Low‐Loss D‐Band Direct Waveguide‐to‐Chip Transition Using Flip E‐Plane Probe Without Wire Bonding

ABSTRACT This paper presents a waveguide‐to‐chip transition for monolithic microwave integrated circuit packaging, targeting millimeter‐wave and subterahertz applications. The proposed structure employs a flip E‐plane probe that interfaces directly with gold bumps, eliminating bondwires to minimize parasitic inductance and signal path length while reducing radiative leakage. An integrated air window cavity accommodates the chip and acts as a power dissipation shield, suppressing higher‐order modes to enhance broadband performance. Measurement results demonstrate that the transition achieves an average insertion loss of 0.73 dB and a return loss better than 10 dB across the D‐band (110–170 GHz), offering a compact and efficient solution for high‐frequency system integration.