Terminology » RF Components » RF Circulator Selection Guide and Specifications

RF Circulator Selection Guide and Specifications

rf circulator rf component isolation insertion loss rf system

An RF circulator ensures efficient signal routing between ports. This page provides an RF circulator selection guide and technical specifications to consider when selecting or buying an RF circulator for your needs.

An RF circulator is a non-reciprocal ferrite device that consists of 3 or more ports. The input at port (N) will give output at Port (N+1). The RF circulator has many applications. It can be used as an isolator, diplexer, duplexer, or protection for signal generation and analysis test and measurement equipment, and so on.

The following figure is the symbolic representation of the Y-junction circulator.

Y Junction circulator symbol

The following guidelines should be followed while selecting an RF circulator according to your needs:

Frequency range over which the circulator can be used.
The number of ports, i.e., 3 ports or 4 ports.
The direction of input and output, i.e., clockwise or anti-clockwise.
The packaging type, viz., drop-in, surface mount, or connectorized packaging.
The type of design used: waveguide, stripline, or microstrip line-based.
Refer to Table 1 below, which mentions other specifications of the RF circulator while selecting one for your needs.

RF Circulator Specifications

The following table mentions technical specifications of an RF circulator.

RF Circulator Specifications	Description
Frequency range	The figure indicates the range of frequencies over which the RF circulator is useful.
Insertion Loss	It indicates how much energy is lost during signal transfer from one port to the other. For example, from port-1 to port-2. This should be as minimal as possible. It has a value of about 0.5 dB typically. It is expressed by $10*Log_{10}(P_{out}/P_{in})$
Isolation	It is the measure of how well isolation (or decoupling) is carried out from port-2 to port-1. This should be as high as possible. It has a typical value of about 20 to 25 dB.
VSWR	It stands for Voltage Standing Wave Ratio. It is the ratio of the maximum voltage to the minimum voltage created due to imperfect impedance mismatch when two boundaries meet. It should be as low as possible. Lower VSWR refers to lower reflections at a particular port. It is expressed by ratio i.e. 2.0:1 or 1.2:1 etc. Lower the ratio is better for circulator. Hence VSWR with 1.1:1 is better compare to 1.3:1 and so on.
Power Handling	It is a measure of how much power the circulator can handle without degrading its performance.
Group Delay	The time duration a signal takes from entering at input port-1 to coming out at output port-2. It is expressed in units of picoseconds or nanoseconds.
Package Type	Drop-in package Surface mount package Connectorized package
Type of connectors	SMA, Coaxial N-type etc.