PCB板级共模噪声抑制方法研究

发布时间：2018-01-16 10:27

本文关键词：PCB板级共模噪声抑制方法研究　出处：《浙江大学》2016年硕士论文　论文类型：学位论文

【摘要】：随着电子信息技术的快速发展,电子系统的速率和集成度都在不断提高,电磁兼容(EMC, Electromagnetic Compatibility)问题面临越来越多的挑战。共模噪声是电磁干扰(]EMI, Electromagnetic Interference)的重要来源,其抑制技术一直是电磁兼容领域的研究热点。高速电路和射频电路都有受到共模噪声影响的风险。作为专业硕士论文,紧密结合华为公司的实际产品,针对其遇到的PCB板级高速链路和射频电路共模噪声干扰问题进行了研究,对现有技术进行改进和创新,设计了满足工程需求的差分链路共模滤波器,并且将高阻抗表面应用于射频功放腔体内部的共模噪声抑制。高速差分链路携带的共模噪声极易造成EMI超标。随着PCB布线密集程度的增加以及干扰噪声频率的升高,现有的噪声抑制技术已经无法满足工程需求。通过在PCB上设计在板共模滤波器滤除共模噪声的方法早已被提出,但是目前的技术主要被应用在10GHz以下噪声的滤除,而且并未研究各种滤波器在工程应用中的局限性。本文针对线宽和线距只有5～7mil的高速差分链路设计10GHz和25GHz共模滤波器。首先对滤波器位于差分线参考地上的常见结构进行设计分析,发现该类结构对PCB加工中的层间错位极为敏感,导致其在工程中的应用受到限制。继而提出了滤波器与差分线位于同一层的共面型结构,但是由于目前加工工艺的限制使得差分线和滤波器的间距无法做到很小造成滤波器的带宽很窄无法满足工程需求。最终,本文通过在差分线下增加刻槽将共面型滤波器的-10dB带宽拓宽了5倍以上,并且通过优化消除了了引入滤波器后造成的SI问题,使得该结构满足工程应用的要求,并设计了高频测试单板用测试结果验证了其有效性。本文还针对射频功放受到共模噪声干扰问题进行了分析,通过场路混合建模法对包含金属屏蔽腔的功放模块进行建模,通过仿真与理论分析确定了功放增益恶化的原因是由于输出匹配节的噪声耦合到输入匹配节并再次放大。本文将以上共模滤波器扩展为高阻抗表面,在腔体内表面放置高阻抗表面,利用其抑制表面波的特性成功地减小了腔体内共模噪声的耦合,使得加上屏蔽腔后的功放增益更接近于无腔环境下的增益,并通过实验验证了其性能。同时,本文还通过相位补偿法实现了功放增益的改善。
[Abstract]:With the rapid development of electronic information technology, the speed and integration of electronic system are improving, EMC is EMC. The problem of Electromagnetic compatibility is facing more and more challenges. Common-mode noise is electromagnetic interference (] EMI. An important source of Electromagnetic interference. High speed circuits and radio frequency circuits have the risk of being affected by common mode noise. As a master's thesis, it is closely combined with the actual products of Huawei. The common mode noise interference of PCB board high speed link and radio frequency circuit is studied, the existing technology is improved and innovated, and a differential link common mode filter is designed to meet the engineering requirements. The high impedance surface is applied to the common mode noise suppression in the RF power amplifier cavity. The common mode noise carried by the high speed differential link is easy to cause the EMI to exceed the standard. With the increase of the PCB wiring density and the interference noise, it is easy to cause the common mode noise in the RF power amplifier cavity. Increased frequency. The existing noise suppression technology has been unable to meet the needs of engineering. The method to filter the common-mode noise by designing a common-mode filter on the PCB has been proposed for a long time. However, the current technology is mainly used in the filtering of noise below 10GHz. In this paper, 10GHz and 25GHz common mode filters are designed for high-speed differential links with line width and line spacing of only 5 mil. The common structures located on the reference ground of the differential line are designed and analyzed. It is found that this kind of structure is very sensitive to the interlaminar dislocation in PCB machining, so its application in engineering is restricted. Then, a coplanar structure with the same filter and difference line is proposed. However, due to the current processing technology constraints, the difference line and filter spacing can not be very small, the filter bandwidth is very narrow can not meet the requirements of the project. In this paper, the coplanar filter bandwidth of -10dB is expanded by adding grooves under the difference line, and the SI problem caused by the introduction of the filter is eliminated by optimization. The structure meets the requirements of engineering application, and the test results of high-frequency test veneer are designed to verify its effectiveness. In addition, the common mode noise interference problem of RF power amplifier is analyzed in this paper. The power amplifier module containing metal shielding cavity is modeled by field circuit hybrid modeling method. Through simulation and theoretical analysis, it is determined that the reason for the gain deterioration of the amplifier is that the noise of the output matching section is coupled to the input matching node and amplified again. In this paper, the common-mode filter is extended to a high impedance surface. The high impedance surface is placed on the inner surface of the cavity, and the coupling of the common mode noise in the cavity is successfully reduced by using the characteristic of suppressing the surface wave, which makes the gain of the power amplifier after adding the shielded cavity closer to the gain in the environment without the cavity. The performance of the amplifier is verified by experiments, and the gain of power amplifier is improved by phase compensation.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN41;TN03

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