Thursday, August 10, 2017

How wave shaping and modulation works

From one of my previous articles and of course your own knowledge you are familiar by now, s to how we receive all our audio and video signals and how we watch all our transmissions. 
Waves play an essential role in this platform and what’s bigger is the task of "Modulation", Modulation is the basis on which we are able to do every other task on our mobiles, laptops, TV's and radios. Modulation: Modulation is the process by which one or more properties of a periodic wave (carrier signal) is changed by a modulating signal that contains the information to be transferred. 

I’m just going to give a basic insight into a specific type of modulation, "Pulse-Width Modulation". Pulse-Width Modulation: Pulse-Width modulation (PWM) is a modulation technique used to encode a message into a pulsing signal. Pulse-Width Modulation uses a rectangular pulse wave whose pulse width is modulated resulting in the variation of the average value of the waveform. Basic Operation: The Pulse Width Modulator Converts the varying signal into a square wave which has a constant amplitude and frequency, but the square wave changes its duty cycle in accordance to the applied message signal. 

The circuit shown is the basic circuit of a pulse-width modulator. The first op-amp used is an integrator also known as a low pass filter. When we apply a square wave the output at the low pass filter will be a triangular wave. We also apply a sine wave as the message signal. Which will be mixed with the triangular wave (it acts as an adder). Hence the output generated at pin 6 of the first op-amp will be the sum of the triangle and sine wave.

The summed Audio and triangle waves are used as the input for the comparator, the output which will be generated is a square wave having a duty cycle corresponding to the time period that the triangle wave is 'positive with respect to the reference level'.

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