The design of a 90◦ -switched-line phase shifter using composite right/left handed transmission line (CRLH TL) is presented in this paper. To achieve a relatively constant phase shift over a large bandwidth, a CRLH TL implemented using lumped elements and a right-handed transmission line (RH TL) are used as the reference and delay arms, respectively, of the phase shifter. Computer simulation is used to study and design the phase shifter. The phase shifter is also fabricated and measured to verify the simulation results. For comparison, a conventional 90◦ -switched-line phase shifter is also designed and simulated. Simulation and measurement results show that, the proposed phase shifter has a constant phase shift, a high return loss and a low insertion loss across the operating frequency band.