Ka-Band 4×2 Switched Beam Array Based on a 2-D Butler Matrix for 5G Mobile User Equipment

In this article, a Ka-band <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\,\times\, 2$</tex-math> </inline-formula> switched beam array based on a 2-D Butler matrix for 5G mobile user equipment (UE) is presented. By using a 2-D Butler matrix, the feed lines between the IC and antennas are uniform, which is a crucial problem in integrated Butler matrices for 1-D arrays, as they require complex phase-matched routing on the PCB. The proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 2$</tex-math> </inline-formula> switched beam array is composed of a signal distribution IC (SDIC), a switched beamformer IC (SBIC) with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$</tex-math> </inline-formula> transmit/receive (TRX) channels, and stacked patch antennas. The proposed switched beam array can generate 22 beams using reconfigurable switch networks with dual-port excitation. In addition, it achieves an RX system noise figure (NF) of 4.4 dB and can support a TX saturated effective isotropic radiated power (EIRP) of at least 35 dBm for any 3-D spatial angle of ±44° in azimuth and ±43° in elevation directions. Although the proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 2$</tex-math> </inline-formula> switched beam array exhibits slight gain drops between adjacent beams, it enables simple control without any calibration. To the best of the authors’ knowledge, this is the first 2-D switched beam array with integrated ICs and antennas based on the Butler matrix in millimeter-wave bands.