A Stochastic Framework for the Variability Analysis of Textile Antennas

A novel framework to accurately quantify the effect of stochastic variations of design parameters on the performance of textile antennas is developed and tested. First, a sensitivity analysis is applied to get a rough idea about the effect of these random variations on the textile antenna's performance. Next, a more detailed view is obtained by a generalized polynomial chaos technique that accurately quantifies the statistical distribution of the textile antenna's figures of merit, for a given range over which geometry and material parameters vary statistically according to a given distribution. The method is validated both for a simple inset-fed patch textile microstrip antenna and for a dual-polarized textile antenna. For the latter, the probability density function corresponding to its most sensitive design parameter, being the width, is experimentally estimated by means of measurements performed on 100 patches. A Kolmogorov-Smirnoff test proves that, for all considered examples, the results are as accurate as those obtained via Monte Carlo analysis, while the new technique is much more efficient. Indeed, speedups up to a factor 1667 are demonstrated.

I. Introduction

During the past years, wearable textile antennas have acquired a lot of interest as suitable devices for deployment in critical operations such as rescue missions, military interventions and e-health applications. Although they have the potential to provide high gain and large radiation efficiency [1]–[6], even in proximity of the human body [7], their antenna characteristics are typically more subject to variations than observed in conventional rigid planar-circuit-board antennas [8], [9]. Two causes may be identified that lie at the origin of these deviations from the nominal antenna characteristics. First, the production process of the applied materials and of the final antenna assembly is less accurate compared to antennas defined on high-frequency laminates. Second, the operating conditions combined with the flexibility and compressibility of textile antennas may modify the textile antennas' geometry as well as material characteristics, thereby changing their radiation characteristics [2].