PWM

 PWM 

stands for Pulse Width Modulation. To transmit a signal, whether analog or digital, it must be modulated so that it is transmitted without losing power or suffering distortion due to interference.

PWM is a technique used to transmit analog signals whose carrier signal will be digital. In this technique, the duty cycle of a periodic signal (a sinusoidal or a square, for example) is modified, either to transmit information through a communications channel or to control the amount of energy that is sent to a load. The duty cycle of a periodic signal is the width of its positive part, relative to the period. It is expressed as a percentage, therefore, a duty cycle of 10% indicates that it is 10 out of 100 at a high level.

Duty cycle = t / T

t = time partly positive

T = Period, total time

Basically, it consists of activating a digital output for a while and keeping it off for the rest, thus generating positive pulses that are constantly repeated. Therefore, the frequency is constant (that is, the time between firing pulses), while the width of the pulse, the duty cycle, is varied. The average of this output voltage, over time, will be equal to the desired analog value.