Ultra-wideband Low-profile Antenna Loaded With Matching Circuit

Ultra-wideband low-profile antenna loaded with matching circuit is presented in this paper, which is buried in a specific cavity. The proposed antenna is fed through coaxial directly to achieve a low-profile characteristic. The designed antenna is proposed to achieves a $4:1$ bandwidth $(f_{L^{-}}-f_{L})$ with VSWR <3, while the antenna without loaded with matching circuit only reaches a $2.5:1$ bandwidth $(1.6f_{L}-4f_{L})$. The maximum size is only about $0.17\lambda_{lll}$, and the profile height is only $0.055\lambda_{lll}$, which makes the antenna suitable for the application of airborne platforms. The special cavity’s maximum length is $0.33\lambda_{1lw}$, the profile height is the same as the antenna, and the angle of inclination is 15°.