Pulse Repetition Frequency (PRF) Calculator

Pulse repetition frequency calculator

The pulse repetition frequency (PRF) is the measure of the number of pulses per second of a repeating signal. It is expressed in pulses per second or Hz.  Use this online pulse repetition frequency calculator to calculate the pulse repetition frequency (PRF) of a radar system by entering the unambiguous range Rmax (meters) value.  

What is pulse-repetition frequency?

The pulse repetition frequency (PRF) is the measure of the number of pulses per second of a repeating signal. It is expressed in pulses per second or Hz. This term is used in technical disciplines such as radar. 

For example, a radar system sends out a pulsed radio wave at the carrier frequency from the transmitter, waits for returning echoes during listening or rest time, and then radiates the next pulse. The time interval 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 pulse repetition frequency (PRF) as follows:

PRF = 1/PRT

 The radar system used to provide the information about the location (distance) and speed of the object/target.  

 Pulse repetition frequency is an important parameter in radar systems. It determines the maximum target range (Rmax) and maximum Doppler velocity (Vmax) that can be accurately determined by the radar. A high PRF number can improve the target discrimination of the nearer objects. Operators using navigation radars and weather reading radars rely on the adjustment of PRFs for the enhancement and clarity of the radar picture. For example, navigating radars which track objects very close to the earth's surface where waves are reflected from the earth's surface need high values of PRF for less noise.

Formula for calculating the pulse repetition frequency given by:

In a radar system, an unambiguous range is the maximum range (distance) at which a target can be located so as to guarantee that the reflected signal/pulse from that target corresponds to the most recent transmitted pulse to ensure reliable information.

Where;

c = 3 x 10⁸ m/s (Speed of Light) (i.e., speed of pulsed electromagnetic wave)

Unambiguous range (Rmax) measured in metres (m)

PRF(Hz) = Pulse-repetition frequency in Hz

PRT = Pulse-repetition time in second (S) 

This calculator accepts the unambiguous range (Rmax, in meters) as the input and provides the pulse repetition frequency (Hz) and pulse repetition time (S) as the outputs.