Pulse repetition frequency & range ambiguities
The pulse repetition frequency (PRF) is determined primarily by the maximum range at which targets are expected. If the PRF is made too high the likelihood of obtaining target echoes from the wrong pulse transmission is increased. Echo signals received after an interval exceeding the pulse-repetition period are called multiple-time-around echoes.
MAXIMUM UNAMBIGUOUS RANGE: The range beyond which targets appear as second-time-around echoes is called the maximum unambiguous range and is given by:
Where fr = pulse repetition frequency, in cycles per second.
Figure 2.2 RADAR Pulse Relationship
PULSE REPITATION FREQUENCY: The Pulse Repetition Frequency (PRF) of the radar system is the number of pulses that are transmitted per second.
- 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:
- From the maximum unambiguous range is then given by:
Where c0 = the velocity of electromagnetic propagation.