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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 (PRF), the number of pulses in a given time, typically a second. The duty cycle expresses the pulse width as a fraction or percentage of one complete cycle.
The pulse width (or pulse duration) of the transmitted signal is the time, typically in microseconds, each pulse lasts.If the pulse is not a perfect square wave, the time is typically measured between the 50% power levels of the rising and falling edges of the pulse.
Pulse-width modulation (PWM), also known as pulse-duration modulation (PDM) or pulse-length modulation (PLM), [1] is any method of representing a signal as a rectangular wave with a varying duty cycle (and for some methods also a varying period). PWM is useful for controlling the average power or amplitude delivered by an electrical signal.
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 turned on and off; the term "frequency" refers to the carrier, while the PRF refers to the number of ...
In electronics, duty cycle is the percentage of the ratio of pulse duration, or pulse width (PW) to the total period (T) of the waveform. It is generally used to represent time duration of a pulse when it is high (1). In digital electronics, signals are used in rectangular waveform which are represented by logic 1 and logic 0.
Pulse-frequency modulation (PFM) is a modulation method for representing an analog signal using only two levels (1 and 0). It is analogous to pulse-width modulation (PWM), in which the magnitude of an analog signal is encoded in the duty cycle of a square wave .
The ideal model for the simplest, and historically first type of signals a pulse radar or sonar can transmit is a truncated sinusoidal pulse (also called a CW --carrier wave-- pulse), of amplitude and carrier frequency, , truncated by a rectangular function of width, .
For a chirp waveform that sweeps over a frequency range F1 to F2 in a time period T, the nominal bandwidth of the pulse is B, where B = F2 – F1, and the pulse has a time-bandwidth product of T×B. Following pulse compression, a narrow pulse of duration τ is obtained, where τ ≈ 1/B, together with a peak voltage amplification of √ T×B.