Low-Cost Multibeam Millimeter-Wave Array Antennas for 5G Mobile Applications
Amir Mohsen Ahmadi Najafabadi, Firas Abdul Ghani, İbrahim Tekin
Abstract
This paper presents a low-cost, compact, multibeam planar antenna system with a wide <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm 138^{\circ }$</tex-math></inline-formula> beam coverage angle at 28 GHz for 5G applications. The proposed microstrip based design includes two branch-line couplers and a Butler matrix with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2\times 10$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$4\times 10$</tex-math></inline-formula> series-fed array antennas. Unlike the conventional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$4\times 4$</tex-math></inline-formula> Butler matrix and branch-line coupler, which generally can generate 4 and 2 beams, respectively, the designed configuration employs a novel feeding technique which allows the system to generate 7 beams for butler matrix and 3 beams for the branch-line coupler. This system covers a wider spatial range, due to its unique placement of the branch-line couplers and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2\times 10$</tex-math></inline-formula> antennas, perpendicular to the sides of the main beamforming and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$4\times 10$</tex-math></inline-formula> array antenna architecture. The measured gain, for the 13 beams, varied between 11.2 and 14.1 dBi at 28 GHz. A wide impedance bandwidth for the entire 26.5 to 29.5 GHz band was achieved, while more than a 10% fractional radiation bandwidth was obtained with a gain value over 10 dBi. The beamforming networks and rectangular series-fed microstrip array system was fabricated using low-cost PCB prototyping on Rogers 4003 C with dimensions of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$90\times 45\times 11$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{mm}^{3}$</tex-math></inline-formula> .