What is Phase Modulation : Advantages, Disadvantages, and Applications

In our day by day life, we can see many entertainment media sources for communication such as radio, TV, newspaper, mobile phone, internet, and with a lot of people. Communication can be defined as; it is the procedure of two ways or one-way communication of information from one place to another or one person to another person. For example, if we take a basic communication system it comprises of three components namely transmitter (Tx), receiver (Rx), and a communication channel in between them. The designing of a transmitter and a receiver in a communication system can be built with a set of electronic circuits. A transmitter converts the data into a signal to transmit over a communication medium. A receiver is used to change the signal reverse to the original data. The channel is the medium that transmits the signal from one place to another. If we want to transmit a signal from one place to another, then we need to make the signal stronger. Once the signal strengthening process is done then the signal can transmit to a long distance. This is known as the modulation process.

What is Phase Modulation?

The term PM or phase modulation definition is a type of modulation intended for transmitting communication signals. It changes message signal in accordance with the carrier signal due to differences in the immediate phase. This modulation is the combination of two principal forms such as frequency modulation and angle modulation.

The carrier signal’s phase is modulated to follow the amplitude of the message signal. Both pinnacle amplitude, as well as the carrier signal’s frequency, is maintained stable, although when the message signal’s amplitude changes, then the carrier signals phase also changes. Phase Modulation can be defined as the Phase of the carrier (Ø) signal is varied proportional to (in accordance with) the Amplitude of the input modulating signal.

Phase Modulation Waveforms
Phase Modulation Waveforms

PM Equation:

V = A sin [ wct + Ø ]

V = A sin [ wct + mp sin wmt ]

A = Amplitude of PM signal


mp = Modulation Index of PM

wm = 2π fm wc = 2π fc

V = A sin [2π fct + mp sin2π fmt]

The phase modulation diagram is shown above. The carrier phase deviation will be more if the input signal amplitude increases and vice versa. When the input amplitude increases (+ve slope) the carrier undergoes phase lead. When the input amplitude decreases (-ve slope) the carrier undergoes phase lag.

Therefore as the input amplitude increases, the magnitude of the phase lead also goes on increasing from instant to instant. For example, if the phase lead was 30 degrees at t =1 sec, the phase lead increases to 35 degrees at t = 1.1 sec and so on. Increase in phase lead is equivalent to an increase in frequency.

Similarly, as the input amplitude decreases, the magnitude of the phase lag also goes on increasing from instant to instant. For example, if the phase lag was 30 degrees at t =1 sec, the phase lag increases to 35 degrees at t = 1.1 sec and so on. Increase in phase lag is equivalent to decrease frequency.
Therefore phase modulation waveform will be similar to FM waveform in all aspects.

Forms of Phase Modulation

Even though PM is used in analog transmissions, it is widely used as a digital type of modulation wherever it controls among dissimilar phases, which is known as PSK (phase shift keying), and there are several forms are available in this.

It is still possible to merge PSK (phase shift keying) & AK (amplitude keying) in a type of modulation is also called as QAM (quadrature amplitude modulation). Some of the forms of FM that are used are listed below.

  • Phase Modulation (PM)
  • Phase Shift Keying (PSK)
  • Binary Phase Shift Keying (BPSK)
  • Quadrature Phase Shift Keying (QPSK)
  • 8-Point Phase Shift Keying (8 PSK)
  • 16-Point Phase Shift Keying (16 PSK)
  • Offset Phase Shift Keying (OPSK)

The above showed list is some of the forms of PM which are frequently used in the applications of radio.

Advantages and Disadvantages of Phase Modulation

The advantages of phase modulation include the following.

  • Phase modulation (PM) is a simple contrasted to Frequency modulation (FM).
  • It is used to find out the velocity of a target by removing Doppler data. This needs constant carrier which is achievable during phase modulation however not in FM (frequency modulation).
  • The main benefit of this modulation is signal modulation because it permits computer for communicating on high-speed using a telephone system.
  • When the information is being transmitted without intrusion then the speed rates can be observed.
  • And one more advantage of PM (phase modulation) is improved immunity toward the noise.

The disadvantages of phase modulation include the following.

  • Phase modulation needs two signals by a phase variation among them. Through this, both the two patterns are required like a reference as well as a signal.
  • This type of modulation requires hardware which obtains more complex due to its conversion technique.
  • Phase ambiguity arrives if we exceed index pi radian of modulation (1800).
  • Phase modulation index can be enhanced by employing frequency multiplier.

Phase Modulation Applications

The applications of phase modulation include the following.

  • This modulation is very useful in radio waves transmission, and it is an essential element in several digital transmission coding schemes.
  • Phase modulation is widely used for transmitting radio waves and is an integral element of many digital transmission coding schemes that support an ample range of wireless technologies such as GSM, Satellite television, and Wi-Fi.
  • Phase modulation is used in digital synthesizers for generating waveform and signal
  • PM is used for signal and waveform generation in digital synthesizers like Yamaha DX7 for phase modulation synthesis implementation, and Casio CZ for sound synthesis which is known as phase distortion.

Thus, this is all about what is phase modulation, PM equation, a phase modulation graph. From the above information finally, we can conclude that PM is a type of modulation which denotes data as differences in the immediate phase of a carrier wave. Variation in phase based on the low-frequency will provide phase modulation. Here is a question for you, what is a self-phase modulation?


  1. Metjitivi upora says:

    I need a good description about modulation.

    1. Tarun Agarwal says:

      Hi Metjitivi upora
      Please refer to our blog once, there are many articles on the modulation concept.

    2. Tarun Agarwal says:

      Hi Metjitivi upora
      Please refer our blog once to know more about modulation concepts.

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