Magnetic Dipole Coupling TE_1.5,0 Resonance Based on Anisotropic Impedance Surface for <i>Ka</i>-Band Low-Profile Tri-Mode Antenna

This letter proposes a Ka-band low-profile tri-mode antenna mechanism based on anisotropic impedance surface (AIS) with magnetic dipole coupling TE1.5,0 resonance. The stack-patch, TM1,0 leaky wave, and TE1.5,0 surface wave resonances contribute to broadband behavior. The E-field direction of AIS determines the TM1,0 resonance, while the H-field direction determines the TE1.5,0 resonance. The current loops on the coupling edges form magnetic dipoles, which lower the resonant frequency of the TE1.5,0 mode and enhance the in-band impedance matching. The proposed operation mechanism enables the -6 dB, -10 dB, and -15 dB impedance bandwidth (IMBW) design standards. A transition structure with a transmission loss below -25 dB is designed suitable for antenna-in-package (AiP) design. The fabricated prototype with high manufacturing robustness features a footprint of 0.47λ0 × 0.48λ0 and a profile of 0.062λ0 (λ0 is the free space wavelength at the center operating frequency). This antenna achieves a -10 dB IMBW of 33.7%, a maximum realized boresight gain of 8.2 dBi, and a -2 dB gain bandwidth (GBW) of 33.1%, making it an ideal candidate for Ka-band AiP applications.