The reflector is modeled by a grid of curved segments (see Conformal Method of Moments >). The hole sizes are small compared to the wavelength near the center of the parabola, buy they approach half-wavelength away from the center. Most real parabolic antennas are built in this way, so this is a good approximation in those cases. The curved segments are a better approximation than straight segments when a continuous metallic dish surface is used as a reflector.
A 3-element Yagi-Uda antenna is located at the focus of the parabola and its radiation pattern is pointing towards the reflector (secondary radiator). This Yagi antenna then simulates a primary radiator.
A high gain is obtained as can be seen by plotting the radiation pattern, which shows a main lobe pointing towards the parabola axis (y-axis).