Chapter 10, Problem 10.8P

An absolute measure of power is the dBm scale, in which power is specified in decibels relative to one milliwatt. Specifically, $P(\text{dBm})=10{\log }_{10}[P(\text{mW})/1\text{mW]}$. Suppose that a receiver is rated as having a sensitivity of -20 dBm, indicating the mimimum power that it must receive in order to adequately interpret the transmitted electronic data. Suppose this receiver is at the load end of a $50-\Omega$ transmission line having 100-m length and loss rating of 0.09 dB/m. The receiver impedance is $75\Omega$ and so is not matched to the line. What is the minimum required input power to the line in (a) dBm. (b) mW?