Am modulation ,Fm modulation ,Pm modulation  Definition or Advantage or Disadvantage

Amplitude modulation

Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave.

 In amplitude modulation, the amplitude (signal strength) of the carrier wave is varied in proportion to that of the message signal being transmitted.

 The message signal is, for example, a function of the sound to be reproduced by a loudspeaker, or the light intensity of pixels of a television screen.

This technique contrasts with frequency modulation, in which the frequency of the carrier signal is varied, and phase modulation, in which its phase is varied.

AM was the earliest modulation method used to transmit voice by radio. It was developed during the first quarter of the 20th century beginning with Lindell de Moura and Reginald Fessenden's radiotelephone experiments in 1900.

 [1] It remains in use today in many forms of communication; for Example it is used in portable two-way radios, VHF aircraft radio, citizens band radio, and in computer modems in the form of QAM.

 AM is often used to refer to mediumwave AM radio broadcasting.

This page on amplitude modulation(AM) vs frequency modulation(FM) vs phase modulation(PM) describes difference between amplitude modulation, frequency modulation and phase modulation types.

All these modulation types are analog modulation techniques.

All the modulation types are used to transmit information from one place to the distant place.

Mostly this technique are employed in wireless communication.

For any analog modulator type, there are two inputs and one output.

The two inputs are modulating signal (i.e. analog information to be transmitted) and carrier signal waveform. The output is referred as modulated waveform.

Advantages, disadvantages and applications of AM

Different amplitude modulation techniques have their own advantages and disadvantages as mentioned below:

• DSB-SC: It has lower power consumption and it is simple technique of modulation. But it is complex in detection at AM receiver. It is used in analog TV transmission systems to transmit color information.

• SSB-SC: It is used for efficient management of spectrum. But generation of SSB modulation is difficult and it is complex in detection at receiver. It is used for 2-way radio FDM.

• VSB-SC: It is compromise between DSB and SSB types. But demodulation system is complex. Bandwidth of VSB-SC is 25% higher than SSB-SC. It is used for analog TV broadcast systems.

Frequency Modulation(FM)

Frequency Modulation(FM) is the modulation technique in which carrier frequency varies based on analog baseband information signal to be transmitted using wireless device.

Frequency modulation is considered to be superior compare to the Amplitude modulation due to better noise immunity and its ability to reject the interfering signals due to the capture effect.

Advantages, disadvantages and applications of FM

• Advantages: Increased immunity to noise.

• Disadvantage: Requires larger bandwidth.

• Application: Radio Broadcasting, Direct Satellite Broadcasting.

Phase Modulation(PM)

Phase Modulation(PM) is the modulation technique in which carrier phase varies based on analog baseband information signal to be transmitted using wireless device.

If a constant amplitude as well as constant frequency sine wave carrier is given to the phase shifter the output is phase modulated signal.

Phase modulation is referred as indirect frequency modulation due to the fact that phase modulation produces frequency modulation.

The effect of variation in amount of phase shift is proportional to change in the carrier frequency.

Advantages, disadvantages and applications of PM

• Advantages: Increased immunity to noise.

• Disadvantages: More complex hardware at receiver.

• Applications: Used in data communication systems.

By:Engr Israr Ahmad Tanoli Schneider Electric Pakistan