A seed planting assembly is provided having a plurality of planting units supported by a tool bar, each of which being operable to form a seed trench in soil, plant seeds in the seed trench, and close the seed trench. The directional antenna includes an antenna member and a reflecting tube. Even when the maximum value is greater than a center output value and the minimum value is smaller than the center output value, overlapping of capacitor discharge is avoided, thereby reducing a ripple electric current.