Question

Design a narrow band FM modulator and demodulator units based on the following rules. By using your design, assume that you are planning to broadcast music and listen to it. Design Principles 1. Bandwidth of the message signal is 4kHz. II. Carrier frequency is 50MHz III. Allowable maximum frequency deviation in the system is 50kHz.

a) Determine the values of elements (if any; R. C, and L) used in the circuits.

b) In case of noise (N. = 2x10-8W.Hz-1) added to the modulated signal, What can be the SNR at i/p stage of demodulator? What can be the SNR at o/p stage of demodulator?

Answer 1

of = 50kHZ, CM modulator & demodelator ² Fm modulator 1 1 R Vol VICH c I' fe = 50mHz. fon = UKH 2 (B) ㅗ << Rc cu fo ㅗ fm 0.02 MS <<R c.25ms. b) No = 2X10 w/Hz - 8 3 Noise Power Nox B = 2X10 X u X 10 = 8 x 10 Watt. -5 (Pn) let signal Silly = coscomt cascomt = 1. Cosa font signal Power (Psi) ♡ 0.5 Watt 2 (SNR). I lolog (818) = 37.95 dB Psi Pro 0.5 88105 6250

2 * figure of merit of fm = Now (SNR). (SNP) i 3 B2 so 12.5 234.375 fom 2 (SNR) (SNR). 6250 236.375 26.66 11 U 11 234.375 lolog (SNR) i = 14 «26 of B