High-Gain Circularly Polarized Array Antenna With Low Grating Lobe Property Based on TM₃₀/TM₀₃ Mode

In this letter, a high-gain circularly polarized (CP) array antenna with low profile and low grating lobe property is proposed. The array is composed of high-gain and low sidelobe CP patch elements based on odd high-order modes. By adding perturbation structure, a pair of orthogonal modes (TM ₃₀ /TM ₀₃ ) of the patch with 90° phase difference is diagonally excited. Meanwhile, by introducing five circular slots on the patch, four sidelobes of the element radiation pattern in x o z plane and y o z plane are effectively reduced. Consequently, the large grating lobes of array antenna can be avoided. Then, a 2 × 2 array prototype is designed and fabricated for verification. The thickness of array is only 0.5 mm (0.027 λ ₀ ). The peak gain and aperture efficiency reach up to 17.5 dBic and 55.5%, respectively. When the element spacing is more than 1 λ ₀ , the measured maximum grating lobe level at 16.25 GHz is only −15 dB.