[{"insert":"#无线蓝牙技术#\n"},{"attributes":{"color":"#000000"},"insert":"大家好，我是工程师看海，欢迎"},{"attributes":{"color":"#000000","bold":true},"insert":"点赞分享！"},{"insert":"\n"},{"attributes":{"color":"#000000","bold":true},"insert":"引文"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":"包铜箔来屏蔽干扰是EMC整改中最常见的措施之一，铜箔的高电导率会反射高频的辐射干扰，比如手机中的相机或屏幕往往有大面积的包铜箔处理，见下图（既有屏蔽功能也有散热功能），或者主板上有屏蔽罩，可以起到良好的屏蔽作用。"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/08fb4ab22e900de6.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":"在调试时，当有怀疑的干扰源时，会尝试对干扰源进行包铜箔处理，来测试是否会降低干扰，本次分析整理自intel的调试总结，是USB3.0的射频干扰影响了2.4HGz蓝牙无线设备，可以定性和定量看到铜箔屏蔽效果，"},{"attributes":{"color":"#000000","bold":true},"insert":"公众号后台回复：USB屏蔽 可以获取完整PDF原文。"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":" "},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"color":"#000000","bold":true},"insert":"环境"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":"下图是系统工作框图，USB3.0外设通过USB线缆与电能连接，USB线缆会辐射出干扰，这个干扰被PC的无线设备接受后产生噪音。"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/56755ae78c7ad363.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":"下图是测试环境，近场探头放置在USB设备（硬盘）附近，近场探头采集到的干扰被前置放大后由频谱仪来对干扰进行分析。"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/eb14f8cdc4a9cfa6.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":"下图是分析的结果，灰色曲线是没有USB设备连接时的情况，红色曲线是连接USB设备之后的情况，可以看到没有USB连接时噪声水平大约只有-118dB，而USB设备连接后在2.4GHz附近噪声水平达到了-100dB，上升了大约20dB。"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/89ce440ff2a471a7.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":"下面对USB设备硬盘进行包铜箔处理，如下图所示，一共进行了4种程度的包铜处理，从case1到case4，包的越来越严实，如果缝隙大的话还是有干扰会漏出来。"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/add0fae424675f96.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":" "},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000","bold":true},"insert":"结果"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":"下图是包铜箔后的测量结果，整体可以看到包的越严密干扰越小，降低了近12dB。"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/d44bf32b3c54204a.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":"为了进一步降低干扰，又对连接器进行了屏蔽，下图是屏蔽之后的结果，灰色曲线是没有USB设备连接的情况，噪声水平最低。红色是USB连接后的噪声水屏最高，绿色是进行连接器和线缆屏蔽后的结果，干扰得到有效抑制。"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":" "},{"insert":{"image":"https://community-1252773949.cos.ap-guangzhou.myqcloud.com/article/2033/769b07a78b82c3ed.png"}},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":" "},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000","bold":true},"insert":"总结"},{"attributes":{"align":"center"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":"总结来说，屏蔽对高频干扰抑制效果良好，在EMC整改时是非常有效的手段，"},{"attributes":{"color":"#000000","bold":true},"insert":"公众号后台回复：USB屏蔽 可以获取完整PDF原文"},{"attributes":{"color":"#000000"},"insert":"。但是如果是低频的话，则是另一种玩法了。"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"color":"#000000"},"insert":"整理自intel"},{"attributes":{"align":"justify"},"insert":"\n"},{"attributes":{"color":"#000000","bold":true},"insert":"如果看到这里，请点赞、收藏、分享三连！"},{"attributes":{"align":"right"},"insert":"\n"}]
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发表于 2022-11-10 10:59
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