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Antireflection (AR), that is, to enhance the transmittance of electromagnetic (EM) waves through dielectric plate, and reduce loss, plays a critical role in improving the performance of devices such as communication, sensing and detection, and has long been pursued for a wide range of applications. However, existing methods tend to concentrate on the properties of materials itself, which encounters thorny difficulties to make breakthroughs in material system, angle of incidence, and bandwidth, particularly restricting their implementation in the long wavelength microwave regime. Herein, we propose a general and robust approach of overcoming impedance mismatching in broadband and extreme-angle AR device in microwave regime. By incorporating double-layered “U”-shaped structure and double-layered metal wires circular patch structure with symmetrical distribution into dielectric plate, Drude-Lorentzian resonances model is induced to decrease effective permittivity for transverse electric (TE)-polarization and increase that for transverse magnetic (TM)-polarization, so as to improve impedance on one side of the half-wave wall (left or right), link two adjacent half-wave walls and suppress reflection. As a proof-of-principle, an AR device was designed and analyzed in simulation. Encouragingly, a distinct transmission peak appears beside one side of the medium half-wave wall, and average dual-polarized transmission coefficients are increased by 30% compared with dielectric plate of equal size in 13- 21GHz under incident angle [70º, 80º], especially for TM-polarization, which has apparent AR effect in 8-20GHz. This work provides an effective approach of enhancing polarization-insensitive broadband transmission of EM waves at extreme angles and may be readily extended to terahertz and optical frequencies.
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