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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.
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 Rayleigh bandwidth of a simple radar pulse is defined as the inverse of its duration. For example, a one-microsecond pulse has a Rayleigh bandwidth of one megahertz. [1] The essential bandwidth is defined as the portion of a signal spectrum in the frequency domain which contains most of the energy of the signal. [2]
(For simplicity, all further discussion will use metric figures.) If the radar pulse width is 1 μs, then there can be no detection of targets closer than about 150 m, because the receiver is blanked. All this means that the designer cannot simply increase the pulse width to get greater range without having an impact on other performance factors.
Servo and receiver connections A diagram showing typical PWM timing for a servomotor. Servo control is a method of controlling many types of RC/hobbyist servos by sending the servo a PWM (pulse-width modulation) signal, a series of repeating pulses of variable width where either the width of the pulse (most common modern hobby servos) or the duty cycle of a pulse train (less common today ...
The residual phase term adds only minor perturbations to this characteristic within the frequency range /. At frequencies outside this range, Φ 2(ω) deviates rapidly from π /4, and so the total phase will deviate seriously from a square law there. Fortunately, the energy content of the chirp spectrum is very small at these frequencies (as is ...
Modern radar systems are generally able to smoothly change their PRF, pulse width and carrier frequency, making identification much more difficult. Sonar and lidar systems also have PRFs, as does any pulsed system. In the case of sonar, the term pulse-repetition rate (PRR) is more common, although it refers to the same concept.
Fig. 1: Principle of an asynchronous delta pulse-width modulation (PWM). The output signal (blue) is compared with the limits (green). The output signal (blue) is compared with the limits (green). The limits (green) correspond to the reference signal (red), offset by a given value.