The pulse width is a measure of the elapsed time between the leading and trailing edges of a single pulse of energy. The measure is typically used with electrical signals and is widely used in the fields of

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

and

power supplies A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a res ...

. There are two closely related measures. The pulse repetition interval measures the time between the leading edges of two pulses but is normally expressed as the

pulse repetition frequency The pulse repetition frequency (PRF) is the number of pulses of a repeating signal in a specific time unit. The term is used within a number of technical disciplines, notably radar. In radar, a radio signal of a particular carrier frequency is tu ...

(PRF), the number of pulses in a given time, typically a second. The

duty cycle A duty cycle or power cycle is the fraction of one period in which a signal or system is active. Duty cycle is commonly expressed as a percentage or a ratio. A period is the time it takes for a signal to complete an on-and-off cycle. As a formu ...

expresses the pulse width as a fraction or percentage of one complete cycle. Pulse width is an important measure in radar systems. Radars transmit pulses of

radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upp ...

energy out of an antenna and then listen for their reflection off of target objects. The amount of energy that is returned to the radar receiver is a function of the peak energy of the pulse, the pulse width, and the pulse repetition frequency. Increasing the pulse width increases the amount of energy reflected off the target and thereby increases the range at which an object can be detected. Radars measure range based on the time between transmission and reception, and the resolution of that measurement is a function of the length of the received pulse. This leads to the basic outcome that increasing the pulse width allows the radar to detect objects at longer range but at the cost of decreasing the accuracy of that range measurement. This can be addressed by encoding the pulse with additional information, as is the case in

pulse compression Pulse compression is a signal processing technique commonly used by radar, sonar and echography to increase the range resolution as well as the signal to noise ratio. This is achieved by modulating the transmitted pulse and then correlating th ...

systems. In modern

switched-mode power supplies A switched-mode power supply (switching-mode power supply, switch-mode power supply, switched power supply, SMPS, or switcher) is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently. Lik ...

, the voltage of the output electrical power is controlled by rapidly switching a fixed-voltage source on and off and then smoothing the resulting stepped waveform. Increasing the pulse width increases the output voltage. This allows complex output waveforms to be constructed by rapidly changing the pulse width to produce the desired signal, a concept known as

pulse-width modulation Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a method of reducing the average power delivered by an electrical signal, by effectively chopping it up into discrete parts. The average value of voltage (and current) fed ...

References

* {{electronics-stub Signal processing Radar theory