CN115993485A - Parallel-pair multi-core cable equivalent relative dielectric constant estimation method - Google Patents

Parallel-pair multi-core cable equivalent relative dielectric constant estimation method Download PDF

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CN115993485A
CN115993485A CN202211613576.6A CN202211613576A CN115993485A CN 115993485 A CN115993485 A CN 115993485A CN 202211613576 A CN202211613576 A CN 202211613576A CN 115993485 A CN115993485 A CN 115993485A
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cable
dielectric constant
crosstalk
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张刚
陈潇
孙红鹏
张涛
张哲浩
何鑫
王立欣
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Harbin Institute of Technology
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Abstract

The parallel-to-multi-core cable equivalent relative dielectric constant estimation method solves the problem of how to realize non-invasive rapid nondestructive detection of the cable equivalent dielectric constant, and belongs to the technical field of cable parameter measurement. The invention comprises the following steps: step 1, manufacturing a cable sample with the length of l; step 2, measuring crosstalk spectrum of the cable sample by using a vector network analyzer; step 3, identifying maximum points or minimum points in the crosstalk spectrum, calculating average frequency difference delta f between the maximum points or the minimum points, and obtaining an estimated value of the equivalent relative dielectric constant of the cable sample according to the average frequency difference
Figure DDA0004001121540000012
Figure DDA0004001121540000011
c represents the speed of light in vacuum. The invention calculates the relative dielectric constant by measuring the crosstalk amplitude frequency spectrum between the shielded parallel pair cable core wires without damaging the cable structureThe sample of the cable insulating material is manufactured, and the non-invasive rapid nondestructive detection of the equivalent dielectric constant of the cable can be realized.

Description

Parallel-pair multi-core cable equivalent relative dielectric constant estimation method
Technical Field
The invention relates to a parallel-pair multi-core cable equivalent relative dielectric constant estimation method, and belongs to the technical field of cable parameter measurement.
Background
The equivalent relative dielectric constant of a high-speed data cable is an important parameter, and directly determines the magnitude and time delay of the wave velocity in the cable. In addition, the equivalent relative permittivity plays an important role in the estimation of the quality consistency and performance degradation of the cable. On one hand, the equivalent relative dielectric constant of the new production cable is mainly influenced by the quality of the cable material and the process steps in the processing process, so that the equivalent relative dielectric constant can be used as a judging basis for the quality consistency between cables in different batches; on the other hand, the cable is influenced by factors such as mechanical impact, over-high temperature rise and the like in the use process, and the mechanical structure and the material performance of the cable are possibly changed, so that the performance parameters including the equivalent relative dielectric constant are degraded, and the equivalent relative dielectric constant can also be used as an important parameter for representing the performance degradation condition of the cable in service. The traditional low-frequency dielectric constant measuring and calculating method is a plate capacitance method, a material to be measured is required to be manufactured into a cylindrical sample, the cylindrical sample is inserted into a clamp formed by parallel polar plates, and the relative dielectric constant is calculated by measuring the capacitance of a capacitor formed by the cylindrical sample; the high frequency can be a transmission line method, and it is also necessary to insert a columnar sample into a coaxial jig, and calculate the relative dielectric constant by measuring the scattering parameter after the insertion of the sample. When the method is used for detecting the dielectric constant of the cable insulating material, the material to be detected needs to be manufactured into a sample with a specific shape, so that the cable to be detected cannot be damaged irreversibly, normal operation is impossible, the dielectric parameter of the material is possibly influenced in the process of processing the sample, and the test value deviates from the actual value. Therefore, the most ideal method for measuring the dielectric constant of the cable is to measure the dielectric constant of the cable through proper transmission characteristics by utilizing the structural characteristics of the cable. Based on the structural characteristics of the coaxial cable, the IEC 61196-1-125 standard describes a method for calculating the equivalent relative permittivity of the coaxial cable by using the phase difference at two ends of the cable, but the method is not applicable to non-coaxial cables with poor uniformity.
Disclosure of Invention
Aiming at the problem of how to realize noninvasive rapid nondestructive detection of the equivalent dielectric constant of a cable, the invention provides a parallel-to-multi-core cable equivalent relative dielectric constant estimation method.
The invention relates to a parallel-to-multi-core cable equivalent relative dielectric constant estimation method, which comprises the following steps:
step 1, manufacturing a cable sample with the length of l;
step 2, measuring crosstalk spectrum of the cable sample by using a vector network analyzer;
step 3, identifying maximum points or minimum points in the crosstalk spectrum, calculating average frequency difference delta f between the maximum points or the minimum points, and obtaining an estimated value of the equivalent relative dielectric constant of the cable sample according to the average frequency difference
Figure BDA0004001121520000021
Figure BDA0004001121520000022
c represents the speed of light in vacuum.
Preferably, in step 3, the average frequency difference is:
Figure BDA0004001121520000023
arranging the identified s maximum value points or minimum value points from small to large into a frequency point sequence f i I=1, 2, …, s, s represents the number of maximum points or minimum points;
Figure BDA0004001121520000024
preferably, in step 3, a maximum point n in the crosstalk spectrum is identified max Or minimum point n min The method meets the following conditions:
A(n max )≥max{A(n max -t:n max +t)}
A(n min )≤min{A(n min -t:n min +t)}
wherein A (n 1 :n 2 ) Represents the nth 1 To the nth 2 The set of crosstalk amplitudes at each frequency point, t represents the threshold value of the search range of the extreme point, a (n max ) Representing the maximum point n max Cross-talk amplitude, A (n min ) Representing a minimum value point n min Is used for the crosstalk amplitude of the (a).
Preferably, in step 3, the extreme point search range threshold t satisfies:
Figure BDA0004001121520000025
n represents the total frequency point number sampled by the vector network analyzer, f M Represents the upper limit of the frequency range to be estimated, f m Represents the lower limit epsilon of the frequency range to be estimated rM The upper limit value of the equivalent dielectric constant is shown.
Preferably, in step 3, if the number s of maximum points or minimum points in the crosstalk spectrum is recognized as not matching the expected number according to the threshold t of the extreme point search range, the total frequency point number N sampled by the vector network analyzer is increased.
Preferably, in step 1, length l:
Figure BDA0004001121520000026
f m represents the lower limit epsilon of the frequency range to be estimated rM Represents the upper limit value of the equivalent dielectric constant epsilon rm Indicating the lower limit value of the equivalent dielectric constant.
The method for measuring the average equivalent relative permittivity of the cable in a certain frequency range has the beneficial effects that the relative permittivity is calculated by measuring the crosstalk amplitude frequency spectrum between the shielded parallel pair cable core wires, the cable structure is not required to be destroyed to manufacture a sample of the cable insulating material, and the noninvasive rapid nondestructive detection of the equivalent permittivity of the cable can be realized.
Drawings
FIG. 1 is a schematic diagram of a measurement circuit of the present invention;
FIG. 2 is a sample of a connection between a connection vector network and a cable;
FIG. 3 is a schematic diagram of a local disturbance in the crosstalk spectrum, with frequency on the abscissa and crosstalk amplitude on the ordinate;
FIG. 4 is a graph of a cross-talk spectrum measured at 25℃and a graph of identified maxima points, with frequency on the abscissa and cross-talk amplitude on the ordinate;
fig. 5 is a plot of equivalent relative permittivity scatter measured at different temperatures, with temperature on the abscissa and equivalent relative permittivity on the ordinate.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The invention is further described below with reference to the drawings and specific examples, which are not intended to be limiting.
The present embodiment calculates the equivalent relative permittivity of the parallel pair cable based on the crosstalk spectrum: a length of parallel pair cable containing shielding can be considered a typical three conductor transmission line system whose crosstalk amplitude is affected by frequency. When the cable transmits high-frequency electromagnetic waves, the cable is an electrical long wire, the wave process on the cable cannot be ignored, the near-end crosstalk signal of the crosstalk affected by the superposition of the waves on the cable shows a relationship which changes with frequency in a similar manner, the crosstalk amplitude changes with the frequency in a periodic manner, and the changing frequency period is directly related to the wavelength and equivalent relative dielectric constant of the electromagnetic waves on the cable. The frequency spectrum of the crosstalk amplitude is not a perfect periodic spectral line under the influence of the attenuation and arrangement modes of the cable, and the frequency period of the crosstalk spectrum can be estimated through the average interval between the maximum value points or the minimum value points of the crosstalk spectrum in a certain frequency range, so that the average equivalent relative dielectric constant of the cable in the certain frequency range is estimated.
Proof of periodic variation of the spectral amplitude of the near-end crosstalk of the three conductors with frequency under lossless conditions, ignoring the dispersion effect:
considering the lossless uniform three-conductor transmission line problem, define:
Figure BDA0004001121520000041
Figure BDA0004001121520000042
Figure BDA0004001121520000043
Figure BDA0004001121520000044
Figure BDA0004001121520000045
l, C the transmission line current vector, transmission line voltage vector, transmission line inductance parameter matrix per unit length, and transmission line capacitance parameter matrix per unit length; />
Figure BDA0004001121520000046
Representing the current phasors at the positions z on the crosstalk transmit line and the crosstalk receive line, respectively; />
Figure BDA0004001121520000047
Representing the voltage phasors at the locations z on the crosstalk transmit lines and the crosstalk receive lines, respectively; l (L) G 、l m 、l R The self inductance of the crosstalk transmitting line, the self inductance of the crosstalk receiving line, and the mutual inductance between the crosstalk transmitting line and the crosstalk receiving line are respectively represented; c G 、c m 、c R The self-capacitance of the crosstalk transmitting line, the self-capacitance of the crosstalk receiving line, and the mutual capacitance between the crosstalk transmitting line and the crosstalk receiving line are respectively represented;
there is a frequency domain lossless three conductor transmission line equation:
Figure BDA0004001121520000048
Figure BDA0004001121520000049
in turn defining a termination source and an impedance matrix:
Figure BDA00040011215200000410
Figure BDA00040011215200000411
Figure BDA0004001121520000051
V S 、R S 、R L respectively representing a source end voltage vector, a source end resistance vector and a load end resistance vector;
Figure BDA0004001121520000052
R S 、R NE 、R L 、R FE the crosstalk emission line source terminal voltage, the crosstalk emission line source terminal output resistor, the crosstalk receiving line source terminal output resistor, the crosstalk emission line load terminal input resistor and the crosstalk receiving line load terminal input resistor are respectively represented.
The solution of the transmission line of length L satisfies the terminal condition:
Figure BDA0004001121520000053
Figure BDA0004001121520000054
the transmission line equations at this time are decoupled, and the chain parameter matrix can be solved from (5) (6):
Figure BDA0004001121520000055
wherein:
Φ 11 ＝cos(βL)1 2 (13)
Figure BDA0004001121520000056
Figure BDA0004001121520000057
Φ 22 ＝cos(βL)1 2 (16)
beta represents the propagation constant of a three conductor transmission line system, 1 2 Representing a second order identity matrix.
In combination with the terminal conditions (10) (11) are available:
Figure BDA0004001121520000058
/>
Figure BDA0004001121520000059
regarding (17), taking the resistance between the two wires of the load and the ground to be equal, and taking the resistance to be R, the (17) becomes:
Figure BDA0004001121520000061
dividing the two sides by R to obtain:
Figure BDA0004001121520000062
let R go to positive infinity, equivalent to the case of a two-wire load-side open circuit, the above equation becomes:
Figure BDA0004001121520000063
the unfolding is as follows:
Figure BDA0004001121520000064
taking into account wave velocity
Figure BDA0004001121520000065
The crosstalk receiving end current is easy to calculate by using the Cramer rule:
Figure BDA0004001121520000066
Figure BDA0004001121520000067
B＝c m cos(βL)+jvsin(βL)(c G +c m )c m (R S -R NE ) (25)
recording device
Figure BDA0004001121520000068
For the electrical angle of the cable, then:
Figure BDA0004001121520000069
Figure BDA00040011215200000610
/>
Figure BDA0004001121520000071
neglecting dispersion effects, V R (0) Is a pi-periodic function of θ, i.e., a λ/2 periodic function of L, with respect to frequency
Figure BDA0004001121520000072
To->
Figure BDA0004001121520000073
As a function of the period.
The parallel-to-multi-core cable equivalent relative dielectric constant estimation method of the present embodiment includes:
step 1, determining the length l of a cable sample according to a required estimated frequency band, and manufacturing the cable sample;
step 2, measuring crosstalk spectrum of the cable sample by using a vector network analyzer;
step 3, identifying maximum points or minimum points in the crosstalk spectrum, calculating average frequency difference delta f between the maximum points or the minimum points, and obtaining an estimated value of the equivalent relative dielectric constant of the cable sample according to the average frequency difference
Figure BDA0004001121520000077
In this embodiment, according to the conclusion that the crosstalk spectrum amplitude varies with the periodicity of the frequency, from the direct correlation between the varying frequency period and the wavelength of the electromagnetic wave on the cable, that is, the equivalent relative permittivity, it can be determined that the average frequency difference between the extreme points of the crosstalk spectrum satisfies the following relationship:
Figure BDA0004001121520000074
easy obtaining:
Figure BDA0004001121520000075
c represents the speed of light in vacuum.
According to the method, the relative dielectric constant of the shielded parallel pair cable core wires is calculated by measuring the crosstalk amplitude frequency spectrum between the shielded parallel pair cable core wires, a cable structure is not required to be damaged to manufacture a sample of the cable insulating material, and non-invasive rapid nondestructive detection of the equivalent dielectric constant of the cable can be realized.
In step 1 of this embodiment, a parallel pair cable sample is fabricated, and the parallel pair cable used needs to include a shielding layer to form a three-conductor system to generate crosstalk. Let us assume the frequency range to be estimated f m ,f M ]General f M <10f m So as to ensure that the frequency points are uniform and sufficient between the adjacent spectrum maximum value or minimum value points. The length of the cable sample is determined by the lower limit f of the frequency range to be estimated m Determining, estimating with the following formula:
Figure BDA0004001121520000076
wherein, l represents the length of the cable sample to be manufactured; c represents the speed of light in vacuum, about 3×10 8 m/s；ε rM Represents an equivalent dielectric constant upper limit value; epsilon rm Indicating the lower limit value of the equivalent dielectric constant. Wherein the upper and lower limits epsilon of the equivalent dielectric constant rM And epsilon rm Can be made of insulating materialThe type of material or nominal wave velocity of the cable is estimated.
And (3) manufacturing a cable sample according to the calculated cable length, cutting one end of the cable sample by about 1cm, separating two single-core cables and a shielding layer, removing insulation with proper length outside the single-core cables to expose conductors, and facilitating port connection of a vector network analyzer.
In step 2 of the present embodiment, a circuit diagram at the time of crosstalk spectrum measurement is shown in fig. 1. Wherein, two heart yearns C, V of cable one end are connected with the signal line of two ports Port 1 and Port 2 of vector network analyzer respectively through the connecting piece, and insulating layer G is connected with the ground connection of two ports of vector network analyzer through the connecting piece, and the other end of cable is opened a way completely.
The function of the connecting piece is to complete the conversion from the coaxial port of the vector network analyzer to the parallel shielded pair port of the cable, and meanwhile, the function of reducing the reflection of electromagnetic waves and enhancing the accuracy of crosstalk spectrum measurement results is achieved. The connecting piece can be made of a PCB board, the two ends of the connecting piece can be respectively provided with an SMA seat and a wire holder, and the transmission line part can be designed into a 50 omega microstrip line which is as short as possible to be matched with the vector network analyzer, as shown in fig. 2.
After the circuit is built, the crosstalk spectrum can be measured by using a vector network analyzer. When the vector network analyzer is configured, the upper and lower frequency limits are set as f M And f m The number of sweep frequency points should be as large as possible, the sweep frequency mode is set as linear sweep, and the signal power selects the maximum power in the selectable range. If the connection is made in the manner shown in fig. 1, S21 measured by the vector network analyzer is the crosstalk spectrum.
Step 3 of the present embodiment obtains the S21 data and the near-end crosstalk spectrum of the vector network analyzer after measurement, and then obtains the equivalent relative dielectric constant of the cable through data processing. Firstly, identifying the maximum (or minimum) value points in the crosstalk spectrum, and then calculating the average frequency difference between the extreme points, so as to estimate the wave velocity in a certain frequency range and further calculate the equivalent dielectric constant.
Step 31, identifying extreme points:
ideally, the near-end crosstalk spectrum is monotonous between the extreme value point to be identified and the minimum value point, and considering that the probability of measuring the crosstalk data of different frequency points by the vector network analyzer is 1 unequal, the condition that the maximum (small) value point meets is that the crosstalk amplitude of the point is larger (smaller) than that of the left and right points, namely:
A(n max -1)＜A(n max )＞A(n max +1) (32)
A(n min -1)＞A(n min )＜A(n min +1) (33)
wherein A (n) represents the crosstalk amplitude of the nth frequency point, and n is the sequence number of the discrete sweep frequency point from small to large; n is n max A sequence number indicating a maximum point; n is n max A sequence number indicating the minimum point.
In practice, however, the crosstalk spectrum may be slightly dithered, as shown in the circles of fig. 3, due to factors such as non-uniformity caused by the state of the art of the cable itself, reflection between the connection points, external electromagnetic interference, etc., resulting in points satisfying the equation (32) or (33) not necessarily being points desired to be identified.
Considering that such a shake point is a local maximum (minimum) value point in a small range in the vicinity and an extreme point desired to be recognized is in the vicinity, the methods of the formula (32) and the formula (33) can be improved, the extreme point satisfying:
A(n max )≥max{A(n max -t:n max +t)} (34)
A(n min )≤min{A(n min -t:n min +t)} (35)
wherein A (n 1 :n 2 ) Represents the nth 1 To the nth 2 A set of crosstalk amplitudes at each frequency point; t represents the extreme point search range.
The selection of the search range t is important for successful identification of the extreme points: t is selected for too small, so that interference of shaking points cannot be effectively removed; t is selected so large that it is larger than the frequency interval between part of the adjacent extreme points, it is possible to miss part of the extreme points desired to be identified. Both cases lead to errors in the estimated equivalent dielectric constant, t can be chosen according to the following formula:
Figure BDA0004001121520000091
where N represents the total frequency points sampled by the vector network analyzer.
The number of frequency points expected to be identified can be manually counted through observing the crosstalk frequency spectrum, if the number of extreme points identified according to t selected in the step (36) is inconsistent with the expected number, the total sampling point number N of the vector network analyzer is insufficient, and the total frequency point number N sampled by the vector network analyzer is increased.
Step 32, calculating the equivalent relative dielectric constant:
arranging the identified s maximum value points or minimum value points from small to large into a frequency point sequence f i ：
f 1 ＜f 2 ＜...＜f s-1 ＜f s (37)
i=1, 2, …, s, s representing the number of maximum or minimum points;
the subscript i is taken as an independent variable, and the frequency point f i As a dependent variable, consider fitting it to:
f i ＝ai+b (38)
this is a typical linear regression problem, with the result of the least squares fit:
Figure BDA0004001121520000092
Figure BDA0004001121520000093
wherein:
Figure BDA0004001121520000094
Figure BDA0004001121520000101
obviously, the average frequency difference to be found is:
Figure BDA0004001121520000102
the method comprises the following steps:
Figure BDA0004001121520000103
calculating an estimated value of the equivalent relative permittivity of the cable sample from Δf using formula (30)
Figure BDA0004001121520000104
And (3) experimental verification: taking an ePTFE (expanded polytetrafluoroethylene) insulated parallel pair cable as an example, the average equivalent relative dielectric constant in the range of 200MHz to 1.2GHz is to be estimated. The relative dielectric constant of the parameter data provided by the manufacturer is within the interval [1.0,2.0], the length l=5m of the selected sample is calculated according to the step (31), and the maximum sampling point number of the vector network analyzer is 4001.
The cable near-end crosstalk spectrum under the conditions of a plurality of discrete temperature points of 25-140 ℃ is measured respectively by placing the cable near-end crosstalk spectrum in an incubator and connecting the incubator with a crosstalk measuring circuit. Taking t=20, the near-end crosstalk spectrum at 25 ℃ and the identified crosstalk maxima point locations are shown in fig. 4.
The equivalent relative dielectric constants at each temperature were analyzed and calculated by the same method, and the relationship between the equivalent relative dielectric constants and the temperature of the obtained cable was as shown in fig. 5, and the result was consistent with the temperature change characteristics of the known ePTFE dielectric constants.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein may be combined in ways other than as described in the original claims. It is also to be understood that features described in connection with separate embodiments may be used in other described embodiments.

Claims (10)

1. The method for estimating the equivalent relative dielectric constant of the parallel-to-multi-core cable is characterized by comprising the following steps:
step 1, manufacturing a cable sample with the length of l;
step 2, measuring crosstalk spectrum of the cable sample by using a vector network analyzer;
step 3, identifying maximum points or minimum points in the crosstalk spectrum, calculating average frequency difference delta f between the maximum points or the minimum points, and obtaining an estimated value of the equivalent relative dielectric constant of the cable sample according to the average frequency difference
Figure FDA0004001121510000011
Figure FDA0004001121510000012
c represents the speed of light in vacuum.
2. The parallel-to-multi-core cable equivalent relative permittivity estimation method according to claim 1, wherein in step 3, the average frequency difference is:
Figure FDA0004001121510000013
arranging the identified s maximum value points or minimum value points from small to large into a frequency point sequence f i I=1, 2, …, s, s represents the number of maximum points or minimum points;
Figure FDA0004001121510000014
3. the method for estimating an equivalent relative permittivity of a parallel-to-multicore cable according to claim 1, wherein in step 3, a maximum point n in a crosstalk spectrum is identified max Or minimum point n min The method meets the following conditions:
A(n max )≥max{A(n max -t:n max +t)}
A(n min )≤min{A(n min -t:n min +t)}
wherein A (n 1 :n 2 ) Represents the nth 1 To the nth 2 The set of crosstalk amplitudes at each frequency point, t represents the threshold value of the search range of the extreme point, a (n max ) Representing the maximum point n max Cross-talk amplitude, A (n min ) Representing a minimum value point n min Is used for the crosstalk amplitude of the (a).
4. The parallel-to-multicore cable equivalent relative dielectric constant estimation method according to claim 3, wherein in step 3, the extreme point search range threshold t satisfies:
Figure FDA0004001121510000015
n represents the total frequency point number sampled by the vector network analyzer, f M Represents the upper limit of the frequency range to be estimated, f m Represents the lower limit epsilon of the frequency range to be estimated rM The upper limit value of the equivalent dielectric constant is shown.
5. The method for estimating an equivalent relative permittivity of a parallel-to-multicore cable according to claim 4, wherein in step 3, if the number s of maximum points or minimum points in the crosstalk spectrum is recognized as not matching the expected number according to the threshold t of the extremum searching range, the total frequency point number N sampled by the vector network analyzer is increased.
6. The parallel-to-multi-core cable equivalent relative permittivity estimation method according to claim 1, wherein in step 1, the length l:
Figure FDA0004001121510000021
f m represents the lower limit epsilon of the frequency range to be estimated rM Represents the upper limit value of the equivalent dielectric constant epsilon rm Indicating the lower limit value of the equivalent dielectric constant.
7. The method for estimating the equivalent relative permittivity of a parallel-to-multicore cable according to claim 6, wherein in the step 1, a shielding layer and two single-core cables are separated at one end of a cable sample, and an insulating layer with a proper length outside the single-core cables is removed to expose conductors for connection to a vector network analyzer.
8. The method for estimating the equivalent relative permittivity of parallel-to-multicore cables according to claim 7, wherein in step 2, conductors of two single-core cables C, V at one end of the cable sample are respectively connected to signal lines of Port 1 and Port 2 of the vector network analyzer via connectors, insulating layers G of two single-core cables C, V are respectively connected to ground lines of Port 1 and Port 2 of the vector network analyzer via connectors, and the other end of the cable sample is completely opened.
9. The method for estimating the equivalent relative dielectric constant of the parallel-to-multicore cable according to claim 8, wherein the connecting piece is made of a PCB board, the SMA base and the wire holder are respectively arranged at two ends, and the transmission line is a 50Ω microstrip line.
10. The method for estimating equivalent relative permittivity of parallel-to-multicore cables according to claim 1, wherein in step 2, the upper and lower frequency limits of the vector network analyzer during measurement are f respectively M And f m The sweep frequency mode is set as linear sweep, and the signal power selects the maximum power;
frequency range to be estimated [ f m ,f M ]，f M Represents the upper limit of the frequency range to be estimated, f m Representing the lower limit of the frequency range to be estimated;
s21 measured by the vector network analyzer is the crosstalk spectrum.
CN202211613576.6A 2022-12-15 2022-12-15 Parallel-pair multi-core cable equivalent relative dielectric constant estimation method Pending CN115993485A (en)

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