D-Band Stripline Interconnection Using Capped Cavity via Transition

A capped cavity via transition for impedance matching of the stripline interconnection of the multilayered board is proposed at the
$D$
-band frequency. Equivalent circuits and equations were used to analyze the input impedance of the multilayered via transitions and striplines. The mechanisms that cause narrow bandwidth and high insertion loss were explored. Subsequently, a capped cavity structure for achieving impedance matching between via transitions is proposed. This method allows the capacitance between the via transition and ground planes to be reduced to minimize the reflection coefficient over a wide bandwidth. Measurements were conducted to validate the effects of the proposed method, which demonstrated an increase in bandwidth of over 50 GHz.