This is given by the dashed lines used to emphasize the waveforms in the transition regions.
82 CHAPTER TWO
I(t)
Q(t)
FIGURE 2.52 Phase changes for BFSK with 1.
As we can see, the instantaneous phase reversals that occurred at the bit boundaries have slowed
down. For this example, the Q-channel doesn??™t have the opportunity to go to zero at the bit boundaries.
Also, we see the I-channel doesn??™t reach its maximum value of 1 at those corresponding time
instances. We see there is an interchannel relationship or cross-correlation property between the complex
signal components.
Continuing along the lines of using the complex envelope theory in presenting the FSK waveform,
we now discuss the receiver block diagram (see Fig. 2.54).
An alternative and simplified representation is obtained by carrying out the mathematical operations
shown below. The instantaneous frequency variation is the time derivative of the phase signal.
(2.36) wi(t)
d
dt c tan 1QQ
I Rd
t
t
t
Data
I(t)
Q(t)
+1
??“1
+1
??“1
+1
??“1
Tb
Tb
Tb
FIGURE 2.53 Filtered complex envelope of BFSK with 1
(2.37)
Using the above equations, it is easy to draw the alternative block diagram of a frequency discriminator
(see Fig.
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