The schematic diagram of a circulator is shown above. The arrows within the circulator signify the direction of the magnetic field when the signal is applied to one of the ports of these devices. If there is a difference at port-B, the signal can be reproduced from port-B that will be directed toward port C.
The circulators are classified into two types namely ferrite circulators and non-ferrite circulators. This revolving can depend on the communication of the electromagnetic signal by magnetized ferrite. The transmitter energy turns in an anticlockwise direction toward the antenna port. Waveguide always provides the best loss and power handling.
Here's a WR Ku-band waveguide circulator we found on Ebay:. A circulator is sometimes called a " duplexer ", meaning that is duplexes two signals into one channel e. This is not to be confused with the term "diplexer" which is refers to a filter arrangement where two frequency bands are separated into two channels from a single three-terminal device.
A lot of people mix up these terms. You can remember the correct definitions because "filter" and "diplexer" both have an "i" in them, and "circulator" and "duplexer" both have a "u". What are circulators good for? Energy can be made to flow from the transmitter port 1 to the antenna port 2 during transmit, and from the antenna port 2 to the receiver port 3 during receive.
Circulators have low electrical losses and can be made to handle huge powers, well into kilowatts. They usually operate over no more than an octave bandwidth, and are purely an RF component they don't work at DC. A circulator's isolation is roughly equal to its return loss, and should always be specified to the same requirement.
A circulator with 20 dB isolation will need to have a return loss of 20 dB. Think about it, if you terminate the third arm in a perfect 50 ohms, the clockwise isolation you will measure in a CCW circulator won't be better than the stray signal that is bouncing off the loaded port due to the reflected signal due to its mismatch to 50 ohms.
They can be packaged as planar microstrip components, coaxial components or as waveguide components. Waveguide circulators and isolators have by far the best electrical characteristics.
It transmits an input signal in one direction — A signal that enters port 1 is transmitted to port 2 and isolated from port 3, a signal incident at port 2 is transmitted to port 3 and isolated from port 1, a signal incident at port 3 is transmitted to port 1 and isolated from port 2. Circulators are typically designed to have minimal loss when transmitting an input signal from one port to the next.
When selecting an RF circulator it is important to know the parameters that you need to specify. Below are a list of the key parameters to look out for when selecting a circulator:. Frequency MHz : This is the frequency range over which the device can operate while providing minimal insertion loss and a constant level of isolation. Insertion Loss dB : The signal loss of the incident signal from one port to the next.
It is the difference in the incident power at one port to the power received at the next port. Isolation dB : This is a measure of signal levels at the adjacent ports of the circulator i. The higher this value the better the performance of the circulator.
It is measured in decibel dB. Power W : This is the level of power that the device can handle while maintaining its electrical characteristics. Package Type: These are ferromagnetic devices and are packaged in various form factors — Drop-In, Surface mount, modules with connectors etc. You can use parametric filters to specify the required frequency, isolation, and power levels — the search tool will look through multiple manufacturer catalogs to find RF circulator products that meet your requirement.
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