A Compact and Vialess Vertical Microstrip-to-Microstrip Differential Transition

In this paper, a new compact, vialess and vertical microstrip-to-microstrip differential transition is presented based on half-wavelength slotline structure. The equivalent-circuit model is constructed, and theoretical analyses based on equivalent circuit model reveal that good differential mode (DM) signal transmission between the top- and bottom-layer differential microstrip lines can be achieved over a wide frequency range determined while the common mode (CM) signal is rejected. Moreover, the systematic design method is presented to extract the values of electrical parameters from prescribed performance in terms of its operating bandwidth and ripple levels. In addition, owing to the employment of half-wavelength slot, the proposed differential transition has a compact size. Finally, the proposed differential transition and design theories are well vindicated by an exemplary circuit centered at 2.45 GHz with the measured relative frequency bandwidth (FBW) of 114 %.