This tool uses the impedance of the source and load to calculate the impedance mismatch. It also calculates
- Reflection Coefficient
- VSWR (Voltage Standing Wave Ratio)
- Return loss
- Mismatch loss
- Forward power
- Reflected power
Source Impedance = Z0
Complex Load Impedance = R + j*X
Absolute Load Impedance = √(R2 + X2)
Γ = √[(R-Z0)2 + X2] / √[(R+Z0)2 + X2]
Mismatch Loss (dB) = -10*Log10(1 – |Γ|2)
Return Loss (dB) = -20*Log10(|Γ|)
Reflected Power (%) = 100*(|Γ|2)
Transmitted Power (%) = 100*(1 – |Γ|2)
For a source impedance of 50 ohm and complex load impedance of 25 + j*25, the return loss is 7 dB and 20% of the power is reflected back with the balance of 80% transferred forward.
If the source and the load are perfectly matched, the VSWR is 1 and 100% of the power is transferred.
50 ohm – 75 ohm mismatch loss
A question that comes up often in the context of using an amplifier or filter designed for 75 ohm in a 50 ohm system. In this case, what’s the mismatch loss?
When you use those numbers in the calculator above for the load Impedance = R + j*X with R= 75, X = 0
The mismatch loss is calculated to be 0.18 dB. As a result of this mismatch, only 4% of the incident power is reflected back, while 96% is transmitted forward.
- VSWR to S11 – use this tool to find the S11 (S-parameter at port 1 of a two port network)