<p><strong>1. 什么是车载Ethernet</strong></p>
<p>车载Ethernet：“汽车所用的通信方式”</p>
<p>汽车内部根据用途使用各种不同的接口标准。</p>
<p>表1：汽车所用的通信方式</p>
<p><img alt="表1：汽车所用的通信方式" data-entity-type="file" data-entity-uuid="387837c9-15dc-4505-a121-02d356b2b9f6" src="/sites/default/files/inline-images/1_5.PNG" /></p>
<p>表2：车载Ethernet标准</p>
<p><img alt="表2：车载Ethernet标准" data-entity-type="file" data-entity-uuid="3408ecc1-b47c-45a0-b04a-49f70cf8b223" src="/sites/default/files/inline-images/2_5.PNG" /></p>
<p><strong>2. 车载Ethernet降噪措施的必要性</strong></p>
<p>1.差分信号传输噪声</p>
<p>Ethernet等差分信号传输中因各种原因共模电流会产生噪声。</p>
<p><img alt="差分信号传输噪声" data-entity-type="file" data-entity-uuid="99d1e3ea-62ac-4955-9c39-49e69695bbbe" src="/sites/default/files/inline-images/3_157.jpg" /></p>
<p>2.Ethernet的问题</p>
<p>Ethernet所用的电缆与USB、HDMI等的电缆存在不同。</p>
<p><img alt="Ethernet的问题" data-entity-type="file" data-entity-uuid="a21e9e2d-1ea8-48f1-a90b-2802684ef338" src="/sites/default/files/inline-images/4_132.jpg" /></p>
<p><img alt="Ethernet的问题" data-entity-type="file" data-entity-uuid="4d4749bc-92ba-4475-ad30-c40c679c69c3" src="/sites/default/files/inline-images/5_121.jpg" /></p>
<p>3.车载设备的降噪标准</p>
<p><img alt="Ethernet" data-entity-type="file" data-entity-uuid="640b575b-e359-4b3f-96c5-5eddae83fc9a" src="/sites/default/files/inline-images/6_102.jpg" /></p>
<p>与民用产品相比，车载设备与天线的距离较短且具有更加严格的限度值。</p>
<p><br />
<strong>推荐！</strong><br />
<strong>差分信号传输的降噪措施使用共模扼流圈甚为有效。</strong></p>
<p><img alt="差分信号传输" data-entity-type="file" data-entity-uuid="2f68ccfb-9bc3-4263-a201-4c625305c687" src="/sites/default/files/inline-images/7_84.jpg" /></p>
<ul>
<li>反相（差模)信号，磁场消除 → 穿透</li>
<li>同相（共模）的噪声，磁场重叠 → 反射</li>
</ul>
<p><strong>能够选择性地只将共模消除！</strong></p>
<p>作为对100Base-T1的降噪措施最佳共模扼流圈，我们推荐DLW43MH系列。</p>
<p><img alt="DLW43MH201XK2" data-entity-type="file" data-entity-uuid="7ee1633a-5fcc-4c4c-952b-93a3fd1658a9" src="/sites/default/files/inline-images/8_67.jpg" /></p>
<p><a href="https://www.murata.com/zh-cn/products/productdetail?cate=luNoiseSupprFi…; DLW43MH201XK2的详情请看这里 ></a></p>
<p><img alt="9" data-entity-type="file" data-entity-uuid="889d05bd-c95f-4ab5-8aa1-d518c5682a18" src="/sites/default/files/inline-images/9_2.PNG" /></p>
<p><strong>3.辐射噪声评价</strong></p>
<p>Test Condition<br />
通过辐射噪声测定确认了共模扼流圈的降噪效果。</p>
<p><img alt="10" data-entity-type="file" data-entity-uuid="70d02647-5472-4bdb-b83f-91ca6e9b3de4" src="/sites/default/files/inline-images/10_50.jpg" /></p>
<p>测定结果</p>
<p><img alt="11" data-entity-type="file" data-entity-uuid="5e43b766-24aa-433b-a384-bf8f4df4b116" src="/sites/default/files/inline-images/11_42.jpg" /></p>
<p><img alt="12" data-entity-type="file" data-entity-uuid="d6eaca68-d437-49c3-aa2a-be251345ba0c" src="/sites/default/files/inline-images/12_36.jpg" /></p>
<p><img alt="13" data-entity-type="file" data-entity-uuid="a6c24d5e-8628-4714-a2ee-90e1e3a70c5e" src="/sites/default/files/inline-images/13_32.jpg" /></p>
<p><strong>4. 传导噪声评价</strong></p>
<p>Test Condition</p>
<p><img alt="14" data-entity-type="file" data-entity-uuid="0bc31509-7385-4970-910b-58573fde8881" src="/sites/default/files/inline-images/14_27.jpg" /></p>
<p>Ethernet Test Board</p>
<p><img alt="Ethernet Test Board" data-entity-type="file" data-entity-uuid="f52589f0-d897-40e7-bf0e-b77c6be35460" src="/sites/default/files/inline-images/15_25.jpg" /></p>
<p>Test Board Circuit</p>
<p><img alt="Test Board Circuit" data-entity-type="file" data-entity-uuid="741bf366-7553-4476-bed6-59d3b47808eb" src="/sites/default/files/inline-images/16_21.jpg" /></p>
<p>测定結果</p>
<p><img alt="測定結果" data-entity-type="file" data-entity-uuid="8640556e-d658-4952-ba23-4755da09f62c" src="/sites/default/files/inline-images/17_15.jpg" /></p>
<p>支持CAN、FlexRay的DLW43SH101XK2在有些频率下噪声会增加，降噪效果不佳，但使用支持100Base-T1的DLW43MH201XK2能有效地降噪。</p>
<p><strong>5. DPI评价</strong></p>
<p>进行DPI(Direct Power Injection)试验，确认了共模扼流圈的抗扰性改善效果。</p>
<p>Test Condition</p>
<p><img alt="18" data-entity-type="file" data-entity-uuid="8ac7f245-3d40-4791-aeb8-64e1c8c3f6fa" src="/sites/default/files/inline-images/18_14.jpg" /></p>
<p><img alt="19" data-entity-type="file" data-entity-uuid="89285271-9ca8-49d5-9e30-b9352fdac5bd" src="/sites/default/files/inline-images/19_13.jpg" /></p>
<p>测定結果</p>
<p><img alt="测定結果" data-entity-type="file" data-entity-uuid="d4571668-958e-42cf-b433-d4b9ea92583f" src="/sites/default/files/inline-images/20_11.jpg" /></p>
<p><strong>6. 总结</strong></p>
<p>车载Ethernet使用容易放出噪声的非屏蔽电缆，而且需要支持车载噪声标准，因此必须采取降噪措施。<br />
使用支持100Base-T1的共模扼流圈‘DLW43MH201XK2’，辐射噪声便能符合CISPR25 Class5。<br />
对传导噪声和DPI发挥出比CAN、FlexRay用CMC更高的降噪效果。</p>