An advanced equivalent circuit of spiral-shaped defected ground structure

An advanced modeling technique to achieve the equivalent circuit of spiral-shaped defected ground structures (DCS) is presented. The equivalent circuit is composed of a short-circuited stub and an inductor to express the spurious frequency as well as the resonant frequency. The elements of the equivalent circuit are extracted from the related theories on step impedance resonators (SIR) and the S-parameters calculated by electromagnetic simulation. While the existing equivalent circuit model adopts the SIR composed of transmission line elements with the same-length[1], the proposed equivalent circuit uses the SIR composed of different length of transmission line elements. It is shown that the modeled S-parameters from the proposed equivalent circuit are in excellent agreement with those obtained from the electromagnetic simulation.