Define Modulation. Mention the basic methods of Modulation.

Hint: 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.

Complete step by step answer:

In electronics and telecommunications, 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. Most radio systems in the 20th century used frequency modulation (FM) or amplitude modulation (AM) for radio broadcast.
A modulator is a device that performs modulation. A demodulator (sometimes detector or demod) is a device that performs demodulation, the inverse of modulation. A modem (from modulator–demodulator) can perform both operations.

Types of Modulation:
A. Analog modulation
B. Digital modulation

A. Analog modulation:-

In this modulation, a continuously varying sine wave is used as a carrier wave that modulates the message signal or data signal. The Sinusoidal wave’s general function is shown in the figure below, in which, three parameters can be altered to get modulation – they are amplitude, frequency and phase, so the types of analog modulation are:

A. Amplitude modulation
B. Frequency modulation
C. Phase modulation

Amplitude modulation - In amplitude modulation, the amplitude of the carrier wave is varied in proportion to the message signal, and the other factors like frequency and phase remain constant.

Frequency modulation (FM) - It varies the frequency of the carrier in proportion to the message or data signal while maintaining other parameters constant.

Phase modulation - In phase modulation, the carrier phase is varied in accordance with the data signal. In this type of modulation, when the phase is changed it also affects the frequency, so this modulation also comes under frequency modulation.

B. Digital modulation:-

For a better quality and efficient communication, digital modulation technique is employed. The main advantages of the digital modulation over analog modulation include permissible power, available bandwidth and high noise immunity. In digital modulation, a message signal is converted from analog to digital message, and then modulated by using a carrier wave.

Additional information:
The advantage of FM over AM is the greater suppression of noise at the expense of bandwidth in FM. It is used in applications like radio, radar, telemetry seismic prospecting, and so on. The efficiency and bandwidths depend on modulation index and maximum modulating frequency.

Note: Analog modulation (AM, FM and PM) is more sensitive to noise. If noise enters into a system, it persists and gets carried till the end receiver. Therefore, this drawback can be overcome by the digital modulation technique.