The PCB Power/Ground Resonant Impedance Damping Based on The Cavity Resonant Model

The power bus structure in PCB or IC, which is consisting of two parallel planes separated by an insulator, behaves as a cavity resonator. The high resonant impedance at certain resonant frequency between the IC or PCB's power and ground layers is the cause of some signal integrity problems. Based on the theory of parallel planes cavity resonator, this paper deducts the relation functions between the resonant impedance, resonant frequency, resonant quality factor and the electromagnetic parameters of power/ground planes structure. By using the deductions above, this paper investigated 2 main new ways to reduce the resonant impedance, which are using magnetic substance or graphite as plane conductor material and adopting insulator material with high permittivity and loss tangent. And the effects of the two ways above in resonant impedance damping are expressed clearly by the simulation results.