> "The full range on the ADCs is 2V peak to peak, and the input is 50 ohms > differential. This is equates to 40mW, or 16dBm." > > Please may someone enlighten me, how the 40mW and 16dBm values were > calculated?
Hello Aadil --- The impedance (effective resistance to ground) seen from the input pin on the USRP coax, is 50 ohms. The calculation you quote assumes a sinusoidal input at Vpp = 2 Volts peak-to-peak, which means the root mean square amplitude is Vrms = (Vpp/sqrt(2)) = (2/sqrt(2)) = sqrt(2). This RMS voltage is going through a 50 ohm resistor, so the power dissipated is Vrms^2/R = (sqrt(2)^2)/50 = 2/50 = 0.04 Watts, or 40 milliWatts. To convert linear mW to logarithmic (decibel) mW, or dBm, we calculate 10*log(40) = 16dBm. That's the short answer, please feel free to ask for more detail. --Scott McDermott _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
