FM vs. PM

FM and PM are the two types of angle modulation. Angle Modulation is defined as the modulation where the frequency or phase of the carrier varies with the instantaneous value of the message signal. Angle modulation is a non-linear process, while Amplitude modulation is a linear process.

The essential elements of the modulation are the message signal and the carrier signal. A message signal contains information or a message. It is the original signal that needs to be transmitted from the transmitter to the receiver. The carrier signal and the message signal share the same medium of propagation. It is the same sinusoidal waveform signal as a message signal with greater frequency.

Frequency Modulation

When the frequency of the carrier wave varies with the amplitude of the message signal, it is defined as frequency modulation. It operates in the VHF (Very High Frequency) range from 88M Hz to 108M Hz and can easily travel upto long distances. FM is further categorized as, Wideband FM and Narrowband FM. Wideband Frequency Modulation operates in the wider frequency range, while Narrowband operates in the small frequency range. FM is used in various applications, such as radio broadcasting, telemetry, and magnetic tape recording systems.

Phase Modulation

The modulation process of FM and PM are the same except for the additional requirement of the integrator in FM. When the carrier wave phase varies with the amplitude of the message signal, it is defined as phase modulation. PM is considered one of the fastest types of modulation. Hence, it is widely used in applications that require high-speed transmission. PM is used in various applications, such as telephone communication, digital synthesizers, etc.

FM vs. PM

The differences between Frequency Modulation (FM) and Phase modulation (PM) are listed as follows:

Category	Frequency Modulation (FM)	Phase Modulation (PM)
Definition	When the frequency of the carrier wave varies with the amplitude of the message signal, the modulation process is known as frequency modulation.	When the phase of the carrier wave varies with the amplitude of the message signal, the modulation process is known as phase modulation.
Signal's quality	High	Low
SNR	Signal to noise ratio is better in FM than PM.	Signal to noise ratio is worst than FM.
Modulation and demodulation	Complex than PM	Easier than FM
Noise Immunity	Good	Less than FM
Varying element	Frequency	Phase
Conversion	FM can be converted to PM.	PM can be converted to FM.
Applications	Telemetry, radio broadcasting, magnetic tape recording, etc.	Telephone communication, radio communication, digital synthesizers, etc.

Let's discuss the concepts of the above differences in detail under Frequently Asked Questions.

FAQs

Let's discuss some Frequently Asked Questions.

Question 1: Which type of angle modulation has better noise immunity?

Answer: Noise immunity refers to the ability of a system to get less affected by the noise. Angle modulation is categorized as PM and FM. Among these, FM has better noise immunity. In FM, the frequency of the carrier signal varies with the amplitude of the message signal. The frequencies are less affected by external disturbances. Hence, FM has better noise immunity than PM.