Question

5. Answer the following questions about angle modulation systems. a. Explain threshold effect in FM systems, and how and how much this effect can be circumvented by threshold extension. (5 points). b. What is the objective of pre-emphasis and de-emphasis filtering in FM systems ? How much the output signal-to-noise ratio can be improved with the pre-emphasis and de-emphasis filtering? (5 points).

Answer 1

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1 a) Threshold effect in FH; * EM_Horshold is usually defirudos Corsvier-to-Noise_gatio at which derresulated Signal = 60 - Noise_satio falls 1dB_bihan the liñcan relationship. This is effect predelad in an FM receive when nove limits 'desired information Signal. It occurs at about lode, as earlies stated in * conventional EM reception is characterized Liye threshold levels above which op signal- -to-noise ratio increass_linearly with the received Carrier level, and below this level there is a very sapid deterioration of sinho as received caskey_level falls. This thresbod. fend therefore delines mazurom operation sange of EM Coromunication system. The determined threshold value of less is lodbok about 55 MHZ Scanned with CamScanner