Directional Coupler Directivity Definition

Directional couplers are devices used in radio technology and microwave signal routing. The directivity of a directional coupler is a measure of how well the coupler isolates the microwave signals leaving it.

Directional Couplers

Directional couplers have one port through which the microwave signal enters, and two ports through which the signal leaves. The output ports are two transmission lines set close enough together that the signal passing through one line is coupled to the other line. This way, the signal flowing in the mainline is split, and a second signal is injected into the network.

Directional Coupler Directivity

The directivity of a directional coupler is a measure of how well the coupler isolates the two signals leaving the coupler. The higher the directivity, the more accurate any measurements of the signal will be.

Measuring Directional Coupler Directivity

Directivity is measured as the difference in decibels of the signal at the two coupled ports. In general, it is best to use the directional coupler with the highest directivity.

References

• RFMD: Couplers
• Agilent RF and Microwave Test Accessories: Directional Couplers and Bridges
• Mini-Circuits: Directional Couplers
• Microwaves 101: Couplers and Splitters