Modulation: Process of Frequency Translation
PULSE MODULATION TECHNIQUES
INTRODUCTION
• Modulation is the process of frequency translation in which any one parameter(Amplitude, frequency or phase) of high frequency carrier signal is varied in accordance with instantaneous value of low frequency modulating signal.
• Modulation is either analog or digital.
INTRODUCTION
• Many signals in modern communication systems are digital
• Additionally, analog signals are transmitted digitally
• Digitizing a signal results in reduced distortion and improvement in signal-to-noise ratios
INTRODUCTION
• A digital signal is superior to an analog signal because it is more robust to noise and can easily be recovered, corrected and amplified. For this reason, the tendency today is to change an analog signal to digital data.
• The process of transmitting signals in the form of pulses (discontinuous signals) by using special techniques.
PULSE MODULATION INCLUDES
• Pulse Amplitude Modulation
• Pulse Width Modulation
• Pulse Position Modulation
• Pulse Code Modulation
• Delta Modulation
PULSE MODULATION
Sampling
• The process of transmitting signals in the form of pulses (discontinuous signals) by using special techniques.
• The signal is sampled at regular intervals such that each sample is propotional to the amplitude of signal at that instant.This technique is called “sampling”.
• Sampling is common in all pulse modulation techniques.
Sampling
• Analog signal is sampled every TS secs.
• Ts is referred to as the sampling interval.
• fs = 1/Ts is called the sampling rate or sampling frequency.
• There are 3 sampling methods:
• Ideal - an impulse at each sampling instant
• Natural - a pulse of short width with varying amplitude
• Flat top - sample and hold, like natural but with single amplitude value
Three different sampling methods for PCM
Sampling Rate
• Nyquist showed that it is possible to reconstruct a band-limited signal from periodic samples, as long as
INTRODUCTION
• Modulation is the process of frequency translation in which any one parameter(Amplitude, frequency or phase) of high frequency carrier signal is varied in accordance with instantaneous value of low frequency modulating signal.
• Modulation is either analog or digital.
INTRODUCTION
• Many signals in modern communication systems are digital
• Additionally, analog signals are transmitted digitally
• Digitizing a signal results in reduced distortion and improvement in signal-to-noise ratios
INTRODUCTION
• A digital signal is superior to an analog signal because it is more robust to noise and can easily be recovered, corrected and amplified. For this reason, the tendency today is to change an analog signal to digital data.
• The process of transmitting signals in the form of pulses (discontinuous signals) by using special techniques.
PULSE MODULATION INCLUDES
• Pulse Amplitude Modulation
• Pulse Width Modulation
• Pulse Position Modulation
• Pulse Code Modulation
• Delta Modulation
PULSE MODULATION
Sampling
• The process of transmitting signals in the form of pulses (discontinuous signals) by using special techniques.
• The signal is sampled at regular intervals such that each sample is propotional to the amplitude of signal at that instant.This technique is called “sampling”.
• Sampling is common in all pulse modulation techniques.
Sampling
• Analog signal is sampled every TS secs.
• Ts is referred to as the sampling interval.
• fs = 1/Ts is called the sampling rate or sampling frequency.
• There are 3 sampling methods:
• Ideal - an impulse at each sampling instant
• Natural - a pulse of short width with varying amplitude
• Flat top - sample and hold, like natural but with single amplitude value
Three different sampling methods for PCM
Sampling Rate
• Nyquist showed that it is possible to reconstruct a band-limited signal from periodic samples, as long as