Why is range resolution important in radar, and which parameter primarily determines it?

• A. Range resolution is the ability to distinguish two targets at different ranges; it improves with shorter pulse widths.
• B. Range resolution is the angular separation of targets.
• C. Range resolution depends on antenna size only.
• D. Range resolution is the speed of the target.

Answer: (B)

Range resolution is the radar’s ability to distinguish two targets at different ranges along the line of sight. It’s like being able to separate two echoes that return at slightly different times. The key factor that sets this separation is how long the transmitted pulse lasts. A shorter pulse provides a shorter return duration, so echoes from targets that are close together in range produce temporally distinct signals. In a simple pulsed radar, range resolution ΔR is approximately c times the pulse width τ divided by 2, so shorter pulse widths yield finer range resolution. Shorter pulses also imply a wider signal bandwidth, which supports better range discrimination, though the dominant factor is the pulse duration.

The other concepts don’t map to range resolution as directly: angular separation is about how far apart targets appear in angle (not range), which is determined by antenna size and beamwidth; range resolution isn’t set by antenna size alone; and target speed affects Doppler shift, not how closely you can resolve ranges.