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prelab1 wireless Briefly explain the function of the \"SPAN\" setting on the Spe

ID: 2079013 • Letter: P

Question

prelab1 wireless

Briefly explain the function of the "SPAN" setting on the Spectrum Analyzer. Setup a Mathcad file to perform the calculations shown below. You may want to check for correctness against a hand calculator. If a 1GHz RF signal is measured on a spectrum analyzer to have an amplitude of -3dBm, what is the corresponding power in mW and Watts? Power = _____ mW = _____ Watts If an RF power level for a sinusoidal signal is determined to be 200 mW across a 50 ohm termination, calculate the peak voltage V_Peak and the root-mean-square (RMS) voltage V_RMS. V_peak = _____ Volts V_RMS = _____ Vrms If an oscilloscope is used to display a sinusoidal RF signal in the time domain and the peak voltage is measured as V_PEAK = 20mV. What is the corresponding RF power level in mW and dBm, assuming that the input impedance of the Oscilloscope is set to 75 ohms?

Explanation / Answer

1. Spectrum Anayzer is used to display signal power versus frequency.

    But using SPAN setting the Spectrum Analyzer displays signal power as the function of time.

2. 20log(P) = 3dBm where P = Power

   logP = 3/20

           = 0.15

          P = 100.15

           P = 1.4125 W

        P = 1412.5 mW

3.   P = V2RMS / R

      200mW = V2RMS / 50

      V2RMS = 200 * 10-3 * 50

      VRMS = squar root of 10

                  = 101/2

      VPEAK = VRMS * 21/2

                  = 201/2

4. P =   V2RMS / R

          = V2PEAK/ 2R

            = 202 /(2*75)

            = 2.67 micro Watts