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Introduction of Test Antenna in Electromagnetic Compatibility Test for Civil Products

Release time:

2023-06-21 15:26

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An antenna can be used to either receive or transmit a signal. During the radiated disturbance test, the antenna is used to receive the signal. During the radiated immunity test, the antenna is used to transmit the signal. The test antennas commonly used in electromagnetic compatibility testing include: radiation transmitting antenna (loop antenna, three loop antenna, double cone logarithmic periodic antenna, horn antenna), radiation immunity antenna (stacked logarithmic periodic antenna, ultra wideband antenna).

The technical requirements, measurement requirements and measurement cycles of antennas involved in different standards are clearly defined in the CNAS-CL01-A008 "Application of the Accreditation Guidelines for Testing and Calibration Laboratories in the Field of Electromagnetic Compatibility Testing". The main measurement parameters of the receiving antenna are the antenna coefficient, and the main measurement parameters of the transmitting antenna are the standing wave ratio.

　　1 antenna types commonly used in electromagnetic compatibility testing

　　1.1 loop antenna

1.1.1 Reference profile

Figure 1

1.1.2 Application

The magnetic field loop antenna described in GB/T 6113.104 -2021/CISPR 16-1-4:2019 "Specification for Radio Disturbance and Immunity Measuring Equipment and Methods-Part 1-4: Radio Disturbance and Immunity Measuring Equipment-Radio and Test Sites for Radiated Disturbance Measurement" can be sized to be completely surrounded by a square with a side length of 60cm. The loop antenna is used for the test of induction cookware. It is clearly stated in GB 4824-2019 "Limits and Measurement Methods of RF Disturbance Characteristics of Industrial, Scientific and Medical Equipment" that the emission requirements of induction cookware are in accordance with the requirements of GB 4343.1-2018. Compared with GB 4343.1-2009, the main technical content changes in the foreword of GB 4343.1-2018 "Electromagnetic Compatibility Requirements for Household Appliances, Electric Tools and Similar Appliances-Part 1: Launch" clearly state: Annex B requirements for induction cooking utensils have been added. Induction cookware was transferred from GB 4824 to GB 4343. 1. The requirements for induction cookware are given in Appendix B of GB 4343.1-2018. Appendix B .1.3 describes the radiation disturbance magnetic field strength limit (dB (μA/m)) of commercial and household induction cookware with diagonal size exceeding 1.6 m in the frequency range of 9kHz ~ 30MHz, the test distance of 3m, the antenna shall be installed vertically, and the height of the lower edge of the loop antenna from the ground shall be 1m.

1.1.3 Measurement requirements and application of calibration results

CNAS-CL01-A008 to Appendix I YYY0505 and Appendix J GB 4824 in the Application Description of Accreditation Criteria for Testing and Calibration Laboratories in Electromagnetic Compatibility Testing Field, the technical requirements of the equipment are specified: the antenna shall fully meet the requirements of Article 4.3.2 of GB/T 6113.104, the measurement requirements are: antenna coefficient, and the measurement period is 1 year. The relevant parameters and theory of the loop antenna can refer to the antenna factory data provided by the manufacturer. The antenna shall provide a calibration curve before leaving the factory, and the antenna coefficient shall be input when it is used for the first time. After the antenna is calibrated every year, the laboratory personnel are required to calibrate and confirm the calibration results, and input the calibrated magnetic field antenna coefficient into the test software. The test results use the combination of the test value and the correction factor, and the update of the calibration result affects the accuracy of the value traceability. Taking the test software EMC32 as an example, the magnetic field antenna coefficient of the antenna needs to be input to EMC32 ->System -> Correction Tables ->Transducer, and the test module calls.

1.2 three-loop antenna

1.2.1 Reference profile

Figure 2

1.2.2 Application

GB/T 6113.104-2016/CISPR 16-1-4:2012 The loop antenna system (LLAS) described in Annex C is composed of 3 mutually perpendicular large loop antennas with a standard diameter of 2m. The loop antenna system is used to measure the magnetic field component of radiated electromagnetic disturbance (9kHz ~ 30MHz), the products involved include GB/T 17743-2021, lighting equipment in YY 9706.102-2021, and household induction cookers with diagonal size less than 1.6 m involved in Annex B of GB 4343.1-2018. GB/T 17743-2021 also gives the current quasi-peak limit of the magnetic field component of the radiated disturbance field strength measured by loop antenna with diameter of 3m or 4m. The limit of loop antenna diameter of 2m is applicable to equipment with length not exceeding 1.6m, the limit of loop antenna diameter of 3m is applicable to equipment with length between 1.6m and 2.6m, and the limit of loop antenna diameter of 4m is applicable to equipment with length between 2.6m and 3.6m. In the frequency range below 30MHz, the maximum allowable diameter is 4m, and a continuous increase in diameter will cause a non-repeatable resonant response of the loop antenna system at the high frequency end of the test frequency range. The equipment to be tested is placed at the center of the three-loop antenna, the distance between the edge of the equipment to be tested and the three-loop antenna is greater than 20cm, and the distance between the three-loop antenna and other objects is greater than 0.5m.

1.2.3 Measurement Requirements and Application of Calibration Results

The technical requirements for large three-loop antenna are specified in Annex I YY0505 of the CNAS-CL01-A008:

1) The test frequency range is 9kHz ~ 30MHz;

2) The structure and measurement method shall fully meet the requirements of Annex C in GB/T 6113.104.

Measurement requirements: 1) antenna coefficient; 2) frequency response. Measurement cycle: 1 year.

The calibration method of loop antenna can refer to the confirmation of C.4 large loop antenna in Annex C of GB/T 6113.104 -2016/CISPR 16-1-4:2012 "Specification for radio disturbance and immunity measuring equipment and measurement methods-Part 1-4: Antenna and test site for radiated disturbance measurement of radio disturbance and immunity measuring equipment. The X, Y and Z directions shall be confirmed, and the deviation between the measured confirmation coefficient and the confirmation coefficient given in Figure C.8 of GB/T 6113.104 shall not exceed ± 2dB. After the antenna is calibrated every year, laboratory personnel are required to calibrate and confirm the calibration results. The three-loop antenna does not need to input the confirmation coefficient into the test software.

　　1.3 biconical log-periodic antenna

1.3.1 Reference profile

Figure 3

1.3.2 Application

In the frequency range of 30MHz ~ 6GHz, the electromagnetic radiation disturbance is measured in the electric field (dB(μV/m)). The standards GB/T 9254.1-2021,GB 4824-2019,GB/T 17743-2021,GB 4343.1-2018, etc. involved in civil products all involve this test item. The test distance is 3m, which is the distance from the center of the double cone logarithmic periodic antenna to EUT. The antenna has vertical and horizontal polarization directions, which can be realized by rotation and varies with the height of the antenna tower at 1~4m.

1.3.3 Measurement requirements and application of calibration results

The technical requirements and measurement requirements for the antenna in different standards in the CNAS-CL01-A008 appendix are the same, but the measurement cycle requirements are different. The following figure.

Figure 4

The relevant parameters and theories of the double cone logarithmic periodic antenna can refer to the antenna factory data provided by the manufacturer. The antenna shall provide a calibration curve before leaving the factory, and the antenna coefficient shall be input when it is used for the first time.

After each calibration of the antenna, the laboratory personnel are required to calibrate and confirm the calibration results, and input the calibrated antenna coefficient into the test software. The test results use the combination of the test value and the correction factor, and the update of the calibration results affects the accuracy of the value traceability. Taking the test software EMC32 as an example, the antenna coefficient of the antenna needs to be input to EMC32->System->Correction Tables-> Transducer, and the test module calls.

　　1.4 horn antenna

1.4.1 Reference profile

Figure 5

1.4.2 Application

In the frequency range of 1GHz to 18GHz, the electromagnetic radiation disturbance is measured by the electric field (dB(μV/m)). The standards GB/T 9254.1-2021,GB 4824-2019,GB/T 17743-2021,GB 4343.1-2018, etc. involved in civil products all involve this test item. The test distance is 3m, which is the distance from the front edge of the horn antenna to EUT. The horn antennas used here are mostly two-ridged horn antennas with good linear polarization direction, high gain and convenient vertical and horizontal conversion. The direction of the ridge determines the horizontal vertical direction of the horn antenna.

1.4.3 Measurement requirements and application of calibration results

Different standards in the CNAS-CL01-A008 appendix have the same measurement requirements for the antenna, and the technical requirements and measurement cycle requirements are different. The following figure.

Figure 6

The relevant parameters and theory of the horn antenna can refer to the factory data of the antenna provided by the manufacturer. The calibration curve of the antenna shall be provided before the antenna leaves the factory. The antenna coefficient shall be input when it is used for the first time.

After each calibration of the antenna, the laboratory personnel are required to calibrate and confirm the calibration results, and input the calibrated antenna coefficient into the test software. The test results use the combination of the test value and the correction factor, and the update of the calibration results affects the accuracy of the value traceability. Taking the test software EMC32 as an example, the antenna coefficient of the antenna needs to be input to EMC32->System->Correction Tables-> Transducer, and the test module calls.

　　1.5 stacked log-periodic antenna, ultra-wideband antenna

1.5.1 Reference profile

　　

Figure 7

1.5.2 Application

Stacked logarithmic periodic antenna and ultra-wideband antenna are used for electromagnetic radiation immunity test. The method standard is GB/T 17626.3-2016 "Electromagnetic Compatibility Test and Measurement Technology Radio Frequency Electromagnetic Field Radiation Immunity Test". As a transmitting antenna, stacked logarithmic periodic antenna test frequency band is 80MHz ~ 1000MHz, and ultra-wideband antenna test frequency band is 1GHz ~ 6GHz. The test distance of civil products test is 3m, which refers to the distance from the top of stacked logarithmic periodic antenna and ultra-wideband antenna to EUT. The antenna has vertical and horizontal polarization directions.

1.5.3 Measurement requirements and application of calibration results

The CNAS-CL01-A008 makes clear requirements for the measurement requirements and measurement period of the transmitting antenna when used in different standards, and also makes clear requirements for the measurement requirements and measurement period of the field strength probe and field strength meter, as shown in the following figure.

Figure 8

The electromagnetic radiation immunity test does not need to input the calibration parameters of the antenna into the test software. Whether the electromagnetic radiation immunity test level can be achieved depends on the calibration with the field strength probe before the test.

　　2 Summary

Antenna is an essential test instrument for electromagnetic compatibility testing, and the traceability of antenna directly affects the accuracy of test results. Laboratory testing personnel should be able to understand and distinguish the technical parameters of different antennas, the technical requirements and measurement requirements when used in different standards, and be able to accurately trace the value to ensure the accuracy of the test results.

If you need to know more about electromagnetic compatibility testing instruments, you can visit the company's website http://www.emc-mall.com/查看 。

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