  This work presents a differential FBAR circulator that uses the bending mode
to mechanically modulate the FBAR mode without any varactors or switches. The
differential FBAR circulator achieves a 61.5 dB isolation (IX) with an
insertion loss (IL) of 1.8 dB at 2.68 GHz, demonstrating the first MEMS-only
circulator. The isolation bandwidth at -25 dB is 4.7 MHz and power handling of
the circulator is limited by the FBARs to +34 dBm.
