A Low-Profile Shared-Aperture Antenna Using Electromagnetic Transparent Structure and AMC

In this letter, a low-profile shared-aperture antenna based on electromagnetic transparent structure (ETS) and artificial magnetic conductor (AMC) is proposed. The upper-layer low band (LB) antenna based on ETS operates normally while also exhibiting transmission characteristics for the high-frequency electromagnetic waves radiated from the lower layer. The -10 dB impedance bandwidth of the LB antenna is 2.20 to 2.48 GHz and its transmission coefficient is greater than -1 dB in the 4.6 to 6.0 GHz band. The lower-layer high band (HB) antenna based on AMC provides a -10 dB impedance bandwidth from 4.6 GHz to 6.0 GHz and can reflect low-frequency electromagnetic waves with a reflection phase between -45° and 45°, achieving a low-profile design. Consequently, both the LB and HB antennas are successfully integrated into a compact space measuring 0.36 × 0.36 × 0.05 λ_L³ (λ_L is the free-space wavelength at 2.2 GHz). The measurement results demonstrate that the proposed antenna has a stable half-power beamwidth (HPBW), with peak gain reaching 4.4 dBi in the LB and 7.4 dBi in the HB. Additionally, the radiation efficiency is above 83% in the LB.