Search

CN-122026952-A - Self-calibration method and system of VNA port expansion test system and test system

CN122026952ACN 122026952 ACN122026952 ACN 122026952ACN-122026952-A

Abstract

The invention provides a self-calibration method, a self-calibration system and a self-calibration test system of a VNA port extension test system, wherein the method comprises the steps of recalibrating to ensure that a path between a VNA port and a corresponding switch matrix output port is in a disconnected state; the method comprises the steps of transmitting signals by ports, measuring reflected frequency domain data and time domain response of the reflected frequency domain data in an off state, obtaining time domain data of directional errors, time domain data of reflected tracking errors and corresponding frequency domain response through a first gate and a second gate, calculating drift amount of a reflected error item, updating the directional errors and the reflected tracking errors of each port, measuring S parameters of a DUT to be tested, obtaining the drift amount of ET by the obtained drift amount of the reflected error item, updating a transmission type error item based on the drift amount of ET, and correcting the measured data of the DUT to be tested to obtain accurate S parameters. The invention can realize the self-calibration function without interrupting production and improve the test efficiency.

Inventors

  • HUANG SHUNCHANG
  • DENG YANG

Assignees

  • 深圳市极致汇仪科技有限公司

Dates

Publication Date
20260512
Application Date
20260302

Claims (10)

  1. 1. The self-calibration method of the VNA port expansion test system is characterized by comprising the following steps of: S1, self-calibration initialization is carried out to obtain original error items ED_orig, ES_orig, ER_orig, ET_orig and EL orig of each port under each frequency, and frequency domain response reference values Γ1_init and Γ2_init of directional error ED time domain data; S2, recalibrating, namely switching the switch matrix to a specific state, so that a path between a port k of the VNA and an output port of the corresponding switch matrix is in a disconnected state, wherein k is a port number of the VNA, and VAN is a vector network analyzer; S3, transmitting signals by a port k and measuring reflected frequency domain data gamma_new (k) in an off state and time domain response of the reflected frequency domain data gamma_new (k); s4, setting a first gate and a second gate to obtain time domain data G1_new of a directivity error ED and time domain data G2_new of a reflection tracking error ER; S5, carrying out Fourier transformation on the G1_new and the G2_new to obtain corresponding frequency domain responses Γ1_new and Γ2_new; S6, calculating the drift amount of a reflection error term based on the frequency domain responses Γ1_new and Γ2_new obtained through recalibration relative to a frequency domain response reference value, and updating the directivity error ED and the reflection tracking error ER of each port based on the drift amount; s7, connecting a high-speed cable, and measuring S parameters of the DUT to be tested; s8, acquiring the drift amount of the ET based on the drift amount of the reflection error item acquired in the step S6, and updating the transmission type error item based on the drift amount of the ET; And S9, the VNA loads all updated error items, and corrects the measurement data of the DUT to be tested to obtain accurate S parameters.
  2. 2. The method of self-calibration of a VNA port expansion test system according to claim 1, wherein in step S1, each port of the VNA and switch matrix combination is calibrated using a calibration component to obtain and store in the VNA the original error terms ED_orig, ES_orig, ER_orig, ET_orig, EL orig for each port at the respective frequencies.
  3. 3. The method for self-calibration of the VNA port extension test system according to claim 1, wherein in step S1, the following operations are performed for each port of the VNA, and frequency domain response reference values Γ1_init and Γ2_init of each port are obtained as self-calibration references of reflection type error terms of each port: A1, switching the switch matrix to a specific state, so that a path between a VNA port k and a corresponding switch matrix output port is in an off state; a2, VNA port k emits signals and measures the reflection coefficient Γ_init (f) of the disconnected state; a3, performing inverse Fourier transform on the measured frequency domain data Γ_init (f) to obtain time domain response; a4, setting two time domain gating gates on the time domain response diagram to obtain a time domain data reference value G1_init of a directivity error ED and a time domain data reference value G2_init of a reflection tracking error ER; A5, carrying out Fourier transform on the G1_init and the G2_init to obtain corresponding frequency domain response reference values Γ1_init and Γ2_init; A6, storing the calculated frequency domain response reference values Γ1_init and Γ2_init in the VNA together with the corresponding port and frequency information.
  4. 4. The method of self-calibration of a VNA port expansion test system according to claim 3, wherein the first gate is set before the switch is turned off, and the energy in the gate mainly corresponds to a directivity error ED of the system from negative time to a moment close to a reflection peak of the switch, and the time domain data in the gate is calculated to obtain a reference value G1_init of the directivity error ED.
  5. 5. The method for self-calibration of a VNA port expansion test system according to claim 3, wherein the second gate is a window centered on a reflection peak of a switch off position, the range covers all main time domain energy in an open state, the energy in the second gate corresponds to a reflection tracking error ER of the system, and the time domain data in the second gate is calculated to obtain a reference value G2_init of the reflection tracking error ER.
  6. 6. The method for self-calibration of a VNA port expansion test system according to claim 1, wherein in step S5, the calculation formula of the drift amount ΔED_drift of the directivity error is ΔED_drift=Γ1_new- Γ1_init, and the calculation formula of the drift amount ΔER_drift of the reflection tracking error ER is ΔER_drift=Γ2_new/Γ2_init.
  7. 7. The method for self-calibrating a VNA port expansion test system according to claim 6, wherein in step S8, the method for obtaining the drift amount of ET and updating the transmission type error term comprises the steps of: S801, calculating the current drift of a product of the transmission tracking items based on the drift amount of the reflection tracking items, wherein DeltaET 21_drift is DeltaET 12_drift approximately equal to DeltaER11_drift, deltaER22_drift is carried out, wherein a first port and a second port of the VNA are communicated through a DUT (under test), deltaET 21_drift is a drift value of a transmission tracking error ET from the first port to the second port, deltaET 12_drift is a drift value of a transmission tracking error ET from the second port to the first port, deltaER11_drift is a drift amount of a reflection tracking error ER of the first port, and DeltaER22_drift is a drift amount of a reflection tracking error ER of the second port; S802. according to 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 from the first port to the second port of the measured piece after compensation, S12 is the S parameter related term of the measured value from the second port to the first port of the measured piece after compensation, S803, after updating the transmission type error item, the method comprises the following steps: ET21_new = ET21_orig*ΔET21_drift, ET12_new = ET12_orig*ΔET12_drift, where 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. 8. The method for self-calibration of a VNA port expansion test system according to claim 7, wherein the method is characterized in that the switch matrix is formed into a plurality of differential pairs based on the corresponding connection relation between the switch matrix and the VNA, each differential pair is respectively connected with each port of the VNA, step S2-step S8 are periodically executed, the differential pairs connected with a DUT are sequentially measured to obtain a plurality of groups of error items, and then the drift amount of ET is calculated based on average measurement data of a plurality of times of measurements.
  9. 9. A self-calibration system of a VNA port extension test system for implementing the self-calibration method of the VNA port extension test system of any one of claims 1-8, comprising: The initialization module is used for self-calibrating initialization to obtain original error items ED_orig, ES_orig, ER_orig, ET_orig and EL orig of each port under each frequency, and frequency domain response reference values Γ1_init and Γ2_init of the directional error ED time domain data; the switching module is used for switching the switch matrix to a specific state when recalibration is needed, so that a path between a port k of the VNA and an output port of the corresponding switch matrix is in a disconnected state, k is a port number of the VNA, and VAN is a vector network analyzer; the first time domain response acquisition module is used for transmitting signals through a port k and measuring reflection frequency domain data gamma_new (k) in a disconnection state and time domain response of the reflection frequency domain data gamma_new (k); the time domain data acquisition module is used for obtaining time domain data G1_new of the directivity error ED and time domain data G2_new of the reflection tracking error ER through the set first gate and second gate; the second frequency domain response acquisition module is used for carrying out Fourier transform on the G1_new and the G2_new to obtain corresponding frequency domain responses Γ1_new and Γ2_new; The reflection error correction module is used for calculating the drift amount of a reflection error term based on the frequency domain responses Γ1_new and Γ2_new obtained through recalibration relative to the frequency domain response reference value, and then updating the directivity error ED and the reflection tracking error ER of each port based on the drift amount; The S parameter measurement module is connected with the high-speed cable and is used for carrying out S parameter measurement on the DUT to be measured; the transmission type error correction module is used for acquiring the drift amount of the ET based on the drift amount of the reflection error item acquired in the step S6 and updating the transmission type error item based on the drift amount of the ET; and the S parameter correction module is used for loading all updated error items by the VNA, correcting the measurement data of the DUT to be tested to obtain accurate S parameters.
  10. 10. A VNA port expansion test system comprises a VNA and a switch matrix connected with the VNA, and is characterized in that a self-calibration system of the VNA port expansion test system is arranged in the VNA.

Description

Self-calibration method and system of VNA port expansion test system and test system Technical Field The invention relates to the technical field of communication test, in particular to a self-calibration method and a self-calibration system of a VNA port expansion test system, and also relates to the VNA port expansion test system. Background In modern high speed digital communications, such as USB4, PCIe, 5G/6G communications, etc., high speed cables and connectors are critical physical media for signal transmission, where signal integrity (SIGNAL INTEGRITY, SI) performance is critical. Vector network analyzer (Vector Network Analyzer, VNA) is a core instrument for measuring S parameters (e.g., insertion loss, return loss, etc.) of cable assembly, and is a standard tool for evaluating SI performance With the rapid development of high-speed communication, the number of channels increases from a few conventional channels to tens or even hundreds of channels, and the number of cable channels increases sharply, and an automated test system is usually built by using a four-port or multi-port VNA in combination with a large-scale switch matrix (e.g., 16 ports or more) to achieve efficient measurement of all channels. Currently, in order to ensure the measurement accuracy of the VNA test system, a strict system calibration must be performed before performing the S-parameter test. The traditional calibration method is to connect a known calibration element (typically an electronic calibration element E-Cal, or a mechanical calibration kit consisting of an Open-Open, a Short-Short, a Load-Load, a pass-through-thre) to each port of the switch matrix in turn, and the VNA calculates a mathematical error model by measuring the responses of these standard elements and comparing them to their known electrical characteristics. The model contains a plurality of error terms, such as directivity Error (ED), source match Error (ES), reflection tracking Error (ER), transmission tracking Error (ET), load match Error (EL), etc. In subsequent measurements of the device under test (Device Under Test, DUT), the VNA uses this error model to correct the raw measurement data, eliminating systematic errors introduced by test instruments, cables, clamps, etc., thus obtaining the true S-parameters of the DUT. This process requires connection and measurement of each port of the switch matrix until all ports are calibrated. The above-mentioned traditional calibration method of VNA plus switch matrix has the following serious drawbacks when applied to large-scale and high-efficiency testing of production lines: (1) Time and effort consuming, inefficient, large numbers of ports (e.g., 64 or more) in the switch matrix, high port density, and small pitch. The operator needs to manually connect the calibration piece to each port in turn, which is cumbersome, takes very long, and typically takes several hours to complete a full port calibration. (2) Limiting productivity and being costly, the whole test system must stop normal production test work, i.e. "off-line", each time calibration is performed. This directly results in a reduction in the effective man-hours of the production line, which forms a serious constraint on productivity and increases the test cost per unit product. (3) The performance of the VNA test system may drift with changes in ambient temperature, humidity, etc. To ensure accuracy, calibration needs to be performed frequently. However, the calibration itself is huge in time consumption, so that high-frequency calibration cannot be achieved in actual operation, and therefore, measurement errors caused by system drift gradually accumulate in the interval between two calibrations, and accuracy and consistency of test results are affected. (4) The physical loss is increased, namely, the calibration piece and the test clamp are frequently inserted and pulled out, so that mechanical abrasion is caused to the expensive connector, the cable and the clamp, the service life of the connector is shortened, and the maintenance cost is increased. Therefore, there is an urgent need for a calibration method that can be done quickly, automatically, and without interrupting production, to solve the bottlenecks of the prior art. Disclosure of Invention In order to solve the fundamental problems of time consumption and influence on productivity of the VNA calibration in the prior art, the invention provides a self-calibration method of the VNA port expansion test system, a self-calibration system for realizing the self-calibration method, and a VNA port expansion test system provided with the self-calibration system. The self-calibration method of the invention comprises the following steps: S1, self-calibration initialization is carried out to obtain original error items ED_orig, ES_orig, ER_orig, ET_orig and EL orig of each port under each frequency, and frequency domain response reference values Γ1_init and Γ2_init of directional error ED t