COMMUNICATION SYSTEM FUNDAMENTALS
CHAPTER 2 MODULATION TECHNIQUES
2.1 Modulation and Demodulation Modulation is a process of changing one or more properties of the high frequency analog carrier signal either its amplitude, frequency or phase in proportion with the values of the low frequency information signal. Information Signal (Low Frequency)
Modulator
Modulated Signal (High Frequency)
Carrier Signal (High Frequency)
Figure 2.1: Modulation Process The analog or digital information signals combines with the carrier in the modulator to produce a high frequency modulated signal. Modulated signal is the carrier signal that has been changed by information signal. The modulation is performed in a transmitter while the demodulation is performed in a receiver.
Modulated Signal (High Frequency)
Demodulator
Demodulated Signal (Low Frequency)
Figure 2.2: Demodulation Process Demodulation is the reverse process of modulation where the information signal is extracted from the modulated signal in the demodulator. The demodulated signal is the original information signal.
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