When one compares the new Microstrip-fed Vivaldi with the staple feed Vivaldi which was included in Version 1.3, it has some notable practical advantages.
Tapered-slot antennas are often etched with other components onto the same dielectric substrate. The Microstrip-fed Vivaldi has the advantage that it can easily be integrated in the circuit.
The microstrip to slotline transition is realized by etching the slotline on one side of a substrate. On the opposite side of the substrate, a microstrip line crosses below and perpendicular to the slotline (as shown in the next image). After crossing below the slotline, the microstrip line is flared to form a radial stub which acts as a wideband, virtual short circuit. Antenna Magus has taken care of this non-trivial design process and includes the designed feed section detail in the antenna model as shown in the image below....
This endfire antenna can be designed for a 3:1 performance bandwidth and up to 17 dBi gain.The Microstrip-fed Vivaldi slot with transparent enlarged view showing the feed section detail