半电波暗室3m法辐射骚扰测试的实验_胡文涛_百度文库
两大类热门资源免费畅读
续费一年阅读会员，立省24元！
半电波暗室3m法辐射骚扰测试的实验_胡文涛
上传于||文档简介
&&电​磁​兼​容​测​试​实​验​介​绍
阅读已结束，如果下载本文需要使用1下载券
想免费下载本文？
定制HR最喜欢的简历
你可能喜欢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
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
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。
已投稿到：
以上网友发言只代表其个人观点，不代表新浪网的观点或立场。 上传我的文档
 下载
 收藏
该文档贡献者很忙，什么也没留下。
 下载此文档
正在努力加载中...
半电波暗室3／10米法辐射场强换算的研究
下载积分：898
内容提示：半电波暗室3／10米法辐射场强换算的研究
文档格式：PDF|
浏览次数：56|
上传日期： 08:07:38|
文档星级：
该用户还上传了这些文档
半电波暗室3／10米法辐射场强换算的研究
官方公共微信EMC测试常用设备使用时的注意事项
EMC测试的频率范围都很宽，因为事先并不知道骚扰的频率是多少，所以，测试必须借助各种探测天线来把场强转换成电压。一般来讲，EMC测试用的天线都工作在近场区，测试结果对测试距离非常敏感。因为电场、磁场之比（波阻抗）在近场区不再是个常数，所以这些天线虽然给出了电场、磁场的校正系数，但只有当这些天线作远场测试时才有效，测量近场干扰时，电场与磁场测试结果不能再按此换算。
2. 人工电源网络
要注意人工电源网络与接地平板成低阻抗良好连接。
3. 频谱分析仪
要注意根据测试要求选取频率分辨率、灵敏度、动态范围、扫频宽度等参数合适的频谱分析仪。
频率分辨率：能够分辨的最小谱线间隔，它表征了频谱分析仪能将频率紧挨在一起的信号区分开来的能力。
灵敏度：表征了频谱分析仪测量微小信号的能力。频谱分析仪的噪声电平决定于中频滤波器带宽，一般在-80dB~-130dB。
动态范围：表征了它同时显示大信号和小信号的真实频谱的能力，动态范围的上限由频谱分析仪的非线性失真所决定。频谱分析仪动态范围一般在60dB以上，甚至100dB。
扫频宽度：频谱分析仪在一次测量分析过程中显示的频率范围。
4. 测量接收机
频谱分析仪只有峰值检波，而测量接收机除了峰值检波外，还有准峰值检波和平均值检波，要根据不同的标准或法规选择合适的检波器。
峰值检波只测试骚扰信号振幅的最大值，适用于单一脉冲或重复频率很低的脉冲骚扰信号的测试。而有些骚扰信号对音频影响的客观效果是随着重复频率增高而增大的，对这种信号仅仅测量信号的振幅无法客观反映其影响效果，因此，这时就要用准峰值检波。准峰值检波器其充电时间常数比峰值检波器大，放电时间常数比峰值检波器小，不仅可以测量出骚扰信号信号幅度，还反映它的时间分布。
如何避免EMI测量接收机发生过载OVLD故障
测量接收机是EMC测试中使用最多的设备，由于测量信号未知，经常会发生过载OVLD故障。一般来说，OVLD故障是由于RF Converter模块中的第一混频器受到损坏所引起的。
导致第一混频器损坏有如下几种可能性：
1、输入功率过载
2、输入脉冲过载
3、针尖脉冲
4、有直流电平馈入
5、EMI接收机与被测设备的接地不好
6、静电损伤
测量接收机是非常精密的设备，维修费用高昂，为尽量避免发生以上的故障，影响试验室的试验进度，在日常的使用中，应注意的事项如下：
1、使用外接脉冲限幅器或者衰减器，型号ENV216的人工电源网络自带了10dB的衰减器，避免了因忘记接限幅器或者衰减器而造成的损伤
2、EMI接收机与被测设备的接地要良好，且为低阻抗
3、被测设备已正常工作后，再将人工电源网络到测量接收机的同轴电缆接上，避免因被测设备突然启动时的骚扰对测量接收机的损坏
4、在EMI测量接收机与人工电源网络之间的同轴电缆未断开前，不要带电插拨或开/关被测设备，避免因被测设备突然启动时的骚扰对测量接收机的损坏
5、在连接人工电源网络到测量接收机的同轴电缆时，测试人员要注意自己手上、身体上可能带的静电电荷
以型号ESCI的测量接收机为例，RF INPUT端最大的能量只能在如下的限制内，使用时要特别小心。
For DC-coupling, the max. DC voltage is 0 V. For ACcoupling, the max. DC voltage is 50 V. The maximum power is 1 W ( 30 dBm at ≥ 30 dB attenuation)
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。
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。
61000-4系列标准试验布置细节比较:p736_10m法半电波暗室是电气医疗设备辐射骚扰测量场地的最优选择_百度文库
两大类热门资源免费畅读
续费一年阅读会员，立省24元！
p736_10m法半电波暗室是电气医疗设备辐射骚扰测量场地的最优选择
上传于||暂无简介
阅读已结束，如果下载本文需要使用0下载券
想免费下载更多文档？
定制HR最喜欢的简历
下载文档到电脑，查找使用更方便
还剩1页未读，继续阅读
定制HR最喜欢的简历
你可能喜欢