Question

The noise at the input of an ideal frequency detector is white, the power spectral density of the noise at the output is:

• A. Gaussian
• B. Flat
• C. Raised cosine
• D. Parabolic

Hint:

Differentiation → PSD $\propto f^2$ → Parabolic.

Answer 1

The Correct Option is D

Concept: White noise has constant power spectral density.

Step 1: Frequency detector behavior A frequency discriminator differentiates the signal.

Step 2: Effect on noise Differentiation causes PSD to increase with frequency squared. \[ S(f) \propto f^2 \]

Step 3: Shape This results in a parabolic shape. \[ \therefore \text{Correct answer is (D)} \]