Noman Khan, a 4th semester Computer Science student at GSSCP College, presented on digital modulation techniques ASK, FSK, and PSK. ASK varies the amplitude of a carrier signal to transmit information, making it susceptible to noise interference. FSK varies the frequency, keeping amplitude and phase constant. PSK varies the phase of the carrier while keeping amplitude and frequency constant. PSK has become more common than ASK or FSK and requires less bandwidth than FSK.

1.  NAME > > > > > > > > > NOMAN KHAN
 CLASS NO > > > > > > > CS-14
 SEMESTER > > > > > > > > > > > 4TH
 DEPT > > > > > > > > >COMPUTER SCIENCE
 COLLEGE > > > > > > > > > GSSCP
 PRESENTATION TOPIC: ASK, FSK, PSK.

2.  ASK is implemented by changing the
amplitude of a carrier signal to reflect
amplitude levels in the digital signal.
 In this mechanism, both frequency and
phase remain constant while the
amplitude changes.

4.  ASK is highly susceptible to noise interference
 NOISE: Unintentional voltages introduced onto a line by
various sources such as Heat or Electromagnetic
Radiation from other sources
 These unintentional voltages combine with signal to
change the amplitude
 1 can be changed to 0 and 0 to 1
 Noise usually affects the amplitude, therefore ASK is
the modulating method, that is most affected by Noise

5.  It is the popular ASK technique.
 In OOK, one of the bit values is represented by
no voltage.

6.  The bandwidth ‘‘B’’ of ASK is proportional
to the signal rate ‘‘S’’.
B = (1+d)S
 “d” is due to modulation and filtering,
lies between 0 and 1.

7.  Frequency of signal is varied to represent
binary 1 or 0
 The frequency of the signal during each
bit duration is constant and depends on
the bit (0 or 1)
 Both peak amplitude and phase remains
constant

9. If the difference between the
two frequencies (f1 and f2) is 2f,
then the required BW B will be:
B = (1+d)x S +2f

10.  In phase shift keying, the phase of the carrier is
varied to represent two or more different signal
elements
 Both peak amplitude and frequency remain
constant as the phase changes
 Today, PSK is more common than ASK or FSK
 However, we will se the QAM, which combines
ASK and PSK
 The bandwidth requirement, B is:
B = (1+d)xS
