# 15 FM_Problems-Indirect_FM.pdf

28. May 2023
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### 15 FM_Problems-Indirect_FM.pdf

• 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.