Signals and Systems - Electrical Engineering

734 CHAPTER 12: Applications of Discrete-Time Signals and Systems

0 1 2 3 4 5 6 7

− 1

−0.5

0

0.5

1

(a)

(c)

(d)

(b)

t (sec)

m

( 1

t),

x^1

(t

)

0 1 2 3 4 5 6 7

−1

−0.5

0

0.5

1

t (sec)

m

( 2

t),

x^2

(t)

m

( 1

t),

y^1

(t)

m

( 2

t),

y^2

(t

)

0 1 2 3 4 5 6 7

−1

−0.5

0

0.5

1

t (sec)

0 1 2 3 4 5 6 7

−1

−0.5

0

0.5

1

t (sec)

FIGURE 12.10

Pulse signals (continuous line)m 1 (t)andm 2 (t)corresponding to binary sequence 01001101. (a, c), ASK signals

x 1 (t)=m 1 (t)cos( 4 πt)andx 2 (t)=m 2 (t)cos( 4 πt)in dashed lines. (b, d) In dashed lines the FSK signalsy 1 (t)

andy 2 (t)equalcos( 4 πt)whenm 1 (t),m 2 (t)are 1 andcos( 8 πt)whenm 2 (t)is 0 or− 1.