Consider a system shown below. Let X(f) and Y(f) denotes

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Consider a system shown below. Let X(f) and Y(f) denotes the Fourier transform of x(t) and y(t) respectively. The positive frequencies where Y (f) has spectral peak are—

1. 1 kHz and 24 kHz
2. 2 kHz and 24 kHz
3. 1 kHz and 14 kHz
4. 2 kHz and 14 kHz

Correct Option: B

From given figure since x(f) has spectral peak at 1kHz, output of balanced modulator will give
(f_c ± f_m) i.e. (10 ± 1)
which passes through the HPF with cut-off frequency ω_c = 10 kHz. So output after HPF get only 11 kHz signal, again after mixing with balanced modulator the output frequencies will be (f_c ± f₁) kHz i.e. 24 kHz and 2 kHz. Hence alternative (B) is the correct choice.