line 304 on the horizontal projection plane the feed line 404 arranged near to the inner edge and the outer edge of ring shaped radiant metal sheet 402 is linear including a first segment l 1 4041 arranged near to the inner edge of the ring shaped radiant metal sheet 402 and a second segment l 2 4043 arranged near to the outer edge of the ring shape radiant metal sheet 402 wherein the first segment l 1 4041 passes through the intersection b and the endpoint c and the second segment l 2 4043 passes through the intersection a and feeding point f when the length of the feed line 404 from the intersection a to the endpoint c is the length ls the current distribution of the ring shaped radiant metal sheet 402 also matches successfully with that in the relatively higher order operation mode the relatively higher order operation mode of the microstrip antenna 40 is excited successfully and the omnidirectional radiation pattern of the microstrip antenna is obtained on the horizontal projection plane please refer to fig9 wherein is the diagram showing the frequency and the return loss of the relatively higher order operation mode of the microstrip antenna in accordance with a second embodiment of the present invention it is recognized that the bandwidth of the microstrip antenna is about 200 mhz 9 and the biggest antenna gain is also 5 dbi therefore the obvious operation efficiency of the wireless network is achieved please refer to fig1 which is a structural diagram showing the microstrip antenna in accordance with the third preferred embodiment of.