Detailed explanation of radiation emission
Company News2023 23Asia/ShanghaiamTue, 15 Aug 2023 09:31:39 +0800 08 08202383109 15 15am23
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Radiation emission refers to the electromagnetic waves emitted by electronic, electrical products or systems from their internal circuits to the surrounding space. This transmission is carried out through the air as a propagation path rather than wires (including signal and power lines). Since it is called a transmission, there must be receiving objects or devices present in the surrounding space. Radiation emission mainly tests the radiation interference intensity of electronic and electrical equipment or systems to the outside world during normal operation, including radiation interference from all components such as circuit boards, chassis, cables, and connecting wires.
The following content refers to GB/T 9254.1-2021 regulatory specifications
Scope of application :
GB/T 9254.1-2021 has a wider scope of application, including information equipment, audio equipment, video equipment, broadcast receiving equipment, entertainment lighting control equipment, and their combinations.
Test :
Working voltage: The working voltage and frequency range of GB/T 9254.1 should consider the requirements of the EUT target market, with a general rated voltage of 220V 50Hz in China; CISPR 32 is applicable to EUTs worldwide, measured at frequencies of 50Hz or 60Hz under two rated voltages of 230V (± 10V) and 110V (± 10V).
EUT typically has several different functions, with varying numbers of operating modes for each function. EUT should select one function or a set of functions to operate, and should have a representative mode. The formal measurement should select the operating mode that produces the maximum emission.
If possible, the effective length of the power cord should be 1m ± 0.1m. If the power cable provided by the manufacturer is longer than 1m, fold it back and forth in the middle of the cable to form a 1m long cable, with a folding length not exceeding 0.4m. If the cable cannot be folded into a length of 1m due to the limitations of EUT layout, it should also be as close to 1m as possible.
Radiation emission testing is divided into two levels based on the operating environment of the tested equipment, A and B, with required limits
Class A: Equipment used in non household and non directly connected residential low-voltage power supply facilities
B-class: Equipment used in household and directly connected to residential low-voltage power grid facilities
Introduction to 3-meter anechoic chamber site
A 3-meter darkroom generally consists of a darkroom, a control room, and an amplifier room. A darkroom is a shielded room with absorbing materials installed inside. The function of the shielded room is to prevent electromagnetic waves from entering the laboratory and block the transmission of electromagnetic waves from the laboratory to the outside; The function of absorbing materials is to absorb electromagnetic waves emitted by the tested object in the laboratory, avoiding test result errors caused by reflection; The control room is used to place fully compatible receivers, signal generators, and monitoring computers to monitor the testing process and results; Place power amplifiers inside the amplifier room. The power amplifier itself has strong radiation, which can be harmful to humans, so it is placed separately. It can be widely used for electromagnetic compatibility testing in IT products, household appliances, medical equipment, automotive parts, small military electronic products, industrial electronic products, communication fields, etc.
TECHNICAL INDEX
Outer Dimensions | 9000mm x 6000 x 6000mm（L x W x H） |
Frequency range | 30MHz-18GHz |
Distance measurement from antenna to EUT | 3m |
radiation test | Compliant with CISPR11, CISPR14, CISPR15, CISPR22 and other standard requirements |
Radiation immunity test | 3-meter radiation immunity test in accordance with IEC/EN 61000-4-3 |
Introduction to the Site of a 10 meter Radio Wave Darkroom
The 10 meter anechoic chamber has a quiet area of 3 meters or more, which can meet the radiation interference testing requirements of larger volume test subjects, such as automobiles, large medical equipment, large IT products, etc. Moreover, the 10 meter anechoic chamber has become an ideal testing site for many EMC testing standards due to its superior chamber performance. This chamber fully meets multiple international certification requirements such as FCC and CE.
TECHNICAL INDEX
Outer Dimensions | 22000mm x 14000 x 12000mm（L x W x H） |
Frequency range | 30MHz-18GHz |
Distance measurement from antenna to EUT | 10m |
radiation test | 符合CISPR11、CISPR14、CISPR15、CISPR22等标准要求 |
Radiation immunity test | 符合IEC/EN 61000-4-3的3米法辐射抗扰度测试 |
Open field OATS site introduction
Open Field Measurement (OATS) is a standard part of electromagnetic radiation measurement. According to the standard requirements, the effective testing field of the testing environment is usually elliptical, with the length of the long axis being twice the measurement distance and the length of the short axis being √ 3 times the measurement distance. The transmitting and receiving antennas are placed on the two focal points of the ellipse, and the distance between the two focal points is the measurement distance we require. According to existing standards, it can be divided into 3 meters, 10 meters, and 30 meters. Most of the existing standards in China are based on 3 meters, while the United States and the United Kingdom use 10 meters as the standard for measurement.
OATS requires a flat and open environment, away from building sites, towers, power lines, forests, underground cables, and metal pipelines, with minimal electromagnetic interference background (such as general electromagnetic compatibility standards and specifications requiring at least 6dB below the allowable limit).
Radiation emission testing arrangement
EUT and AE should be arranged realistically in the testing space, with the center point of this arrangement located at the center of the turntable. The testing distance is the shortest horizontal distance between an imaginary circular boundary that exactly surrounds the arrangement and the antenna calibration reference point.
test method
Experimental equipment: receiver, antenna (broadband antenna is generally used for antennas below 1G, horn antenna is used for antennas above 1G), preamplifier
Test frequency band: If the highest frequency of the EUT internal source is below 108MHz, the measurement will only be conducted up to 1GHz; If the highest frequency of the EUT internal source is between 108MHz and 500MHz, the measurement will only be conducted up to 2GHz; If the highest frequency of the EUT internal source is between 500MHz and 1GHz, the measurement will only be conducted up to 5GHz; If the highest frequency of the EUT internal source is higher than 1G, the measurement will be conducted up to 5 times the highest frequency or 6GHz, whichever is lower.
Radiation emission test limits: The limits given in this article are in accordance with GB/T 9254.1-2021. In actual testing, the corresponding standard limits should be selected based on the product category.
Testing process: 30MHz-1GHz: Conducted in a semi anechoic chamber, EUT rotates 360 degrees with the turntable, and the antenna rises and falls up and down at a height of 1-4m to find the maximum radiation value. The results are represented by QP values. Measure the polarization directions of both vertical and horizontal antennas.
The criteria for determining radiation emission results are still compared with the limit line. Below PASS, above FAIL.
Source: WeChat Official Account of Shenzhen Qianhong Electrical Testing Co., Ltd
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