Enter your Input Power (P1), Output Power (P2), Isolated Port Power (P3), and Coupled Power (P4) — along with each value's unit — and the Directional Coupler Calculator will work out your Coupling, Coupling Loss, Insertion Loss, and Directivity in one shot.
Coupling
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Coupling Loss
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Insertion Loss
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Directivity
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A directional coupler is a passive microwave device that samples a portion of the signal traveling in one direction while providing isolation for signals traveling in the opposite direction. It has four ports: input, output, coupled, and isolated.
Coupling is calculated as the ratio of input power to coupled power, expressed in dB. It represents how much signal is coupled from the main transmission line to the coupled port.
Coupling loss is the difference between input and coupled power, while insertion loss is the difference between input and output power. Insertion loss represents the signal loss in the main transmission path.
Directivity is the ability of the coupler to distinguish between forward and reverse signals. It's calculated as the difference between coupling and isolation, expressed in dB. Higher directivity indicates better performance.
Yes, you can mix units for different power measurements. The calculator automatically converts between dBm and Watts as needed for accurate calculations.
Common coupling values range from 3 dB to 30 dB. Tighter coupling (lower dB values) provides more coupled power but higher insertion loss, while looser coupling provides less coupled power with lower insertion loss.
The isolation port (P3) should ideally have very low power, indicating good isolation between the coupled and output ports. High isolation values (low power) indicate better coupler performance.