Modulation

Modulation

• Modulation is the addition of information to an electronic or optical carrier signal. 
• A carrier signal is one with a steady waveform -- amplitude and frequency. 
• Information can be added to the carrier by varying its amplitude, frequency, phase, polarization and even quantum-level phenomena like spin. 

	AM	FM
Stands for	AM stands for Amplitude Modulation	FM stands for Frequency Modulation
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.	FM is less prone to interference than AM. FM has better sound quality due to higher bandwidth.
Frequency Range	AM radio ranges from 535 to 1705 KHz (OR) Up to 1200 bits per second.	FM radio ranges in a higher spectrum from 88 to 108 MHz. (OR) 1200 to 2400 bits per second.
Complexity	Transmitter and receiver are simple but syncronization is needed in case of SSBSC AM carrier.	Tranmitter and reciver are more complex as variation of modulating signal has to beconverted and detected from corresponding variation in frequencies.
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.