The Relationship between Complete Vehicle and Components in Narrowband Radiation Emission Limits in the Standard of ECE R10

The narrowband radiated emission limit curve of the vehicle has changed significantly in the sixth revision of ECER 10. In this article, the emission value of electromagnetic waves at different distances in different frequency bands is measured. Meanwhile, the correspondence between the narrowband radiation emission limits of the whole vehicle and the components is explored. Finally, the correspondence between the far field and near field applicable to narrowband radiation emission of components in automotive inspection engineering is proposed.


Introduction
As an important standard for China's automobile export certification test, ECE R10 has been widely used in Europe, ASEAN, Customs Union, and many other countries and regions.The sixth edition of ECE R10 revises the technology of the electromagnetic compatibility test part of the complete vehicle and will be officially used after September 1, 2022.K. T. Selvan et al. [1][2] showed that the narrow-band limit line of vehicle radiation emission changed clearly, and the new limit line was 2 dB lower than the mean detection limit line of CISPR 12:2009.Compared with the original limit line, the maximum difference is 6 dB μV/m in the 30 MHz-75 MHz band.
Generally speaking, the electromagnetic interference generated by the vehicle is detected by the 10-meter method [3][4][5] .The method detects that the horizontal distance between the phase center of the antenna and the exterior surface of the vehicle is 10 m.While the component uses the one-meter method to detect the electromagnetic interference generated by the component.In this method, the horizontal distance between the phase center of the detection antenna and the outer surface of the component is 1 m.For the same test standard, the conversion formula of its limit value is inversely proportional to the test distance.Therefore, it can be said that the vehicle and components have a corresponding relationship for the wide-band radiation emission limit value.In this paper, narrow-band emission limit curves of components under actual working conditions are proposed by exploring the corresponding relationship between narrow-band limit lines of vehicles and components.

Theory of electromagnetic radiation
The far and near fields are very important for electromagnetic radiation.The propagation routes of electromagnetic radiation disturbance are mainly divided into space propagation and wire conduction.For ideal small electric objects such as electric dipoles and magnetic dipoles, the boundary between the far and near fields is shown in Equation 1.

SECMP-2023
where r represents the distance from the field source to the observation point; λ represents the wavelength of the electromagnetic field.
In the field of automotive electromagnetic compatibility, the antenna is a particularly critical part of testing electromagnetic radiation, and its role is to transmit and receive electromagnetic waves.The near and far field distances of the antenna are very important for the measurement of the antenna.The field area of the antenna includes the Fresnel region and the Fraunhofer region, where the angular field distribution in the Fresnel region is related to the distance of the antenna, and the angular field distribution in the Fraunhofer region is independent of the distance of the antenna.The Fraunhofer region is related to the maximum permissible phase error and is calculated as follows: where D is the maximum geometric size of the field source (antenna); Φ is the maximum allowable phase error; λ is the wavelength.According to the array antenna theory, the field around the antenna to be measured is usually divided into three regions, namely the sensing near-field region, the radiating near-field region, and the radiating far-field area [6][7][8] , as shown in Figure 1.

Figure 1 Illustration of the division of antenna near and far fields
The regions that radiate the near field are: where D is the maximum aperture size of the field source (antenna).When It is worth noting that when the field source (antenna) moves from the near field to the far field, the characteristics of the field change.Therefore, to explore the boundary between the far and near fields emitted by the electromagnetic radiation of the vehicle under actual working conditions, in this paper, the relationship between the far and near field limits of a single comb source in the 30 MHz-80 MHz frequency band is studied by measuring the electromagnetic wave emission value of the comb source at different positions from the phase center of the bipyramid antenna in the 10-meter chamber of the whole vehicle.

Experimental conditions
In this experiment, the specific parameters are set according to Table 1.
Table 1  The measurement antenna used in this experiment needs to meet the requirements of ECE R10, and the R&S®HK116E double-cone antenna is used in the experiment with a measurement range of 20 MHz~300 MHz and a maximum geometric size of 1.37 m.The antenna satisfies the horizontal and vertical directions, and the vertical orientation is used in this experiment, and the antenna is connected with a coaxial cable.In this experiment, a 10-meter semi-anechoic chamber was used, and the absorbing material was spread in a 10-meter semi-anechoic chamber to simulate the fully anechoic chamber to ensure the repeatability of the test environment.

Methods of Experimentation
In this experiment, a comb source was used as the signal generation source, and the horizontal distance between the phase center of the bipyramidal antenna and the comb source decreased from 4 m to 0.5 m at a distance of 0.5 m.The test layout diagram is shown in Figure 2. In this experiment, an alternative method is adopted.When the distance between the combing source and the bipyramidal antenna phase center is 1 m, the measured data is the narrowband radiation emission limit of the component.When the distance between the dressing source and the phase center of the bipyramidal antenna exceeds 1 m, the measured data is the narrowband radiation emission limit of the whole vehicle.
Figure 2 Simulating an all-radio anechoic chamber

Experimental process
The test uses a comb-like source to emit electromagnetic waves, and the bipyramidal antenna receives electromagnetic waves.The peak detector and the average detector were used to perform frequency point sweeps simultaneously to obtain the limit values at frequencies of 30 MHz, 65 MHz, 70 MHz, 75 MHz, 80 MHz, and 85 MHz.The results are shown in Table 2.

Experimental data analysis
The field structure of the far field is relatively simple, and its electric field, magnetic field, and radio wave propagation direction are perpendicular to each other, and the wave impedance, that is, the ratio of electric field strength to magnetic field strength is 377 Ω.The field structure of the near field is relatively complex, and there are components of electric or magnetic fields in the direction of radio wave propagation.These three components do not necessarily exist perpendicular to each other.Table 2 shows that when the distance between the DUT and the antenna center is 0.5 m and 1 m, the measured data values at different frequency points differ by about 10 dB.When the distance between the DUT and the antenna center is greater than 1 m, the difference between the measured data value and the distance attenuation at different frequency points is 0.5 dB-4.6 dB.The limit value decays less with distance.Therefore, the boundary between near and far fields is measured under this experimental condition of 1 m.The standard gives the conversion formula for the limit value in inverse proportion to the distance: where L1 and L2 are the radiation limits for the test distances d1 and d2, respectively.The difference between the radiated emission limit of 0.5 m from the antenna center of the DUT and the radiated emission limit of 1 m from the center of the antenna is 10 dB.The formula L2=L1(dB)+20lg(1/0.5)*1.66 is satisfied.As shown in Equation 1, in actual engineering, the attenuation of the near-field plane wave transmitted by the antenna radiation in space is inversely proportional to the distance.
where A and B represent the distance from the DUT to the antenna, m; Q represents the plane wave attenuation value between the two points A and B, dB; x stands for 1.66.The difference between the radiated emission limit of 0.5 m from the antenna center of the DUT and the radiated emission limit of 1 m from the center of the antenna is 10 dB.According to Appendix A of GB 18387-2017, since the electric field and magnetic field are predominantly proportional to the cube of the distance when measuring the near field, the third-order conversion method is adopted, and the boundary distance condition of the near field is shown in Equation 1 [5][6] .For 80 MHz, its wavelength , and the actual working conditions obtained by this experimental data show that the dividing line between the radiation far field and the radiation near field is r=1 m.Therefore, under actual working conditions, the calculation formula of the dividing line of the near and far field is as follows. .In the actual working conditions, the dividing line between the radiation far field and the radiation near field is 2.67 m.Therefore, for the DUT and antenna phase center distance of 1 m, that is, the part narrowband radiated emission 1 m method test, the limit value difference between the whole vehicle and the component is as follows.In conclusion, in actual engineering, the dividing line between radiated far-field and radiated near-field is 3.75 λ , and the radiated emission narrowband limit of the whole vehicle and parts is 25 dB.As shown in Figure 3, a certain correspondence between the narrowband limit line of the fifth version of ECE R10 and the narrowband limit line of the fifth version of the vehicle is found.The two limit lines differ by 20 dB in the 30 MHz-1 GHz band, and by 30 dB at only 30 MHz, and at 75 MHz and 400 MHz, the limit line inflection point.At the same time, the limit line inflection point is at the 75 MHz and 400 MHz frequency points.The new limit line is looser than the overall requirements of the fifth version, and the maximum difference of the limit value is 6 dB in the 30 MHz-75 MHz frequency band.The corresponding sixth version of the part radiation emission narrowband limit has not changed.According to CISPR TR 16-4-4:2020 [9][10] , the influencing factor of the radiation emission limit is The effect of vehicle components on the external receiver is strongly correlated with the influence of the vehicle on the external receiver, and the limit value difference between the two is only the test distance relative to the radiated emission measurement, due to the 6th edition of the vehicle radiated emission narrowband limit increased by 6 dB in the 30 MHz-75 MHz band.According to the correspondence, the radiated emission narrowband limit of the sixth edition component should also be increased by 6 dB in the same frequency band.It follows that the narrowband radiated emission limit curve of the component in ECE R10 should be shown in Figure 4.

Conclusion
Based on a large number of experiments, this paper analyzes the narrowband radiated emission value of the phase center of the bipyramidal antenna within 0.5-4 m from the outer surface of the dressing source in the 30 MHz -85 MHz band.New limits for radiated emission from ECE R10 narrowband components are proposed.
1) In actual working conditions, the limit of narrowband radiated emission between the whole vehicle and the component should differ by 10 dB at the 30 MHz frequency.
2) 80 MHz is the dividing point between the radiating far field and the radiating near field and the dividing line is calculated as: 3.75 r λ = . ( where r represents the distance from the field source to the observation point, and λ represents the wavelength of the electromagnetic field.
is called the radiated far field.

1 2 1 (
) 20 lg( ) *1.66 0.5 L L dB = + is satisfied.As shown in Equation1, in actual engineering, the attenuation of the near-field plane wave transmitted by the antenna radiation in space is inversely proportional to the distance.

Figure 3
Figure 3 Emission limit line of narrowband radiation with antenna measurement distance of 10 m

Figure 4
Figure 4 Narrowband emission limit curve of parts

Table 2
Test Data Results of 30 MHz~85 MHz