Ultracompact On-Chip Branch Line Coupler Based on Through-Silicon Via Technology
Yue Deng, Fengjuan Wang, Xiangkun Yin, Sa Xiao, Yuan Yang, Ningmei Yu
Abstract
A compact branch line coupler with lumped elements on silicon substrate is realized by employing through-silicon via (TSV) technology, in which the lumped elements adopt high-density, high-<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> 3-D solenoid inductors, and double-layer interdigital capacitors, and the proposed coupler is fabricated and measured. The results show that the return loss of the coupler is less than -19.7 dB, the isolation is less than -15.2 dB at 4.7–5.3 GHz, and the phase imbalance within the operating frequency range is within ±1.2°. In addition, the size of the branch line coupler 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">$1.2\times 1.36$ </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> (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.069\times 0.078~\lambda _{\text {g}}^{2}$ </tex-math></inline-formula>).