Name: Phase Modulation
Uploaded: 2019-07-19
Duration: 2 min 6 s
Description: Modulation is the process of converting data to an electrical signal. Is there any modulation pattern for conditioning signals? Let us answer this.

Question

How can an amplitude modulated wave be generated?

Accepted Answer

To produce an amplitude modulated wave we need to superimpose this signal with another signal of higher frequency. This signal is the 'Carrier Signal' and differs from one carrier to another.
A radio signal has a particular carrier signal different from that of a TV signal and so on. Let us assume this carrier signal to be represented as; $Y = A^{'} \sin (ω^{'} t)$
Thus, the carrier signal has a different amplitude and frequency to the message signal. Both these signals superimpose with each other. To perform this function we use simple triode to superimpose these signals.

As shown above, the message signal 'c' and the carrier signal 'A' are superimposed to give the modulated signal 'B' as shown. But the signal 'B' which is obtained is in only one phase. To overcome this problem we use a square law device placed in the circuit to square the waveform generated. The square law device is a non- linear device, the output for which can be understood better with the diagram given below:

A square law device which is a non-linear device which produces an output,
$y (t) = B x (t) + C x^{2} (t) . . . . . w h e r e B a n d C a r e c o n s t a n t s .$
This square waveform passes through a bandpass filter. The bandpass filter is a device which as the name implies filters out the noise that is the unwanted frequencies. For example, if the frequencies of the system differ from those including $' ω' a n d' ω \pm ω',$ Then the bandpass filter automatically rejects them.

Yet, the process is incomplete. The modulated signal generated is quite weak and cannot sustain attenuation over a large distance. This demands to the signal using an amplifier diode.The quality of the signal does not change only its strength increases by the amplifier which forms the second last part of the circuit.
Finally, the amplified and modulated signal goes to a transmitter or antenna for radiation at a particular bandwidth frequency. This antenna transmits the signal over large distance using radiation. But this alone does not ensure the signal will reach its destination.

We repeat the signal using repeaters at regular intervals to reduce attenuation and noise.
Image shows a typical Amplitude Modulation Circuit used normally. Thus, we have seen the various processes involved in the production of an amplitude modulated wave.

How can an amplitude modulated wave be generated?

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