SIW Multibeam Array for 5G Mobile Devices

Abstract

This paper presents a substrate integrated waveguide (SIW) multibeam slot array operating at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 30$ </tex-math></inline-formula> GHz for future 5G mobile terminal applications. The multibeam forming network is realized with a Butler matrix that is composed of hybrid couplers, crossovers, and phase shifters (135° and 0°). The crossovers are formed with two cascaded hybrid couplers. In the design of 135° and 0° phase shifters, the phase compensation technique is employed. The slot array is a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 \times 4$ </tex-math></inline-formula> type, in which each column has two slot elements that are longitudinally staggered with respect to one another (in half-wavelength). In addition, mutual couplings reduction techniques applied in the proposed slot array are also discussed. The SIW technique is adopted in case for the related components, as it can be highly integrated in mmWave circuits at low fabrication cost and has low profile characteristics. The overall dimension of the SIW multibeam slot array (including the Butler matrix feeding network) is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$72 \times 27.4 \times 0.508$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , and the total area of the slot array is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10.1\times 20.4$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The measured 10 dB bandwidth was 28–32 GHz, and the measured gains at 30 GHz for each port were 10.8, 12.1, 12, and 11 dBi. The proposed slot array also possesses wide angle coverage of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 40^{\circ }$ </tex-math></inline-formula> with good steerable radiation.