Reference: http://www.radartutorial.eu/01.basics/Range%20Resolution.en.html
Range Resolution:
Range resolution is the ability of a radar system to distinguish between two or more targets on the same bearing but at different ranges. The degree of range resolution depends on the width of the transmitted pulse, the types and sizes of targets, and the efficiency of the receiver and indicator. Pulse width is the primary factor in range resolution. A well-designed radar system, with all other factors at maximum efficiency, should be able to distinguish targets separated by one-half the pulse width time τ. Therefore, the theoretical range resolution cell of a radar system can be calculated from the following equation: