a microstrip antenna is provided . the microstrip antenna includes a first substrate with a first surface and a second surface paralleled to each other , a metal ground plane with an aperture disposed on the first surface and exposing parts of the first substrate via the aperture and a metal feed line disposed on the second surface , the metal feed line has at least two intersections with the aperture on a horizontal projection plane , in order to feed a signal received or transmitted by the microstrip antenna .