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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.
Full width at half maximum. In a distribution, full width at half maximum (FWHM) is the difference between the two values of the independent variable at which the dependent variable is equal to half of its maximum value. In other words, it is the width of a spectrum curve measured between those points on the y-axis which are half the maximum ...
If the maximum gain is 0 dB, the 3 dB bandwidth is the frequency range where attenuation is less than 3 dB. 3 dB attenuation is also where power is half its maximum. This same half-power gain convention is also used in spectral width, and more generally for the extent of functions as full width at half maximum (FWHM).
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.
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 ...
For example, a signal (10101010) has 50% duty cycle, because the pulse remains high for 1/2 of the period or low for 1/2 of the period. Similarly, for pulse (10001000) the duty cycle will be 25% because the pulse remains high only for 1/4 of the period and remains low for 3/4 of the period. Electrical motors typically use less than a 100% duty ...
The full line on the graph of the adjacent figure shows results for linear chirps. It shows, for example, that only about 2% of the total power resides at frequencies outside the sweep range Δ F when the time-bandwidth is 100, and it is less than 1/2% when T. Δ F is 500.
(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.