Brukar:Roger/fag/mattekladd

Frå Wikipedia – det frie oppslagsverket

P_r = (\frac{\lambda}{4 \pi r})^2 G_r G_t P_t

\frac{P_r}{P_t} = (\frac{\lambda}{4 \pi r})^2

r^2 = (\frac{\lambda}{4 \pi})^2 \frac{P_t}{P_r}

r = \frac{\lambda}{4 \pi} \sqrt{\frac{P_t}{P_r}}

P_t = 10 \textrm{dBm} = 10^{\frac{10}{10}} \textrm{mW} = 10 \textrm{mW}

P_r = -105 \textrm{dBm} = 10^{\frac{-105}{10}} \textrm{mW} = 3.16228 \cdot 10^{-11} \textrm{mW}

\lambda = \frac{c}{f} = \frac{3 \cdot 10^8}{433.93 \cdot 10^6} = 0.691 \textrm{m}


r = \frac{0.691}{4 \pi} \sqrt{\frac{10}{3.162 \cdot 10^{-11}}} = 31004 \textrm{m}

b)

P_r = (\frac{\lambda}{4 \pi r})^2 P_t


P_r = (\frac{0.691}{4 \pi 10})^2 \cdot 10 = 3.03 \cdot 10^{-4} \textrm{mW} = -35.19 \textrm{dBm}

− 35.19dBm − ( − 108dBm) = 69.8dB