The impedance matching Network shown in figure is to match a lossless line having characteristic impedance $Z_o= 50 \Omega$ with a load impedance $Z_L$. A quarter - Wave line having a characteristic impedance $Z_1=75 \Omega$ is connected to $Z_L$. Two stubs having characteristic impedance of $75 \Omega$ each are connected to this quarter - wave line. One is a short - circuited (S.C) stub of length $0.25 \lambda$ connected across PQ and the other one in an open - Circuted (O.C) stub of length 0.5 $\lambda$ connected across RS.

The impedance matching is achieved when the real part of $Z_L$ is

A transmission line of length $3 \lambda / 4$ and having a characteristic impedance of $50 \Omega$ is terminated with a load of $400 \Omega$. The impedance (rounded off to two decimal places) seen at the input end of the transmission line is $\_\_\_\_$ $\Omega$.

The impedances $Z=j X$, for all $X$ in the range ( $-\infty, \infty$ ), map to the Smith chart as