Assembly-line-compatible electromagnetic characterization of wearable antenna substrates

Electromagnetic characterization of materials applied in wearable components is of paramount importance for the design and production of reliable devices. Therefore, we propose a novel approach that compares simulations and measurements performed by a resonance-perturbation method. An inset-fed patch antenna operating in the vicinity of the 2.45-GHz Industrial, Scientific, and Medical frequency band enables us to quickly estimate the properties of a given substrate sample. First, the two frequency values at which the simulated return loss peak of the fixture crosses a given threshold value are modeled as polynomial functions of the material's relative permittivity and loss tangent. Then, the comparison between modeled and measured frequencies yields the electromagnetic properties of the material. The approach is validated by characterizing the high-frequency laminate on which the antenna is implemented. Next, the method is applied to several textile materials of interest. It is shown that the proposed technique is fast, precise, and nondestructive. As such, it is suitable for integration into an assembly line, where substrate samples are first quickly characterized before being used in the production of the actual antennas.