Angle Modulation - Basic Concept

Angle modulation is a technique used to modify a carrier signal's phase or frequency in response to a modulating signal. The modulating signal contains the information that needs to be transmitted, and the carrier signal is used to carry this information over a communication channel.

In frequency modulation (FM), the frequency of the carrier signal is varied in proportion to the amplitude of the modulating signal. As the amplitude of the modulating signal changes, the frequency of the carrier signal changes correspondingly. This results in a signal that has a constantly varying frequency, which can be used to transmit information.

In phase modulation (PM), the phase of the carrier signal is varied in proportion to the amplitude of the modulating signal. As the amplitude of the modulating signal changes, the phase of the carrier signal changes correspondingly. This results in a signal that has a constantly varying phase, which can also be used to transmit information.

Both FM and PM are examples of angle modulation, as they modify the angle of the carrier signal in order to carry information. Angle modulation is widely used in telecommunications, including radio and television broadcasting, satellite communication, and digital communication systems.

The key advantage of angle modulation over amplitude modulation (AM) is that it is less susceptible to noise interference. The amplitude of a signal can easily be distorted by noise, while the frequency or phase of a signal is more resistant to distortion. This makes angle modulation a more reliable method of transmitting information over a communication channel.

Phase Modulation (PM)

In this type of modulation, the phase of the carrier signal is directly changed by the message signal. The phase modulated signal will have the form
𝑔𝑝𝑚(𝑡) = 𝐴𝑐𝑜𝑠[𝜔𝐶𝑡 + 𝑘𝑝(𝑡)]
where A is a constant, wc is the carrier frequency, m(t) is the message signal, and kp is a parameter that specifies how much change in the angle occurs for every unit of change of m(t). The phase and instantaneous frequency of this signal are
θ 𝑝𝑚(𝑡) = 𝜔𝐶𝑡 + 𝑘𝑝(𝑡)
𝜔𝑖(𝑡) == 𝜔𝐶 + 𝑘𝑝𝑑/𝑑𝑡(𝑚(𝑡)
So, the frequency of a PM signal is proportional to the derivative of the message signal.

Frequency Modulation (FM)

This type of modulation changes the frequency of the carrier (not the phase as in PM) directly with the message signal. The FM modulated signal is

𝑔𝑓𝑚 (𝑡) = 𝐴𝑐𝑜𝑠[𝜔𝐶 𝑡 + 𝑘𝑓 (𝑡) ∫𝑡 𝑚(⍺)𝑑⍺ ] 

where kf is a parameter that specifies how much change in the frequency occurs for every unit change of m(t). The phase and instantaneous frequency of this FM are

θ𝑓𝑚 (𝑡) = 𝜔𝐶 𝑡 + 𝑘𝑓 (𝑡) ∫−∞𝑡 𝑚(⍺)𝑑⍺

𝜔 (𝑡) = 𝜔 𝑡 + 𝑘 𝑑𝑖 [ ∫ 𝑡 𝑚(⍺)𝑑⍺]

Relation between PM and FM 

Relation between PM and FM
Relation between PM and FM



People also ask

What is the basic concept of angle modulation?
What are the 2 types of angle modulation?
What are the four 4 applications of angle modulation?
Why do we need angle modulation?