LAUSR

This article proposes a new design of a circularly polarized (CP) aperture antenna based on a dual‐mode rectangular waveguide cavity‐resonator. A capacitive iris is employed to attain a strong coupling between the cavity and the input port, resulting in a larger fractional bandwidth (FBW) than a conventional aperture antenna. Another capacitive iris is embedded at the corner of the radiating aperture and extended into the cavity to maintain equal amplitude and a phase difference of 90° between the radiated electric (E) fields of the TE101 and TE110 modes, and thus yielding CP radiation. The proposed antenna has been fabricated using a computer numerical control machine. The antenna has an FBW of 18% at center frequency (f0) f0 = 10 GHz when the reflection coefficient (S11) S11 = −10 dB. The 3‐dB axial ratio bandwidth is 7%. A gain of 8.0 dBic is found at 10.06 GHz. The low profile and competitive performance of the antenna make it a good candidate in radar applications.