The Directional Coupler conversion calculator determines key performance parameters such as coupling, coupling loss, insertion loss, and directivity using measured power levels at different ports. It can accept inputs in either dBm or Watts, automatically converting them for accurate calculation. This tool is essential for RF engineers evaluating coupler performance in transmission and measurement systems.
Formulas
Coupling = -10 * log10( P4 / P1 )
Coupling Loss = -10 * log10( 1 – ( P4 / P1 ) )
Insertion Loss = -10 * log10( P2/P1 + P3/P1 + P4/P1 )
Directivity = -10 * log10( P3 / P4 )
Formula Explanation
- P1: input power to the coupler.
- P2: transmitted (output) power at the through port.
- P3: isolated port power.
- P4: coupled port power.
- Coupling measures how much power is coupled from the main line to the secondary line.
- Coupling loss represents the signal reduction in the coupled path.
- Insertion loss is the total signal loss in the through path.
- Directivity indicates how well the coupler separates forward and reverse signals; higher directivity means better isolation.
Uses of this calculator
- Evaluating RF directional couplers used in signal sampling and monitoring.
- Calculating insertion loss and coupling performance during design or testing.
- Verifying power balance and isolation in RF systems.
- Optimizing coupler performance in transmit-receive or measurement setups.
What is the coupling and directivity for a coupler with P1 = 10 dBm, P4 = 0 dBm, and P3 = -30 dBm?
Input: P1 = 10 dBm, P4 = 0 dBm, P3 = -30 dBm
Output:
- Coupling = -10 * log10( P4 / P1 ) = -10 * log10(10^(0/10) / 10^(10/10)) = -10 * log10(1 / 10) = 10 dB
- Directivity = -10 * log10( P3 / P4 ) = -10 * log10(10^(-30/10) / 10^(0/10)) = -10 * log10(0.001 / 1) = 30 dB
- Coupling = 10 dB, Directivity = 30 dB