RF Isolator Vs Circulator in Microwave

They are both passive microwave devices used in RF (radio frequency) systems, but they serve different functions. RF isolator and circulator are made of ferrite material but they have few differences based on applications of their use. Let us explore difference between isolator and circulator.

RF Isolator

RF isolator is a 2 port device. It is unidirectional. It is mainly used to avoid reflections from its output to the input port, hence prevent damage to the device/component connected to its input port. As shown in the figure it can pass signal from 1 to 2 port.
Refer How RF Isolator Works>>.

rf isolator versus rf circulator

As shown, it allows RF signals to pass in one direction (i.e. from port-1 to port-2) while blocking them in the opposite direction (i.e. from port-2 to port-1). It offers isolation from port-2 to port-1 which prevents reflections from returning to the source side components.

RF Circulator

RF circulator is a 3 port device. It is mainly used to make use of the single antenna between both the transmitter and receiver by connecting them appropriately at its ports. It can pass signal from (1 to 2)/(2 to 3)/(3 to 1) OR from (3 to 2)/(2 to 1)/(1 to 3) based on clockwise or anti-clockwise design.

As shown at port 1 transmitter is connected , port 2 the antenna and port-3 receiver is connected. If the rf circulator is clockwise type, When the signal at port-1 is applied,which is from transmitter,it is transmitted by antenna. And when some signal is received by antenna, it is directed to the receiver connected at port-3. Refer How RF Circulator Works>>.

Difference between isolator and Circulator

Following table compares RF isolator vs circulator in Microwave domain and explore comparison between them.

Features RF Isolator RF Circulator
Function Allows signal transmission in one direction while blocking in the opposite direction Routes signals from one port to the next sequentially, providing isolation between ports
Number of ports Two Three
Isolation High isolation between input and output ports Provides isolation between ports, but typically lower between adjacent ports compared to input/output
Directionality Unidirectional Bidirectional in a specific direction
Complexity Generally simpler More complex
Cost More affordable May be costlier
Applications Prevents signal reflections, used in RF amplifiers, mixers, antennas Signal routing and isolation between multiple components, used in radar systems, RF test equipment, communication systems

Conclusion : In summary, while both RF isolators and RF circulators provide isolation between ports in RF systems, they serve different purposes. Isolators primarily prevent signal reflections, while circulators facilitate signal routing among multiple ports. The choice between the two depends on the specific requirements of the RF system and the desired functionality.

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