What is a Directional Coupler?
A directional coupler is a passive electronic device that samples a small portion of the power passing through a transmission line and delivers it to a separate port. It allows measurement of forward power, reverse power, and monitoring of signal levels in RF and microwave systems.
How to Use This Calculator
- Enter your Input Power (P_in) in dBm. This is the power level entering the coupler.
- Enter the Coupling Factor (C) in dB. This value determines how much power is sampled by the coupler (typically 10-40 dB).
- (Optional) If you know the isolation value, enter it to calculate reverse power.
- Click the Calculate button to compute the results.
Understanding the Results
- Output Power (P_out): The power delivered to the main transmission line after sampling.
- Reverse Power (P_r): The power reflected back from the load, which can indicate transmission line issues or load mismatches.
- Isolation (I): The difference in dB between the input port and the reverse port, indicating how well the coupler isolates the input from the reverse port.
Applications
Directional couplers are used in:
- Power measurement in RF and microwave systems
- Signal monitoring and troubleshooting
- Reflection measurement (by measuring reverse power)
- Monitoring transmitter output levels
Important Notes
Ensure your input values are in the correct units (dBm for power). The coupling factor should typically be a positive value (e.g., 20 dB means 1% of the power is sampled).