For a stable operation of information and telecommunications devices，many data centers have mesh grounding systems called signal reference grids (SRG). While the purpose of an SRG is to provide the devices with an equipotential surface，the frequency range is limited up to megahertz. Due to the increase of operating speed of switching circuits，frequency components above the frequency are involved. The authors measured the frequency characteristics of the SRG. It is cleared from the results that some resonances are observed in a frequency range above 10 MHz， and the SRG cannot provide the devices with an equipotential surface at the resonance frequencies. A grounding method with matching resistors for the SRG is proposed to improve the characteristics.