This is a schematic diagram of the eight error models for two-port measurement in an embodiment of the present invention.
[0019] Figure 4 This is a simplified diagram of a multi-port vector network analyzer in an embodiment of the present invention. Detailed Implementation
[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: The overall process of this invention includes four main steps: S101 (acquiring twelve error parameters), S102 (converting to eight error parameters), S103 (measuring and eliminating switching errors), and S104 (calculating the true S-parameters).
[0021] Example: Take a two-port vector network analyzer as an example.
[0022] S101: First, perform a full two-port calibration at the instrument port using the SOLT calibration kit to obtain the following results: Figure 1 and Figure 2 The twelve error parameters are shown. S102: Convert the twelve error parameters into eight error parameters; like Figure 1 and Figure 2 As shown, after calibration of the vector network analyzer, 12 error terms can generally be obtained directly. Indicates the source port. Indicates the receiving port. This represents the directionality error term at the source port. This represents the source mismatch error term on the source port. This represents the reflection tracking error term at the source port. This represents the directionality error term on the receiving port. This represents the source mismatch error term on the receive port. This represents the reflection tracking error term on the receiving port. This represents the load mismatch term from the source port to the receiver port. This represents the load mismatch term from the receive port to the source port. This represents the transmission tracking error term from the receive port to the source port. This represents the transmission tracking error term from the source port to the receiver port. This represents the crosstalk error term from the source port to the receiver port. This represents the crosstalk error term from the receive port to the source port. , , , These represent the four true S-parameters measured on the test piece.
[0023] Since the 8-term error model and the 12-term error model describe the same system, there is a certain mathematical transformation relationship between them, such as... Figure 3 As shown, the conversion relationship is as follows: ; In the formula: , , , , , , , The eight error terms required for the eight error corrections.
[0024] In addition, the switching term error can be expressed as: ; In the formula: For the source port is hour, Port switching error term; For the source port is hour, Port switching error term.
[0025] S103: Eliminate switching term error; The instrument is connected to the device under test for measurement. During the measurement process, the instrument measures the switching error in real time. For each measured raw S-parameter, the intermediate S-parameter matrix after eliminating the switching error is calculated using a formula. Formula for eliminating switching term errors in multi-port vector network analyzers: ; In the formula: This represents the raw S-parameters measured by the receiver, i.e., the S-parameters including the switching term error; The S-parameters represent the intermediate state, i.e., the S-parameters after eliminating the switching term error; The measurement of the test piece is performed in real time by the receiver.
[0026] ; In the formula Indicates the source port is Receive port At that time, the reference receiver signal is compared with the measured receiver signal.
[0027] S104: Calculates 8 error correction terms to solve for the true S-parameter matrix of the test piece.
[0028] like Figure 4 As shown, the pseudo-scattering parameter of each port can be defined as: ; In the formula: For port The input signal of the error frame, For port The output signal of the error frame; For port The input signal of the device under test, For port The output signal of the device under test.
[0029] like Figure 4 As shown, each error term can be defined as a pseudo-scattering matrix: ; like Figure 4 As shown, in a multiport vector network analyzer, the error box input and output can be defined as: ; In a multiport vector network analyzer, the pseudo-scattering parameter is defined as: ; In the above formula , , , Each of these is a diagonal matrix composed of error terms from each port, i.e.: ; ; The S-parameters of the test piece can be obtained at the input and output terminals of the error frame, respectively: ; In the formula: The true S-parameters of the test piece, The S-parameters for measuring the test piece.
[0030] Through matrix derivation, we can obtain: ; In the formula: It is an n-dimensional identity matrix. The true scattering S-parameters of the multi-port test device. For measuring the scattering S-parameters of a multi-port device under test, In order to derive the scattering parameters of the actual test piece The above expression can be rewritten as: ; make The true scattering parameters of the tested component can be obtained: ; Due to the error matrix , , , All are diagonal matrices. It can be represented as: ; In the formula: Note the above formula The conditions for its establishment are and It is a diagonal matrix; When considering ports With port When crosstalk occurs between the components, the eight error models are affected. It is no longer a diagonal matrix because it is filled with errors from other isolation terms. and They can be rewritten as: ; ; In the formula: Indicates reference receiver Leakage to the measuring receiver The signal.
[0031] Thus, based on the completion of the eight error model correction S-parameters, the influence of switching error was eliminated, thereby obtaining accurate S-parameters of the test component.
[0032] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.
Claims
1. An eight-term error correction method based on a multi-port vector network analyzer, characterized in that, Includes the following steps: Step 1: Obtain the twelve error model parameters of the vector network analyzer; Step 2: Convert the twelve error model parameters into eight error model parameters; Step 3: Measure and eliminate switching term errors to obtain intermediate state S-parameters; Step 4: Calculate the true S-parameters of the test piece based on the eight error model parameters and the intermediate state S-parameters; the calculation of the true S-parameters is not affected by the change in load matching of the vector network analyzer after calibration.
2. The eight-term error correction method based on a multi-port vector network analyzer according to claim 1, characterized in that, The twelve error model parameters are converted into eight error model parameters, which is achieved through the following relationship: ； In the formula: , , , , , , , Eight error terms are required for the eight error corrections; in Indicates the source port. Indicates the receiving port. This represents the directionality error term at the source port. This represents the source mismatch error term on the source port. This represents the reflection tracking error term at the source port. This represents the directionality error term on the receiving port. This represents the source mismatch error term on the receive port. This represents the reflection tracking error term on the receiving port. This represents the load mismatch term from the source port to the receiver port. This represents the load mismatch term from the receive port to the source port. This represents the transmission tracking error term from the receive port to the source port. This represents the transmission tracking error term from the source port to the receiver port. This represents the crosstalk error term from the source port to the receiver port. This represents the crosstalk error term from the receiving port to the source port.
3. The eight-term error correction method based on a multi-port vector network analyzer according to claim 1, characterized in that, The switching term error is measured and eliminated using the following formula: The switching term error is expressed as: ； In the formula: For the source port is hour, Port switching error term; For the source port is hour, Port switching error term; Formula for eliminating switching term errors in multi-port vector network analyzers: ； In the formula: This represents the raw S-parameters measured by the receiver, i.e., the S-parameters including the switching term error; Representing intermediate states S-parameters, i.e., S-parameters after eliminating switching term errors; The measurement is performed in real time by the receiver while the test piece is being measured. ； In the formula, Indicates the source port is Receive port At that time, the reference receiver signal is compared with the measured receiver signal.
4. The eight-term error correction method based on a multi-port vector network analyzer according to claim 1, characterized in that, Step 4 involves calculating the true S-parameters of the test piece, specifically including: Step 4.1: Construct an error matrix consisting of eight error model parameters, including a forward error matrix and a backward error matrix; Step 4.2: Based on the error matrix and intermediate S-parameters, solve for the true S-parameter matrix of the test piece through matrix operations.
5. The eight-term error correction method based on a multi-port vector network analyzer according to claim 1, characterized in that, The true S-parameter matrix of the test part is solved by matrix operations, specifically using the following formula: ； ； Due to the error matrix , , , All are diagonal matrices. Represented as: ； In the formula: The above formula The conditions for its establishment are and It is a diagonal matrix; When considering ports With port When crosstalk occurs between the components, the eight error models are affected. It is no longer a diagonal matrix because it is filled with errors from other isolation terms. and They are respectively: ； ； In the formula: Indicates reference receiver Leakage to the measuring receiver The signal.