Wideband Dual-Polarized Two-Beam Antenna Array With Low Sidelobe and Grating-Lobe Levels for Base-Station Applications

This paper presents a wideband dual-polarized 4 × 6 antenna array with two beams for base-station applications. It consists of three 4 × 2 subarrays. For obtaining ±45° dual-polarized radiation, a wideband crossed dipole is employed as a basic element. For each 4 × 2 subarray, the lower and upper 4 × 1 subarrays are misaligned in the horizontal plane. By using this innovative scheme, the 4 × 2 subarray is equivalent to an 8 × 1 subarray with a half adjacent-element spacing, resulting in good grating-lobe suppression. For achieving stable two-beam radiation with low sidelobe over a wide frequency band, specific wideband beam-forming networks with little magnitude and phase imbalances are designed. Moreover, the adjacent-element spacing is optimized to obtain stable 10 dB beamwidth around 120°, thus satisfying the coverage requirement of 120° in the horizontal plane for base-station applications. For demonstration, the proposed 4 × 6 antenna array is designed, fabricated, and measured. The array exhibits two beams with stable 10 dB beamwidth around 120° in the horizontal plane and around -10 dB cross level between two beams. The impedance bandwidth is measured to be 56.1% (1.64-2.92 GHz) for VSWR <; 1.5 and horizontally, sidelobe and grating-lobe levels of the two beams are measured to be better than 18 dB. Moreover, the proposed method can easily be extended to multibeam base-station antenna array designs.