Once a pulse has been transmitted by the radar, the range to a target is determined by first obtaining the total time elapsed between the time the pulse was transmitted and when it was received. This amount is then multiplied by the speed of light and that quantity is divided by 2. The factor of one-half is required since we are concerned with the range to a respective target and not the total (or round trip) distance traveled by the pulse. In equation form, this can be written as

Equation (11)

where c = speed of light (~ 3 x 10⁸ ms^-1)
and T = time difference between transmission of a pulse and receipt of backscattered energy from the same pulse.

It should be noted that the above Equation (11) only applies to those targets which lie within R_max. Targets which lie beyond R_max will be incorrectly displayed at ranges too close to the radar. This phenomenon is called range folding and occurs most frequently when high PRFs are required to extract accurate velocity information.

Next Page: Range Folding