MEMS-tunable composite right/left-handed (CRLH) transmission line and its application to a phase shifter

This paper reports a novel compact tunable composite right/left-handed transmission line (CRLH TL) with multi-state phase tunability using integrated microelectromechanical system (MEMS) switches and its application to a phase shifter. It is possible to select multiple states with different positive/negative phase responses. The phase states can be determined by controlling the admittance of capacitors and impedance of inductors through MEMS switch operations. The designed devices are analyzed using electromagnetic and circuit simulations. The propagation characteristics and phase lead/lag properties of the devices are investigated. The designed device can be operated as a 90 degrees/-90 degrees phase tunable CRLH TL at 8 GHz and a four-state phase shifter at 9.5 GHz by switch configuration. At 8 GHz, the phase responses of the device were 87 degrees of the phase lead and -80 degrees of the phase lag for the left-handed (LH) and right-handed (RH) states, respectively. At 9.5 GHz, the phase of each state varies among 26.7 degrees, 14.6 degrees, -6.7 degrees, and -11.5 degrees, where the first two states are in the LH region and the others are in the RH region. At 9-15 GHz, insertion losses are measured to be <2.6 dB, and return losses are > 10 dB.