RF Coupler Testing | RF Coupler Test and Measurement

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

About RF Coupler: It is a four port device namely input port, coupled port, transmitted port and isolated port. It is mainly used in testing RF components as well as coupling power for some other use from main transmission path.

RF coupler

The figure-1 depicts rf coupler and device from narda.

Test Setup for RF Coupler Testing

Following specifications are evaluated during RF coupler testing.

RF Coupler Specifications Description
Operating frequency range It is the frequency range over which rf coupler can be used.
Coupling This is the coupling loss between coupled port(P3) and input port(P1). It is specified in the datasheet of the device. The RF coupler are designed for various coupling e.g. 10dB, 15dB, 20dB etc.
Coupling (dB) = -10 Log (P3/P1)
Directivity It is the ratio of power at coupled port (P3) to power at isolated port (P4).
Directivity= -10 Log (P3/P4)
Insertion Loss It is the loss between transmitted port power and input port power. It can be measured by deriving difference of these powers.
Frequency Sensitivity or flatness It is the maximum value of peak-peak variation in coupling which may be expected over desired frequency range of coupler. It is specified in dB(max.).
Power-Peak, Average The power handling capability of the RF coupler. The device should work efficiently till this magnitude of power is applied.
VSWR/Return Loss The matching of rf coupler with the circuit or devices connected to its ports. VSWR should be near to 1.

The test setup for RF coupler can be same as other setups used for testing RF mixer, RF isolator or RF circulator. Refer RF Mixer Testing.

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