A Tunable Isolator Based on Coplanar High Impedance Wire

In this paper, we propose a tunable isolator based on coplanar waveguide (CPW) realized on yttrium iron garnet substrate, in which one of the ground planes of the CPW is periodically loaded with short-circuited slots. With an in-plane DC magnetic field perpendicular to the direction of the propagation, the structure achieves nonreciprocal propagation at a resonant frequency that can be tuned in the Ku-band. The resonant frequency can be tuned either magnetically by tuning the DC magnetic bias field, or mechanically by putting a copper plate at an adjustable distance above the structure. By applying a low magnetic bias field of only 70 Oe, the operating frequency could be tuned mechanically from 13.6 to 15.15 GHz, with the tuning frequency range being 2 GHz. The benefits of choosing mechanical tuning over magnetic tuning are also highlighted. The proposed tunable isolator exhibits immense potential for radio frequency (RF) applications and can be easily implemented in different microwave devices for reconfigurable RF applications.