why CC2530 consumption is so large when join the network?

hi

   I use Zstack 2.5.1a for the CC2530,I found that the end device current consumption is very high as mush as about 39 mA whenlooking for the network builded by the coordinator. but when it successfully join in the network the consunption will draw to about 1 mA. I have set the Beacon Frame interval is 31 seconds,how is the problem?I have enable POWER_SAVING.If anybody encountered this problem,hoping to share with me the solution !

thank you!