Analysis of mushroom-like electromagnetic band gap structure using suspended transmission line technique

Abstract

In this report, an analysis of a mushroom EBG (mEBG) structure using method of suspended transmission line has been discussed. This structure consists of nine elements of metallic patch grounded with metal. The parametric studies are patch width, substrate thickness, relative permittivity, gap width between adjacent patch and the size of via radius. These studies involve the bandstop and bandpass characteristic of the electromagnetic bad gap structure. The result shows that the bandstop frequency of mEBG structure is affected when varying each of the parameters. This is due to the changes of the equivalent LC network of the mushroom-like EBG structures. By increasing the value of the patch width and relative permittivity, the operating frequency and bandwidth will decay due to the increment of the total capacitance value. Varying the gap between adjacent patches does not give significant effect to the band gap frequency because it only changes the value of fringe capacitor, which is very small compared to the overall capacitances. Increasing the size of via radius will increase the frequency band gap and bandwidth due to the reduction of total capacitance. Lastly, increasing the substrate thickness will reduce the operating frequency however increase the bandwidth. This is because the value of inductor increases more than the increment of the total capacitance.