Question

Define modulation. Write its types.

Hint:

An easy analogy for modulation is putting a letter (message signal) inside an envelope and addressing it (superimposing on a carrier wave) to be sent over a long distance. The type of modulation (AM, FM, PM) is like choosing how you write the address on the envelope.

Answer 1

Step 1: Understanding the Concept:
In communication systems, information signals (like voice or data) are typically of low frequency. Such low-frequency signals cannot travel long distances through space as they are prone to attenuation and require impractically large antennas. To overcome this, the information is "carried" by a high-frequency wave, known as a carrier wave. Modulation is the process of embedding the information onto this carrier wave.
Step 2: Detailed Definition:
Modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. In essence, the characteristics of the high-frequency carrier wave are altered in accordance with the instantaneous amplitude of the low-frequency message signal. This process is essential for long-distance communication.
The main reasons for modulation are: - To allow the use of practical antenna sizes. - To reduce interference and noise. - To allow multiplexing (transmitting multiple signals over a single channel).
Step 3: Types of Modulation:
A sinusoidal carrier wave is characterized by three parameters: amplitude, frequency, and phase. By varying one of these parameters, we get different types of modulation.
1. Amplitude Modulation (AM):
In AM, the amplitude of the high-frequency carrier wave is varied in proportion to the instantaneous amplitude of the message signal, while the frequency and phase of the carrier remain constant.
2. Frequency Modulation (FM):
In FM, the frequency of the carrier wave is varied in proportion to the instantaneous amplitude of the message signal, while the amplitude and phase of the carrier remain constant.
3. Phase Modulation (PM):
In PM, the phase of the carrier wave is varied in proportion to the instantaneous amplitude of the message signal, while the amplitude and frequency of the carrier remain constant.
Step 4: Final Answer:
Modulation is the technique of encoding information onto a high-frequency carrier wave. Its primary types are Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM).