Self-calibration method and system of VNA port extension test system and test system

Abstract

The invention provides a self-calibration method and system for a VNA port extension test system and a test system, and the method comprises the steps: recalibration is carried out, so that a path between a VNA port and a corresponding switch matrix output port is in a disconnected state; the port transmits a signal and measures anti-radio frequency domain data in a disconnection state and time domain response of the anti-radio frequency domain data; time domain data of directivity errors, time domain data of reflection tracking errors and corresponding frequency domain responses are obtained through a first gating gate and a second gating gate; the drift distance of a reflection error item is calculated, and the directivity error and the reflection tracking error of each port are updated; performing S parameter measurement on the DUT to be measured; the drift distance of the ET is obtained according to the obtained drift distance of the reflection error term, and the transmission error term is updated based on the drift distance of the ET; and correcting the measurement data of the current DUT to be measured to obtain an accurate S parameter. According to the invention, a self-calibration function without interruption of production can be realized, and the test efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of communication testing technology, and more particularly to a self-calibration method and system for a VNA port extension testing system, and also to a VNA port extension testing system. Background Technology

[0002] In modern high-speed digital communication fields, such as USB4, PCIe, and 5G / 6G communication, high-speed cables and connectors serve as key physical media for signal transmission, and their signal integrity (SI) performance is crucial. The vector network analyzer (VNA) is a core instrument for measuring the S-parameters of cable assemblies (such as insertion loss and return loss) and is a standard tool for evaluating their SI performance. With the rapid development of high-speed communication, the number of channels has increased from a few traditional channels to dozens or even hundreds of channels. The dramatic increase in the number of cable channels usually requires the use of a four-port or multi-port VNA combined with a large switch matrix (such as 16 ports or more) to build an automated testing system to achieve efficient measurement of all channels.

[0003] Currently, to ensure the measurement accuracy of VNA testing systems, rigorous system calibration is essential before S-parameter testing. The traditional calibration method involves sequentially connecting a known calibration kit (typically an electronic calibration kit, E-Cal, or a mechanical calibration kit consisting of an open circuit, a short circuit, a load circuit, and a through circuit) to each port of the switch matrix. The VNA calculates a mathematical error model by measuring the responses of these standard components and comparing them to their known electrical characteristics. This model includes multiple error terms, such as directivity error (ED), source matching error (ES), reflection tracking error (ER), transmission tracking error (ET), and load matching error (EL). In subsequent measurements of the Device Under Test (DUT), the VNA uses this error model to correct the original measurement data, eliminating systematic errors introduced by test instruments, cables, and fixtures, thereby obtaining the true S-parameters of the DUT. This process requires connecting and measuring each port of the switch matrix until all ports are calibrated.

[0004] The traditional calibration method using a VNA and a switching matrix has the following serious drawbacks when applied to large-scale, high-efficiency testing on production lines: (1) Time-consuming and labor-intensive, and inefficient: The number of ports in the switch matrix is ​​huge (e.g., 64 or more), and the port density is high with small spacing. The operator needs to manually connect the calibration components to each port in sequence, which is tedious and time-consuming, usually taking several hours to complete a full port calibration.

[0005] (2) Constraints on production capacity and high costs: Each time calibration is performed, the entire testing system must stop normal production testing, i.e., "line stoppage". This directly leads to a reduction in the effective working hours of the production line, which seriously restricts production capacity and increases the testing cost per unit product.

[0006] (3) Impact on measurement accuracy: The performance of the VNA testing system will drift with changes in ambient temperature, humidity, etc. To ensure accuracy, frequent calibration is required. However, since calibration itself is very time-consuming, high-frequency calibration cannot be achieved in actual operation. Therefore, during the interval between two calibrations, the measurement error caused by system drift will gradually accumulate, affecting the accuracy and consistency of the test results.

[0007] (4) Increased physical wear: Frequent plugging and unplugging of calibration components and test fixtures will cause mechanical wear to expensive connectors, cables and fixtures, shorten their service life and increase maintenance costs.

[0008] Therefore, there is an urgent need for a calibration method that can be completed quickly and automatically without interrupting production, in order to overcome the bottlenecks of existing technologies. Summary of the Invention

[0009] To address the fundamental problems of time-consuming VNA calibration and its impact on production capacity in existing technologies, this invention provides a self-calibration method for a VNA port expansion test system, a self-calibration system for implementing the self-calibration method, and a VNA port expansion test system equipped with the self-calibration system. The test solution of this invention is practical, efficient, and low-cost, and has extremely high industrial application value.

[0010] The self-calibration method of the present invention includes the following steps: S1: Self-calibration initialization, obtaining the original error terms ED_orig, ES_orig, ER_orig, ET_orig, EL orig for each port at each frequency, as well as the frequency domain response reference value Γ1_init for the time domain data of the directivity error ED and the frequency domain response reference value Γ2_init for the time domain data of the reflection tracking error ER; S2: Recalibrate, switch the switch matrix to a specific state, so that the path between port k of the VNA and its corresponding switch matrix output port is disconnected, where k is the VNA port number and VAN is the vector network analyzer. S3: Port k transmits a signal and measures the reflected frequency domain data Γ_new(k) and its time domain response in the disconnected state; S4: Set the first gating gate and the second gating gate to obtain the time-domain data G1_new of the directional error ED and the time-domain data G2_new of the reflection tracking error ER; S5: Perform Fourier transform on G1_new and G2_new to obtain the corresponding frequency domain responses Γ1_new and Γ2_new; S6: Based on the frequency domain responses Γ1_new and Γ2_new obtained from recalibration relative to the frequency domain response reference value, calculate the drift of the reflection error term, and then update the directivity error ED and reflection tracking error ER for each port based on the drift. S7: Connect the high-speed cable to perform S-parameter measurements on the DUT (Device Under Test); S8: Obtain the drift amount of ET based on the drift amount of the reflection error term obtained in step S6, and update the transmission error term based on the drift amount of ET. S9: VNA loads all updated error terms, corrects the measurement data of the current DUT, and obtains accurate S-parameters.

[0011] In a further improvement to this invention, in step S1, a calibration device is used to calibrate each port of the VNA and switch matrix combination system to obtain the original error terms ED_orig, ES_orig, ER_orig, ET_orig, and EL_orig for each port at each frequency, and these are stored in the VNA.

[0012] The present invention is further improved in that, in step S1, the following operation is performed on each port of the VNA to obtain the frequency domain response reference values ​​Γ1_init and Γ2_init of each port, which are used as the self-calibration reference for the reflection error terms of each port: A1: Switch the switch matrix to a specific state so that the path between VNA port k and its corresponding switch matrix output port is disconnected; A2: VNA port k transmits a signal and measures the reflection coefficient Γ_init(f) in this disconnected state; A3: Perform an inverse Fourier transform on the measured frequency domain data Γ_init(f) to obtain its time domain response; A4: Set two time-domain gating gates on the time-domain response diagram to obtain the time-domain data reference value G1_init of the directional error ED and the time-domain data reference value G2_init of the reflection tracking error ER; A5: Perform Fourier transform on G1_init and G2_ini to obtain their corresponding frequency domain response reference values ​​Γ1_init and Γ2_init; A6: Store the calculated frequency domain response reference values ​​Γ1_init and Γ2_init together with the corresponding port and frequency information in the VNA.

[0013] The present invention is further improved in that the first gating gate is set before the switch is in the open position, and the range is from the negative time to a moment close to the switch reflection peak. The energy in this gating gate mainly corresponds to the system directivity error ED. The time domain data in this gate is calculated to obtain the reference value G1_init of the directivity error ED.

[0014] The present invention is further improved in that the second gating gate is a window centered on the reflection peak at the switch-off position, covering all the main time-domain energy in the open-circuit state. The energy in the second gating gate corresponds to the reflection tracking error ER of the system. The reference value G2_init of the reflection tracking error ER is obtained by calculating the time-domain data in the second gating gate.

[0015] The present invention is further improved in that, in step S5, the formula for calculating the drift amount ΔED_drift of the directional error is: ΔED_drift=Γ1_new-Γ1_init; the formula for calculating the drift amount ΔER_drift of the reflection tracking error ER is: and ΔER_drift=Γ2_new / Γ2_init.

[0016] The present invention is further improved in that, in step S8, the method for obtaining the drift amount of ET and updating the transmission error term is as follows: S801: Based on the drift of the reflection tracking term, calculate the current drift of the transmission tracking term product: ΔET21_drift * ΔET12_drift ≈ ΔER11_drift * ΔER22_drift, where the first and second ports of the VNA are connected through the device under test (DUT), ΔET21_drift is the drift value of the transmission tracking error ET from the first port to the second port, ΔET12_drift is the drift value of the transmission tracking error ET from the second port to the first port, ΔER11_drift is the drift of the reflection tracking error ER at the first port, and ΔER22_drift is the drift of the reflection tracking error ER at the second port. S802: Based on the transmission characteristic S21=S12, the drift amount of ET is obtained: ΔET21_drift=sqrt(ΔER11_drift * ΔER22_drift * S21 / S12), ΔET12_drift=(ΔER11_drift * ΔER22_drift) / ΔET21_drift, Wherein, S21 is the S-parameter related term of the measured value of the device under test from the first port to the second port after compensation, and S12 is the S-parameter related term of the measured value of the device under test from the second port to the first port after compensation. S803: The updated transmission error term is as follows: ET21_new = ET21_orig*ΔET21_drift, ET12_new = ET12_orig*ΔET12_drift, Wherein, ET21_new is the transmission tracking error from the first port to the second port, and ET12_new is the transmission tracking error from the second port to the first port.

[0017] The present invention is further improved by forming several differential pairs based on the corresponding connection relationship between the switch matrix and the VNA. Each differential pair is connected to each port of the VNA. Steps S2-S8 are executed periodically to measure the differential pairs connected to the device under test (DUT) in sequence to obtain several sets of error terms. Then, based on the average measurement data of multiple measurements, the drift of ET is calculated.

[0018] The present invention also provides a self-calibration system for a VNA port expansion test system, for implementing the self-calibration method of the VNA port expansion test system, comprising: Initialization module: Used for self-calibration initialization, obtaining the original error terms ED_orig, ES_orig, ER_orig, ET_orig, EL orig for each port at each frequency, as well as the frequency domain response reference value Γ1_init for the time domain data of the directivity error ED and the frequency domain response reference value Γ2_init for the time domain data of the reflection tracking error ER. Switching module: Used to switch the switch matrix to a specific state when recalibration is required, so that the path between port k of the VNA and its corresponding switch matrix output port is disconnected, where k is the VNA port number and VAN is the vector network analyzer; First time-domain response acquisition module: Port k transmits a signal and measures the reflected frequency domain data Γ_new(k) and its time-domain response in the disconnected state; Time-domain data acquisition module: used to obtain the time-domain data G1_new of the directivity error ED and the time-domain data G2_new of the reflection tracking error ER through the set first and second gating gates; The second frequency domain response acquisition module performs Fourier transform on G1_new and G2_new to obtain the corresponding frequency domain responses Γ1_new and Γ2_new. Reflection error correction module: It is used to calculate the drift of the reflection error term based on the frequency domain responses Γ1_new and Γ2_new obtained by recalibration relative to the frequency domain response reference value, and then update the directivity error ED and reflection tracking error ER of each port based on the drift. S-parameter measurement module: Connects to a high-speed cable and is used to perform S-parameter measurements on the DUT (Device Under Test). Transmission error correction module: used to obtain the drift amount of ET based on the drift amount of the reflection error term obtained in step S6, and update the transmission error term based on the drift amount of ET; S-parameter correction module: The VNA loads all updated error terms and corrects the measurement data of the current DUT to obtain accurate S-parameters.

[0019] The present invention also provides a VNA port expansion test system, including a VNA and a switch matrix connected to the VNA, wherein the VNA is provided with a self-calibration system of the VNA port expansion test system.

[0020] Compared with the prior art, the beneficial effects of the present invention are: By utilizing the stable electrical characteristics (open circuit state of the switch) within the testing system as a calibration reference, a self-calibration function is achieved without interrupting production or requiring manual intervention, thereby increasing production capacity and improving testing efficiency.

[0021] This invention changes the traditional concept that calibration can only be performed using standard parts. It creatively treats the device under test (DUT) itself as an "unknown through standard part" and uses its physical reciprocity to separate and correct the drift of VNA transmission error terms. It can also perform calibration at irregular intervals during the test, thereby improving measurement accuracy.

[0022] This invention combines the use of open-circuit state correction for reflection error terms (ED, ER) and DUT correction for transmission error terms (ET), enabling online real-time correction of drift in almost all critical error terms. Furthermore, by monitoring and comparing the energy within a specific time-domain window, it accurately separates and quantifies the drift of the two critical error terms, directivity (ED) and reflection tracking (ER), over time, thus solving the problem of how to monitor system errors online. Attached Figure Description

[0023] Figure 1 This is a flowchart of the self-calibration method of the present invention; Figure 2 This is a schematic diagram illustrating the calculation process for each error term in this invention; Figure 3 This is a schematic diagram of the VNA port expansion test system of the present invention. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0025] like Figure 1 As shown, the self-calibration method of the present invention includes the following steps: S1: Self-calibration initialization, obtaining the original error terms ED_orig, ES_orig, ER_orig, ET_orig, EL orig for each port at each frequency, as well as the frequency domain response reference value Γ1_init for the time domain data of the directivity error ED and the frequency domain response reference value Γ2_init for the time domain data of the reflection tracking error ER; S2: Recalibrate, switch the switch matrix to a specific state, so that the path between port k of the VNA and its corresponding switch matrix output port is disconnected, where k is the VNA port number and VAN is the vector network analyzer. S3: Port k transmits a signal and measures the reflected frequency domain data Γ_new(k) and its time domain response in the disconnected state; S4: Set the first gating gate and the second gating gate to obtain the time domain data G1_new of the directional error ED and the time domain data G2_new of the reflection tracking error ER; S5: Perform Fourier transform on G1_new and G2_new to obtain the corresponding frequency domain responses Γ1_new and Γ2_new; S6: Based on the frequency domain responses Γ1_new and Γ2_new obtained from recalibration relative to the frequency domain response reference value, calculate the drift of the reflection error term, and then update the directivity error ED and reflection tracking error ER for each port based on the drift. S7: Connect the high-speed cable to perform S-parameter measurements on the DUT (Device Under Test); S8: Obtain the drift amount of ET based on the drift amount of the reflection error term obtained in step S6, and update the transmission error term based on the drift amount of ET. S9: VNA loads all updated error terms, corrects the measurement data of the current DUT, and obtains accurate S-parameters.

[0026] Since the measured drift requires a measurement reference, subsequent measurements can only be calculated based on this reference, thus correcting the measured value. Before recalibration, this invention requires obtaining various data references, which are acquired in step S1 and are prerequisites for measurement.

[0027] Specifically, in step S1, firstly, a traditional full-port calibration is performed. Each port of the VNA and switch matrix combination system is calibrated using calibration kits to obtain the raw error terms ED_orig, ES_orig, ER_orig, ET_orig, and EL_orig for each port at various frequencies, and these are stored in the VNA.

[0028] Then, a self-calibration reference for reflection-related error terms is established. This example performs the following operations on each port of the VNA. In this example, the device under test (DUT) is a high-speed cable, and the VNA has four ports. Port 1 will be used as an example: A1: Switch the switch matrix to a specific state so that the path between VNA port 1 and its corresponding switch matrix output port is in an "open" state; A2: VNA port 1 transmits a signal and measures the reflection coefficient Γ_init(f) in this disconnected state; A3: Perform an inverse Fourier transform on the measured frequency domain data Γ_init(f) to obtain its time domain response; A4: Set two time-domain gating gates on the time-domain response diagram to obtain the time-domain data reference value G1_init of the directivity error ED and the time-domain data reference value G2_init of the reflection tracking error ER; A5: Perform Fourier transform on G1_init and G2_ini to obtain their corresponding frequency domain response reference values ​​Γ1_init and Γ2_init; A6: Store the calculated frequency domain response reference values ​​Γ1_init and Γ2_init together with the corresponding port, frequency and other information in the VNA.

[0029] Then, repeat steps A1-A6 for the other ports of the VNA (ports 2, 3, and 4) to establish a self-calibration reference for the reflection error term for each port.

[0030] Preferably, in this example, the first gate (Gate 1) is set before the switch is in the open position, ranging from negative time to a moment very close to the switch reflection peak. The energy within this gate mainly corresponds to the system's directivity error ED. The time-domain data within this gate is calculated to obtain the reference value G1_init of the directivity error ED.

[0031] In this example, the second gate (Gate 2) is a window centered on the reflection peak at the switch-off position, covering all the main time-domain energy in the open-circuit state. The energy within the second gate mainly corresponds to the system's reflection tracking error ER. The reference value G2_init of the reflection tracking error ER is obtained by calculating the time-domain data within the second gate.

[0032] like Figure 2 As shown, after obtaining the measurement reference data in this example, the recalibration process can be automatically executed before each formal DUT test or after a set time interval, which is step S2-S9 of the present invention.

[0033] The detailed implementation process of this example is as follows: 1. Correct reflection-related error terms (ED, ER).

[0034] (1) Switch the switch matrix to a specific state so that the path between VNA port 1 and its corresponding switch matrix output port is in the "open" state; (2) VNA port 1 transmits a signal and measures the reflection coefficient Γ_new(f) in the "disconnected" state; (3) Perform inverse Fourier transform (IFFT) on the measured frequency domain data Γ_new(f) to obtain its time domain response; (4) Set two time-domain gating gates on the time-domain response diagram: §Gate 1: Set before the switch is in the open position, with the same range as the initialized Gate 1. The energy within this gate mainly corresponds to the system's directivity error (ED). The time-domain data within this gate is calculated to obtain the value G1_new.

[0035] §Gate 2: Sets a window centered on the reflection peak at the switch-off position, with the same range as the initialized Gate 2. The energy within this gate mainly corresponds to the system's reflection tracking error (ER). The reference value G2_new is obtained by calculating the time-domain data within this gate.

[0036] These two gates are consistent with the measurement reference data, thus ensuring the accuracy of the drift amount; (5) Perform Fourier transform (FFT) on G1_new and G2_new to obtain their frequency domain responses Γ1_new and Γ2_new; (6) Calculate the drift amount ΔED_drift=Γ1_new-Γ1_init and ΔER_drift=Γ2_new / Γ2_init, and update the error terms to obtain ED11_new and ER11_new; Repeat steps (1)-(6) for the other ports of the VNA (ports 2, 3, 4) to obtain the drift ΔER_drift of ED, ER and reflection tracking error ER for each port.

[0037] 2. Correct transmission error terms (ET).

[0038] (1) Connect the high-speed cable DUT to perform normal S-parameter measurements; (2) In the error model of VNA, there is a theoretical relationship between the drift of the transmission error term ET (ET21, ET12) and the reflection error term ER (ER11, ER22): ΔET21_drift * ΔET12_drift ≈ ΔER11_drift * ΔER22_drift; Using the drift amount of the corrected reflection tracking term, the current drift of the transmission tracking term product can be calculated: ΔET21_drift * ΔET12_drift ≈ ΔER11_drift * ΔER22_drift and ΔET43_drift * ΔET34_drift ≈ ΔER33_drift * ΔER44_drift (Here it is assumed that VNA ports 1-2 are connected through the DUT, and ports 3-4 are connected through the DUT. If the connection method is different, the corresponding port indices can be modified).

[0039] (3) The high-speed cable DUT under test is considered as an "unknown straight-through standard component". Since the high-speed cable is a passive reciprocal network, its actual transmission characteristics satisfy S21 = S12. In the measurement, the measured value of S21 is mainly affected by the ET21 drift, and the measured value of S12 is mainly affected by the ET12 drift. Therefore, the following conditions are met: ΔET21_drift / ΔET12_drift=S21 / S12, ΔET43_drift / ΔET34_drift=S43 / S34; Wherein, ΔET21_drift is the drift value of the transmission tracking error ET from the first port to the second port, ΔET12_drift is the drift value of the transmission tracking error ET from the second port to the first port, ΔET43_drift is the drift value of the transmission tracking error ET from the third port to the fourth port, ΔET34_drift is the drift value of the transmission tracking error ET from the fourth port to the third port, S21 is the S-parameter related term of the measured value of the device under test from the first port to the second port after compensation, S12 is the S-parameter related term of the measured value of the device under test from the second port to the first port after compensation, S43 is the S-parameter related term of the measured value of the device under test from the third port to the fourth port after compensation, and S34 is the S-parameter related term of the measured value of the device under test from the fourth port to the third port after compensation.

[0040] This invention utilizes the distinctness of the DUT to separate the ET drift. For high-speed cables, only two paths are connected (such as ET21 / ET12 and ET43 / ET34 in this embodiment), while other paths (such as ET31 / ET13, ET42 / ET24, ET32 / ET23, and ET41 / ET14) are isolated. Due to their low signal-to-noise ratio, these paths are unsuitable for separating the ET drift. Therefore, this invention can increase the number of connected paths using a switch matrix, directly separating the ET drift through the internal connectivity.

[0041] (4) Based on the transmission characteristics, the drift of ET is obtained: ΔET21_drift=sqrt(ΔER11_drift * ΔER22_drift*S21 / S12) ΔET12_drift=(ΔER11_drift * ΔER22_drift) / ΔET21_drift ΔET43_drift=sqrt(ΔER33_drift * ΔER44_drift*S43 / S34) ΔET34_drift=(ΔER33_drift * ΔER44_drift) / ΔET43_drift The square root involves the choice of positive or negative sign, which can be determined by the fact that the phase shift of adjacent frequencies is continuous, with the phase shift of the first frequency (low frequency) being close to 0 degrees.

[0042] (5) The transmission error term is updated as follows: §ET21_new = ET21_orig*ΔET21_drift §ET12_new = ET12_orig*ΔET12_drift §ET43_new = ET43_orig*ΔET43_drift §ET34_new = ET34_orig*ΔET34_drift Among them, ET21_new is the transmission tracking error from the first port to the second port, ET12_new is the transmission tracking error from the second port to the first port, ET43_new is the transmission tracking error from the third port to the fourth port, and ET34_new is the transmission tracking error from the fourth port to the third port.

[0043] The accuracy of the method depends on the signal-to-noise ratio of S21 (S12) of the DUT. If the DUT insertion loss is too large, the noise will affect the accuracy of the separated ET drift. Preferably, in this example, the drift trace frequency can be smoothed, or the average can be achieved by multiple DUT tests before separating the ET drift.

[0044] The VNA has only four ports, and the drift calculation for each error term is performed on these four ports. The switch matrix has multiple ports (e.g., 64). Every four switch matrix ports form a differential pair. This example uses a switch matrix with 64 ports, the same as the number of ports on the DUT. The 64 switch matrix ports have 16 differential pairs. The four VNA ports are denoted as A, B, C, and D, and the switch matrix ports are denoted as A1, A2, ..., A16; B1, B2, ..., B16; C1, C2, ..., C16; D1, D2, ..., D16. The 64 DUT ports are tested in a time-division multiplexing manner, with each test performing a differential pair of four ports, such as A1, B1, C1, D1, etc. The VNA drift corresponding to the 16 differential tests is the same.

[0045] The open-circuit measurements yielded the ED and ER drift values ​​for the four VNA ports: ΔED11_drift, ΔED22_drift, ΔED33_drift, ΔED44_drift, ΔER11_drift, ΔER22_drift, ΔER33_drift, and ΔER44_drift.

[0046] The error term drift at the switch matrix port is: ΔED_A1_drift=ΔED_A2_drift=…=ΔED_A16_drift=ΔED11_drift, ΔED_B1_drift=ΔED_B2_drift=…=ΔED_B16_drift=ΔED22_drift, ΔED_C1_drift=ΔED_C2_drift=…=ΔED_C16_drift=ΔED33_drift, ΔED_D1_drift=ΔED_D2_drift=…=ΔED_D16_drift=ΔED44_drift, The corresponding relationship for ER drift is similar.

[0047] In this example, the calculation of ET drift can be performed using different difference pairs, since the DUT is measured individually. Alternatively, after 16 sets of measurements are completed, the ET drift calculated from the 16 sets can be averaged to obtain the final ET drift.

[0048] Because drift is a gradual process, performing self-calibration every 10 (or more) DUT measurements can still guarantee the accuracy of self-calibration.

[0049] 3. Complete calibration and testing.

[0050] oVNA loads all updated error terms (ED_new, ES_orig, ER_new, ET_new, EL_orig), corrects the current DUT measurement data, and obtains its accurate S-parameters. The entire recalibration process seamlessly integrates with the normal DUT testing procedure, requiring no additional steps.

[0051] The present invention also provides a self-calibration system for a VNA port expansion test system, for implementing the self-calibration method of the VNA port expansion test system, comprising: Initialization module: Used for self-calibration initialization, obtaining the original error terms ED_orig, ES_orig, ER_orig, ET_orig, EL orig for each port at each frequency, as well as the frequency domain response reference value Γ1_init for the time domain data of the directivity error ED and the frequency domain response reference value Γ2_init for the time domain data of the reflection tracking error ER. Switching module: Used to switch the switch matrix to a specific state when recalibration is required, so that the path between port k of the VNA and its corresponding switch matrix output port is disconnected, where k is the VNA port number and VAN is the vector network analyzer; First time-domain response acquisition module: Port k transmits a signal and measures the reflected frequency domain data Γ_new(k) and its time-domain response in the disconnected state; Time-domain data acquisition module: used to obtain the time-domain data G1_new of the directivity error ED and the time-domain data G2_new of the reflection tracking error ER through the set first and second gating gates; The second frequency domain response acquisition module performs Fourier transform on G1_new and G2_new to obtain the corresponding frequency domain responses Γ1_new and Γ2_new. Reflection error correction module: It is used to calculate the drift of the reflection error term based on the frequency domain responses Γ1_new and Γ2_new obtained by recalibration relative to the frequency domain response reference value, and then update the directivity error ED and reflection tracking error ER of each port based on the drift. S-parameter measurement module: Connects to a high-speed cable and is used to perform S-parameter measurements on the DUT (Device Under Test). Transmission error correction module: used to obtain the drift amount of ET based on the drift amount of the reflection error term obtained in step S6, and update the transmission error term based on the drift amount of ET; S-parameter correction module: The VNA loads all updated error terms and corrects the measurement data of the current DUT to obtain accurate S-parameters.

[0052] This invention also provides a VNA port expansion test system, including a VNA and a switch matrix connected to the VNA, wherein the VNA contains a self-calibration system for the VNA port expansion test system. The accuracy of this method highly depends on the long-term consistency of the electrical characteristics of the switch matrix when switched to the "off" state. To improve the long-term stability of the switch in the "open" state, this example uses high-quality, high-repeatability RF switches for the switch matrix. A monitoring and compensation mechanism for changes in the switches themselves is introduced into the system, thereby enabling real-time detection of the switch matrix's state and avoiding measurement errors caused by switch performance instability.

[0053] Preferably, for a small number of non-reciprocal DUTs, a small, stable through-path can be integrated into the test fixture. Before testing, the system switches to this path, using it as a known through-path standard to separate the drift of ET21 and ET12, and then switches back to the DUT for testing.

[0054] In scenarios requiring higher accuracy, this example demonstrates how a more complex mathematical model can be built by measuring a combination of multiple built-in references (such as open circuits and short circuits) to simultaneously estimate and correct the drift of the three error terms: ED, ER, and ES.

[0055] As can be seen from the above, the present invention has the following innovative points: 1. An online, adaptive VNA calibration method is proposed: The core innovation of this invention lies in using the stable electrical characteristics (open circuit state of the switch) inside the test system as a calibration reference, realizing the "self-calibration" or "recalibration" function without interrupting production or requiring manual intervention; 2. Using the DUT as a calibration standard: The high-speed cable DUT under test is creatively regarded as an "unknown through standard" and its physical reciprocity (S21=S12) is used to separate and correct the drift of VNA transmission error terms (ET21,ET12). This is a major breakthrough in the traditional calibration concept. 3. Real-time correction of all error terms: By combining the use of open-circuit switch state to correct reflection error terms (ED, ER) and the use of DUT to correct transmission error terms (ET), this invention constructs a complete system capable of online real-time correction of drift of almost all key error terms; 4. Creatively combining time-domain gating technology to quantify error term drift: By monitoring and comparing the energy of a specific time-domain window, the drift of two key error terms, directionality (ED) and reflection tracking (ER), over time is accurately separated and quantified, solving the problem of how to monitor system errors online; 5. Solves the core pain points of large-scale multi-port testing systems: Directly addresses the fundamental problem of time-consuming VNA calibration and its impact on production capacity in production line testing, providing a practical, efficient, and cost-effective solution with extremely high industrial application value.

[0056] The specific embodiments described above are preferred embodiments of the present invention and are not intended to limit the specific scope of the present invention. The scope of the present invention includes, but is not limited to, these specific embodiments. All equivalent changes made in accordance with the present invention are within the protection scope of the present invention.

Claims

1. A self-calibration method for a VNA port expansion test system, characterized in that, Includes the following steps: S1: Self-calibration initialization, obtaining the original error terms ED_orig, ES_orig, ER_orig, ET_orig, EL orig for each port at each frequency, as well as the frequency domain response reference value Γ1_init for the time domain data of the directivity error ED and the frequency domain response reference value Γ2_init for the time domain data of the reflection tracking error ER; S2: Recalibrate, switch the switch matrix to a specific state, so that the path between port k of the VNA and its corresponding switch matrix output port is disconnected, where k is the VNA port number and VAN is the vector network analyzer. S3: Port k transmits a signal and measures the reflected frequency domain data Γ_new(k) and its time domain response in the disconnected state; S4: Set the first gating gate and the second gating gate to obtain the time domain data G1_new of the directional error ED and the time domain data G2_new of the reflection tracking error ER; S5: Perform Fourier transform on G1_new and G2_new to obtain the corresponding frequency domain responses Γ1_new and Γ2_new; S6: Based on the frequency domain responses Γ1_new and Γ2_new obtained from recalibration relative to the frequency domain response reference value, calculate the drift of the reflection error term, and then update the directivity error ED and reflection tracking error ER for each port based on the drift. S7: Connect the high-speed cable to perform S-parameter measurements on the DUT (Device Under Test); S8: Obtain the drift amount of ET based on the drift amount of the reflection error term obtained in step S6, and update the transmission error term based on the drift amount of ET. S9: VNA loads all updated error terms, corrects the measurement data of the current DUT, and obtains accurate S-parameters.

2. The self-calibration method for the VNA port expansion test system according to claim 1, characterized in that: In step S1, each port of the VNA and switch matrix combination system is calibrated using a calibration kit to obtain the original error terms ED_orig, ES_orig, ER_orig, ET_orig, and EL_orig for each port at each frequency, and these are stored in the VNA.

3. The self-calibration method of the VNA port expansion test system according to claim 1, characterized in that: In step S1, the following operations are performed on each port of the VNA to obtain the frequency domain response reference values ​​Γ1_init and Γ2_init for each port, which serve as the self-calibration reference for the reflection-type error term of each port: A1: Switch the switch matrix to a specific state so that the path between VNA port k and its corresponding switch matrix output port is disconnected; A2: VNA port k transmits a signal and measures the reflection coefficient Γ_init(f) in this disconnected state; A3: Perform an inverse Fourier transform on the measured frequency domain data Γ_init(f) to obtain its time domain response; A4: Set two time-domain gating gates on the time-domain response diagram to obtain the time-domain data reference value G1_init of the directional error ED and the time-domain data reference value G2_init of the reflection tracking error ER; A5: Perform Fourier transform on G1_init and G2_ini to obtain their corresponding frequency domain response reference values ​​Γ1_init and Γ2_init; A6: Store the calculated frequency domain response reference values ​​Γ1_init and Γ2_init together with the corresponding port and frequency information in the VNA.

4. The self-calibration method of the VNA port expansion test system according to claim 3, characterized in that: The first gating gate is set before the switch is in the open position, ranging from negative time to a moment close to the switch reflection peak. The energy within this gating gate mainly corresponds to the system's directivity error ED. The time-domain data within this gate is calculated to obtain the reference value G1_init of the directivity error ED.

5. The self-calibration method of the VNA port expansion test system according to claim 3, characterized in that: The second gating gate is a window centered on the reflection peak at the switch-off position, covering all major time-domain energies in the open-circuit state. The energy within the second gating gate corresponds to the system's reflection tracking error ER. The reference value G2_init of the reflection tracking error ER is obtained by calculating the time-domain data within the second gating gate.

6. The self-calibration method for the VNA port expansion test system according to claim 1, characterized in that: In step S5, the formula for calculating the drift amount ΔED_drift of the directional error is: ΔED_drift = Γ1_new - Γ1_init; the formula for calculating the drift amount ΔER_drift of the reflection tracking error ER is: and ΔER_drift = Γ2_new / Γ2_init.

7. The self-calibration method for the VNA port expansion test system according to claim 6, characterized in that: In step S8, the method for obtaining the drift amount of ET and updating the transmission error term is as follows: S801: Based on the drift of the reflection tracking term, calculate the current drift of the transmission tracking term product: ΔET21_drift * ΔET12_drift ≈ ΔER11_drift * ΔER22_drift, where the first and second ports of the VNA are connected through the device under test (DUT), ΔET21_drift is the drift value of the transmission tracking error ET from the first port to the second port, ΔET12_drift is the drift value of the transmission tracking error ET from the second port to the first port, ΔER11_drift is the drift of the reflection tracking error ER at the first port, and ΔER22_drift is the drift of the reflection tracking error ER at the second port. S802: Based on the transmission characteristic S21=S12, the drift amount of ET is obtained: ΔET21_drift=sqrt(ΔER11_drift * ΔER22_drift * S21 / S12), ΔET12_drift=(ΔER11_drift * ΔER22_drift) / ΔET21_drift, Wherein, S21 is the S-parameter related term of the measured value of the device under test from the first port to the second port after compensation, and S12 is the S-parameter related term of the measured value of the device under test from the second port to the first port after compensation. S803: The updated transmission error term is as follows: ET21_new = ET21_orig*ΔET21_drift, ET12_new = ET12_orig*ΔET12_drift, Wherein, ET21_new is the transmission tracking error from the first port to the second port, and ET12_new is the transmission tracking error from the second port to the first port.

8. The self-calibration method for the VNA port expansion test system according to claim 7, characterized in that: Based on the corresponding connection relationship between the switch matrix and the VNA, the switch matrix is ​​divided into several differential pairs, and each differential pair is connected to each port of the VNA. Steps S2-S8 are executed periodically to measure the differential pairs connected to the device under test (DUT) in sequence, and several sets of error terms are obtained. Then, based on the average measurement data of multiple measurements, the drift of ET is calculated.

9. A self-calibration system for a VNA port expansion test system, used to implement the self-calibration method for the VNA port expansion test system according to any one of claims 1-8, characterized in that, include: Initialization module: Used for self-calibration initialization, obtaining the original error terms ED_orig, ES_orig, ER_orig, ET_orig, EL orig for each port at each frequency, as well as the frequency domain response reference value Γ1_init for the time domain data of the directivity error ED and the frequency domain response reference value Γ2_init for the time domain data of the reflection tracking error ER. Switching module: Used to switch the switch matrix to a specific state when recalibration is required, so that the path between port k of the VNA and its corresponding switch matrix output port is disconnected, where k is the VNA port number and VAN is the vector network analyzer; First time-domain response acquisition module: Port k transmits a signal and measures the reflected frequency domain data Γ_new(k) and its time-domain response in the disconnected state; Time-domain data acquisition module: used to obtain the time-domain data G1_new of the directivity error ED and the time-domain data G2_new of the reflection tracking error ER through the set first and second gating gates; The second frequency domain response acquisition module performs Fourier transform on G1_new and G2_new to obtain the corresponding frequency domain responses Γ1_new and Γ2_new. Reflection error correction module: It is used to calculate the drift of the reflection error term based on the frequency domain responses Γ1_new and Γ2_new obtained by recalibration relative to the frequency domain response reference value, and then update the directivity error ED and reflection tracking error ER of each port based on the drift. S-parameter measurement module: Connects to a high-speed cable and is used to perform S-parameter measurements on the DUT (Device Under Test). Transmission error correction module: used to obtain the drift amount of ET based on the drift amount of the reflection error term obtained in step S6, and update the transmission error term based on the drift amount of ET; S-parameter correction module: The VNA loads all updated error terms and corrects the measurement data of the current DUT to obtain accurate S-parameters.

10. A VNA port expansion test system, comprising a VNA and a switch matrix connected to the VNA, characterized in that: The VNA is equipped with a self-calibration system as described in claim 9 for the VNA port expansion test system.

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