RF circulator Selection Guide | RF circulator Specifications

This page covers RF circulator selection guide and technical specifications. It mentions RF Circulator specifications one need to consider while selecting or buying RF Circulator for their need.

RF Circulator is a non-reciprocal ferrite device which 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 isolator, as diplexer, as duplexer, as protection for the signal generation and analysis test and measurement equipments and so on. Following figure is the symbolic representation of the Y Junction circulator.

RF Circulator selection guide

Y Junction circulator symbol

Following guidelines should be followed while selecting RF Circulator as per your need.
➤Frequency range over which 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 table-1 below which mentions other specifications of the RF circulator while selecting one for your need.

RF Circulator Specifications

Following table mentions technical specifications of an RF circulator.

RF Circulator Specifications Description
Frequency range The figure indicates range of frequencies over which 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 minimum as possible. It has value of about 0.5 dB typically.
It is expressed by 10*Log10(Pout/Pin)
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 typical value of about 20 to 25 dB.
VSWR It stands for Voltage Standing Wave Ratio. It is the ratio of 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 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 measure of how much power circulator can handle without degrading its performance.
Group Delay The time duration signal takes from entering at input port-1 to come 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.

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