Topic: Electromagnetics
The loss-less, quarter wavelength long, RF transmission of characteristic impedance $50~\Omega$ is terminated in pure resistive load impedance $100~\Omega$, the input impedance is
- A. $5~\Omega$
- B. $10~\Omega$
- C. $25~\Omega$
- D. $500~\Omega$
Answer: C. $25~\Omega$
Explanation: $Z_{o}=50~\Omega$, $Z_{L}=100~\Omega$. Since the wave is quarter wavelength long line, the input impedance is given as $Z_{in}=\frac{Z_{0}^{2}}{Z_{L}}=\frac{2500}{100} = 25~\Omega$.