RF Circulator Testing | RF Circulator Test and Measurement

This article on RF Circulator testing covers various test and measurement parameters used to evaluate RF Circulator. It mentions test setup used for RF Circulator testing.

About RF Circulator: It is a three port device as shown in the figure. The power at port-1 can be directed to port-2, input power at port-2 can be directed to port-3 and so on. The reverse is not possible. This is possible with anti-clockwise type of RF circulator as depicted in the figure-1.

RF Circulator

There different versions of models of RF circulator used for various applications such as coaxial, drop-in and waveguide types. The major application of rf circulator is to use single antenna between transmit and receive sections.

Test Setup for RF Circulator Testing

The table-1 below mentions typical specifications of RF circulator. These are verified during RF circulator testing.

RF Circulator Specifications Description
Frequency Range of operation The operational range of frequency at which RF circulator can be used.
Direction Clockwise or anticlockwise
Isolation The loss to the signal traveling in the reverse direction. For example, when input is fed to port-2 and output is derived from port-1.
Insertion Loss The loss incurred to the signal while traveling from one port to the other nearby port. For example, from port-1 to port-2 and so on.
VSWR or return loss It is a measure of how efficiently circulator gets matched with its ports so that it will have minimum reflection and good coupling for transmission of power.
Return Loss = 20* Log10(VSWR+1/VSWR-1)
Peak and Average Power (In Forward and Reverse direction) The peak power and average power handling capability of the RF circulator in forward and reverse direction without damaging it.

RF circulator testing setup

Figure-2 shows typical setup used for RF circulator testing. First drop-in circulator is mounted on the test fixture and connected between input and output ports of vector network analyzer (VNA). The third port of RF circulator is terminated with 50 Ohm. The test fixture is not required when rf circulator is connectorized one.

What is difference between or comparison between

Following links mention difference or comparison between various equipments:
comparison between VSG and VSA
DIfference between SNA ans VNA
Oscilloscope Bandwidth versus Rise time
Oscilloscope vs Logic Analyzer
Difference between Oscillscope types
Comparison between spectrum and network analyzer