The frequency resonance of the plane is 1.4GHz. So, the power/ground plane techniques are efficient for high frequencies if the distance between the source and the load is short. These planes are not very efficient in low frequency because the equivalent capacitor is not so high and the impedance across the circuit increases and the emission levels, too (figure 7). In low and medium frequency ranges additional decoupling capacitors help to maintain this impedance low.

 

Fig. 7 PWR(VCC)-GND(VSS) planes characteristics