With a pulse repetition frequency of 6 kHz, what is the aliasing frequency (Nyquist limit)?

With a pulse repetition frequency of 6 kHz, what is the aliasing frequency (Nyquist limit)?

• A. 1.5 MHz
• B. 5 MHz
• C. 3 kHz
• D. 6 kHz

Answer: (C)

The key idea is that the Nyquist limit is half the sampling (or pulse repetition) frequency. With a PRF of 6 kHz, the highest frequency you can represent without aliasing is 6 kHz / 2 = 3 kHz. Frequencies above this fold back into lower frequencies, causing aliasing. So the correct value is 3 kHz. The other numbers don’t fit: 6 kHz is the PRF itself, not the limit; 5 MHz and 1.5 MHz are far outside the relevant frequency range and don’t reflect half of the PRF.

The key idea is that the Nyquist limit is half the sampling (or pulse repetition) frequency. With a PRF of 6 kHz, the highest frequency you can represent without aliasing is 6 kHz / 2 = 3 kHz. Frequencies above this fold back into lower frequencies, causing aliasing. So the correct value is 3 kHz. The other numbers don’t fit: 6 kHz is the PRF itself, not the limit; 5 MHz and 1.5 MHz are far outside the relevant frequency range and don’t reflect half of the PRF.