EN 55014-1 标准解读2

table 2b这个图表讲述的是：如果骚扰功率在200M-300M的裕量满足了table2b的要求，则不需要测试RE。如果不满足，则需要测试RE，在家电中一般是很少测试RE，因为现在的家电的电路根本不可能产生300M以上的信号。在工程上，我们一般认为10次谐波以后的信号的幅值和限值相比已经可以忽略掉了。假设家电最高的时钟频率是8M。则80M以上的信号干扰和限值相比已经可以忽略掉了。
但是table 2b中的裕量是怎么来的，为什么会出现这种关系，这个我也不是很明白，有懂得朋友，请指点下。谢谢了。

table 2b中 note1的意义是table 2a和table2b放在一起用的，二者不能分割开来单独使用，其实在现在的测量脚本中，在200M-300M的限值位置会描绘出减去table2b中的裕量的曲线。这样在测试的时候就非常方便的看出来了是不是满足裕量的要求了。

LZ太厉害哇，感受到你的用心。继续坚持啊！

4.1.2.2 Radiated disturbances measurement in the frequency range 30 MHz to 1000 MHz
The limits of radiated disturbances are given in Table 3. Radiated disturbances are measured
in accordance with the standards and testing methods given in Table 3.

辐射骚扰：其实家电中一般很少测试辐射的，对于电源类器具要看骚扰功率的在频段200M-300M的裕量是否满足要求，如果不满足要求则要测试的；对于电池供电的器具，传导和骚扰功率是没有测试端口的，则需要测试辐射，尤其是有电机等主要部件的电池供电类器具。

辐射限值图片，table 3

辐射测量有四种方法，开阔场、半电波暗室、全电波暗室和TEM小室。据说现在TEM小室现在已经很少用了。本人也没有见过。在EN 55014-1中，最常用的半电波暗室3m法测量的。

关于3m和10m的换算，原理是按照远场区电场（磁场）幅度与距离成反比得来的。因此在10m的限值加上修正因子20lg（10/3）的基础上，得到3m的准峰值分别为47dB和40dB.

但是关于3m和10m的换算的限值，是否真的完全等效，我以前看过一篇文章来解析，请大家参考下：

文章如下：

3m场地的辐射数据可以直接代替10m场地的数据吗？

One problem with 3m testing is that there is a fall-off projection problem that is usually seen below 200 MHz in vertical polarization. if tested at 3m, the maximum vertical field propagates along the ground plane (normal to the ground plane) due to the reflection. Since the antenna is scanned between 1 and 4m, some of the energy goes under the antenna.



At 10m the wavefront is more developed and with the same scan window, 1 to 4m more of the main lobe of the total field propagating on the ground plane is measured. the 3m data has to subtract 10 dB from the measured data to account for the 3 to 10m fall-off. But that is free-space assumption without the ground plane effect.



At 10m, more of the energy is measured and when compared to the projected fields done at 3m, up to 7 dB errors have been reported. the 3m data actually underpredicts the field at 10m. This has caused products that were thought to pass when tested at 3m to then fail at 10m facilities.



This is not much of a problem in horizontal and actually the opposite problem exists with 3m measuring more energy than will be seen at 10m. But the differences are much less. The other reason this is not a bigger problem at 3m, is that there is not much horizontal emission below 100 MHz since the horizontal fields on the ground plane are zero. the direct and reflected are 180 degrees out of phase on the ground plane and cancel. So emissions are measured up around 4m in height for horizontal plus products don't tend to efficiently radiate horizontal fields below 100 MHz.



        以上信息是某位国外资深EMC工程师对3m/10m半电波暗室场地测试结果的比较，从测量模型分析了为什么3m的数据和10m场的数据不同，以及对3m数据转换成10m数据的看法。

       我个人认为，在某一场地测试的数据，不同简单地通过加10或者减10进行相互换算，因为10dB这个数据是来自自由场（free-space ）的模型。

4.1.2.3 Application of the limits：（RE)限值的应用
4.1.2.3.1 General
This subclause describes application of the limits for all appliances (see Figure 10).
Regulating controls which incorporate semiconductor devices, electric fence energizers,
rectifiers, battery chargers and converters, which do not contain any clock frequency higher
than 9 kHz, are not subject to the requirements in the frequency range 30 MHz to 1 000 MHz.

4.1.2.3这个条款讲述的是限值的应用。

一般情况下，所有的产品都是要测试RE的，这句话是总论。
但是对于半导体设备控制器、电栅栏激发器、整流器、电池充电器和转换器等器件，如果时钟频率不超过9k，则是不需要测试30M-1000M的的RE的。

其实在实际情况中：家电中很少有测试辐射的。一般情况下，骚扰功率中table2a和table2b的限值都是满足的。