(14 Marks) A student performs the following experiment with a cellphone. First t
ID: 3590324 • Letter: #
Question
(14 Marks) A student performs the following experiment with a cellphone. First the student puts the cellphone on a pedestal, and observes the received signal power PA110 dBm. The student then removes the pedestal and holds the phone tightly on the same location, and observes the received signal power PB-119 dBm. a. What is the attenuation (reduction in dB) caused by tightly holding phone? b. Compute the ratio of (Power received by tightly holding phone)/ (Power received when phone is on pedestal) using absolute power (not in decibel). c. What percentage reduction of absolute power occurred once the phone was tightly held?Explanation / Answer
a) Let Power received by tightly holding the phone as P2 and Power received when phone is on pedestal P1
Attenuation or Reduction in decibels is given by the formula: P2 / P1
= -119 / -110
= 1.08 dB
b) Power ratio(not in decibels) = Power received by tightly holding the phone / Power received when phone is on pedestal).
Let Power received by tightly holding the phone as P2 and Power received when phone is on pedestal P1
= 10 log10( P2 / P1)
= 10 log10(-119 / -110)
= 10 log10(1.08)
= 10 (0.03)
= 0.3
c) Percentage reduction is given by : Change in Power / Absolute Power
= ( -119 - (-110) / -110) * 100
= (-9 / -110) * 100
= 0.081 * 100
= 8.1 %
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