Improving Power Integrity by Using Magnetodielectric Absorbers Along the Perimeters of Printed Circuit Boards

Maintaining low and smooth impedance over a wide range of frequency is one of the main issues in designing high-speed digital systems or mixed signal integrated circuits. Cavity resonances of a printed circuit board coupled with discontinuous return current paths, series inductance of the power distribution network, and parasitic inductance make potentials at power/ground planes unstable. One possible solution to improve power integrity and electromagnetic interference is to utilize a magnetodielectric absorber on the perimeter of the board. A mode-matching method and an impedance boundary condition are employed to obtain a computationally inexpensive model of the system. A contour plot of transfer impedance versus normalized surface impedance is introduced to provide useful information for determining the most suitable absorber. Numerical and measurement results are discussed. The results from the proposed modeling agree with those from the measurement and the simulation. The selected absorber effectively reduces selfimpedance and transfer impedance at resonant frequencies, but resonances are not completely eliminated at low frequencies due to the low loss of the absorber.