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研究了多层印制电路板(PCB)中含有一个信号过孔的电源/地平面返回路径阻抗的频域特性,并分析采用添加短路过孔的方法减小多层PCB的输入阻抗。电源/地平面形成了径向传输线结构,反焊盘处的输入阻抗即为信号电流在电源/地平面间的返回路径阻抗。在电源/地平面外部边界施加PMC(完全导磁体)边界条件,在反焊盘处施加电流激励源,短路过孔轴向电场为零,采用高效的二维边界元法求解。计算了10GHz内电源/地平面返回路径的输入阻抗。结果表明:在两特性相同的平面之间添加短路孔可以降低输入阻抗,同时,电源、地平面的输入阻抗随频率变化交替呈现容性或感性,在反谐振频率处输入阻抗值可达几百欧姆,此外,在频率较低时输入阻抗可用静态电容或静态电感表示。采用基于全波分析的有限元软件验证了计算结果和计算方法的正确性。
The frequency-domain characteristics of the return path impedance of the power / ground plane with one signal via hole in a multi-layer printed circuit board (PCB) are studied. The method of adding short-circuit vias is used to reduce the input impedance of the multi-layer PCB. The power / ground plane forms a radial transmission line structure and the input impedance at the anti-pad is the return path impedance of the signal current between the power / ground plane. PMC (perfect magnetism) boundary conditions are applied at the outer boundary of the power / ground plane, a current excitation source is applied at the anti-pad, and the axial electric field of the short-circuit via is zero, which is solved by an efficient two-dimensional boundary element method. Calculate the input impedance of the power / ground return path within 10GHz. The results show that the input impedance can be reduced by adding short-circuit holes between the same two planes. At the same time, the input impedance of the power supply and the ground plane alternately exhibit capacitive or inductive changes with the frequency, and the input impedance can reach several hundreds at the anti-resonance frequency Ohms. In addition, the input impedance can be expressed as static capacitance or static inductance at lower frequencies. The finite element software based on full wave analysis is used to verify the correctness of the calculation results and calculation method.