Numerical Short-Open (and Load) Calibration Technique for Unified Extraction of Equivalent Circuit Parameters in FSS Design

This communication presents a unified method for extracting and characterizing the equivalent circuit parameters of frequency-selective surface/structure (uniformly abbreviated as FSS), by introducing the concept of numerical short-open and short-open-load calibration techniques using a “field-circuit” combination approach. Each periodic element of an FSS is modeled as a two-port network, which is then divided into three cascaded sub-networks: two spatially excited feedlines and a core element loading. By establishing the perfect standards of ideal short-circuit, open-circuit, and matching load at reference planes along all the feeding parts, the entire network parameters can be solved across a wide frequency band under periodic boundary conditions. A suitable equivalent circuit model (ECM) is then formulated, allowing for systematic and quantitative characterization of all circuit parameters via extractions. The effectiveness of the proposed method is demonstrated by extracting simple and regular 2-D element models, as well as 3-D stacked slotline element models. The method yields accurate extraction results with specified ECM for arbitrary incident angles or polarizations within fundamental mode operation.