A novel left-handed microstrip transmission line(LH-TL) structure was presented.Based on this structure,feed lines with composite right/left-handed transmission line(CRLH-TL) structure for microstrip arrays were also presented.By controlling the lengths of LH-TL.and RH-TL parts in CRLH-TL, naught phase shifts of the transmission line can be obtained.As an application,the CRLH-TL has been used as feed line in series fed millimeter wave microstrip arrays.Numerical results show that,by means of the CRLH-TL,the insertion phase shifts at excited ports of microstrip elements can be eliminated.As a result,the inherent beam shifts disappear.