Band-Stop Filter Effect of Power/Ground Plane on Through-Hole Signal Via in Multilayer PCB

length, its inductance and fringing capacitance are below 1 nano-henry (nH) and 1 pico-farad (pF), respectively, and it leads only 14 pico-second (ps) time delay [1]. These values are not serious problems of signal integrity (SI). However, when the power/ground plane is considered as a return current path of the through-hole signal via, the electrical performance of the through-hole signal via is easily affected by the power/ground plane due to its small parasitic parameters, and consequently, signal distortion, power integrity (PI) degradation or power/ground plane noise voltage, and radiated emission are caused at the through-hole signal via by reflection and loss due to high impedance of the power/ground plane. Especially, the power/ground plane is originally designed to supply quiet DC powers. Therefore, the noise voltage and the radiated emission related to the power/ground plane mean the degradation of its performance. Unfortunately, the studies about via have not took the power/ground plane effect into consideration by focusing on the parameters of via [2], [3]. And another studies about the power/ground plane have not considered the through-hole signal via effect such as the return current path discontinuity by calculating the frequency-dependent input and transfer impedances of the power/ground plane [4]-[6]. Therefore, we focus on demonstrating the interactions between the through-hole signal via and the power/ground plane. First, we explain the coupling mechanism between them by defining return current distributions of the throughhole signal via, and then, we demonstrate that the effect of the power/ground plane on the through-hole signal via is same as that of a band-stop filter inserted middle of signal trace by measuring S-parameter and TDRTDT responses of test vehicles, whose power/ground plane impedances related to the through-hole signal via are different. At the same time, the through-hole signal via effect on the degradation of the power/ground plane performance is shown by measuring power/ground plane noise voltage excited by TDR source on the through-hole signal via. Finally, we applied the analysis to the clock transmission through the throughhole signal via. Since a clock concentrates its power on its discrete harmonics, the interactions can be more clearly confirmed by showing the measurements of the distorted clock waveforms, the power/ground plane noise voltages, and the radiated emissions. The first measured result will show the degradation of clock signal integrity (SI) due to the power/ground plane effect on the through-hole signal via. The last two measured results will show the degradation of the power/ground plane performance due to clocks SUMMARY The effect of the power/ground plane on the through-hole signal via is analyzed in a viewpoint of a band-stop filter. When the through-hole signal via passes through the power/ground plane, the return current path discontinuity of the through-hole signal via occurs due to the high impedance of the power/ground plane. Since the high impedance is produced by the power/ground plane resonance, it acts as a band-stop filter, which is connected to the signal trace in series. Therefore, the power/ground plane filters off its resonance frequency component by absorbing and reflecting from the signal on the through-hole signal via, and consequently the signal distortion, the power/ground plane noise voltage, and the consequent radiated emission occur. With S-parameter and TDRTDT measurements, the band-stop effect of the power/ground plane on the through-hole signal via is confirmed. And then, this analysis is applied to the clock transmission through the through-hole signal via to obtain the clearer confirmation. The measurements of the distorted clock waveforms, the induced power/ground plane noise voltages, and the radiated emissions depending on the power/ground plane impedance around the through-hole signal via are shown. key words: power/ground plane, signal via, return current, signal integrity, power integrity, radiated emission