Measuring device for low frequency electromagnetic compatibility testing

Abstract

The measuring device for low-frequency electromagnetic compatibility testing mainly includes a reverberation chamber (10), a stirrer (20), and three telescopic tunable linear polarization transmitting antennas; the three antennas are connected to three transmitters and placed on three mutually perpendicular walls, the polarization direction of the antenna is perpendicular to the wall on which it is located, and the position of the antenna on the wall on which it is located should avoid being located at the zero point position of the electric field of the mode to be excited, and excite multiple continuous modes from the lowest order to the high order. The measuring device can excite modes in any direction of the electric field and realize the adjustment of the relative size of the excitation mode. The transmitting antenna can achieve the best matching in the entire test frequency band. The number of excited modes is large. When the measurement frequency is low, such as 30MHz to 80MHz, the uniformity of the field strength inside the reverberation chamber can still be improved, and the excitation efficiency is high.

Description

Technical Field

[0001] The invention relates to electromagnetic compatibility testing, in particular to a measuring device for low-frequency electromagnetic compatibility testing. Background Art

[0002] The purpose of electromagnetic compatibility testing is to test the sensitivity of the tested electrical and electronic products or systems (collectively referred to as test pieces) to external electromagnetic fields. During the test, the test piece needs to be placed in a uniform electromagnetic field, and the test device needs to be shielded to avoid interference with the external environment. Electromagnetic compatibility testing usually needs to be carried out in an anechoic chamber or a reverberation chamber. Compared with the two, the test efficiency of the anechoic chamber is relatively low. With the application of a large number of new technologies such as 5G communications, electronic tags, and power carriers, many products use complex high-frequency radiation patterns. The repeatability of electromagnetic compatibility measurements in existing anechoic chambers is relatively low, and reverberation chambers will become the preferred test environment. At present, the reverberation chamber method has been successively applied in military standards MIL-STD-461F / G, GJB151B, airborne electronic equipment standards DO-160, and automotive parts standards ISO 11452-11. The reverberation chamber method is particularly suitable for electromagnetic compatibility testing at the large-scale equipment level. A typical application is the RF radiation immunity test of complete vehicles. The U.S. complete vehicle reverberation chamber method test standard SAE J551-16 has released three versions in 2005, 2012 and 2017. However, there are currently no corresponding standards in either the international or Chinese community.

[0003] As an electromagnetic compatibility measurement device, the reverberation chamber includes a shielded room, a stirrer in the room, and a transmitting antenna. The shielded room can shield the test device from external interference. In order to achieve this shielding, the isolation material of the shielded room is metal. In this way, the shielded room, i.e., the reverberation chamber, is equivalent to a metal waveguide resonant cavity. Since the field strength in the cavity presents a standing wave distribution during resonance, the electromagnetic field uniformity is poor and cannot meet the test requirements of electromagnetic compatibility radio frequency radiation immunity. Therefore, the general reverberation chamber needs to excite multiple resonant modes to ensure sufficient multi-mode resonance. At the same time, the stirrer is used to randomly "stir" the movable parts to change the boundary conditions, thereby changing the field distribution of the resonant mode and achieving the uniformity of the electromagnetic field distribution in the sense of time statistical average. The reverberation chamber usually uses a broadband logarithmic periodic antenna as the transmitting antenna to transmit electromagnetic waves of the test frequency and excite the required mode in the reverberation chamber. Nevertheless, when the test frequency is relatively low, such as 30MHz to 80MHz, there are still some problems.

[0004] A single transmitting antenna is difficult to meet the requirements of position, polarization and ratio for exciting multiple modes, and the number of modes that can be excited is relatively small. If a certain mode is to be excited, the antenna must generate an electric field with the same polarization as the electric field of the mode at the location of the antenna. Any mode in the reverberation chamber has a point where the electric field is zero. If it happens that the point where the electric field of the mode is zero is exactly where the antenna is located, then no matter how powerful the transmitting antenna is, it cannot excite the mode. If it is a single transmitting antenna, it may have high excitation efficiency for a certain mode and low excitation efficiency for another mode. Even because the polarization direction of the antenna is different from the electric field direction of the excited mode, it is completely impossible to excite the mode with only the electric field in the polarization direction. Therefore, the number of modes that can be excited is relatively small. At the location of the antenna, an antenna must excite multiple different modes at the same time. Due to the different electric field distributions of different modes, the relative size ratio of these modes in the different modes excited by a single antenna is fixed. This ratio of different modes is likely to not meet the test requirements.

[0005] The antenna cannot achieve optimal matching in the entire test frequency band. Mismatch will increase the antenna port reflection and reduce the excitation efficiency. The minimum operating frequency of the broadband log-periodic antenna usually used in the reverberation chamber is 80MHz. When the test frequency is lower than the antenna's operating frequency, the antenna port reflection increases, so that only a small part of the transmitter power can be sent into the antenna for radiation, the excitation efficiency is low, and the power reflected by the antenna also affects the operation of the transmitter. Even if a larger broadband log-periodic antenna is used, the minimum operating frequency of the antenna can reach 30MHz, but because it is a broadband antenna of fixed size, its standing wave curve actually has fluctuations, and it cannot guarantee that the best match can be achieved in the entire test frequency band.

[0006] Therefore, the current reverberation chamber cannot be used for 30MHz to 80MHz electromagnetic compatibility tests, limiting the application scope of the reverberation chamber as an electromagnetic compatibility test device. Since cars may encounter various electromagnetic environments while driving, relevant standards stipulate that the frequency range of automotive electromagnetic compatibility RF radiation immunity tests is 10kHz to 18GHz, among which the test of the 30MHz to 80MHz frequency band is currently in urgent need of resolution. Existing test devices based on reverberation chambers cannot meet such test requirements. Summary of the invention

[0007] Technical problem: The present invention proposes a measuring device for low-frequency electromagnetic compatibility testing to solve the problem that a single transmitting antenna is difficult to meet the requirements of position, polarization and ratio for exciting multiple modes, to solve the problem of small number of excitation modes and single polarization type, to solve the problem that the antenna cannot achieve optimal matching in the entire test frequency band and the problem of low excitation efficiency, so that when the test frequency is low, the uniformity of the field strength inside the reverberation chamber can still be improved and the excitation efficiency can be improved.

[0008] Technical solution:

[0009] The measuring device for low-frequency electromagnetic compatibility test of the present invention is characterized in that the device comprises a reverberation chamber, a stirrer, and three transmitting antennas; the three transmitting antennas are respectively a front wall antenna, a side wall antenna, and a top surface antenna; the internal shape of the reverberation chamber is a rectangular parallelepiped, and there are six wall surfaces in total, namely, a front wall, a rear wall, a first side wall, a second side wall, a bottom surface, and a top surface; the stirrer is located on the rear wall of the reverberation chamber; the front wall antenna, the side wall antenna, and the top surface antenna are all linearly polarized, telescopic tuning antennas; the front wall antenna is located on the front wall, and the polarization direction of the front wall antenna is perpendicular to the front wall, so as to excite multiple modes of an electric field having a component of the polarization direction of the front wall antenna; the top surface antenna is located on the top surface, and the polarization direction of the top surface antenna is perpendicular to the top surface, so as to excite multiple modes of an electric field having a component of the polarization direction of the top surface antenna; the side wall antenna is located on the first side wall or the second side wall, and the polarization direction of the side wall antenna is perpendicular to the first side wall, so as to excite multiple modes of an electric field having a component of the polarization direction of the side wall antenna.

[0010] The front wall antenna, side wall antenna and top antenna can be connected to different transmitters, and the transmission power of each antenna can be adjusted according to specific test requirements so that the relative size of different modes meets the test requirements.

[0011] The lengths of the front wall antenna, the side wall antenna, and the top antenna are adjusted according to the test frequency band so that the front wall antenna, the side wall antenna, and the top antenna all reach their respective best matching states.

[0012] The position of the front wall antenna on the front wall should avoid being located at the zero point of the electric field of the mode to be excited, and should excite multiple continuous modes from the lowest order to the higher order; the front wall antenna is not located at the center of the front wall to effectively excite the even-order mode; the distance between the front wall antenna and the edge closer to the front wall is between one-fifth and one-quarter of the distance from the edge to the opposite edge, but not two-ninths or three-elevenths.

[0013] The position of the top antenna on the top surface should avoid being located at the zero point of the electric field of the mode to be excited, and should excite multiple continuous modes from the lowest order to the higher order; the top antenna is not located at the center of the top surface to effectively excite the even-order mode; the distance between the top antenna and the edge closer to the top surface is between one-fifth and one-quarter of the distance from the edge to the opposite edge, but not two-ninths or three-elevenths.

[0014] The side wall antenna is located on the side wall so as to avoid being located at the zero point of the electric field of the mode to be excited; the side wall antenna is not located at the center of the side wall so as to effectively excite the even-order mode and excite multiple continuous modes starting from the lowest order to the higher order; the distance between the side wall antenna and the edge nearer to the side wall is between one-fifth and one-quarter of the distance from the edge to the opposite edge, but not two-ninths or three-elevenths.

[0015] In this device, the three transmitting antennas in the entire reverberation chamber are distributed on three mutually perpendicular walls, so there are corresponding polarized antennas in all three orthogonal directions. We use a coordinate system to describe the reverberation chamber, and take the intersection of the front wall, the bottom surface and the first side wall as the origin of the coordinate system. The direction of the x-axis points from the origin to the intersection of the front wall, the bottom surface and the second side wall, the direction of the y-axis points from the origin to the intersection of the top surface, the front wall and the first side wall, and the direction of the z-axis points from the origin to the intersection of the back wall, the first side wall and the bottom surface. The specific position of the front wall antenna can ensure that all modes in the TMmnp or TEmnp mode with an electric field in the z direction, where p is arbitrary, m is not greater than 16, and n is not greater than 16, are excited. Similarly, the specific position of the top antenna can ensure that all modes in the TMmnp or TEmnp mode with an electric field in the y direction, where m is arbitrary, n is not greater than 16, and p is not greater than 16, are excited; the specific position of the side wall antenna can ensure that all modes in the TMmnp or TEmnp mode with an electric field in the x direction, where n is arbitrary, m is not greater than 16, and p is not greater than 16 are excited. In the above manner, more modes in all polarization directions can be effectively excited.

[0016] The three transmitting antennas can be placed on any three mutually perpendicular walls of the reverberation chamber. The three transmitting antennas working simultaneously can not only excite the mode with only one directional component of the electric field, but also excite the mode with two and three components of the electric field. The number of modes in the test frequency band is greatly increased, which not only greatly improves the uniformity of the internal field strength, but also improves the matching state of the transmitting antenna and improves the excitation efficiency.

[0017] Since the input powers of the three transmitting antennas can be adjusted separately, changing the input power ratio of the three antennas provides a means to control the relative size of the excited modes. After simulation design, the optimized input power ratio can be found to further improve the uniformity of the field strength inside the entire reverberation chamber or the uniformity of the field strength in the local area of ​​the test piece.

[0018] Since a retractable transmitting antenna is used, the central operating frequency of the antenna can be changed to be equal to the test frequency by changing the retracted length according to the test needs, so that the transmitting antenna can be in the best matching state.

[0019] The technical solution of the measuring device for low-frequency electromagnetic compatibility testing increases the modes of the reverberation chamber and improves the matching of the transmitting antenna. As a result of these two combined effects, the field strength in the reverberation chamber can reach the field strength that previously required several kilowatts with only about one hundred watts of transmitting power.

[0020] Beneficial effects: The beneficial effects of the present invention are: the proposed measuring device for low-frequency electromagnetic compatibility testing can excite modes in any direction of the electric field and realize the adjustment of the relative size of the excitation mode. The transmitting antenna can achieve the best matching in the entire test frequency band. The number of excited modes is large. When the measurement frequency is low, such as 30MHz to 80MHz, the uniformity of the field strength inside the reverberation chamber can still be improved, and the excitation efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of a measuring device for low-frequency electromagnetic compatibility testing of the present invention;

[0022] Figure 2 It is a side view of the measuring device for low frequency electromagnetic compatibility testing of the present invention

[0023] Figure 3 is a top view of a measuring device for low-frequency electromagnetic compatibility testing of the present invention;

[0024] The figure shows a reverberation chamber (10), a front wall (11), a rear wall (12), a first side wall (13), a second side wall (14), a bottom surface (15), a top surface (16), a stirrer (20), a front wall antenna (31), a side wall antenna (32) and a top surface antenna (33). DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0026] The implementation scheme adopted by the present invention is: a measuring device for low-frequency electromagnetic compatibility testing, the device includes a reverberation chamber 10, a stirrer 20, and three transmitting antennas; the three transmitting antennas are a front wall antenna 31, a side wall antenna 32, and a top antenna 33; the internal shape of the reverberation chamber 10 is a rectangular parallelepiped, with a front wall 11, a rear wall 12, a first side wall 13, a second side wall 14, a bottom surface 15, and a top surface 16, a total of six walls; the stirrer 20 is located on the rear wall 12 of the reverberation chamber 10; the front wall antenna 31, the side wall antenna 32, and the top antenna 33 are all linearly polarized, telescopic tuning antennas The front wall antenna 31 is located on the front wall 11, and the polarization direction of the front wall antenna 31 is perpendicular to the front wall 11, so as to excite multiple modes of the electric field having the polarization direction component of the front wall antenna 31; the top surface antenna 33 is located on the top surface 16, and the polarization direction of the top surface antenna 33 is perpendicular to the top surface 16, so as to excite multiple modes of the electric field having the polarization direction component of the top surface antenna 16; the side wall antenna 32 is located on the first side wall 13 or the second side wall 14, and the polarization direction of the side wall antenna 32 is perpendicular to the first side wall 13, so as to excite multiple modes of the electric field having the polarization direction component of the side wall antenna 32.

[0027] The front wall antenna 31, the side wall antenna 32 and the top antenna 33 can be connected to different transmitters, and the transmission power of each antenna can be adjusted according to specific test requirements so that the relative sizes of different modes meet the test requirements.

[0028] The lengths of the front wall antenna 31 , the side wall antenna 32 and the top surface antenna 33 are adjusted according to the test frequency band, so that the front wall antenna 31 , the side wall antenna 32 and the top surface antenna 33 all reach their respective best matching states.

[0029] The position of the front wall antenna 31 on the front wall 11 should avoid being located at the zero point of the electric field of the mode to be excited, and should excite multiple continuous modes from the lowest order to the higher order; the front wall antenna 31 is not located at the center of the front wall 11 to effectively excite the even-order mode; the distance between the front wall antenna 31 and the closer edge of the front wall 11 is between one-fifth and one-quarter of the distance from the edge to its opposite edge, but not two-ninths or three-elevenths.

[0030] The position of the top surface antenna 33 on the top surface 16 should avoid being located at the zero point of the electric field of the mode to be excited, and should excite multiple continuous modes from the lowest order to the higher order; the top surface antenna 33 is not at the center of the top surface 16 to effectively excite the even-order mode; the distance between the top surface antenna 33 and the closer edge of the top surface 16 is between one-fifth and one-quarter of the distance from the edge to its opposite edge, but not two-ninths or three-elevenths.

[0031] The side wall antenna 32 is positioned on the side wall to avoid being located at the zero point of the electric field of the mode to be excited; the side wall antenna 32 is not located at the center of the side wall to effectively excite the even-order mode and to excite multiple continuous modes starting from the lowest order to the higher order; the distance between the side wall antenna 32 and the edge nearer to the side wall is between one-fifth and one-quarter of the distance from the edge to the opposite edge, but not two-ninths or three-elevenths.

[0032] In this device, the three transmitting antennas in the entire reverberation chamber 10 are distributed on three mutually perpendicular walls, so there are corresponding polarized antennas in all three orthogonal directions. We use a coordinate system to describe the reverberation chamber 10, and take the intersection of the front wall 11, the bottom surface 15 and the first side wall 13 as the origin of the coordinate system. The direction of the x-axis points from the origin to the intersection of the front wall 11, the bottom surface 15 and the second side wall 14, the direction of the y-axis points from the origin to the top surface 16, the intersection of the front wall 11 and the first side wall 13, and the direction of the z-axis points from the origin to the intersection of the rear wall 12, the first side wall 13 and the bottom surface 15. The specific position of the front wall antenna 31 can ensure that all modes in the TMmnp or TEmnp mode with an electric field in the z direction, where p is arbitrary, m is not greater than 16, and n is not greater than 16, are excited. Similarly, the specific position of the top antenna 33 can ensure that all modes in the TMmnp or TEmnp mode with an electric field in the y direction, where m is arbitrary, n is not greater than 16, and p is not greater than 16, are excited; the specific position of the side wall antenna 32 can ensure that all modes in the TMmnp or TEmnp mode with an electric field in the x direction, where n is arbitrary, m is not greater than 16, and p is not greater than 16 are excited. In the above manner, more modes in all polarization directions can be effectively excited.

[0033] The three transmitting antennas can be placed on any three mutually perpendicular walls of the reverberation chamber 10. The three transmitting antennas work simultaneously, which can not only excite a mode with only one directional component of the electric field, but also excite a mode with two and three components of the electric field. The number of modes in the test frequency band is greatly increased, which not only greatly improves the uniformity of the field strength inside the reverberation chamber 10, but also improves the matching state of the transmitting antenna and improves the excitation efficiency.

[0034] Since the input powers of the three transmitting antennas can be adjusted separately, changing the input power ratio of the three antennas provides a means to control the relative size of the excited modes. Through simulation design, the optimized input power ratio can be found to further improve the uniformity of the field strength inside the entire reverberation chamber 10, or the uniformity of the field strength in a local area of ​​the test piece.

[0035] Since a retractable transmitting antenna is used, the central operating frequency of the antenna can be changed to be equal to the test frequency by changing the retracted length according to the test needs, so that the transmitting antenna can be in the best matching state.

[0036] The technical solution of the measuring device for low-frequency electromagnetic compatibility testing increases the modes of the reverberation chamber and improves the matching of the transmitting antenna. As a result of these two combined effects, the field strength in the reverberation chamber can reach the field strength that previously required several kilowatts with only about one hundred watts of transmitting power, thus meeting the test requirements.

[0037] According to the above description, the present invention can be realized.

Claims

1. Measurement device for low frequency electromagnetic compatibility testing, Features The device comprises a reverberation chamber (10), a stirrer (20), and three transmitting antennas; the three transmitting antennas are respectively a front wall antenna (31), a side wall antenna (32), and a top surface antenna (33); the internal shape of the reverberation chamber (10) is a rectangular parallelepiped, having a total of six walls, namely a front wall (11), a rear wall (12), a first side wall (13), a second side wall (14), a bottom surface (15), and a top surface (16); the stirrer (20) is located on the rear wall (12) of the reverberation chamber (10), which is actually a wall of the reverberation chamber (10) whose position changes; the front wall antenna (31), the side wall antenna (32), and the top surface antenna (33) are all linearly polarized, telescopic tuning antennas The front wall antenna (31) is located on the front wall (11), and the polarization direction of the front wall antenna (31) is perpendicular to the front wall (11), so as to excite multiple modes of the electric field having a component in the polarization direction of the front wall antenna (31); the top surface antenna (33) is located on the top surface (16), and the polarization direction of the top surface antenna (33) is perpendicular to the top surface (16), so as to excite multiple modes of the electric field having a component in the polarization direction of the top surface antenna (16); the side wall antenna (32) is located on the first side wall (13) or the second side wall (14), and the polarization direction of the side wall antenna (32) is perpendicular to the first side wall (13), so as to excite multiple modes of the electric field having a component in the polarization direction of the side wall antenna (32); The front wall antenna (31), the side wall antenna (32) and the top surface antenna (33) are connected to different transmitters, and the transmission power of each antenna is adjusted according to specific test requirements so that the relative sizes of different modes meet the test requirements.

2. The measuring device for low-frequency electromagnetic compatibility testing according to claim 1, Features The lengths of the front wall antenna (31), the side wall antenna (32) and the top surface antenna (33) are adjusted according to the test frequency band, so that the front wall antenna (31), the side wall antenna (32) and the top surface antenna (33) all reach their respective best matching states.

3. The measuring device for low-frequency electromagnetic compatibility testing according to claim 1, Features The position of the front wall antenna (31) on the front wall (11) should avoid being located at the zero point of the electric field of the mode to be excited, and should excite a plurality of continuous modes from the lowest order to the higher order; the front wall antenna (31) is not located at the center of the front wall (11) to effectively excite the even-order mode; the distance between the front wall antenna (31) and the edge closer to the front wall (11) is between one-fifth and one-quarter of the distance from the edge to the opposite edge, but not two-ninths or three-elevenths.

4. The measuring device for low-frequency electromagnetic compatibility testing according to claim 1, Features The position of the top antenna (33) on the top surface (16) should avoid being located at the zero point of the electric field of the mode to be excited, and should excite multiple continuous modes from the lowest order to the higher order; the top antenna (33) is not at the center of the top surface (16) to effectively excite the even-order mode; the distance between the top antenna (33) and the edge closer to the top surface (16) is between one-fifth and one-quarter of the distance from the edge to the opposite edge, but not two-ninths or three-elevenths.

5. The measuring device for low-frequency electromagnetic compatibility testing according to claim 1, Features The side wall antenna (32) is located on the side wall so as to avoid being located at the zero point of the electric field of the mode to be excited; the side wall antenna (32) is not located at the center of the side wall so as to effectively excite the even-order mode and excite a plurality of continuous modes starting from the lowest order to the higher order; the distance between the side wall antenna (32) and the edge of the side wall on which it is located is between one fifth and one quarter of the distance from the edge to the opposite edge, but not two ninths or three elevenths.

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