An isolator is a two-port device that transmits microwave or radio frequency power in one direction only. The non-reciprocity observed in these devices usually comes from the interaction between the propagating wave and the material, which can be different with respect to the direction of propagation.
Resonance absorption isolator consisting of WG16 waveguide containing two strips of ferrite (black rectangle near right edge of each broad wall), which are biased by a horseshoe permanent magnet external to the guide. Transmission direction is indicated by an arrow on the label on the right
An X band isolator consisting of a waveguide circulator with an external matched load on one port
Two isolators each consisting of a coax circulator and a matched load
In electrical engineering, a circulator is a passive, non-reciprocal three- or four-port device that only allows a microwave or radio-frequency (RF) signal to exit through the port directly after the one it entered. Optical circulators have similar behavior. Ports are where an external waveguide or transmission line, such as a microstrip line or a coaxial cable, connects to the device. For a three-port circulator, a signal applied to port 1 only comes out of port 2; a signal applied to port 2 only comes out of port 3; a signal applied to port 3 only comes out of port 1. An ideal three-port circulator thus has the following scattering matrix:
A waveguide junction circulator used as an isolator by placing a matched load on port 3. The label on the permanent magnet indicates the direction of circulation.
Rotating modes in a junction circulator.
Internal construction of a stripline junction circulator having triangular ferrites and an irregular triangle-shaped resonator.
Internal construction of stripline junction circulator having disk ferrites and a disk-shaped resonator.
