EMC testing-Basic 2EMI test _ radiation emission

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EMI test Project-re radiation emission

In the re test, the height of the antenna, the polarization direction of the antenna and the angle of the turntable need to be constantly changed in order to find the maximum radiation point of the device.

The RE test can be carried out in a semi-electric dark room in an open environment.

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The radiation emission (radiated emission) test is a measure of the radiated disturbance field strength of the eut through space transmission. Can be divided into magnetic field radiation, electric field radiation, the former for lamps and electromagnetic furnace, the latter is widely used. In addition, appliances and power tools, AV products auxiliary equipment has the power radiation requirements (called disturbance power).
1. Test criteria
A) electric field radiation: Cispr22,cispr13,cispr11,cispr14-1 (Specific category of toys);
b) Magnetic field radiation: CISPR15 (lamps with operating current frequency exceeding 100Hz), CISPR11 (induction cooker);

c) Disturbance power: cispr14-1 (except for a portion of the device operating at frequencies not exceeding 9kHz), CISPR13 (only for assistive devices).

CISPR is a special Committee on international Radio interference, so the rules that this committee publishes are named after Cisprxx, such as the test of an ITE product for CISPR22.
While en is an English version published by the European Union, when other languages have different names, the test of the ITE product is called EN55022.
The biggest difference between the two is that the CISPR will be published first, and then the European Union decides whether to cite Cispr's standard after the group has discussed it,
For example, cispr22:2005 and en55022:2006 in the content of the difference, but on the en55022:2008, quoted the latest standard of CISPR

ITE is an acronym for Information technology Equipment information technology equipment, which refers to information technology equipment products, including computers, monitors, routers, mobile phones, power supplies and a range of products.

2. Test Method 1) Instruments and equipment:
A) electric field radiation: Receiver (1G or less), Spectrum meter (1G above), anechoic chamber, Antenna (1G of the general use of double cone and logarithmic period combination or broadband composite antenna, 1G above the horn antenna);
b) Magnetic field radiation: receiver, three-ring antenna or single small-loop antenna; c) Disturbance power: Receiver, power absorption clamp.
The receiver follows the requirements of cispr16-1-1, the antenna and the site follow the requirements of cispr16-1-4, and the absorption pliers follow the cispr16-1-3 requirements.
2) Test layout:
A) electric field radiation: is also sub-benchtop and floor-standing, the same as the conduction emission (because the radiation emission results and product layout is particularly closely related, it is necessary to strictly according to the standard layout including products, ancillary equipment, all cables, including the sample);
b) Magnetic field radiation: three-ring antennas of different sizes are limited to the maximum size of the eut that can be tested, with a 2m diameter annular three-ring antenna as an example, Eut with a length of less than 1.6m can be placed in a three-ring antenna center test; in CISPR11, more than 1.6m of the induction cooker with 0.6m diameter of the single-loop far antenna measured outside 3m, the lowest height 1m;
c) Disturbance power: table and Floor, The benchtop device is placed on a 0.8m non-metallic table, at least 0.8m from other metal objects (usually the metal inner wall of the shielding chamber, which is required to be at least 0.4m in the cispr14-1), the floor-standing device is placed on a non-metallic support of 0.1m, and the measured cable (LUT) is arranged at high 0.8m, Long 6m power absorption clamp guide rail, absorption clamp sleeve on-line cable, the current transformer end toward the device being tested. If the device under test has other cables, it can be disconnected without affecting the function, and cannot be disconnected with the ferrite absorption clamp.
3) Test band: electric field radiation is generally 30mhz-1ghz (some products need to measure more than 1G, according to specific standards), magnetic field 9khz-30mhz, harassment power 30-300mhz.
4) test limits: With different standards, the site is 3m, 10m or other size, different product categories (Group, Class A/b) and the limit value is different.
5) test Process:
A) 30mhz-1ghz electric field radiation: In the semi-anechoic chamber, Eut with the turntable 360 degrees of rotation, the antenna in the 1-4m height up and down, looking for the maximum radiation. The results are expressed in QP values. The polarization direction of the two antennas is measured vertically and horizontally.
b) More than 1G of electric field radiation: the operating frequency of more than 108MHz of ITE equipment, more than 400MHz of ISM equipment needs to be tested, is in the 3m site, the use of spectrum measurement. ITE Equipment test method is basically the same as 30mhz-1ghz, the result is expressed by peak and AV value. ISM products a little different, need to be measured in the full anechoic chamber, the antenna with the product of the same height, does not rise and fall, the turntable is still rotating to find the maximum radiation value;
c) Substitution method: The use of ERP (effective transmitting power) to replace, and then converted into field strength values. This is often used in RF testing and is rarely used by conventional EMC. The purpose of the substitution test is to test the radiation of the eut shell, requiring the removal of all detachable cables and the use of a ferrite ring on a non-detachable cable. First, the maximum disturbance value of eut is measured with antenna A and receiver, then the eut is replaced by Antenna b, and the output power of the signal generator is adjusted until the measurement receiver achieves the same value. Record the input power of the replacement antenna B, which is the radiated power of the eut shell. The selection of antennas depends on the test frequency;
d) Magnetic field radiation: a magnetic field radiation test using a three-ring antenna there's nothing to say, the sample is placed in the center of the antenna, x/y/z in three directions to measure the results of a set of magnetic field radiation. When using a single small loop antenna, the antenna is placed vertically, the lowest part is above the ground 1m, because it is near field measurement, but also considering the ground reflection, the measured value reflects the horizontal and vertical magnetic field components of eut;
e) Disturbance power: All cables exceeding 25cm in length of the device (including the cable for auxiliary equipment) are required. Because the disturbance of different frequency points in the 30-300mhz is distributed in standing wave form in the measured cable. It is therefore necessary to pull the power absorbing pliers along the rails in the measurement to find the maximum disturbance power at each final frequency point (roughly at a distance from the device's half wavelength).
3. Result determination: The comparison is still with the limit value line. Below pass, high out of fail.

4. Note: Test layout is still the most necessary part of testing. In addition, because it is a high-frequency test, venues, equipment, etc. are important factors that will affect the final outcome.

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3 M method and 10 m method

The radiation was three meters before the test. In 2011, the new test site was set to become 10 meters. The difference is that the test distances are different. The 10-meter method is more standard. But now many test organizations still use the 3-meter method. The test data is also recognized. Unless some of the more special products are certain to require a 10-meter method of the venue. such as some wireless products.