GATE EC 2017 Set 2 — Question 50
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Communications → Analog Communications → AM Modulation & Demodulation
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Question
The unmodulated carrier power in an AM transmitter is . This carrier is modulated by a sinusoidal modulating signal. The maximum percentage of modulation is . If it is reduced to , then the maximum unmodulated carrier power (in kW) that can be used without overloading the transmitter is ___________
Correct answer
5.19 to 5.23
Solution
The total power in an AM signal is given by the formula:where is the unmodulated carrier power and is the modulation index.Step 1: Determine the maximum power limit of the transmitter.
Initially, and the maximum modulation index is (). The maximum total power the transmitter can handle without overloading is:Step 2: Calculate the new maximum carrier power.
When the modulation index is reduced to (), we want to find the new maximum unmodulated carrier power such that the total power does not exceed :Rounding to two decimal places, the value is . The official range is to .
Initially, and the maximum modulation index is (). The maximum total power the transmitter can handle without overloading is:Step 2: Calculate the new maximum carrier power.
When the modulation index is reduced to (), we want to find the new maximum unmodulated carrier power such that the total power does not exceed :Rounding to two decimal places, the value is . The official range is to .
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