Which factor determines the range resolution of a radar?

Range resolution is the ability of a radar to distinguish between two or more targets which are very close to each other.

The degree of range resolution depends on:

• the width of the transmitted pulse.
• the type and size of the target.
• on the efficiency of the receiver.
• Pulse width is the primary factor in range resolution. A well-designed radar system can distinguish targets separated by one-half the pulse-width time (τ).

There the theoretical range resolution of radar can be calculated as-

S_r(separation between targets)  

Where τ = Pulse width.

And Bandwidth of the pulse ∝ 

This can be understood with the help of the following diagram: