CN111579913A - Electromagnetic interference detection device between cables - Google Patents

Abstract

The invention relates to an electromagnetic interference detection device between cables, wherein the output end of a device to be detected is separated into a common-mode component and a differential-mode component in electromagnetic coupling between the cables inside the device through a common-differential-mode separator, and finally the output common-mode component and the output differential-mode component are respectively detected through a frequency spectrograph, so that specific values of the common-mode electromagnetic coupling and the differential-mode electromagnetic coupling between the cables inside the device can be respectively obtained, and the detection result is accurate.

Description

Electromagnetic interference detection device between cables

Technical Field

The invention relates to the field of electromagnetic fields, in particular to a device for detecting electromagnetic interference between cables.

Background

The cable is an important link in the electromagnetic compatibility design, the problem of complex electromagnetic coupling between the cable and the ground due to inductance and capacitance is solved, and most of the problems of electromagnetic interference sensitivity, electromagnetic interference emission and signal crosstalk are caused by the cable.

The existing detection device can only test the total amount of electromagnetic interference caused by the reasons, but can not accurately test common-mode and differential-mode components in the electromagnetic interference, so that the problem of the electromagnetic interference is solved without a goal, and a large amount of time and engineering cost are wasted for rectification.

When a power supply EMI filter is used for testing the insertion loss performance of the power supply EMI filter for inhibiting cable interference, although a method for testing common mode insertion loss and differential mode insertion loss is established by specifications, an input test signal can be set as a common mode signal and a differential mode signal, the detection device can only test the total amount of insertion loss due to the fact that an output test device does not have the capability of distinguishing the common mode from the differential mode, in other words, the output test device cannot guarantee that a test result is a pure common mode signal or a pure differential mode signal, and obviously, the problem of test accuracy exists.

Disclosure of Invention

The invention aims to provide an electromagnetic interference detection device between cables, which can accurately measure common-mode signals or differential-mode signals.

In order to achieve the purpose, the invention provides the following scheme:

an inter-cable electromagnetic interference detection apparatus, the apparatus comprising: the device to be detected, the common differential mode separator and the spectrometer;

the device to be detected, the common differential mode separator and the frequency spectrograph are connected in sequence.

Optionally, the detected device comprises a signal source and a detected unit; the detected unit is a single-path cable of passive equipment;

the signal source, the detected unit, the common differential mode separator and the frequency spectrograph are connected in sequence.

Optionally, the detected device includes a signal source, a signal converter and a detected unit; the detected unit is a double-path cable of passive equipment;

the signal source, the signal converter, the detected unit, the common differential mode separator and the frequency spectrograph are connected in sequence.

Optionally, the signal source, the common differential mode separator and the spectrometer are all grounded.

Optionally, the detected device is a two-way cable of an active device.

Optionally, the working frequency domain of the common differential mode separator is 10kHz to 300 MHz;

the common-mode and differential-mode separator comprises a common-mode channel and a differential-mode channel;

the common mode channel and the differential mode channel are completely isolated, and the isolation degree meets the requirements that 10 kHz-30 MHz is more than 40dB, 50MHz is more than 30dB, and 300MHz is more than 20 dB.

Optionally, the working frequency domain of the signal source is 10kHz to 300 MHz.

Optionally, the working frequency domain of the frequency spectrograph is 10kHz to 300 MHz.

According to the specific embodiment provided by the invention, the invention discloses the following technical effects: the common-mode component and the differential-mode component in the electromagnetic coupling between the cables inside the equipment are separated from the output end of the equipment to be detected through the common-differential mode separator, and finally the output common-mode component and the output differential-mode component are detected through the frequency spectrograph, so that the specific values of the common-mode electromagnetic coupling and the differential-mode electromagnetic coupling between the cables inside the equipment can be obtained respectively, and the detection result is accurate.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a schematic view of an apparatus for detecting electromagnetic interference between cables;

FIG. 2 is a schematic diagram of a single cable EMI detection apparatus for passive devices;

FIG. 3 is a schematic diagram of a two-way cable EMI detection apparatus for passive devices;

FIG. 4 is a schematic diagram of a two-way cable EMI detection apparatus for an active device;

FIG. 5 is a schematic diagram of the coupling of the electric field (distributed capacitance) between two test lines of a passive device;

FIG. 6 is a schematic diagram of an apparatus for testing magnetic field (mutual inductance) coupling between two wires for a passive device;

fig. 7 is a schematic diagram of an apparatus for testing the shielding effect of one of the two wires by using a shielded cable and different grounding modes of the cable by using a passive device;

fig. 8 is a schematic view of a device for shielding effect between a wire and a shielded cable and different grounding modes of the cable inside an active equipment device;

fig. 9 is a schematic view of an arrangement of two shielded cables and the shielding effect between different grounding modes of the cables inside an active device;

FIG. 10 is an apparatus diagram of various electromagnetic couplings between twisted pairs within an active device;

fig. 11 is an illustration of an arrangement of various electromagnetic couplings between two cables inside an active device.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terms "first," "second," "third," and the like in the description and in the claims, as well as in the drawings, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the objects so described are interchangeable under appropriate circumstances. Furthermore, the terms "comprising" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions.

In this patent document, the drawings discussed below and the embodiments used to describe the principles of the present disclosure are by way of illustration only and should not be construed in any way to limit the scope of the present disclosure. Those skilled in the art will understand that the principles of the present invention may be implemented in any suitably arranged system. Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. Further, a terminal according to an exemplary embodiment will be described in detail with reference to the accompanying drawings. Like reference symbols in the various drawings indicate like elements.

The terms used in the description of the present invention are only used to describe specific embodiments, and are not intended to show the concept of the present invention. Unless the context clearly dictates otherwise, expressions used in the singular form encompass expressions in the plural form. In the present specification, it is to be understood that terms such as "comprising," "having," and "containing" are intended to specify the presence of stated features, integers, steps, acts, or combinations thereof, as taught in the present specification, and are not intended to preclude the presence or addition of one or more other features, integers, steps, acts, or combinations thereof. Like reference symbols in the various drawings indicate like elements.

The invention aims to provide a device for obtaining a common mode component and a differential mode component of a tested circuit or equipment accurately.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

As shown in fig. 1, the present invention provides an apparatus for detecting electromagnetic interference between cables, comprising: the device to be detected 1, the common difference mode separator 2 and the spectrometer 3 are connected in sequence, and the device to be detected 1, the common difference mode separator 2 and the spectrometer 3 are connected in sequence.

The invention is characterized in that a common-mode and differential-mode separator is introduced into the device, and the accurate common-mode component and differential-mode component of a tested circuit or equipment can be obtained. The common mode component and the differential mode component are the comprehensive result of the complex electromagnetic coupling, and whether the tested circuit or equipment meets the technical or specification requirements or is used for guiding the technical improvement work of the tested circuit or equipment in the field can be judged through the measured accurate common mode component and the measured differential mode component.

The device can be divided into active devices and passive devices according to the characteristics of detected devices, the passive devices can test the problem of electromagnetic coupling between cables inside the device under the excitation of external signals, and the electromagnetic coupling between the cables inside the active devices exists objectively, so that the excitation of a signal source from the outside is not needed.

Fig. 2 and 3 are schematic diagrams of a single-cable electromagnetic interference detection device of a passive device and a two-cable electromagnetic interference detection device of the passive device, respectively.

In fig. 2, 101 is a signal source, 102 is a detected unit, 103 is a common differential mode separator, and 104 is a spectrometer; the signal source 101, the detected unit 102, the common differential mode separator 103 and the spectrometer 104 are connected in sequence.

In fig. 3, 201 is a signal source, 202 is a signal converter, 203 is a detected unit, 204 is a common differential mode splitter, and 205 is a spectrometer; the signal source 201, the signal converter 202, the detected unit 203, the common differential mode separator 204 and the spectrometer 205 are connected in sequence.

The signal source, the common-difference mode separator and the spectrometer are all grounded.

FIG. 4 is a schematic diagram of a two-way cable EMI detection apparatus for an active device; because there is the electromagnetic coupling phenomenon between the equipment under test double-circuit cable, need not additionally provide the power, then the equipment under test can be directly for the double-circuit cable of active equipment. The two-way cable 301, the common mode splitter 302 and the spectrometer 303 of the source device are connected in sequence.

The working frequency domain of the common differential mode separator is 10 kHz-300 MHz; the differential-mode filter comprises a common-mode channel and a differential-mode channel, wherein the common-mode channel and the differential-mode channel are completely isolated, and the isolation degree meets the requirements that 10 kHz-30 MHz >40dB, 50MHz >30dB and 300MHz >20 dB.

The working frequency domain of the signal source is 10 kHz-300 MHz.

The working frequency domain of the frequency spectrograph is 10 kHz-300 MHz.

Fig. 5-11 are schematic diagrams of the testing device for different tested objects.

Fig. 5 and fig. 6 are diagrams illustrating the coupling of the electric field (distributed capacitance) between two lines of the passive device, respectively, the coupling diagram of the electric field (distributed capacitance) between two lines of the passive device and the apparatus for testing the coupling of the magnetic field (mutual inductance) between two lines of the passive device, and fig. 7 is a diagram illustrating the apparatus for testing the shielding effect of one of the two lines of the passive device by using the shielded cable and different grounding methods of the cable; the three figures are connected with a signal source, a detected unit, a common differential mode separator and a spectrometer in sequence.

Fig. 8 to 11 are schematic diagrams of various electromagnetic couplings between any two cables inside the test equipment, which are respectively a device schematic diagram of a shielding effect between one wire and one shielded cable inside the active equipment and between different grounding modes of the cables, a device schematic diagram of a shielding effect between two shielded cables and between different grounding modes of the cables inside the active equipment, a device schematic diagram of various electromagnetic couplings between twisted pairs inside the active equipment, and a device schematic diagram of various electromagnetic couplings between two cables inside the active equipment. The four figures are connected with a detection unit, a common differential mode separator and a spectrometer in sequence.

The specific embodiments can respectively obtain specific values of common mode electromagnetic coupling and differential mode electromagnetic coupling between cables in the equipment, and the detection result is accurate.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.

Claims (8)

1. An inter-cable electromagnetic interference detection apparatus, the apparatus comprising: the device to be detected, the common differential mode separator and the spectrometer;

the device to be detected, the common differential mode separator and the frequency spectrograph are connected in sequence.

2. The device for detecting electromagnetic interference between cables as claimed in claim 1, wherein said device to be detected comprises a signal source and a unit to be detected; the detected unit is a single-path cable of passive equipment;

the signal source, the detected unit, the common differential mode separator and the frequency spectrograph are connected in sequence.

3. The device for detecting electromagnetic interference between cables as claimed in claim 1, wherein the device to be detected comprises a signal source, a signal converter and a unit to be detected; the detected unit is a double-path cable of passive equipment;

the signal source, the signal converter, the detected unit, the common differential mode separator and the frequency spectrograph are connected in sequence.

4. The apparatus of claim 2 or 3, wherein the signal source, the common differential mode separator and the spectrometer are all grounded.

5. The apparatus according to claim 1, wherein the apparatus to be detected is a two-way cable of an active device.

6. The apparatus according to any one of claims 1 to 5, wherein the operating frequency domain of the co-differential separator is 10 kHz-300 MHz;

the common-mode and differential-mode separator comprises a common-mode channel and a differential-mode channel;

the common mode channel and the differential mode channel are completely isolated, and the isolation degree meets the requirements that 10 kHz-30 MHz is more than 40dB, 50MHz is more than 30dB, and 300MHz is more than 20 dB.

7. The apparatus according to claim 6, wherein the operating frequency of the signal source is 10 kHz-300 MHz.

8. The apparatus according to claim 7, wherein the frequency spectrum analyzer has an operating frequency range of 10kHz to 300 MHz.

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