We frequently have to transmit digital data via analog transmission media, such as the telephone network. It is critical to convert digital data to analog signals in such scenarios. The figure depicts the basic technique. This is done with the help of specific equipment like modems (modulator-demodulators), which convert digital data into analog signals and vice versa.
One method of transferring digital data to an analog signal is modulation. The signal level of a digital signal is discrete. Discrete signals, like digital signals, have a finite number of levels (i.e., amplitude or voltage levels). The digital modulation technique starts with a simple modulation technique (shift keying) and progresses to more complex systems modulation techniques (quadrature amplitude modulation).
.png)
Because modulation requires operations on one or more of the carrier signal's three characteristics, amplitude, frequency, and phase, there are three main encoding or modulation techniques for converting digital data to analog signals. The three techniques: are amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK). ASK and PSK techniques are frequently combined, resulting in a modulation technique known as Quadrature Amplitude Modulation (QAM).
In the above figure, the digitalized signal goes through ASK (amplitude shift keying modulation), where the carrier signal's amplitude is varied according to the message signal's amplitude. In this situation, we can modulate our message signal with two amplitude levels. One amplitude level for binary '1' and another amplitude level for binary '0'. We have modulated binary '1' with amplitude of sine wave (carrier wave) and binary '0' is modulated with no signal.
As we've mentioned above transmission media, like wireless channels, fiber cables, etc. are analog in nature. So, we can not transmit digital signals thru these mediums. It becomes essential to convert the digital signal into analog form. In modulation digital signal is modulated with a high-frequency carrier signal which is a continuous signal or analog in nature. The generated modulated signal is also analog in nature as well. There are also other benefits of modulation. But in this article, our portfolio is why we can't transmit a digital signal directly from antennas. The modulated signal, especially for wireless communication, is transmitted from the antenna. The receiver receives the modulated signal and demodulates it to retrieve the message signal.
Q. Why can't we use the digital signal as carrier for wireless communication?
A. See the answer above
Why can't a Digital Signal be Transmitted Directly from Antenna?
