CN202837416U - System for testing shielding performance of cables - Google Patents
System for testing shielding performance of cables Download PDFInfo
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- CN202837416U CN202837416U CN 201220329984 CN201220329984U CN202837416U CN 202837416 U CN202837416 U CN 202837416U CN 201220329984 CN201220329984 CN 201220329984 CN 201220329984 U CN201220329984 U CN 201220329984U CN 202837416 U CN202837416 U CN 202837416U
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Abstract
The utility model relates to a system for testing shielding performance of cables. The system for testing shielding performance of cables comprises a test table, a grounding metal plate, two shielding boxes, a signal source, an antenna and a signal analysis device. The grounding metal plate is placed on the test table; the two shielding boxes are placed on the grounding metal plate, and a tested cable is connected between the two shielding boxes; the signal source is used for inputting alternating signals to the tested cable; the antenna is used for receiving radiation signals of the tested cable; and the signal analysis device is used for analyzing the radiation signals received by the antenna to obtain the field intensity of the tested cable.
Description
Technical field
The present invention relates to a kind of test macro of the shielding properties for shielded cable, can test in scope is the shielding properties of cable under the frequency of 10kHz～18GHz.
Background technology
Development along with electronic equipment high frequency, integrated, intelligent, microminiaturized, high power, and the development of 3G network, high speed processor, the interconnecting cable of equipment room is as effective electromagnetic interference emission antenna and receiving antenna, unavoidably cause electromagnetic radiation and the electromagnetic coupled of electronic equipment, caused a large amount of electromagnetic interference problems.For electromagnetic radiation and the coupling that solves cable, a large amount of shielded cables is used for the shielding of signal.
Sign for the shielded cable shielding properties, following two kinds of characteristic manner are arranged at present, a kind of is indirectly to characterize shielding properties by transfer impedance, and the less shielding properties of transfer impedance is better, and transfer impedance is defined as the open-circuit voltage of unit length screen layer and heart yearn and the ratio of the screen layer electric current of flowing through; Another kind is direct characteristic manner, i.e. when shielding properties, shielding properties are defined as cable and have or not screen layer can radiation or field intensity or the power ratio of reception.
The measurement of transfer impedance is mainly based on the measurement of circuit, mainly contain at present following three kinds of modes, three coaxial methods, Line Injection, absorbing clamp method, its main thought is to make up two measuring circuits, inner looping and external loop, in measuring, the electrical parameter values of external loop, thereby obtain open-circuit voltage and the screen layer electric current of heart yearn and screen layer, by calculating transfer impedance.Because be based on the principle of circuit, its survey frequency scope can only be in hundreds of MHz.The below describes the measurement mechanism of transfer impedance as an example of three coaxial methods example, three coaxial method frequency ranges are 10kHz～100MHz.Test unit has three coaxial configurations, and as shown in Figure 1, tested shielded cable consists of the inner wire of the outer coaxial system of feed, is again the outer conductor of interior coaxial system simultaneously.Its main measuring process is, injects alternating signal U with the heart yearn of axis body and outer screen layer with axis body outside
1, by U
1With terminal resistance R
1Try to achieve outer electric current I with axis body heart yearn (namely interior with the axis body screen layer)
1, measure again interior with axis body screen layer and interior voltage U with the axis body heart yearn
2, l is effective measurement length of cable, then
Be the transfer impedance of this screen layer.
The measurement of shielding properties mainly is based on the measuring principle of field, mainly contain at present Reverberation room method, reverberation chamber is IEC specified standard testing laboratory, is mainly used in the electronic product electromagnetic sensitivity measurement, EM sensitivity measurement, and in fact reverberation chamber is exactly the shielded cubicle that worked in the mould state that stirrer is housed.By rotating mixer, change the boundary condition of field, thereby change the energy distribution of each pattern, form the field distribution of statistics homogeneous isotropism at the whole test zone of reverberation chamber.The measurement of Reverberation room method is arranged as shown in Figure 2, its measuring principle is that signal source is exported by emitting antenna, stirrer stirs, performance number by interference receiver difference witness mark antenna and the reception of tested cable, the ratio of two performance numbers is its shielding properties, the field intensity value that can receive when characterizing unshielded layer by reference antenna.The low-limit frequency of reverberation chamber test is subjected to the impact of reverberation chamber physical dimension, and reverberation chamber is larger, and lowest operating frequency can be lower, be that the lowest operating frequency of 17 cubic metres of reverberation chambers is 300MHz such as volume, and 1360 cubic metres lowest operating frequency is 30MHz.
Table 1 is the relatively tabulation of four kinds of common method of testings, and as can be known, 4 kinds of above-mentioned method of testings are measured the shielding properties of shielded cable from the low frequency to the high frequency because the impact of tested person frock, testing tool, test site all can't be satisfied from table.
Table 1 method of testing relatively
Summary of the invention:
The purpose of this invention is to provide a kind of test macro of shielding properties of cable, thereby overcome the problems referred to above of the prior art.
According to the present invention, a kind of test macro of shielding properties of cable is provided, comprising: test desk; Grounding plate is placed on the described test desk; Two shielding case bodies are placed on the described grounding plate, and tested cable is connected between described two shielding case bodies; Signal source is used for to described tested cable input alternating signal; Antenna is for the radiation signal that receives described tested cable; Signal analysis device is used for the described radiation signal of described antenna reception is analyzed, and obtains the field intensity of described tested cable.
The test macro of the shielding properties of described cable can further comprise signal input cable and signal output cable, one end of described signal input cable is electrically connected to described signal source, is electrically connected to an end of described tested cable in the shielding case body of the other end in described two shielding case bodies; One end of described signal output cable is electrically connected to described antenna, and the other end of described signal output cable is electrically connected to described signal analysis device.
The test macro of the shielding properties of described cable further comprises resistance, and this resistance is arranged in another shielding case body of described two shielding case bodies, is electrically connected with the other end of described tested cable.
Description of drawings
Fig. 1 is the schematic diagram of three coaxial method test macros in the prior art.
Fig. 2 is the schematic diagram of Reverberation room method test macro.
Fig. 3 is coaxial cable structure figure.
Fig. 4 is the schematic diagram according to the test macro of the embodiment of the invention.
Description of reference numerals
101 outer coaxial system 102 tested shieldings
103 interior coaxial system 104 sheaths
1 interference receiver, 2 signal sources
3 stube cables, 4 tested cables
5 insulating supportings, 6 emitting antennas
7 reference antennas, 8 stirrers
10 inner insulating layers, 20 heart yearns
30 screen layers, 40 external insulation layers
11 semi-anechoic chambers, 22 frequency spectrographs
2 signal sources, 111 antennas
112 metal tubes, 113 tested cables
Husky 11550 ohm load of 114 bronze medals
116 grounding plates, 117 shielded boxes
118 test desks, 221 signals output concentric cable
211 signals input concentric cable
Embodiment
According to the definition from shielding properties of method of testing of the present invention and test macro, can measure the shielding properties of cable under the wideband of 10kHz～18GHz.Shielding properties is defined as: under same test environment conditions, when shielding properties has or not screen layer by cable field intensity or the power ratio of energy radiation or reception.Receiving namely is that cable is placed high power field intensity environment, by measuring the field intensity value that can receive when cable has or not screen layer.And Reverberation room method just is based on the principle that field intensity receives, but owing to being subjected to the impact of reverberation chamber physical dimension, its low-limit frequency is restricted.Emission then is based on cable core and injects alternating signal, when the measurement cable has or not screen layer, and the ratio of the field intensity value of receiving antenna, the ratio of twice field intensity value is shielding properties.The present invention just is being based on the mechanism of emission, has made up the method for testing of shielded cable shielding properties.
The standard codes such as GJB151A, GB9254, IEC the measuring method of electronic product field intensity radiation-emitting, stipulated that the measurement place is semi-anechoic chamber, semi-anechoic chamber is on the basis of electromagnetic shielding chamber, paste electromagnetic wave absorbent material at inwall four walls and top board dress, ground is desirable reflecting surface.Thereby the test condition of simulation open area test site, owing to there being absorbing material, electromagnetic wave does not reflect, screened room has been isolated external Electromagnetic Interference simultaneously.Semi-anechoic chamber is as the test place of standard, the test of widespread use electronic equipment, and its field strength measurement frequency can be 10kHz～18GHz.
The present invention can implement under this semi-anechoic chamber environment.The present invention is used for measuring concentric cable.The structural drawing of concentric cable as shown in Figure 3.Concentric cable comprises heart yearn, inner insulating layer, screen layer and external insulation layer from inside to outside successively.
Fig. 4 illustrates the schematic diagram according to the test macro of the embodiment of the invention.As shown in Figure 4, this test macro comprises test desk, grounding plate, shielding case body, antenna, signal source and signal analysis device, such as frequency spectrograph etc.Test desktop terrain clearance h2 is 80～90cm, is covered with grounding plate on the test desk, and shielding case body is fixed on the metal ground plate, and is connected with the metal ground plate conduction, two shielding case bodies be 1m apart from s.The distance L of tested cable and reference antenna is 1 meter, and the tested cable length that exposes outside shielding case body is 1 meter.Be filled with copper sand in the shielding case body, the diameter of copper sand is 1mm～2mm.Spike antenna reference point terrain clearance is contour with the test desktop, and other antenna terrain clearances are 120 centimetres.
For so that measure the field intensity value that the field intensity value only radiates for tested cable, eliminate the field intensity radiation of other relief cables, made up two shielding case bodies and specified signal is inputted, the mode of output cable.In this system, tested cable core is connected between two shielding case bodies, with grounding plate distance h 1 in height be 10cm.Particularly, an end of tested cable core is connected to signal input cable in the first shielding case body, and the other end of tested cable is connected with 50 ohm of matched loads (for example 50 Ohmage heart yearns) in the secondary shielding casing.One end of 50 Ohmage heart yearns is connected with tested cable, and the other end is connected with the secondary shielding casing.The perfusion diameter is about the conducting metal particles of 1mm～2mm in the shielding case body, such as copper particle, silver-colored particle.In a preferred embodiment, fill conducting metal particles in the shielding case body, be used on the one hand shield gasket cable the junction, (junction of tested cable core and coaxial signal input cable, and the junction of tested cable core and coaxial load), reduce the electromagnetic leakage of casing; On the other hand, fill conducting metal particles so that cable shield can be connected with metal ground plate 360 degree conductions, reduce the impact that imperfect earth is brought.
This system also comprises signal input cable and signal output cable.Signal input cable and signal output cable adopt coaxial shielded cable to add the shielding mode of metal tube, eliminate the electromagnetic radiation of input, output cable.Signal input concentric cable one end is connected with signal source, and the other end passes metal tube and is connected with shielded box, and the form that this metal tube passes through screw thread or welding and shielding case body are connected housing and are conducted electricity and be connected with semi-anechoic chamber.Signal output cable one end is connected with antenna, and the other end passes metal tube and is connected with frequency spectrograph, and this metal tube is connected with the housing conduction of semi-anechoic chamber by the form of screw thread or welding.
According to another embodiment of the present invention, the method that adopts above-mentioned test macro that the shielding properties of concentric cable is tested is as follows, wherein example such as RG5U coaxial wire, and its structure is as shown in Figure 3.The method specifically can may further comprise the steps:
Remove the external insulation layer of cable, to described cable input alternating signal;
The field intensity of measuring described cable is the first field intensity;
Remove the screen layer of described cable, input described alternating signal to described cable;
The field intensity of measuring described cable is the second field intensity;
More described the first field intensity and described the second field intensity are determined the shielding properties of described cable according to the comparative result of described the first field intensity and described the second field intensity.
Wherein, the cable that only removes behind the external insulation layer of cable is called test cable, and removes external insulation layer and screen layer only stays the cable of heart yearn and inner insulating layer to be called the contrast cable.
In this embodiment, the making of contrast cable can divest the external insulation layer of concentric cable and screen layer and only stay heart yearn and inner insulating layer, intercepts approximately 1.3 meters length.The making of test cable can intercept approximately 1.3 meters length of concentric cable, divests respectively approximately 15 centimetres external insulation layer of two ends, exposes screen layer, keeps 1 meter long complete cable.
Before test, with the end of heart yearn of contrast cable in the first shielding case body with the heart yearn welding of the coaxial input cable of signal, and do insulation and process, the other end in the secondary shielding casing with 50 ohm heart yearn welding, two welds are carried out insulation processing.Two shielding case bodies are filled copper sand, and metal cover board is installed, carry out shield gasket.Distance between two shielding case bodies can be 1 meter, and heart yearn can be 10 centimetres from the height of grounding plate, and the antenna reference point can be 1 meter from the heart yearn distance.Regulate antenna terrain clearance (spike antenna reference point terrain clearance and test desk are contour, and other antenna terrain clearances are 120 centimetres).The input end connecting signal source of the coaxial input cable of signal, antenna is connected to frequency spectrograph by the signal output cable, carries out test macro by Fig. 4 and arranges.
In test process, at first select frequency, conditioning signal source output power, by antenna reception and observe the shown field intensity value of frequency spectrograph, until the field intensity value that shows is during greater than noise of instrument 70dB, frequency, the power of the output of record signal source this moment, and the field intensity value E1 that shows of frequency spectrograph.(having guaranteed that greater than noise of instrument 70dB the dynamic range of measuring shielding properties is at least 70dB).
Test cable is also arranged according to the method identical with the contrast cable.Afterwards when this test cable of test, at first frequency values and the performance number with the signal source output to the contrast wireline test time of the output frequency of signal source and power adjustments is identical, by antenna reception and observe the shown field intensity value of frequency spectrograph, the frequency of record signal source this moment output, and the field intensity value E2 of frequency spectrograph demonstration.
The field intensity value E1 of the contrast cable that test is obtained and the field intensity value E2 of test cable compare, and determine the shielding properties SE of cable, and shielding properties SE can determine according to following formula: SE=20Log (E1)-20Log (E2).
Table 2 illustrates the shielding properties of testing this concentric cable that obtains.
As seen, by method of testing of the present invention and test macro, can measure the test performance of coaxial cable under wide frequency ranges.
Frequency spectrograph in above-described embodiment can also replace with receiver.And when the signal source output power was inadequate, signal source connect signal input cable after can input signal being amplified by power amplifier again.
Claims (6)
1. cable shield performance test system comprises:
Test desk;
Grounding plate is placed on the described test desk;
Two shielding case bodies are placed on the described grounding plate, and tested cable is connected between described two shielding case bodies;
Signal source is used for to described tested cable input alternating signal;
Antenna is for the radiation signal that receives described tested cable;
Signal analysis device is used for the described radiation signal of described antenna reception is analyzed, and obtains the field intensity of described tested cable.
2. cable shield performance test as claimed in claim 1 system, further comprise signal input cable and signal output cable, one end of described signal input cable is electrically connected to described signal source, is electrically connected to an end of described tested cable in the shielding case body of the other end in described two shielding case bodies; One end of described signal output cable is electrically connected to described antenna, and the other end of described signal output cable is electrically connected to described signal analysis device.
3. cable shield performance test as claimed in claim 2 system further comprises resistance, and this resistance is arranged in another shielding case body of described two shielding case bodies, is electrically connected with the other end of described tested cable.
4. cable shield performance test as claimed in claim 3 system further comprises the metal tube that is enclosed within on the described signal input cable and is enclosed within metal tube on the described signal output cable.
5. conducting metal particles is filled in wherein said two shielding case bodies by cable shield performance test as claimed in claim 1 system.
6. cable shield performance test as claimed in claim 5 system, the diameter of wherein said conducting metal particles is 1mm～2mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220329984 CN202837416U (en) | 2012-07-10 | 2012-07-10 | System for testing shielding performance of cables |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220329984 CN202837416U (en) | 2012-07-10 | 2012-07-10 | System for testing shielding performance of cables |
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| CN 201220329984 Expired - Fee Related CN202837416U (en) | 2012-07-10 | 2012-07-10 | System for testing shielding performance of cables |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103323644A (en) * | 2013-05-27 | 2013-09-25 | 中国舰船研究设计中心 | Method for testing potential distribution of wide band large-scale metal plate |
| CN103543342A (en) * | 2012-07-10 | 2014-01-29 | 中国兵器工业新技术推广研究所 | Method and system for testing shielding performance of cable |
| CN104391199A (en) * | 2014-11-27 | 2015-03-04 | 江西洪都航空工业集团有限责任公司 | Method for testing shielding effectiveness of cable shielding layer |
| CN105116249A (en) * | 2015-08-06 | 2015-12-02 | 西安电子科技大学 | Broadband shielding effectiveness test device of small shielding chassis and method |
| CN107656158A (en) * | 2017-09-28 | 2018-02-02 | 江苏通鼎光电科技有限公司 | Preferable the screening factor test system and its measuring method of communication cable |
| CN110412370A (en) * | 2019-07-20 | 2019-11-05 | 中国船舶重工集团公司第七二四研究所 | Multi-coaxial cable assembly shield effectiveness detection method based on radiation method |
| CN113419114A (en) * | 2021-05-13 | 2021-09-21 | 北京航空航天大学 | Miniaturized broadband electromagnetic shielding testing device and testing method |
| TWI764072B (en) * | 2019-12-25 | 2022-05-11 | 李志宏 | Semi-anechoic chamber and floor structure thereof |
-
2012
- 2012-07-10 CN CN 201220329984 patent/CN202837416U/en not_active Expired - Fee Related
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103543342A (en) * | 2012-07-10 | 2014-01-29 | 中国兵器工业新技术推广研究所 | Method and system for testing shielding performance of cable |
| CN103323644A (en) * | 2013-05-27 | 2013-09-25 | 中国舰船研究设计中心 | Method for testing potential distribution of wide band large-scale metal plate |
| CN103323644B (en) * | 2013-05-27 | 2016-03-16 | 中国舰船研究设计中心 | The Potential distribution method of testing of wide band large-scale metal plate |
| CN104391199A (en) * | 2014-11-27 | 2015-03-04 | 江西洪都航空工业集团有限责任公司 | Method for testing shielding effectiveness of cable shielding layer |
| CN105116249A (en) * | 2015-08-06 | 2015-12-02 | 西安电子科技大学 | Broadband shielding effectiveness test device of small shielding chassis and method |
| CN107656158A (en) * | 2017-09-28 | 2018-02-02 | 江苏通鼎光电科技有限公司 | Preferable the screening factor test system and its measuring method of communication cable |
| CN110412370A (en) * | 2019-07-20 | 2019-11-05 | 中国船舶重工集团公司第七二四研究所 | Multi-coaxial cable assembly shield effectiveness detection method based on radiation method |
| TWI764072B (en) * | 2019-12-25 | 2022-05-11 | 李志宏 | Semi-anechoic chamber and floor structure thereof |
| CN113419114A (en) * | 2021-05-13 | 2021-09-21 | 北京航空航天大学 | Miniaturized broadband electromagnetic shielding testing device and testing method |
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| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20130327 Termination date: 20140710 |
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| EXPY | Termination of patent right or utility model |