Modulation

What is modulation?

• The process of transmission of information signal using a high frequency signal.
• The info signal which is low frequency signal is called Modulating signal.
• The high frequency signal used to carry this signal is called Carrier signal.
• The modulation is achieved by either by changing the amplitude or the frequency of the carrier signal in accordance with the modulating signal.

What is the need for modulation?

The low frequency signal cannot travel a large distance, So there is need for modulation to transmit this signal to over a larger distance.

What are the types of modulation?

Based on the change in the characteristic of the carrier wave in accordance with the info signal There are three types of modulation.
Out of these three the two are most commercially used in the radio communication.

1. Amplitude Modulation:
AM works by modulating (varying) the amplitude of the carrier wave transmitted according to the information being sent, while the frequency remains constant.

2. Frequency Modulation:
FM works by varying the frequency of the carrier wave transmitted according to the information being sent, while the frequency remains constant.

AM vs FM:

Comparision AM vs FM	AM	FM
Stands for	AM stands for Amplitude Modulation	FM stands for Frequency Modulation
Origin	AM method of audio transmission was first successfully carried out in the mid 1870s.	FM radio was developed in the United states in the 1930s, mainly by Edwin Armstrong.
Modulating differences	In AM, a radio wave known as the "carrier" or "carrier wave" is modulated in amplitude by the signal that is to be transmitted. The frequency and phase remain the same.	In FM, a radio wave known as the "carrier" or "carrier wave" is modulated in frequency by the signal that is to be transmitted. The amplitude and phase remain the same.
Pros and cons	AM has poorer sound quality compared with FM, but is cheaper and can be transmitted over long distances. It has a lower bandwidth so it can have more stations available in any frequency range.	FM is less prone to interference than AM. However, FM signals are impacted by physical barriers. FM has better sound quality due to higher bandwidth.
Frequency Range	AM radio ranges from 535 to 1705 KHz.	FM radio ranges in a higher spectrum from 88 to 108 MHz.
Noise	AM is more susceptible to noise because noise affects amplitude, which is where information is "stored" in an AM signal.	FM is less susceptible to noise because information in an FM signal is transmitted through varying the frequency, and not the amplitude.