Empirical Insights into Backward Directivity Estimation of CPW-Fed Flexible Antennas Using Characteristic Mode Analysis
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Abstract
This research proposes an empirical approach for estimating the backward directivity of a coplanar waveguide (CPW) flexible patch antenna using characteristic mode analysis (CMA). The proposed methodology involves developing a simple formula to calculate substrate-independent antenna backward directivity from the antenna's characteristic modes (CMs). It establishes a relationship between the characteristic modes and the antenna structure's natural resonant frequency, accounting for resonant frequency variations caused by substrate property changes. The approach remains valid for both traditional and complex antenna designs. Calculation results showed satisfactory agreement with simulation results, achieved without considering substrate or excitation effects. Finally, the approach demonstrated low error rates and rapid backward directivity. The method is verified with four antennas whose bandwidths range from 2 GHz to more than 11 GHz. Results illustrate that the estimation approach for conventional design attains a low rate of error (RoE) of 0.044.
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