This has made small antennas more popular, despite some limitations. [Tech Minds] reviews the GA-450 indoor active HF loop antenna and finds it better than expected. You can see the video review ...

Abstract: While the theory of operation and the procedure for measurement are similar for all loop antennas, the electrical and mechanical design of aircraft loop antennas differs considerably from ...

Abstract: 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 ...