This document describes techniques, apparatuses, and systems utilizing a high-isolation transition design for differential signal ports. A differential input transition structure includes a first layer and a second layer made of a conductive metal and a substrate positioned between the first and second layers. The second layer includes a first section that electrically connects to a single-ended signal contact point and to a first contact point of a differential signal port. The first section includes a first stub based on an input impedance of the single-ended signal contact point and a second stub based on a differential input impedance associated with the differential signal port. The second layer includes a second section that electrically connects to a second contact point of the differential signal port and to the first layer through a via housed in a pad. The second section includes a third stub associated with the differential input impedance.