A Broadband Multilayer Vertical Transition at 79 GHz Employing FR4 as Core Material

Abstract

A novel vertical transition through a multilayer printed circuit board is presented. The transition is designed to fulfill the cost and manufacturing constraints of next generation automotive radar sensors. This is achieved both by employing FR4 as material in the transition core and the fabrication in a standard high density interconnect process. The modified design of a quasi-coaxial structure solves the limitations determined by the constraints. Although FR4 has high dielectric losses, a vertical transition through multiple FR4 layers is realized with a low insertion loss of less than 2.1 dB within the automotive radar frequency range of 76 GHz to 81 GHz. A return loss better than 10 dB is achieved up to a frequency of 83.2 GHz. The reliability and repeatability of the transition is shown by measurements of several transitions from different production cycles.

System Performance of a 79 GHz High-Resolution 4D Imaging MIMO Radar With 1728 Virtual Channels

“…Therefore, the top layer of the PCB is reserved exclusively for the antennas and no components are mounted on it. By using an low-loss vertical transition through FR4 [30], the PCB can be fabricated in a cost effective high-density interconnect process. The losses of 2 dB from the MMICs into the stripline are comparable to a conventional MMIC to microstrip line transition.…”