Three-Dimensional Interconnection With Magnetically Coupled Transition for W-Band Integration Applications

In this article, a new class of 3-D interconnection with the magnetically coupled transition is proposed at <inline-formula> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula>-band. In contrast to planar approaches, it can connect different components or modules in a complex package with wideband and low-loss performance, even if in separate circuit boards. To overcome the radiation loss, the micromachined rectangular microcoaxial line (<inline-formula> <tex-math notation="LaTeX">$\text{R}\mu $ </tex-math></inline-formula>CL) is chosen to be the 3-D signal line, owing to its low-weight robust structure and low-crosstalk transmission. The substrate integrated waveguide (SIW) is chosen to act as the common signal line around the components and modules. The soldering process will introduce the unpredictable parasitic reactance, which can deteriorate the transmission performance. To construct a nonsoldering field transformation structure from the TEM mode to the TE10 mode, the U-shaped magnetic slot is etched on the SIW through the direction orthogonal to the current field vector, and the tail of the <inline-formula> <tex-math notation="LaTeX">$\text{R}\mu $ </tex-math></inline-formula>CL is directly open. Meanwhile, the transmission characteristics is studied by analyzing the physics-based equivalent-circuit model of this interconnection. The extraction methods of the key parameters, such as turn ratios in the equivalent circuit, are studied for simplifying the synthesis approach. A back-to-back interconnection prototype is designed by the synthesis guideline. The prototypes are fabricated and measured to validate the correctness of this design. The measured results show that the proposed transition achieves a bandwidth from 85 to 100 GHz with the return loss better than 13 dB and the insertion loss around 1.5 dB, which make it promising for high-density interconnection applications at <inline-formula> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula>-band.