Design of 3-D Printed Wideband THz Spatial Power Dividers Based on Two-Stage Phase Optimization Method for Heterodyne Detector Array Applications

This article presents a 3-dimensional (3-D) printed wideband <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M \times M$ </tex-math></inline-formula> terahertz (THz) spatial power divider (SPD) based on the two-stage phase optimization method. It consists of a feed source and two cascading transmitarrays (TAs), providing independent manipulation of amplitude and phase for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M \times M$ </tex-math></inline-formula> focuses. To generate the electric field distribution with equal amplitude and phase for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M \times M$ </tex-math></inline-formula> focuses with a small separation, a two-stage phase optimization method is proposed to tune the phases of TAs. The electric field distribution on the target plane with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M \times M$ </tex-math></inline-formula> focuses remains constant within a wide bandwidth by using the height-varying dielectric TA element with a linear phase shift. Two 270-GHz 3-D printed <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> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> THz SPDs with a focus separation of 2.2 mm are designed and fabricated. For the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$ </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">$4\times 4$ </tex-math></inline-formula> THz SPDs, the measured amplitude and phase imbalances are in the range of 0.2–0.7 dB and 6°–10° within 230–320 GHz for the former and 1–1.6 dB and 9°–17° within 250–310 GHz for the latter. The proposed wideband <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M \times M$ </tex-math></inline-formula> THz SPD can be applied for THz heterodyne detector array applications.