Topic: Microwave Engineering
A dual directional coupler is connected in a microwave reflectometer measurement setup. The reading of the power meter in the forward direction is 100 mw and in the reverse direction 4 mw. The VSWR is
- A. 4
- B. 0.4
- C. 1.5
- D. 10
Answer: C. 1.5
Explanation: The magnitude of the reflection coefficient is $|\rho|=\sqrt{P_{r}/P_{i}}=\sqrt{4/100}=2/10=0.2$. The Voltage Standing Wave Ratio is given by $VSWR=\frac{1+|\rho|}{1-|\rho|}=\frac{1+0.2}{1-0.2}=\frac{1.2}{0.8}=1.5$.