CN113933631A - Multi-conductor cable electromagnetic parameter automatic testing method - Google Patents

Abstract

The invention discloses an automatic test method for electromagnetic parameters of a multi-conductor cable, wherein the multi-conductor cable comprises N single-conductor cables, and N is a positive integer greater than or equal to 2; each single conductor cable comprising an a-terminal and a B-terminal, the method comprising the steps of: sequentially controlling two ends of the same single-conductor cable to be connected into a test system, and acquiring a first scattering parameter and a second scattering parameter of each single-conductor cable; calculating electromagnetic parameters of each single-conductor cable according to the scattering parameters and the cable length, wherein the electromagnetic parameters comprise characteristic impedance and a phase constant; acquiring multiple scattering parameters of all groups of single-conductor cables; electromagnetic parameters of the multi-conductor cable are acquired. The invention can reflect the real performance of the cable by a real measurement method, utilizes the vector network analyzer to test the scattering parameters of the cable, and obtains the electromagnetic parameters of the cable by deducing the relation between the scattering parameters and the electromagnetic parameters of the cable.

Description

A method for automatic testing of electromagnetic parameters of multi-conductor cables

technical field

The invention relates to the field of multi-conductor cable parameter testing, in particular to an automatic testing method for multi-conductor cable electromagnetic parameters.

Background technique

As the hub of electrical and electronic equipment and systems, cable harnesses are used to efficiently transmit information and energy between different systems. Cables usually exist outside or inside the housing of electronic system equipment in the form of many single wires bundled into cable bundles. They are very easy to pick up the field formed in space due to the electromagnetic emission of equipment, etc., or produce crosstalk between each other. Due to the induced voltage and induced current generated by the cable coupling, the terminal circuit connected to the cable will have an undesired response, resulting in degradation of circuit performance and even electromagnetic compatibility failure.

In the electromagnetic compatibility analysis of the actual cable, we need to obtain the electromagnetic parameters of the cable. The extraction of electromagnetic parameters usually includes approximate analytical methods, numerical calculation methods, and actual measurement methods. The approximate analytical method is to simplify the model under certain conditions. The electromagnetic parameters are obtained by analytical solution. The actual cable cannot fully meet the conditions of the simplified model, so the accuracy of the electromagnetic parameters obtained by the analytical method is not high; the common numerical analysis methods mainly include the difference method, the variational method and the finite element method. , because the numerical method is a full-wave method, its computational complexity is large. In the actual use of the cable, the geometric parameters and physical parameters of the cable itself will change in the process of use, transportation or storage. The actual measurement method can better reflect the performance of the real cable.

Therefore, it is an urgent problem to be solved in the art to provide a test method that can automatically obtain the electromagnetic parameters of the multi-conductor cable, so as to provide quantifiable parameters for the study of cable electromagnetic compatibility.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies of the prior art and provide an automatic testing method for electromagnetic parameters of a multi-conductor cable.

The purpose of this invention is to realize through the following technical solutions:

A first aspect of the present invention provides an automatic testing method for electromagnetic parameters of a multi-conductor cable. The multi-conductor cable includes N single-conductor cables, where N is a positive integer greater than or equal to 2, and each single-conductor cable is Including A end and B end, described method comprises the following steps:

Control both ends of the same single-conductor cable to access the test system in turn, and obtain the first scattering parameter and the second scattering parameter of each single-conductor cable;

Calculate the electromagnetic parameters of each single-conductor cable according to the scattering parameters and the cable length, the electromagnetic parameters including characteristic impedance and phase constant;

Perform combined control: including controlling the A-end of any two single-conductor cables to access the test system and obtaining the third scattering parameter, controlling the A-end of one of the two single-conductor cables and the other one of the two single-conductor cables. The B end of a single-conductor cable enters the test system and obtains the fourth scattering parameter; until the multi-scattering parameters of all groups of single-conductor cables are obtained, all groups are defined as: any single-conductor cable has participated in the combination;

The electromagnetic parameters of the multi-conductor cables are obtained according to the electromagnetic parameters of the single-conductor cables and the multi-scattering parameters of all groups of the single-conductor cables, and the electromagnetic parameters of the multi-conductor cables include mutual inductance and mutual capacitance.

Further, the test system includes a computer, a first radio frequency switch, a second radio frequency switch, and a vector network analyzer; the first radio frequency switch is used to control the access of the A terminal of each single-conductor cable, and the second radio frequency switch The radio frequency switch is used to control the access of the B end of each single-conductor cable; the vector network analyzer is connected to the first radio frequency switch and the second radio frequency switch, respectively, for obtaining test parameters; the computer is respectively connected to the vector network The analyzer, the first radio frequency switch, and the second radio frequency switch are connected, and are used for acquiring and calculating test parameters, and controlling the access of the single-conductor cable by controlling the first radio frequency switch and the second radio frequency switch.

Further, the computer is connected with the first radio frequency switch, the second radio frequency switch and the vector network analyzer through the Usb interface; the computer uses Matlab to complete the control of the first radio frequency switch, the second radio frequency switch and the vector network analyzer.

Further, according to the scattering parameters and the cable length, the electromagnetic parameters of each single-conductor cable are calculated, and the electromagnetic parameters include characteristic impedance and phase constant, including the following formula:

In the formula, S ₁₁ is the first scattering parameter, S ₂₁ is the second scattering parameter, Z _c is the characteristic impedance of the single-conductor cable, Z ₀ is the impedance of the vector network analyzer port, and β is the phase constant of the single-conductor cable , l is the cable length of a single-conductor cable.

Further, the impedance of the port of the vector network analyzer is 50Ω.

Further, the electromagnetic parameters of the multi-conductor cables are obtained according to the electromagnetic parameters of the single-conductor cables and the multi-scattering parameters of all groups of the single-conductor cables, and the electromagnetic parameters of the multi-conductor cables include mutual inductance and mutual capacitance, include:

Calculate the set of mutual inductance and mutual capacitance of each group of single-conductor cables, and calculate the average value as the mutual inductance and mutual capacitance of the electromagnetic parameters of multi-conductor cables; the calculation methods of the mutual inductance and mutual capacitance of each group of single-conductor cables include: the following steps,

Using the obtained scattering parameters, the intermediate parameters can be obtained:

In the formula, S ₃₁ is the third scattering parameter, S ₄₁ is the fourth scattering parameter, Z _c1 and Z _c2 are the characteristic impedances of the two single-conductor cables to be calculated, respectively, and β ₁ is the phase constant of the first single-conductor cable. ;

Using (5)(6) as known quantities yields (7)(8):

a _s =T ₁ /a _2R (7)

b _s =T ₁ /b _2L (8)

in,

According to (4)(5)(7)(8), we get:

According to formulas (9) and (10), the intermediate quantities are brought in to obtain:

t _b =T _b /K ₂

t _f =T _f /K ₁

in,

Finally, the coupled electromagnetic parameters are obtained:

where f is the frequency.

The beneficial effects of the present invention are:

(1) In an exemplary embodiment of the present invention, the performance of the real cable can be reflected by the actual measurement method, and the scattering parameters of the cable are tested by using a vector network analyzer, and the relationship between the scattering parameters and the electromagnetic parameters of the cable is deduced, Then, the electromagnetic parameters of the cable are obtained through testing.

(2) In another exemplary embodiment of the present invention, a specific implementation manner of the test system and a specific connection manner of the computer and other parts in the test system are disclosed.

(3) In yet another exemplary embodiment of the present invention, the specific implementation manner of each step is disclosed.

Description of drawings

FIG. 1 is a flowchart of a method disclosed by an exemplary embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a test system disclosed by an exemplary embodiment of the present invention;

FIG. 3 is a schematic diagram of port numbering of a single-conductor cable disclosed in an exemplary embodiment of the present invention.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. The indicated direction or positional relationship is based on the direction or positional relationship described in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation or a specific orientation. construction and operation, and therefore should not be construed as limiting the invention.

In the description of the present invention, it should be noted that, unless otherwise expressly specified and limited, “installation”, “connection” and “connection” should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; it can be mechanical connection or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this application and the appended claims, the singular forms "a," "the," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It will also be understood that the term "and/or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

It should be understood that although the terms first, second, third, etc. may be used in this application to describe various information, such information should not be limited by these terms. These terms are only used to distinguish the same type of information from each other. For example, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information without departing from the scope of the present application. Depending on the context, the word "if" as used herein can be interpreted as "at the time of" or "when" or "in response to determining." Furthermore, the references to "first" and "second" are for descriptive purposes only, and should not be construed as indicating or implying relative importance.

In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

Referring to FIG. 1, FIG. 1 shows an automatic testing method for electromagnetic parameters of a multi-conductor cable provided in an exemplary embodiment of the present invention. The multi-conductor cable includes N single-conductor cables, and N is greater than or equal to 2 A positive integer of , each single-conductor cable includes an A end and a B end, and the method includes the following steps:

S1: Control both ends of the same single-conductor cable to access the test system in turn, and obtain the first scattering parameter and the second scattering parameter of each single-conductor cable;

S2: Calculate the electromagnetic parameters of each single-conductor cable according to the scattering parameters and the cable length, where the electromagnetic parameters include characteristic impedance and phase constant;

S3: Perform combined control: including controlling the A-end of any two single-conductor cables to access the test system and obtaining the third scattering parameter, controlling the A-end of one of the two single-conductor cables Enter the test system with the B end of another single-conductor cable to obtain the fourth scattering parameter; until the multi-scattering parameters of all groups of single-conductor cables are obtained, the all groups are: any single-conductor cable has participated in the combination ;

S4: Obtain the electromagnetic parameters of the multi-conductor cables according to the electromagnetic parameters of the single-conductor cables and the multi-scattering parameters of all groups of the single-conductor cables, where the electromagnetic parameters of the multi-conductor cables include mutual inductance and mutual capacitance.

Specifically, in this exemplary embodiment, the performance of the real cable can be reflected by the actual measurement method, the scattering parameters of the cable are tested by a vector network analyzer, and the relationship between the scattering parameters and the electromagnetic parameters of the cable is deduced, and then the test is passed. Obtain the electromagnetic parameters of the cable.

For the description in step S3, for example, there are 5 single-conductor cables, which can be combined in the form of 1+2, 2+3, 3+4, 4+5; or 1+3, 1+2, 1+4, 1+5 combination; also 1+3, 3+4, 3+2, 2+5 combination. That is, any relationship can be used.

More preferably, in an exemplary embodiment, as shown in FIG. 2 , the test system includes a computer, a first radio frequency switch, a second radio frequency switch and a vector network analyzer; the first radio frequency switch is used to control each The A-end of a single-conductor cable is connected, and the second RF switch is used to control the B-end of each single-conductor cable to be connected; the vector network analyzer is connected to the first RF switch and the second RF switch respectively. connected to obtain test parameters; the computer is respectively connected to the vector network analyzer, the first radio frequency switch, and the second radio frequency switch, and is used to obtain test parameters and perform calculations, and to pass the first radio frequency switch and the second radio frequency switch. control to control the access of single-conductor cables.

More specifically, the computer is connected to the first radio frequency switch, the second radio frequency switch and the vector network analyzer through the Usb interface; the computer uses Matlab to complete the control of the first radio frequency switch, the second radio frequency switch and the vector network analyzer. In addition, a transition box may also be arranged between the radio frequency switch and the multi-conductor cable.

In the following exemplary embodiment, as shown in FIG. 3 , the ports of N single-conductor cables are numbered first. The port numbers of the same single-conductor cable are consecutive, and the port numbers of different cables on the same side differ by 2. Numbered 1, 2, 3...2N-2, 2N-1, 2N respectively, N≥2, N is a positive integer (single number is A-end, even number is B-end).

The implementation of step S1 is specifically: for the first single-conductor cable, connect to both ends of the same multi-conductor cable numbered 1 and ₂ to obtain the first scattering parameter _S11 and the second scattering parameter S21 ; Repeat the above content multiple times until the first scattering parameter and the second scattering parameter of the N single-conductor cables are obtained.

For the implementation of step S2, in a preferred exemplary embodiment, for the first single-conductor cable, the electromagnetic parameters of each single-conductor cable are calculated according to the scattering parameters and the cable length, and the electromagnetic parameters include Characteristic impedance and phase constant, including the following formulas:

In the formula, S11 is the first scattering parameter, S21 is the second scattering parameter, _Zc is the characteristic impedance of the single-conductor cable, and _Z0 is the impedance of the vector network analyzer port (in an exemplary embodiment, the vector The impedance of the network analyzer port is 50Ω), β is the phase constant of the single-conductor cable, and l is the cable length of the single-conductor cable.

In a further exemplary embodiment, it also includes calculating the phase velocity v:

v=2πf/β

where f is the frequency.

The electromagnetic parameters of other single-conductor cables are the same. For example, for the first single-conductor cable and the second single-conductor cable, the characteristic impedances of the two cables can be calculated as Z _c1 and Z _c2 respectively, and the phase constants are respectively are β ₁ and β ₂ .

For the implementation of step S3, taking the first single-conductor cable and the second single-conductor cable as examples, the cable ports 1 and 3 are connected to the vector network analyzer, and the third scattering parameter S ₃₁ is measured; Cable ports 1 and 4 are connected to a vector network analyzer, and the scattering parameter S ₄₁ is measured. Other groups of single-conductor cable groups are calculated in the same way.

的散射参数S_j,i和S_j+1,i，自动存储数据到计算机中，i,j＝1,3,5…2N-1。And in an exemplary embodiment, all groups are calculated for the previous cable and the next cable: that is, to obtain any two cables

The scattering parameters S _j,i and S _j+1,i are automatically stored in the computer, i,j=1,3,5...2N-1.

For the implementation of step S4, the electromagnetic parameters of the multi-conductor cables are obtained according to the electromagnetic parameters of the single-conductor cables and the multi-scattering parameters of all groups of the single-conductor cables, and the electromagnetic parameters of the multi-conductor cables include mutual Inductance and mutual capacitance, including:

Calculate the set of mutual inductance and mutual capacitance of each group of single-conductor cables, and calculate the average value as the mutual inductance and mutual capacitance of the electromagnetic parameters of multi-conductor cables; the calculation method of the mutual inductance and mutual capacitance of each group of single-conductor cables ( Taking the first single-conductor cable and the second single-conductor cable as an example, ) includes the following steps,

Using the obtained scattering parameters, the intermediate parameters can be obtained:

In the formula, S ₃₁ is the third scattering parameter, S ₄₁ is the fourth scattering parameter, Z _c1 and Z _c2 are the characteristic impedances of the two single-conductor cables to be calculated, respectively, and β ₁ is the phase constant of the first single-conductor cable. ;

Using (5)(6) as known quantities yields (7)(8):

a _s =T ₁ /a _2R (7)

b _s =T ₁ /b _2L (8)

in,

According to (4)(5)(7)(8), we get:

According to formulas (9) and (10), the intermediate quantities are brought in to obtain:

t _b =T _b /K ₂

t _f =T _f /K ₁

in,

Finally, the coupled electromagnetic parameters are obtained:

where f is the frequency.

Obviously, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation manner. For those of ordinary skill in the art, changes or changes in other different forms can also be made on the basis of the above-mentioned descriptions. . There is no need and cannot be exhaustive of all implementations here. And the obvious changes or changes derived from this are still within the protection scope of the present invention.

Claims (6)

1. A multi-conductor cable electromagnetic parameter automatic test method, the said multi-conductor cable includes N single conductor cables, N is greater than or equal to the positive integer of 2; every single conductor cable all includes A end and B end, its characterized in that: the method comprises the following steps:

sequentially controlling two ends of the same single-conductor cable to be connected into a test system, and acquiring a first scattering parameter and a second scattering parameter of each single-conductor cable;

calculating electromagnetic parameters of each single-conductor cable according to the scattering parameters and the cable length, wherein the electromagnetic parameters comprise characteristic impedance and a phase constant;

performing combined control: controlling the end A of any two single-conductor cables to enter a test system, obtaining a third scattering parameter, controlling the end A of one single-conductor cable and the end B of the other single-conductor cable to enter the test system, and obtaining a fourth scattering parameter; until the multi-scattering parameters of all groups of single conductor cables are acquired, said all groups being defined as: any single-conductor cable participates in the combination;

and acquiring the electromagnetic parameters of the multi-conductor cable according to the electromagnetic parameters of the single-conductor cable and the multi-scattering parameters of all the groups of single-conductor cables, wherein the electromagnetic parameters of the multi-conductor cable comprise mutual inductance and mutual capacitance.

2. The method for automatically testing the electromagnetic parameters of the multi-conductor cable according to claim 1, wherein the method comprises the following steps: the test system comprises a computer, a first radio frequency switch, a second radio frequency switch and a vector network analyzer; the first radio frequency switch is used for controlling the access of the A end of each single-conductor cable, and the second radio frequency switch is used for controlling the access of the B end of each single-conductor cable; the vector network analyzer is respectively connected with the first radio frequency switch and the second radio frequency switch and is used for acquiring test parameters; the computer is respectively connected with the vector network analyzer, the first radio frequency switch and the second radio frequency switch and used for obtaining and calculating the test parameters and controlling the access of the single-conductor cable by controlling the first radio frequency switch and the second radio frequency switch.

3. The method for automatically testing the electromagnetic parameters of a multi-conductor cable according to claim 2, characterized in that: the computer is connected with the first radio frequency switch, the second radio frequency switch and the vector network analyzer through a Usb interface; and the computer completes the control of the first radio frequency switch, the second radio frequency switch and the vector network analyzer by utilizing Matlab.

4. The method for automatically testing the electromagnetic parameters of a multi-conductor cable according to claim 2, characterized in that: according to the scattering parameters and the cable length, calculating electromagnetic parameters of each single-conductor cable, wherein the electromagnetic parameters comprise characteristic impedance and phase constants, and the electromagnetic parameters comprise the following formula:

in the formula, S₁₁Is a first scattering parameter, S₂₁Is a second scattering parameter, Z_cIs the characteristic impedance, Z, of a single-conductor cable₀For the impedance of the vector network analyzer port, β is the phase constant of the single conductor cable and l is the cable length of the single conductor cable.

5. The method for automatically testing the electromagnetic parameters of a multi-conductor cable according to claim 4, wherein: the impedance of the vector network analyzer port is 50 Ω.

6. The method for automatically testing the electromagnetic parameters of a multi-conductor cable according to claim 4, wherein: the acquiring the electromagnetic parameters of the multi-conductor cable according to the electromagnetic parameters of the single-conductor cable and the multi-scattering parameters of all the groups of single-conductor cables, wherein the electromagnetic parameters of the multi-conductor cable comprise mutual inductance and mutual capacitance, and the acquiring comprises the following steps:

calculating to obtain a set of mutual inductance and mutual capacitance of each group of single-conductor cables, and solving an average value to be used as the mutual inductance and mutual capacitance of the electromagnetic parameters of the multi-conductor cables; the mutual inductance and mutual capacitance of each set of single conductor cables is calculated by the following steps,

intermediate parameters can be obtained by using the obtained scattering parameters:

in the formula, S₃₁Is the third scattering parameter, S₄₁Is the fourth scattering parameter, Z_c1And Z_c2Respectively characteristic impedance, beta, of two single-conductor cables to be calculated₁Is the phase constant of the first single conductor cable;

using (5) (6) as known, (7) (8):

a_s＝T₁/a_2R (7)

b_s＝T₁/b_2L (8)

wherein,

according to (4), (5), (7) and (8):

according to the equations (9) (10), intermediate quantities are substituted to yield:

t_b＝T_b/K₂

t_f＝T_f/K₁

wherein,

finally, obtaining coupling electromagnetic parameters:

wherein f is the frequency.

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