Improved Design of a Dual-Band Circularly Polarized Square Loop Antenna under Even-Mode Resonance

An improved design of a dual-band circularly polarized (CP) square loop antenna under even-mode resonance is presented in this paper. The designed antenna is fed by a pair of orthogonal dipole launcher with fork-like stubs and connected with a simple balun above the ground plane. Four L-shaped tuning stubs can simultaneously excite the first two, odd-order even-modes. An approximate dual-band ratio design formula is also deduced by using data fitting technique. The proposed antenna exhibits identical CP sensing at its two resonant modes. The proposed approach is expected to get applications in dual-band circularly polarized antenna designs.