squarepulse

A square pulse, often referred to as a square or rectangular pulse, is a time-domain waveform that stays at a high or low constant amplitude for a finite interval before abruptly switching to the opposite level. It is a transient, non-periodic form of a square wave defined by its width (pulse duration), amplitude, and timing. Key parameters include the amplitude A, pulse width tau, repetition period T (for a pulse train), and duty cycle D = tau / T. Rise and fall times describe the finite slopes of the transitions, with idealized pulses having instantaneous edges.

In the time domain, a single square pulse can be described as A times a rectangular function. In the frequency domain, a square pulse has a broad spectrum consisting of harmonics whose amplitudes depend on the pulse width and edge steepness. Narrower pulses contain more high-frequency content, while finite rise times reduce high-frequency components. For a periodic train of pulses, the spectrum consists of harmonics at multiples of the repetition frequency, with amplitudes shaped by the duty cycle.

Generation methods include function generators, digital timing circuits, microcontroller timers, and PWM (pulse-width modulation) systems. Square pulses also arise in oscillator circuits with comparators or Schmitt triggers and in digital logic where clock or trigger signals are required. Applications span timing references, clock distribution, gating signals, measurement triggers, and pulsed-modulated communications or radar systems. Practical considerations involve jitter, duty-cycle stability, edge smoothness, and bandwidth limitations, all of which affect pulse fidelity in real-world circuits.