The process of imposing an input signal on top of a carrier signal is called modulation. The process of modulation will change the amplitude, phase or frequency of the carrier wave. When there is a change in the frequency of the carrier signal it is called frequency modulation. The frequency is the number of waves passing through a point in a given time. The carrier amplitude will remain the same but there will be a change in the frequency. When the radio signal is imposed on the carrier signal the modulated signals frequency will go up and down.

A carrier signal is an electromagnetic wave with high-frequency and with a constant amplitude. The carrier wave is used to carry the input signal through a long distance. The carrier signals are used in the transmission of information-bearing signals as it can travel at the speed of light and is not affected by the earth’s atmosphere. The input signal can be an audio, video or a digital signal.

Modulation Index of Frequency Modulation

Two of the important parameters of frequency modulated signals are – Frequency Deviation and Modulation Index. These parameters help define the characteristics of the FM signal being analysed.

The difference between the instantaneous frequency of the modulating signal and the carrier frequency is called frequency deviation. The modulation index of frequency modulation is the ratio of the frequency deviation of the carrier to the frequency of the modulating signal.  For instance, if a signal has frequency deviation of ±10 kHz, and the frequency of the modulating signal is 2 kHz, then the modulation index for this particular example will be 10/2 = 5

Frequency Demodulation

The process of separating the information signal from the carrier signal is called demodulation. The demodulator is the electronic circuit that is used in extracting the information-carrying signal from the carrier.

The most common type of FM demodulator is the Foster-Seeley discriminator. This device consists of an electronic filter followed by an AM demodulator. The electronic filter is to decrease the amplitude of some frequency in relation to others. This change in amplitude is corrected by the AM demodulator.

Advantages of Frequency modulation

  1. When the frequency is modulated, the reception is not affected by the noise.
  2. Power consumption is much lesser when compared with Amplitude modulation.
  3. They have a large number of sidebands. Hence the efficiency is high.
  4. FM radio has a significantly larger bandwidth than the AM  radio.

Disadvantages of  Frequency Modulation

  1. The bandwidth is 10 times larger than AM transmission. Therefore, a wider frequency channel is required for transmission.
  2. Complex equipment is required  for sending and receiving the signal
  3. It is a complex process to modulate and demodulate a carrier wave with frequency modulation.
Please refer BYJU’S for more related topics like Transistor and Transistor as a switch. The transistor is an electronic device made using semiconductors. It is a device used to amplify or switch electronic signals. The most common form of a transistor is Bipolar Junction Transistor (BJT). The Bipolar Junction transistors are of two types- PNP transistor and NPN transistor. Both NPN and PNP transistors can be used as a switch.