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.
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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.
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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?
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Source: elprocus
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