Dwell time (T_D) in surveillance radar is the time that an antenna beam spends on a target.^[1] The dwell time of a 2D–search radar depends predominantly on

• the antenna's horizontal beam width θ_AZ, and
• the turn speed n of the antenna (in rotations per minute or rpm, i.e. 360 degrees in 60 seconds = multiplied by a factor of 6).

Dwell time is calculated by:

${\displaystyle T_{D}={\frac {\theta _{AZ)){6\cdot n))\quad \quad {\text{(in seconds)))}$

A block of constant PRF and coherently phased RF pulses, is referred to as a coherent dwell interval or coherent dwell time.^[2]