Tri-mode wideband filtering antenna using characteristic mode analysis

This paper presents a single-layer, tri-mode, wideband filtering antenna designed using Characteristic Mode Analysis (CMA). Through CMA, the contributions of each structural component were analyzed, leading to the development of an antenna with three resonant frequencies within the passband and two radiation nulls for out-of-band suppression. With dimensions of 30 mm $ \times $ × 28 mm $ \times $ × 3 mm (0.59 $ {\lambda _0} $ λ0 $ \times \textrm{ } $ ×0.55 $ {\lambda _0} $ λ0 $ \times \textrm{ } $ ×0.059 $ {\lambda _0} $ λ0), the fabricated antenna demonstrates a 42% impedance-matching bandwidth (4.66–7.14 GHz) and out-of-band suppression levels of 15 and 27 dB at low and high frequencies, respectively. The antenna exhibits stable broadside radiation patterns, with a gain variation of less than 1.5 dB across the 5.0–7.0 GHz range. These characteristics make it highly suitable for wireless applications, including sub-6G, Wi-Fi 6E, and Wi-Fi 7.