Instituto Tecnológico y de Estudios Superiores de MonterreyCampus Puebla

Analysis of Signals and SystemsDr. David Antonio Torres

Final Proyect“Frequency Division Multiplexing (FDM) and the Single Sideband

(SSB) techniques in Amplitude-Modulation (AM) Systems.”

José Luis Arellano Camacho A01323890

February 11th, 2015

Frequency Division Multiplexing (FDM) and the Single Sideband (SSB) techniques in Amplitude-Modulation (AM) Systems.

ObjetiveThe student will develop a Scilab script file to demonstrate the Frequency Division Multiplexing (FDM) and the Single Sideband (SSB) techniques in Amplitude-Modulation (AM) Systems.

Introduction Amplitude Modulation (AM) is the method that consist in using the information signal to modulate the amplitude of another signal, which is usually of higher frequency.Single-Sideband Modulation (SSB) Frequency Division Multiplexing (FDM) is used when the bandwidth of the cannel is larger than the bandwidth of an information channel. To recover the individual channels in the demultiplexing procces requires two basics steps:

1. Band-Pass Filtering to extract the modulated signal corresponding to a specific channel

2. Demodulation to recover and retain the original signal.

BodyOne method to retain the Upper Sidebands of an information signal lis through ideal high pass filtering. The carrier frecuencies of the sinusoidal modulator W A ,W B∧W cmust be chosen so that he signals X A (t ) , XB ( t )∧X c (t )do not overlap to each other. The sinusoidal demodulator must recover one signal of the group of signals.

We can obtain a BPF by shifting the frecuency response of a LPF by two deltas, which is the same as multiplying in time domain the sinc fuction and a cosine function. It is neccesary to implement the modulation and the demodulation as multiplication of signals and the filtering of signals as convolution, therefore the filters must be characterized by their unite-impulse response.

Group A, recover signal XC( t), upper sidebands.

Plots

1. Plot the spectrum of the filter that retains the sidebands.

2. Plot the spectrum of the three signals that have been treated with FDM and SSB (the plot must show three spectra together, both positive and negative frequencies).

3. Plot the spectrum of the BPF and LPF that demultiplex one of the three signals (these filters are part of the demultiplexor of the FDM).

4. Plot the spectrum of the recovered signal.

Conclusions

References