Since the artificial left-handed material was realized in 2001

it has been devoting to design left-handed microwave components and antennas with large bandwidth

low loss and high integration ability.In this paper

two lands of left-handed structunes used in microwave canponents and antennas are reviewed

one of which is the composite right/left-handed sttucttue

and the other of which is the complementary split-ring resonator stnxture.Both structures have been widely studied and applied in the design of microwave components and antennas.The progress of the related researches on these two structures is summarized in this paper

in addition to some of our achievements.The principles and applications of planar left-handed circuits are analyzed and demonstrated in details.