Design of a Broadband Millimeter-Wave Array Antenna for 5G Applications

A broadband coplanar feed patch antenna for 5G millimeter-wave (mmWave) applications is initially studied. To achieve good beam scanning/steering characteristics, the single-patch antenna element design is applied to form a 1 × 4 antenna array with a gap distance (center-to-center) of 6 mm (about 0.5 λ ₀ at 25 GHz) between two adjacent antenna elements. To achieve better impedance matching (broad bandwidth) and isolation level, four sets of 2 × 3 parasitic square array patches are also loaded into the proposed 1 × 4 antenna array. The measured overlapped 10 dB impedance bandwidth of the proposed 1 × 4 antenna array was 28% (23–30.5 GHz), which can cover the 5G NR (new radio) bands n257/n258/n261 (24.25–29.5 GHz). Across the bands of interest, the isolation between any two adjacent array elements is greater than 16 dB with a maximum gain of 9.76 dBi and total efficiency >68%. Even though the overall size of the proposed 1 × 4 antenna array is 26 × 5 × 1.524 mm, a wide range of beam scanning angles covering ±40° can still be obtained at 27 GHz.