A circulator (100) is comprised of a transmission line three port Y junction
(104). At least one cylindrical cavity structure (113, 115) is disposed
adjacent to the Y junction and contains a ferromagnetic fluid (114). One
or more magnets (112) are provided for applying a magnetic field (118)
to the ferromagnetic fluid and the Y junction in a direction normal to a plane
defined by said Y junction. A composition processor (301) is provided for
dynamically changing a composition of the ferromagnetic fluid in response to a
control signal to vary the permittivity and permeability of the ferromagnetic fluid.
