UNIT 10

Comparative Study

10.1 Comparative study of SNR in AM, FM and PM System

Signal to Noise Ratio

Signal-to-Noise Ratio (SNR) is the ratio of the signal power to noise power. The higher the value of SNR, the greater will be the quality of the received output.

Figure of Merit

The ratio of output SNR and input SNR can be termed as Figure of Merit. It is denoted by F. It describes the performance of a device.

F=(SNR)O(SNR)IF=(SNR)O(SNR)I

SNR for AM

Consider the following receiver model of AM system to analyze noise.

SNR for FM

SNR for PM

Numericals:

2. 

10.2 Use of emphasis Circuit in FM for SNR optimization

Use of Pre-emphasis and DE-emphasis circuit:

De-emphasis network                          Pre-emphasis network

The improvement in signal-to-noise ratio which results from pre-emphasis depends on the frequency dependence of the PSD of the baseband signal.

References:

1. Communication system by Bruce carison . TMH.
2. Electronic Communication system by Kennedy IV Edition. TMH.
3. Electronic Communication system by Roddey & Coolen, Pearson.
4. Telecommunication system Engg. By Freeman John Wiley
5. Communication system by Haykin,Wiley