Error calibration method and system applied to dual-tone group delay test
By combining secondary calibration with fixture extraction using a vector network analyzer, the problems of neglecting mixer calibration errors and complex calibration in existing technologies are solved, achieving high-precision group delay testing and simplifying the calibration process.
Patent Information
- Application Number
- CN202511585879.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-31
- Publication Date
- 2026-01-27
AI Technical Summary
In existing technologies, the two-tone excitation method ignores the error introduced by the calibration mixer, while the absolute phase control method requires an additional comb wave generator and has a complex calibration process, making it difficult to improve the test accuracy and calibration complexity of the communication system.
A method combining secondary calibration and fixture extraction is adopted. Two calibrations are performed using a vector network analyzer to obtain the group delay error of the calibrated mixer and test instrument. The error term is calculated using the least squares method, and the group delay value is calculated using the fixture extraction principle, thus simplifying the calibration process.
It accurately acquires and eliminates errors introduced by the calibration mixer, improves test accuracy, reduces calibration complexity, requires no additional equipment, and is suitable for group delay testing of multi-level frequency conversion links.
Smart Images
Figure CN121418005A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of testing technology, specifically relating to an error calibration method and system for two-tone group delay testing. Background Technology
[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.
[0003] Multi-stage frequency conversion receivers are widely used in satellite and mobile communications. The group delay of multi-stage frequency conversion links significantly impacts communication quality. For example, in satellite communications, where signal transmission distances are long and the environment is complex with competition for spectrum resources, receivers often employ a superheterodyne double-conversion structure. This effectively suppresses strong interference signals across a wide bandwidth, improves suppression of adjacent channels, and expands the dynamic range of the input level, enabling reliable communication under conditions of strong interference and congestion. Mobile communication receivers mostly use double-conversion schemes, with some employing triple-conversion schemes. Particularly in some mobile communication systems, the first intermediate frequency (IF) is chosen at a higher level to suppress image frequency interference, while the second IF is chosen at a lower level to suppress adjacent channel interference. The group delay of multi-stage frequency conversion links significantly affects communication quality, particularly causing signal waveform distortion and inter-symbol interference (ISI).
[0004] For multi-stage frequency converter group delay, existing technologies generally employ two-tone excitation or absolute phase control testing methods. However, the inventors have discovered that the two-tone excitation method often uses a normalized calibration method, neglecting the calibration error introduced by the calibrating mixer; while the error calibration of the absolute phase control testing method requires an additional comb wave generator, making calibration and the calibration process complex. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an error calibration method and system for two-tone group delay testing. By adopting a scheme that combines secondary calibration and fixture extraction, it can accurately acquire and eliminate calibration errors introduced by the calibration mixer and group delay of the test instrument and cable, thereby eliminating system errors at the source, effectively improving test accuracy, and reducing the complexity of test calibration.
[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: On one hand, the technical solution of the present invention provides an error calibration method for two-tone group delay testing, including: Basic parameters for configuring a vector network analyzer based on the frequency converter under test; A set of short-circuit standard components are connected sequentially to the RF port of the vector network analyzer for the first calibration, and the first set of error terms is calculated based on the measurement equation. Connect the RF port of the calibration mixer to the local oscillator and the vector network analyzer. Connect the same set of short-circuit standard components to the IF port of the calibration mixer in sequence for a second calibration. Calculate the second set of error terms based on the measurement equation. Based on the first group of error terms and the second group of error terms, the first group of time delay values are calculated using the fixture extraction principle. Connect the terminal interface of the calibrator to the test port of the vector network analyzer for pass-through measurement to obtain the second group delay value; calculate the difference between the second group delay value and the first group delay value to obtain the group delay error. Obtain the original group delay value of the frequency converter under test, and based on the group delay error, obtain the group delay value of the frequency converter under test.
[0007] In at least one embodiment, the basic parameters of the vector network analyzer include the scanning bands of radio frequency, local oscillator and intermediate frequency, excitation power and intermediate frequency bandwidth.
[0008] In at least one embodiment, the measurement equation is specifically expressed as:
[0009] In the formula, Indicates the measured value of a standard part; Indicates the calibration value of a standard part; Indicates directional error; Indicates reflection tracking error; This indicates the source matching error.
[0010] In at least one embodiment, the first calibration process specifically includes: A set of short-circuited standard components are connected sequentially to the RF port of a vector network analyzer. The first set of standard component measurement values are obtained by measuring the first set of standard component measurements at a specific frequency point using the vector network analyzer. Based on the first set of standard component measurement values, the measurement equation is solved using the least squares method to obtain the first set of error terms. The first set of error terms includes the first directivity error, the first reflection tracking error, and the first source matching error.
[0011] In at least one embodiment, the RF port of the calibration mixer is connected to the local oscillator and the vector network analyzer, specifically: the RF port of the calibration mixer is connected to the RF port of the vector network analyzer, and the local oscillator of the calibration mixer is connected to the port of the excitation source 2 of the vector network analyzer or an external signal generator.
[0012] In at least one embodiment, the second calibration process specifically includes: connecting the RF port of the calibration mixer to the local oscillator and a vector network analyzer; sequentially connecting the same set of short-circuit standard components to the IF port of the calibration mixer; measuring the second set of standard component values using the vector network analyzer; and solving the measurement equation using the least squares method based on the second set of standard component values to obtain the second set of error terms; wherein the second set of error terms includes a second directivity error, a second reflection tracking error, and a second source matching error.
[0013] In at least one embodiment, the first group delay value is calculated using the fixture extraction principle, specifically including: calculating the frequency conversion S-parameters of the calibrator based on the first group error terms and the second group error terms, and calculating the first group delay value based on the forward transmission coefficient in the frequency conversion S-parameters.
[0014] In at least one embodiment, the group delay error is specifically expressed as:
[0015] In the formula, Indicates group delay error; This represents the second group delay value, which is the total group delay value of the vector network analyzer, test cable, and calibration mixer. This represents the group delay value, which is the group delay value for calibrating the mixer.
[0016] In at least one embodiment, the original group delay value of the frequency converter under test is obtained, and the difference between the original group delay value and the group delay error is calculated to obtain the final group delay value of the frequency converter under test.
[0017] On the other hand, the technical solution of the present invention also provides an error calibration system for two-tone group delay testing, comprising: The initialization module is configured to: configure the basic parameters of the vector network analyzer based on the frequency converter under test; The first calibration module is configured to perform the first calibration when a set of short-circuit standard components are connected to the RF port of the vector network analyzer in sequence, and calculate the first set of error terms based on the measurement equation; The second calibration module is configured to perform a second calibration when the RF port of the calibration mixer is connected to the local oscillator and the vector network analyzer, and the same set of short-circuit standard components are sequentially connected to the IF port of the calibration mixer, and calculate the second set of error terms based on the measurement equation. The first group delay value calculation module is configured to calculate the first group delay value based on the first group error terms and the second group error terms using the fixture extraction principle. The second group delay value acquisition module is configured to perform pass-through measurement when the terminal interface of the calibrator is connected to the test port of the vector network analyzer to obtain the second group delay value; The group delay error calculation module is configured to: calculate the difference between the second group delay value and the first group delay value to obtain the group delay error; The group delay calibration module is configured to: acquire the original group delay value of the frequency converter under test, and obtain the group delay value of the frequency converter under test based on the group delay error.
[0018] The beneficial effects of the above-described technical solution of the present invention are as follows: 1) The error calibration method of the present invention for two-tone group delay testing adopts a combination of secondary calibration and fixture extraction, which can accurately acquire and eliminate the calibration error introduced by the calibration mixer and the group delay of the test instrument and cable, thereby eliminating system error from the root, effectively improving test accuracy and reducing the complexity of test calibration.
[0019] 2) This invention does not rely on additional complex and expensive calibration equipment such as comb wave generators, and also avoids the complex calibration process in the absolute phase control method, greatly simplifying the calibration process and configuration.
[0020] 3) This invention can obtain the group delay of the calibrated mixer through single-port reciprocity. It has a simple connection, high reliability, and can be applied to multi-level frequency converter group delay test scenarios. It removes the group delay error of the link, improves test accuracy, and reduces the complexity of test calibration. Attached Figure Description
[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0022] Figure 1 This is a schematic diagram of the error calibration method for two-tone group delay testing disclosed in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram illustrating the application of the error calibration method for two-tone group delay testing disclosed in Embodiment 1 of the present invention. Detailed Implementation
[0023] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0024] Example 1 In low-Earth orbit (LEO) satellite transponders and microwave backhaul systems for mobile communication, the group delay of multi-stage frequency conversion links significantly impacts system performance. Testing and calibration are critical challenges, especially since the radio frequency (RF) and intermediate frequency (IF) frequencies in these links are not synchronized, making link-related errors difficult to correct. Furthermore, the introduction of higher frequency bands such as the D-band has brought challenges to testing wideband frequency conversion links, requiring the use of multiple short-circuit calibration components to obtain error terms. Applying these components to frequency conversion device testing is also a significant challenge.
[0025] There are two main methods: one is to use a calibration mixer with a small delay for normalization, ignoring the error introduced by the delay of the calibration mixer; the other is to use a mixer with a known group delay, and perform normalization calibration after connecting it to the link. However, its error calibration requires an additional comb wave generator, and the calibration process is complicated.
[0026] Based on this, in a typical embodiment of the present invention, such as Figure 1 and Figure 2 As shown, this embodiment discloses an error calibration method for two-tone group delay testing, including the following steps: S1. Basic parameters for configuring a vector network analyzer based on the frequency converter under test; S2. Connect a set of short-circuit standard components sequentially to the RF port of the vector network analyzer for the first calibration, and calculate the first set of error terms based on the measurement equation; S3. Connect the RF port of the calibration mixer to the local oscillator and the vector network analyzer. Connect the same set of short-circuit standard components to the IF port of the calibration mixer in sequence for a second calibration. Calculate the second set of error terms based on the measurement equation. S4. Based on the first group of error terms and the second group of error terms, the first group of time delay values are calculated using the fixture extraction principle; S5. Connect the terminal interface of the calibrator to the test port of the vector network analyzer to perform a pass-through measurement and obtain the second group delay value; S6. Subtract the second group delay value from the first group delay value to obtain the group delay error; S7. Obtain the original group delay value of the frequency converter under test, and obtain the group delay value of the frequency converter under test based on the group delay error.
[0027] This method, through an innovative calibration architecture, combines secondary calibration, fixture de-embedding techniques, and a least-squares algorithm, successfully achieving a significant improvement in test accuracy and a substantial simplification of the calibration process simultaneously without increasing system complexity. Furthermore, this method features simple equipment connection and high reliability, making it particularly suitable for widespread application in the R&D and production testing of multi-stage frequency converter devices in modern complex communication systems (such as satellite communication and mobile communication backhaul). It provides an efficient and reliable solution to the challenge of group delay testing in high-frequency broadband frequency converter links. The following detailed description of the error calibration method applied to two-tone group delay testing, along with specific implementation details, further illustrates this approach.
[0028] A Vector Network Analyzer (VNA) is an electromagnetic wave energy testing device that measures the complete amplitude and phase information of electromagnetic waves (radio frequency signals) as they are transmitted and reflected in a network. It is mainly used to measure the scattering parameters (S-parameters) of electronic components such as radio frequency microwave devices, antennas, and cables over a wide bandwidth.
[0029] In step S1, the vector network analyzer is first initialized with hardware, and then the basic parameters of the vector network analyzer are configured according to the frequency converter under test, including the scanning frequency bands of radio frequency, local oscillator and intermediate frequency, excitation power and intermediate frequency bandwidth and other basic parameters.
[0030] In step S2, based on the vector network analyzer with its initial configuration, the error term of the vector network analyzer is obtained in the high-frequency band using a multi-short-circuit characterization method, serving as the first calibration. Specifically, a set of multiple short-circuit standard components... Connect the components sequentially to port 1 (RF port) of the vector network analyzer. Use the vector network analyzer to measure at a specific frequency point in the high-frequency band, obtaining the measurement values of these multiple short-circuited standard components, thus obtaining the first set of standard component measurement values. .
[0031] Then, based on the single-port error model of the vector network analyzer, the measurement equation of the vector network analyzer can be obtained, specifically expressed as:
[0032] In the formula, Indicates the measured value of the standard part. ; Indicates the calibration value of a standard part; Indicates directional error; Indicates reflection tracking error; This indicates the source matching error.
[0033] The measurement values of the first set of standard parts Substituting the above measurement equations, we obtain the following system of equations:
[0034] The least squares method is used to solve the above simultaneous measurement equations for directional error, reflection tracking error, and source matching error, yielding the first set of error terms, which is expressed as the first directional error. First reflection tracking error Matching error with the first source .
[0035] After step S2 is completed, the first set of error terms obtained is the single-port error of the vector network analyzer. Next, it is necessary to obtain the single-port error terms of the entire port 1, including the vector network analyzer, the test cable, and the calibration mixer, after connecting to the calibration mixer.
[0036] In step S3, the RF port of the calibration mixer is connected to the RF port of the vector network analyzer, and the local oscillator of the calibration mixer is connected to the port of excitation source 2 of the vector network analyzer or an external signal generator. Then, the same set of short-circuit standards from step S2 are sequentially connected to the intermediate frequency port of the calibration mixer, and the measurement values of the second set of standards are obtained by measuring with the vector network analyzer. Substituting the measured values of the second set of standard parts into the measurement equation, the least squares method is used to solve the measurement equation for directional error, reflection tracking error, and source matching error, yielding the second set of error terms, which are expressed as the second directional error. Second reflection tracking error Second source matching error This process is the same as the calculation process in step S2, and will not be described in detail here.
[0037] In step S4, based on the first set of error terms and the second set of error terms calculated in steps S2 and S3, the frequency conversion S-parameters of the calibrated mixer are obtained according to the fixture extraction principle, specifically expressed as follows:
[0038]
[0039]
[0040] Then based on the calculations... Calculate the group delay value of the calibration mixer and record it as the first group delay value. .
[0041] In step S5, the terminal interface of the calibration mixer is connected to the test port (port 2) of the vector network analyzer for pass-through measurement to obtain the total group delay value of the vector network analyzer, test cable, and calibration mixer, which is recorded as the second group delay value. .
[0042] In step S6, the group delay error is obtained by subtracting the second group delay value from the first group delay value, and is expressed as:
[0043] In the formula, This represents the group delay error, which is the group delay error of the test instrument, namely the vector network analyzer and the test cable.
[0044] In step S7, after obtaining the group delay error of the vector network analyzer and the test cable, the frequency converter under test is connected, the original group delay value of the frequency converter under test is obtained, and the original group delay value is compared with the group delay error. By subtracting the values, the final group delay value of the frequency converter under test can be obtained.
[0045] The error calibration method for two-tone group delay testing in this embodiment obtains the group delay of a calibration mixer with reciprocity characteristics through two single-port calibrations using a vector network analyzer. Then, after connecting this calibration mixer to the link under test (DUT), the group delay of the entire link is acquired. Finally, the DUT is connected, and the original group delay value is obtained. Subtracting the group delay error yields the final group delay characteristic of the DUT. This method, through a two-stage calibration scheme, allows for the calculation of the calibration mixer's group delay using single-port reciprocity. It features simple connection, high reliability, and can be applied to multi-stage frequency converter group delay testing scenarios. It removes the group delay error of the link, improves test accuracy, and reduces the complexity of test calibration.
[0046] Example 2 In a typical embodiment of the present invention, this embodiment discloses an error calibration system for two-tone group delay testing, comprising: The initialization module is configured to: configure the basic parameters of the vector network analyzer based on the frequency converter under test; The first calibration module is configured to perform the first calibration when a set of short-circuit standard components are connected to the RF port of the vector network analyzer in sequence, and calculate the first set of error terms based on the measurement equation; The second calibration module is configured to perform a second calibration when the RF port of the calibration mixer is connected to the local oscillator and the vector network analyzer, and the same set of short-circuit standard components are sequentially connected to the IF port of the calibration mixer, and calculate the second set of error terms based on the measurement equation. The first group delay value calculation module is configured to calculate the first group delay value based on the first group error terms and the second group error terms using the fixture extraction principle. The second group delay value acquisition module is configured to perform pass-through measurement when the terminal interface of the calibrator is connected to the test port of the vector network analyzer to obtain the second group delay value; The group delay error calculation module is configured to: calculate the difference between the second group delay value and the first group delay value to obtain the group delay error; The group delay calibration module is configured to: acquire the original group delay value of the frequency converter under test, and obtain the group delay value of the frequency converter under test based on the group delay error.
[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. An error calibration method applied to two-tone group delay testing, characterized in that, include: Basic parameters for configuring a vector network analyzer based on the frequency converter under test; A set of short-circuit standard components are connected sequentially to the RF port of the vector network analyzer for the first calibration, and the first set of error terms is calculated based on the measurement equation. Connect the RF port of the calibration mixer to the local oscillator and the vector network analyzer. Connect the same set of short-circuit standard components to the IF port of the calibration mixer in sequence for a second calibration. Calculate the second set of error terms based on the measurement equation. Based on the first group of error terms and the second group of error terms, the first group of time delay values are calculated using the fixture extraction principle. Connect the terminal interface of the calibrator to the test port of the vector network analyzer for pass-through measurement to obtain the second group delay value; The group delay error is obtained by subtracting the delay value of the second group from the delay value of the first group. Obtain the original group delay value of the frequency converter under test, and based on the group delay error, obtain the group delay value of the frequency converter under test.
2. The error calibration method for two-tone group delay testing as described in claim 1, characterized in that, The basic parameters of a vector network analyzer include the scanning frequency bands of radio frequency (RF), local oscillator (LO), and intermediate frequency (IF), as well as the excitation power and IF bandwidth.
3. The error calibration method for two-tone group delay testing as described in claim 1, characterized in that, The measurement equation is specifically expressed as follows: In the formula, Indicates the measured value of a standard part; Indicates the calibration value of a standard part; Indicates directional error; Indicates reflection tracking error; This indicates the source matching error.
4. The error calibration method for two-tone group delay testing as described in claim 1, characterized in that, The first calibration process specifically includes: A set of short-circuited standard components are connected sequentially to the RF port of a vector network analyzer. The first set of standard component measurement values are obtained by measuring the first set of standard component measurements at a specific frequency point using the vector network analyzer. Based on the first set of standard component measurement values, the measurement equation is solved using the least squares method to obtain the first set of error terms. The first set of error terms includes the first directivity error, the first reflection tracking error, and the first source matching error.
5. The error calibration method for two-tone group delay testing as described in claim 1, characterized in that, Connect the RF port of the calibration mixer to the local oscillator and the vector network analyzer. Specifically, connect the RF port of the calibration mixer to the RF port of the vector network analyzer, and connect the local oscillator of the calibration mixer to the port of excitation source 2 of the vector network analyzer or an external signal generator.
6. The error calibration method for two-tone group delay testing as described in claim 1, characterized in that, The second calibration process specifically includes: connecting the RF port of the calibration mixer to the local oscillator and the vector network analyzer; connecting the same set of short-circuited standard components to the IF port of the calibration mixer in sequence; and obtaining the measurement values of the second set of standard components through the vector network analyzer. Based on the measurement values of the second set of standard components, the measurement equation is solved using the least squares method to obtain the second set of error terms. The second set of error terms includes the second directivity error, the second reflection tracking error, and the second source matching error.
7. The error calibration method for two-tone group delay testing as described in claim 1, characterized in that, The first group of time delay values is calculated using the fixture extraction principle. Specifically, this includes: calculating the frequency conversion S-parameters of the calibrator based on the first and second group of error terms using the fixture extraction principle, and calculating the first group of time delay values based on the forward transmission coefficient in the frequency conversion S-parameters.
8. The error calibration method for two-tone group delay testing as described in claim 1, characterized in that, The group delay error is specifically expressed as: In the formula, Indicates group delay error; This represents the second group delay value, which is the total group delay value of the vector network analyzer, test cable, and calibration mixer. This represents the group delay value, which is the group delay value for calibrating the mixer.
9. The error calibration method for two-tone group delay testing as described in claim 1, characterized in that, Obtain the original group delay value of the frequency converter under test, and subtract the original group delay value from the group delay error to obtain the final group delay value of the frequency converter under test.
10. An error calibration system applied to two-tone group delay testing, characterized in that, include: The initialization module is configured to: configure the basic parameters of the vector network analyzer based on the frequency converter under test; The first calibration module is configured to perform the first calibration when a set of short-circuit standard components are connected to the RF port of the vector network analyzer in sequence, and calculate the first set of error terms based on the measurement equation; The second calibration module is configured to perform a second calibration when the RF port of the calibration mixer is connected to the local oscillator and the vector network analyzer, and the same set of short-circuit standard components are sequentially connected to the IF port of the calibration mixer, and calculate the second set of error terms based on the measurement equation. The first group delay value calculation module is configured to calculate the first group delay value based on the first group error terms and the second group error terms using the fixture extraction principle. The second group delay value acquisition module is configured to perform pass-through measurement when the terminal interface of the calibrator is connected to the test port of the vector network analyzer to obtain the second group delay value; The group delay error calculation module is configured to: calculate the difference between the second group delay value and the first group delay value to obtain the group delay error; The group delay calibration module is configured to: acquire the original group delay value of the frequency converter under test, and obtain the group delay value of the frequency converter under test based on the group delay error.