Pulse Repetition Frequency (PRF)
Figure 1: Radar pulse relationships
The Pulse Repetition Frequency (PRF) of the radar system is the number of pulses that are transmitted per second.
Radar systems radiate each pulse at the carrier frequency during transmit time (or Pulse Width PW), wait for returning echoes during listening or rest time, and then radiate the next pulse, as shown in the figure. The time between the beginning of one pulse and the start of the next pulse is called pulse-repetition time (prt) and is equal to the reciprocal of prf as follows:
The radar system pulse repetition frequency determines its ability to unambiguously measure target range and range rate in a single coherent processing interval as well as determining the inherent clutter rejection capabilities of the radar system. In order to obtain an unambiguous measurement of target range, the interval between radar pulses must be greater than the time required for a single pulse to propagate to a target at a given range and back. The maximum unambiguous range is then given by
|Runamb. =||c0||=||c0 · PRT||(2)|
|2 · PRF||2|
where c0 is the velocity of electromagnetic propagation.