Which parameter most directly limits the maximum unambiguous range in pulsed radar?

Which parameter most directly limits the maximum unambiguous range in pulsed radar?

• A. Pulse repetition frequency
• B. Pulse width
• C. Transmitter power
• D. Antenna gain

Answer: (A)

Pulsed radar can uniquely assign a returned echo to the pulse that produced it only if the echo arrives before the next pulse is transmitted. When echoes come from ranges beyond what fits in one pulse interval, they get mixed with echoes from subsequent pulses, creating range ambiguity. The quantity that sets this limit is the pulse repetition interval, which is the reciprocal of the pulse repetition frequency. The unambiguous range is about c times the PRI divided by two, so increasing the PRF (shorter PRI) reduces the unambiguous range, while decreasing the PRF expands it. Pulse width affects how finely you can resolve targets in range (range resolution), not the maximum unambiguous range. Transmitter power and antenna gain influence how far you can detect echoes (signal strength), but they don’t set the unambiguous range limit.

Pulsed radar can uniquely assign a returned echo to the pulse that produced it only if the echo arrives before the next pulse is transmitted. When echoes come from ranges beyond what fits in one pulse interval, they get mixed with echoes from subsequent pulses, creating range ambiguity. The quantity that sets this limit is the pulse repetition interval, which is the reciprocal of the pulse repetition frequency. The unambiguous range is about c times the PRI divided by two, so increasing the PRF (shorter PRI) reduces the unambiguous range, while decreasing the PRF expands it. Pulse width affects how finely you can resolve targets in range (range resolution), not the maximum unambiguous range. Transmitter power and antenna gain influence how far you can detect echoes (signal strength), but they don’t set the unambiguous range limit.