Advantages of RF coupler | Disadvantages of RF coupler

This page covers advantages and disadvantages of RF coupler. It mentions benefits or advantages of RF coupler and drawbacks or disadvantages of RF coupler.

What is RF coupler ?

RF coupler is a passive device which couples certain amount of input RF signal power and redirect it to another port. This port is called coupled port. Remainder of the RF input signal signal power will be directed to output port after certain amount of insertion loss. The coupler is directional in delivering outputs and hence it is known as directional coupler.

The figure depicts 10 dB directional coupler which its ports marked as Input port, Output port, Isolated port and Coupled port.

RF coupler

Following are the specifications of RF coupler considered for selection.
• Operating frequency range
• VSWR or return loss
• Intermodulation point for 2 tones
• Power rating (Max.)
• Directivity
• Impedance
• Coupling value ( 6 dB, 10 dB, 15 dB, 20 dB, 30 dB)
• Frequency sensitivity
• Coupled loss
• Dissipative loss
• Connectors at its ports
• Other parameters : Weight, Size, Cost

4 port RF coupler

The figure depicts 4 port RF coupler schematic. It shows input port (P1), transmitted port (P2), coupled port (P3) and isolated port (P4). In 3 port coupler, isolated port is not provided as external connection. Coupler factor can be expressed as follows.
➨C = 10 * log10 (P1/P3)
P1 is the input power
P3 is the power at coupled port

Benefits or advantages of RF coupler

Following are the benefits or advantages of RF coupler:
➨It is used to monitor an RF signal by coupling without any disruption. It is used in test & measurement and troubleshooting.
➨It is used to split the signal into multiple outputs as shown in the figure.
➨They are designed for wide range of frequencies and power levels and are useful for wide applications.
➨They are very easy to install and use.
➨Low insertion loss RF couplers can help to improve SNR of signal and consecutively improves system efficiency.

Drawbacks or disadvantages of RF coupler

Following are the drawbacks or disadvantages of RF coupler:
➨It introduces insertion loss to the RF signal. Hence RF couplers are not suitable for applications where signal strength and quality of signal are crucial parameters.
➨RF couplers handle certain amount of power through it. Hence check maximum power handled by the RF coupler before purchase.
➨RF couplers support specific frequency range. Moreover it supports different amount of isolation between its input and output ports. Hence check frequency range and isolation as per application or usage otherwise it will not deliver desired performance.

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