Cable defect detection device and method based on phase shift coupling frequency domain reflection

Abstract

The invention discloses a cable defect detection device and method based on phase shift coupling frequency domain reflection, and belongs to the technical field of power cable detection, the cable defect detection device comprises a master control module, a signal generator, a phase shifter, a first coupler, a second coupler, a first signal comparator and a second signal comparator; the signal generator generates an original sweep frequency signal; the phase shifter is used for performing phase shifting processing on the original sweep frequency signal; the first coupler is used for receiving a test signal, inputting the test signal into a cable to be tested, separating a reflected signal, outputting the test signal to the first signal comparator, and outputting the reflected signal to the first signal comparator and the second signal comparator; the second coupler is used for receiving a reference signal and inputting the reference signal into the second signal comparator. According to the cable defect detection device and method based on phase shift coupling frequency domain reflection, the phase shifter is introduced to construct a two-way comparison architecture, phase ambiguity is effectively overcome, and the detection precision and reliability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power cable detection, and in particular to a cable defect detection device and method based on phase-shift coupled frequency domain reflection. Background Art

[0002] With the advancement of infrastructure modernization, power cables have become a core component of modern power transmission and distribution networks. However, during cable manufacturing, installation, and long-term operation, construction defects, mechanical impacts, and complex environmental factors can easily damage the insulation layer. These hazards can cause partial discharge and even lead to insulation breakdown. Therefore, accurately locating local cable defects is not only a key technology for preventing line failures but also an important support for ensuring the reliable operation of the power grid.

[0003] Currently, cable defect location technologies primarily include impedance, partial discharge, and traveling wave methods. The traveling wave method is widely used due to its ease of use and minimal hardware requirements. It injects a unipolar, low-voltage pulse signal into the cable headend, using the reflected wave generated by the defect or impedance mismatch to locate the defect. The defect location is calculated by measuring the time difference between the incident and reflected waves and combining this with the propagation velocity of electromagnetic waves.

[0004] However, the traveling wave method has significant drawbacks: Single pulse signals have low energy, resulting in rapid attenuation of reflected signals in large or multiple defect scenarios, reducing positioning accuracy; single pulses have poor anti-interference capabilities, and noise in complex electromagnetic environments can easily drown out the effective signal; high-frequency pulses severely attenuate over long transmission distances, making it difficult to detect micron-level insulation defects; and the superposition of signal reflections in multi-branch cable networks can easily cause aliasing interference, leading to increased positioning errors. These limitations make it only suitable for short-distance, single-defect scenarios, making it difficult to meet the high-precision detection requirements of modern power systems in complex environments.

[0005] Determining defect locations using single-path frequency domain reflectometry has significant limitations. Due to the non-uniqueness of the reflected signal phase, it is often impossible to accurately determine the true phase of the reflected signal. For example, when the phase difference between reflected signal R1 and test signal S2 is Δθ1, the real part of reflected signal R1 can be expressed by the following formula:

[0006]

[0007] in,

[0008]

[0009] However, due to the periodicity and symmetry of the cosine function, this representation method has multiple possible solutions. That is, when the phase difference Δθ1 is a certain value, the real part of the reflected signal can correspond to multiple phase states. This phenomenon makes it impossible to uniquely determine the phase of the reflected signal by relying solely on a single signal, which leads to phase ambiguity and affects the accuracy of defect location. Summary of the Invention

[0010] The purpose of the present invention is to provide a cable defect detection device and method based on phase-shift coupled frequency domain reflection, which effectively overcomes phase ambiguity and improves detection accuracy and reliability by introducing a phase shifter to construct a dual-path comparison architecture.

[0011] To achieve the above-mentioned objectives, the present invention provides a cable defect detection device based on phase-shift coupled frequency domain reflection, comprising a master control module, a signal generator, a phase shifter, a first coupler, a second coupler, a first signal comparator and a second signal comparator; the signal generator generates an original swept frequency signal; the phase shifter is used to perform phase shift processing on the original swept frequency signal; the first coupler is used to receive a test signal and input it into the cable to be tested to separate the reflected signal, and then output the test signal to the first signal comparator, and output the reflected signal to the first signal comparator and the second signal comparator; the second coupler is used to receive a reference signal and input the reference signal into the second signal comparator; the first signal comparator is used to output information representing the amplitude relationship and phase difference between the test signal and the reflected signal; the second signal comparator is used to output information representing the amplitude relationship and phase difference between the reference signal and the reflected signal; the master control module controls the signal generator to generate a signal and comprehensively processes the two channels of information.

[0012] The present invention provides a cable defect detection method based on phase-shift coupling frequency domain reflection, comprising the following steps:

[0013] S1, the master control module controls the signal generator to generate the original sweep frequency signal. The original sweep frequency signal is processed by the phase shifter to form a test signal S2 which is input into the first coupler, and the other path forms a reference signal S1 which is input into the second coupler.

[0014] S2, the first coupler inputs the test signal S2 into the cable to be tested and separates the reflected signal R1, then outputs the test signal S2 to the first signal comparator, and outputs the reflected signal R1 to the first signal comparator and the second signal comparator at the same time;

[0015] S3, the second coupler inputs the reference signal S1 into the second signal comparator;

[0016] S4, the first signal comparator compares the amplitude and phase of the test signal S2 and the reflected signal R1, and outputs information representing the amplitude relationship and phase difference between the test signal S2 and the reflected signal R1; the second signal comparator compares the amplitude and phase of the reference signal S1 and the reflected signal R1, and outputs information representing the amplitude relationship and phase difference between the reference signal S1 and the reflected signal R1;

[0017] S5. The master control module comprehensively analyzes the two comparison information and uses the known phase difference between the test signal S2 and the reflected signal R1 and the comparison result with the reflected signal R1 to accurately determine the spectrum characteristics of the reflected signal R1 and calculate the defect location.

[0018] Preferably, S5 specifically includes the following operations:

[0019] S5.1. The master control module determines the precise phase spectrum characteristics of the reflected signal R1 based on the phase difference information output by the first signal comparator, the phase difference information output by the second signal comparator, and a preset known phase difference;

[0020] S5.2. The master control module calculates the amplitude spectrum characteristics of the reflected signal R1 based on the amplitude relationship information output by the first signal comparator and / or the second signal comparator and the determined precise phase spectrum characteristics;

[0021] S5.3. The master control module processes the determined spectrum characteristics of the reflection signal R1 to obtain time domain reflection characteristics, and calculates the defect location in combination with the propagation speed of the electromagnetic wave in the cable.

[0022] Preferably, in S5.1, the amplitude spectrum characteristics and phase spectrum characteristics of the reflected signal R1, the test signal S2, and the reference signal S1 are used to accurately calculate the reflection phase of the reflected signal R1, and the reflected signal R1 is decomposed into real and imaginary parts along the direction of the test signal S2, as shown below:

[0023]

[0024] in, is the phase of the reflected signal R1, is the phase of the test signal S2;

[0025] Introduce the reference signal S1 and ensure that the test signal S2 has a preset known phase difference with the reference signal S1 The reflected signal R1 is decomposed into real and imaginary parts along the direction of the reference signal S1, as shown below:

[0026]

[0027] in, is the phase of the reference signal S1;

[0028] The phase differences of the two paths measured respectively are:

[0029]

[0030] Where Δθ1 is the phase difference of the test path, and Δθ2 is the phase difference of the reference path;

[0031] Substituting the preset known phase difference Δθ into formula (5) and formula (6), the following relationship is obtained:

[0032] Δθ2=Δθ1+Δθ (7);

[0033] According to formula (7), we can get The accurate value of can be used to eliminate the phase ambiguity caused by the non-uniqueness of the cosine function generated by the single path measurement.

[0034] Preferably, in S5.2, the amplitude spectrum characteristics and phase spectrum characteristics of the reflected signal R1, the test signal S2, and the reference signal S1 are used to accurately calculate the reflection amplitude of the reflected signal R1, and the reflected signal R1 is decomposed into real and imaginary parts along the direction of the test signal S2, as shown below:

[0035]

[0036] in, is the phase of the reflected signal R1, is the phase of the test signal S2.

[0037] Preferably, the data processing method in S5.3 is:

[0038] For the amplitude, the average value of the two signals is used for optimization. If the amplitudes of the two signals are significantly different, the measurement result is discarded and re-measured.

[0039] For phase, the quality of the phase data is judged and different processing strategies are adopted. The applicable scenarios of the processing strategies include but are not limited to amplitude-only, phase-only, amplitude-only, phase-only, amplitude-only, phase-only, and amplitude-only. The following takes amplitude-only, phase-only as a typical scenario. The specific screening rules are as follows:

[0040] Assume β is the distribution interval of the phase measurement value within its range, set two proportional coefficients α1 and α2, where 0<α1<α2, to evaluate the quality of the data; the specific evaluation indicators are: when β<α1 or β>1-α1, the data quality is low; when α1≤β<α2 or 1-α2<β≤1-α1, the data quality is medium; when α2≤β≤1-α2, the data quality is high; the quality of the data corresponding to the two measured phase values is β1 and β2 respectively, and the phase data is processed as follows:

[0041] (1) When the data quality β1 is in the low data quality range, that is, β1 < α1 or β1 > 1-α1, the data of this channel is considered unreliable and the measurement result of this channel is completely discarded. Only the measurement result of the other channel is used as the final phase value; if the data quality β2 is in the low quality range, only the measurement result of the other channel is used as the final phase value;

[0042] (2) When both β1 and β2 are in the range of high data quality, that is, α2≤β1≤1-α2 and α2≤β2≤1-α2, both data are considered reliable and the arithmetic mean of the two measurement results is used as the final phase value;

[0043] (3) In other cases, if both channels are in the medium data quality range, that is, when α1≤β<α2 or 1-α2<β≤1-α1, or when one channel is high and the other channel is medium quality, a weighted average can be performed based on the specific values of β1 and β2, and a larger weight can be assigned to the channel with higher quality to obtain the final phase value.

[0044] According to the above screening rules, scenarios with one channel for amplitude and one channel for phase, two channels for amplitude and one channel for phase, and two channels for amplitude and two channels for phase can be adapted according to this logic: the quality judgment criteria and processing principles for single / multi-channel amplitude / phase are completely reused, only the number of channels is adjusted, low-quality channels are discarded and high-quality channel results are retained first, and redundancy check is triggered when multiple channels have low quality.

[0045] Therefore, the present invention adopts the above-mentioned cable defect detection device and method based on phase-shift coupled frequency domain reflection, and constructs a dual-path comparison architecture by introducing a phase shifter to effectively overcome phase ambiguity and improve detection accuracy and reliability.

[0046] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a structural schematic diagram of a cable defect detection device based on phase-shift coupled frequency domain reflection according to the present invention;

[0048] Figure 2 The present invention is a method for detecting cable defects based on phase-shift coupling frequency domain reflection, which uses phase-shift coupling signals to accurately determine reflection signals. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0050] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0051] Example 1

[0052] like Figure 1 As shown, the present invention provides a cable defect detection device based on phase-shifted coupled frequency domain reflection, comprising a master control module, a signal generator, a phase shifter, a first coupler, a second coupler, a first signal comparator, and a second signal comparator. The signal generator generates an original sweep frequency signal, which is a sinusoidal sweep frequency signal; the phase shifter is used to perform phase shift processing on the original sweep frequency signal so that a preset known phase difference exists between the test signal and the reference signal. The first coupler is used to receive the test signal and input it into the cable under test to separate the reflected signal, then output the test signal to the first signal comparator, and output the reflected signal to the first signal comparator and the second signal comparator. The second coupler is used to receive the reference signal and input the reference signal into the second signal comparator. The first signal comparator is used to output information representing the amplitude relationship and phase difference between the test signal and the reflected signal; the second signal comparator is used to output information representing the amplitude relationship and phase difference between the reference signal and the reflected signal. The master control module controls the signal generator to generate signals and comprehensively processes the two channels of information.

[0053] The present invention provides a cable defect detection method based on phase-shift coupling frequency domain reflection, comprising the following steps:

[0054] S1, the master control module controls the signal generator to generate the original sweep frequency signal. The original sweep frequency signal is processed by the phase shifter to form a test signal S2 which is input into the first coupler, and the other path forms a reference signal S1 which is input into the second coupler.

[0055] S2, the first coupler inputs the test signal S2 into the cable to be tested and separates the reflected signal R1, then outputs the test signal S2 to the first signal comparator, and outputs the reflected signal R1 to the first signal comparator and the second signal comparator at the same time;

[0056] S3, the second coupler inputs the reference signal S1 into the second signal comparator;

[0057] S4, the first signal comparator compares the amplitude and phase of the test signal S2 and the reflected signal R1, and outputs information representing the amplitude relationship and phase difference between the test signal S2 and the reflected signal R1; the second signal comparator compares the amplitude and phase of the reference signal S1 and the reflected signal R1, and outputs information representing the amplitude relationship and phase difference between the reference signal S1 and the reflected signal R1;

[0058] S5, the master control module comprehensively analyzes the two comparison information, uses the known phase difference between the test signal S2 and the reflected signal R1 and the comparison result with the reflected signal R1, accurately determines the spectrum characteristics of the reflected signal R1 and calculates the defect location. Specifically, it includes the following operations:

[0059] S5.1. The master control module determines the precise phase spectrum characteristics of the reflected signal R1 based on the phase difference information output by the first signal comparator, the phase difference information output by the second signal comparator, and a preset known phase difference to eliminate phase ambiguity.

[0060] The amplitude spectrum characteristics and phase spectrum characteristics of the reflected signal R1, the test signal S2 and the reference signal S1 are used to accurately calculate the reflected phase of the reflected signal R1. The principle of using the phase-shifted coupled signal to accurately determine the reflected signal is as follows: Figure 2 As shown, the reflected signal R1 is decomposed into real and imaginary parts along the direction of the test signal S2, which are shown as follows:

[0061]

[0062] in, is the phase of the reflected signal R1, is the phase of the test signal S2.

[0063] Introduce the reference signal S1 and ensure that the test signal S2 has a preset known phase difference with the reference signal S1 The reflected signal R1 is decomposed into real and imaginary parts along the direction of the reference signal S1, as shown below:

[0064]

[0065] in, is the phase of the reference signal S1;

[0066] The phase differences of the two paths measured respectively are:

[0067]

[0068] Where Δθ1 is the phase difference of the test path, and Δθ2 is the phase difference of the reference path;

[0069] Substituting the preset known phase difference Δθ into formula (5) and formula (6), the following relationship is obtained:

[0070] Δθ2=Δθ1+Δθ (7);

[0071] According to formula (7), we can get The precise value of can eliminate the phase ambiguity caused by the non-uniqueness of the cosine function generated by the single path measurement, and ensure that the phase information of the reflected signal R1 is unique and deterministic.

[0072] S5.2. The master control module calculates the amplitude spectrum characteristics of the reflected signal R1 based on the amplitude relationship information output by the first signal comparator and / or the second signal comparator and the determined precise phase spectrum characteristics;

[0073] The amplitude spectrum characteristics and phase spectrum characteristics of the reflected signal R1, the test signal S2 and the reference signal S1 are used to accurately calculate the reflection amplitude of the reflected signal R1. The principle of using the phase-shifted coupled signal to accurately determine the reflected signal is as follows: Figure 2 As shown, the reflected signal R1 is decomposed into real and imaginary parts along the direction of the test signal S2, which are shown as follows:

[0074]

[0075] in, is the phase of the reflected signal R1, is the phase of the test signal S2.

[0076] S5.3. The master control module processes the determined spectrum characteristics of the reflected signal R1 to obtain the time-domain reflection characteristics, and calculates the defect location based on the propagation speed of the electromagnetic wave in the cable. Based on the precise measurement of amplitude and phase, in order to further improve the reliability and accuracy of the detection results, the data processing method used is as follows:

[0077] For the amplitude, the average value of the two signals is used for optimization. If the amplitudes of the two signals are significantly different, the measurement result is discarded and re-measured.

[0078] For phase, judge the quality of phase data and adopt different processing strategies. The applicable scenarios of the processing strategies include but are not limited to amplitude one channel and phase one channel, amplitude one channel and phase two channels, amplitude two channels and phase one channel, and amplitude two channels and phase two channels. The following takes amplitude one channel and phase two channels as a typical scenario, refer to Figure 1 , and its specific screening rules are as follows:

[0079] Assume β is the distribution interval of the phase measurement value within its range, set two proportional coefficients α1 and α2, where 0<α1<α2, to evaluate the quality of the data; the specific evaluation indicators are: when β<α1 or β>1-α1, the data quality is low; when α1≤β<α2 or 1-α2<β≤1-α1, the data quality is medium; when α2≤β≤1-α2, the data quality is high; the quality of the data corresponding to the two measured phase values is β1 and β2 respectively, and the phase data is processed as follows:

[0080] (1) When the data quality β1 is in the low data quality range, that is, β1 < α1 or β1 > 1-α1, the data of this channel is considered unreliable and the measurement result of this channel is completely discarded. Only the measurement result of the other channel is used as the final phase value; if the data quality β2 is in the low quality range, only the measurement result of the other channel is used as the final phase value;

[0081] (2) When both β1 and β2 are in the range of high data quality, that is, α2≤β1≤1-α2 and α2≤β2≤1-α2, both data are considered reliable and the arithmetic mean of the two measurement results is used as the final phase value;

[0082] (3) In other cases, if both channels are in the medium data quality range, that is, when α1≤β<α2 or 1-α2<β≤1-α1, or when one channel is high and the other channel is medium quality, a weighted average can be performed based on the specific values of β1 and β2, and a larger weight can be assigned to the channel with higher quality to obtain the final phase value.

[0083] According to the above screening rules, scenarios with one channel for amplitude and one channel for phase, two channels for amplitude and one channel for phase, and two channels for amplitude and two channels for phase can be adapted according to this logic: the quality judgment criteria and processing principles for single / multi-channel amplitude / phase are completely reused, only the number of channels is adjusted, low-quality channels are discarded and high-quality channel results are retained first, and redundancy check is triggered when multiple channels have low quality.

[0084] Therefore, the present invention adopts the above-mentioned cable defect detection device and method based on phase-shift coupled frequency domain reflection, and constructs a dual-path comparison architecture by introducing a phase shifter to effectively overcome phase ambiguity and improve detection accuracy and reliability.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A cable defect detection device based on phase-shift coupled frequency domain reflectometry, characterized by: It includes a master control module, a signal generator, a phase shifter, a first coupler, a second coupler, a first signal comparator and a second signal comparator; the signal generator generates an original sweep frequency signal; The phase shifter is used to perform phase shift processing on the original swept frequency signal; the first coupler is used to receive the test signal and input it into the cable under test to separate the reflected signal, then output the test signal to the first signal comparator, and output the reflected signal to the first signal comparator and the second signal comparator; the second coupler is used to receive the reference signal and input the reference signal into the second signal comparator; the first signal comparator is used to output information representing the amplitude relationship and phase difference between the test signal and the reflected signal; The second signal comparator is used to output information representing the amplitude relationship and phase difference between the reference signal and the reflected signal; The master control module controls the signal generator to generate signals and comprehensively processes the two channels of information.

2. A cable defect detection method based on phase-shift coupled frequency domain reflectometry, characterized by: The following steps are involved: S1, the master control module controls the signal generator to generate the original sweep frequency signal. The original sweep frequency signal is processed by the phase shifter to form a test signal S2 which is input into the first coupler, and the other path forms a reference signal S1 which is input into the second coupler. S2, the first coupler inputs the test signal S2 into the cable to be tested and separates the reflected signal R1, then outputs the test signal S2 to the first signal comparator, and outputs the reflected signal R1 to the first signal comparator and the second signal comparator at the same time; S3, the second coupler inputs the reference signal S1 into the second signal comparator; S4, the first signal comparator compares the amplitude and phase of the test signal S2 and the reflected signal R1, and outputs information representing the amplitude relationship and phase difference between the test signal S2 and the reflected signal R1; the second signal comparator compares the amplitude and phase of the reference signal S1 and the reflected signal R1, and outputs information representing the amplitude relationship and phase difference between the reference signal S1 and the reflected signal R1; S5. The master control module comprehensively analyzes the two comparison information and uses the known phase difference between the test signal S2 and the reflected signal R1 and the comparison result with the reflected signal R1 to accurately determine the spectrum characteristics of the reflected signal R1 and calculate the defect location.

3. The cable defect detection method based on phase-shift coupled frequency domain reflectometry according to claim 2, characterized in that: S5 specifically includes the following operations: S5.

1. The master control module determines the precise phase spectrum characteristics of the reflected signal R1 based on the phase difference information output by the first signal comparator, the phase difference information output by the second signal comparator, and a preset known phase difference; S5.

2. The master control module calculates the amplitude spectrum characteristics of the reflected signal R1 based on the amplitude relationship information output by the first signal comparator and the second signal comparator and the determined precise phase spectrum characteristics; S5.

3. The master control module processes the determined spectrum characteristics of the reflection signal R1 to obtain time domain reflection characteristics, and calculates the defect location in combination with the propagation speed of the electromagnetic wave in the cable.

4. The cable defect detection method based on phase-shift coupled frequency domain reflectometry according to claim 3, characterized in that: In S5.1, the amplitude spectrum characteristics and phase spectrum characteristics of the reflected signal R1, the test signal S2, and the reference signal S1 are used to accurately calculate the reflection phase of the reflected signal R1. The reflected signal R1 is decomposed into real and imaginary parts along the direction of the test signal S2, as shown below: in, is the phase of the reflected signal R1, is the phase of the test signal S2; Introduce the reference signal S1 and ensure that the test signal S2 has a preset known phase difference with the reference signal S1 The reflected signal R1 is decomposed into real and imaginary parts along the direction of the reference signal S1, as shown below: in, is the phase of the reference signal S1; The phase differences of the two paths measured respectively are: Where Δθ1 is the phase difference of the test path, and Δθ2 is the phase difference of the reference path; Substituting the preset known phase difference Δθ into formula (5) and formula (6), the following relationship is obtained: Δθ2=Δθ1+Δθ (7); According to formula (7), we can get The accurate value of can be used to eliminate the phase ambiguity caused by the non-uniqueness of the cosine function generated by the single path measurement.

5. The cable defect detection method based on phase-shift coupled frequency domain reflectometry according to claim 4, characterized in that: In S5.2, the amplitude spectrum characteristics and phase spectrum characteristics of the reflected signal R1, the test signal S2, and the reference signal S1 are used to accurately calculate the reflection amplitude of the reflected signal R1. The reflected signal R1 is decomposed into real and imaginary parts along the direction of the test signal S2, as shown below: in, is the phase of the reflected signal R1, is the phase of the test signal S2.

6. The cable defect detection method based on phase-shift coupled frequency domain reflectometry according to claim 5, characterized in that: The data processing method in S5.3 is: For the amplitude, the average value of the two signals is used for optimization. If the amplitudes of the two signals are significantly different, the measurement result is discarded and remeasured. For phase, the quality of phase data is judged and different processing strategies are adopted, as shown below: Assume β is the distribution interval of the phase measurement value within its range, set two proportional coefficients α1 and α2, where 0<α1<α2, to evaluate the quality of the data; the specific evaluation indicators are: when β<α1 or β>1-α1, the data quality is low; when α1≤β<α2 or 1-α2<β≤1-α1, the data quality is medium; when α2≤β≤1-α2, the data quality is high; the quality of the data corresponding to the two measured phase values is β1 and β2 respectively, and the phase data is processed as follows: (1) When the data quality β1 is in the low data quality range, that is, β1 < α1 or β1 > 1-α1, the data of this channel is considered unreliable and the measurement result of this channel is completely discarded. Only the measurement result of the other channel is used as the final phase value; if the data quality β2 is in the low quality range, only the measurement result of the other channel is used as the final phase value; (2) When both β1 and β2 are in the high data quality range, that is, α2≤β1≤1-α2 and α2≤β2≤1-α2, both data are considered reliable and the arithmetic mean of the two measurement results is used as the final phase value; (3) In other cases, if both paths are in the medium data quality range, that is, when α1≤β<α2 or 1-α2<β≤1-β1, or when one path is high and the other path is medium quality, a weighted average can be performed based on the specific values of β1 and β2, and a larger weight can be assigned to the path with higher quality to obtain the final phase value.

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