FM

1. Bessel table (n vs β)

2. Problems
• Given the angle modulated signal
S(t) 10sin[2108
t  200cos2103
t]
• What is the bandwidth?

3. Problems
• Given the angle modulated signal
S(t) 10sin[2108
t  200cos2103
t]
• What is the bandwidth?
• Modulation index is 200
• Based on Carson rule
BW  2(f  fm )  2 fm (1 )

4. Problems
• Given the angle modulated signal
S(t) 10sin[2108
t  200cos2103
t]
• What is the bandwidth?
• Modulation index is 200
• Based on Carson rule
BW  2(f  fm )  2 fm (1 )
BW  2(f  fm )  2 fm (1 )  402KHz

5. Problems
• A block diagram of the Armstrong FM transmitter is shown below.
Compute the maximum frequency deviation Δf at the output of the
transmitter and the carrier frequency if f1=200 KHz and fLO=10.8 MHz,
Δf1=25 Hz,n1=64,n2=48.

6. Problems
• Δf=Δf1xn1xn2=76.8 KHz
f1=200 KHz and fLO=10.8 MHz, Δf1=25 Hz,n1=64,n2=48.

7. Problems
• Δf=Δf1xn1xn2=76.8 KHz
• f2=n1xf1=12.8 MHz
f1=200 KHz and fLO=10.8 MHz, Δf1=25 Hz,n1=64,n2=48.

8. Problems
• Δf=Δf1xn1xn2=76.8 KHz
• f2=n1xf1=12.8 MHz
• f3=f2±fLO=23.6 MHz or 2 MHz
f1=200 KHz and fLO=10.8 MHz, Δf1=25 Hz,n1=64,n2=48.

9. Problems
• Δf=Δf1xn1xn2=76.8 KHz
• f2=n1xf1=12.8 MHz
• f3=f2±fLO=23.6 MHz or 2 MHz
• fc=n2xf3=1132.8 MHz when f3=23.6 MHz
• fc=n2xf3=96 MHz when f3=2 MHz
f1=200 KHz and fLO=10.8 MHz, Δf1=25 Hz,n1=64,n2=48.