Overview
RF isolators and circulators are passive devices used to control the propagation of an RF signal. RF isolators permit a signal to pass in one direction while providing high isolation to reflected energy in the reverse direction. RF circulators consist of three or more ports that allow the signal entering each port to pass to the port adjacent to it (either clockwise or counter-clockwise) but not to the port in the other direction.In an ideal circulator, energy can flow from port 1 to port 2, but not from port 1 to 3, and energy can flow from port 2 to 3, but not from port 2 to 1. In practice, the isolation is not complete, and is in the order of 20 dB or better.
Major use in radars: isolate sensitive receiver from transmit pulse, and funnel received energy into receiver
Phillips has a good Application Note with background information on circulators and isolators.
Lecture Handout (File, PDF)
Images (Click to get larger images)
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| High-power circulator | Small (1 inch) circulators |
Last updated: 19-Jan-2006