Design of a Coupled Feed Structure With Cavity Walls for Extremely Small Anti-Jamming Arrays

This paper proposes a coupled-feed structure accompanied by cavity walls for an extremely small four-element array with an aperture size of less than $0.4\lambda $ . The feeding loop of the proposed structure is connected to two output ports of a hybrid chip coupler, and the radiating loop is coupled to the feeding loop through near electromagnetic fields confined within the substrates. This structure allows to increasing the effective dielectric constant of the antenna, which helps to miniaturize the aperture size of the antenna. Another advantage of the proposed structure is that the effective dielectric constant can be adjusted by varying the height of the cavity walls. To verify the operating principles, an equivalent circuit is built, and variations of magnetic field distributions are also observed. Furthermore, performances on interference mitigation are evaluated based on the power inversion algorithm. The results confirm that the proposed structure is suitable to replace current single-antenna systems for an additional capability of effective interference mitigation in such a restricted area.