1 Communication System Communication System Ass. Prof. Ibrar Ullah BSc (Electrical Engineering) UET Peshawar MSc (Communication & Electronics Engineering) UET Peshawar PhD (In Progress) Electronics Engineering (Specialization in Wireless Communication) MAJU Islamabad E-Mail: [email protected]Ph: 03339051548 (0830 to 1300 hrs)
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Communication System Communication System Ass. Prof. Ibrar Ullah
= instantaneous angular frequency (rad/sec) = instantaneous phase (radians)
)(t
iiw
A carrier can be represented as:
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Phase Modulation (PM)
The instantaneous phase of a harmonic carrier signal is varied in such a way that the instantaneous phase deviation i.e. the difference between the instantaneous phase and that of the carrier signal is linearly related to the size of the modulating signal at a given instant of time.
In PM the angle varies linearly with m(t))(t
)(ti
PM
)(twi
)(tmktw pc
)(cos tmktwA pc
dt
tdmkwc
dt
tmktwd
dt
tdp
pci )()()(
Kp is the phase deviation sensitivity (rad/Volt)
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Frequency Modulation (PM)
The frequency of a harmonic carrier signal is varied in such a way that the instantaneous frequency deviation i.e. the difference between the instantaneous frequency and the carrier frequency is linearly related to the size of the modulating signal at a given instant of time.
If wi is varied linearly with the modulating signal we have FM and instantaneous frequency wi is given by: