Chapter 10: Problem 8
An absolute measure of power is the \(\mathrm{dBm}\) scale, in which power is specified in decibels relative to one milliwatt. Specifically, \(P(\mathrm{dBm})=10 \log _{10}[P(\mathrm{~mW}) / 1 \mathrm{~mW}]\). Suppose that a receiver is rated as having a sensitivity of \(-20 \mathrm{dBm}\), 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 \(100-\mathrm{m}\) length and loss rating of \(0.09 \mathrm{~dB} / \mathrm{m}\). 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 \((a) \mathrm{dBm},(b) \mathrm{mW} ?\)
Short Answer
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Key Concepts
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