This paper investigates the optimal placement of the decoupling capacitors on the printed circuit board (PCB). This method minimizes the impedance characteristics at the power supply in the speafied frequency range, searching the optimal position of decoupling capacitor. In this method, the PCB is model@ as the PEEC model to handle the 3dimensional structures and Krylov-subspace technique is used to obtain dciently the impedance characteristics in the frequency domain.
I. summaryWith the high demand of information exchange, the per€ormance requirements placed on high-frequency circuits is becoming more stringent Because designers have to tackle the problems caused by various electromagnetic dects, including EMI (electmmagnetic interference), coupling between difFerent subcircuits, b d packaging ef€ects. One of the important problems is the mdiated emission from pxinted circuit board (PCB) that is the power distribution plane components, i.e., the power and ground planes. In order to eliminate the radiated emission, the decoupling capacitance is usually used between the power and ground planes. However the deter-. mination of the position of the decoupling capacitor is strongly dependent on the experience of the designersiOn the other hand several numerical methods have been presented to analyze the mdiated emission f?om PCB. In a lot of methods, the three-dimensional structure model has been used to simulate the accurate radiated emission There are two kinds of the methods to simulate the three-dimensional structure models. First is the full-wave analysis, such as the finite element method (FEM), method of moments (MOM), the finite-difference timedomain (FDTD) method, which can directly handle physical structures and parameters such as conductivity, permittivity and permeability. Second one is the partial element equivalent circuit (PEEC) approach, which calculates the equivalent resistance R, capacitance C and inductance L from physical parameters. Although these approaches are available for the simulation of the electromagnetic d e @ , these can not provide the optimal placement of decoupling capacitors.In this paper, we investigate the method for optimal placement of the decoupling capacitors on the printed circuit board (PCB). The distribution of power within digital systems must be done in a manner, which both provides a low impedance voltage and ground connection to the devices and also minimizes their coupling to each other. Stated another way, the ideal power distribution network would present a voltage source of zero impedance at all kquencies to devices. Then we try to minimize the impedance characteristics at the power supply in a speclfied swluency range, searching the optimal position of decoupling capacitor. In this method, the PCB is modeled as the PEEC model, that is to say, 3dimensiod mesh of equivalent lumped elements such as resistor, inductor and capacitor. The circuit -on based on PEEC is constituted by MNA(modSed nodal analysis) and charge consemtion equation in order to calculate the impeda...
