Multioctave tunable 3-port circulator using a y.i.g. sphere

A circulator is described using a single-crystal y.i.g. sphere that is magnetically tunable over two octaves. The circulator is derived from an extension of the simple y.i.g. filter in TEM line and provides an insertion loss less than 1.7 dB and isolation greater than 18 dB over this band.