#### Pulse Repetition Frequency (PRF)

pulse width τ
transmitters pulse
Kontrollimpulse
echo signal
receiving time
Pulse Repetition Time (PRT)

Figure 1: Radar pulse relationships

pulse width τ
transmitters pulse
control pulses
echo signal
receiving time
Pulse Repetition Time (PRT)

Figure 1: Radar pulse relationships

## What is PRF in radar?

#### Pulse Repetition Frequency (PRF)

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:

 PRT = 1 (1) PRF
##### Receiving Time

Generally, the receiving time is the time between the transmitters pulses. The receiving time is always smaller than the difference between the pulse repetition period and the length of the transmitter’s pulse. It is sometimes also limited by a so-called dead time, in which the receiver is already switched off just before the next transmitting pulse.

In some radars between the transmitting pulse and the receiving time, there is a short recovery time of the duplexer. This recovery time occurs when the duplexer must switch off the receiver response to the high transmitting power. At very low transmitting power, however, can already be received during the transmit pulse also. The receiving time includes transmission time then.

next burst
burst
(consisting of
four PRTs here)

Figure 2: Burst mode of a pulse radar

next burst
burst
(consisting of
four PRTs here)

Figure 2: Burst mode of a pulse radar