Topic: Analog Communications
A 10 kW carrier is sinusoidally modulated by two carriers corresponding to amplitude modulation index of 30% and 40% respectively. The total radiated power is
- A. 11.25 kW
- B. 10 kW
- C. 20 kW
- D. 5 kW
Answer: A. 11.25 kW
Explanation: For multi-tone Amplitude Modulation, the total effective modulation index is $m_t = \sqrt{m_1^2 + m_2^2} = \sqrt{0.3^2 + 0.4^2} = \sqrt{0.09 + 0.16} = \sqrt{0.25} = 0.5$.
The total radiated power is $P_t = P_c \left(1 + \frac{m_t^2}{2}\right)$.
$P_t = 10 \left(1 + \frac{0.5^2}{2}\right) = 10 \left(1 + \frac{0.25}{2}\right) = 10 (1 + 0.125) = 11.25$ kW.