Simultaneous switching noise (SSN) is one of the major bottlenecks for successful design of high-performance systems. Especially mixed-signal designs are very sensitive to SSN due to the low voltage levels applied in analog circuits. One way of isolation is by placing the digital and analog domains far from each other. Even then, the power planes can transfer noise voltages both vertically and horizontally through out the board and total board area is a major concern in microminiaturized convergent systems. Electromagnetic bandgap structures (EBG) have been successfully applied for such isolation. Although any periodical shape can be used for isolation, only a few shapes have been reported, with various analysis methods. We present a new EBG with narrow slits, which shows a higher attenuation constant compared with existing structures. We also present a new analysis methodology for 2D EBG structures. Finally, a method to scale such EBG structures for different stopband requirements is introduced.