A series of regularly recurring pulses is made to vary in amplitude, duration, shape, or time as a function of the modulating signal
Used to transmit both analog and digital information, such as voice and data.The analog signal is sampled, digitized and encoded into a digital pulse stream.If the signal is already is in digital form, it may be encoded into a digital pulse train.
Initially invented by A.H. Reeves in 1937
Pulse Code Modulation is the representation of a signal by a series of digital pulses firstly by sampling the signal, quantizing it and then encoding it.
The PCM signal itself is a succession of discrete, numerically encoded binary values derived from digitizing the analog signal.
PCM Steps
Sampling
– PAM
– Nyquist sampling rate theorem
Quantizing
– Uniform and non uniform
– A- Law and m- Law
Encoding
– Binary sequences.
Pulse Modulation Examples
Pulse-amplitude modulation (PAM)
Delta modulation (DM)
Pulse-width modulation (PWM)
Pulse-code modulation (PCM)
Pulse-position modulation (PPM)
ADVANTAGES OF PULSE MODULATION
Noise immunity
Inexpensive digital circuitry
Can be time-division multiplexed with other pulse modulated signals
Transmission distance is increased through the use of regenerative repeaters
Digital pulse streams can be stored.
Error detection and correction is easily implemented
DISADVANTAGES OF PULSE MODULATION
Require a much greater bandwidth to transmit and receive than its analog counterpart
Special encoding and decoding techniques may be necessary to increase transmission rates making the pulse stream more difficult to recover.
May require precise synchronization of clocks between the transmitting and the receiving stations
Used to transmit both analog and digital information, such as voice and data.The analog signal is sampled, digitized and encoded into a digital pulse stream.If the signal is already is in digital form, it may be encoded into a digital pulse train.
Initially invented by A.H. Reeves in 1937
Pulse Code Modulation is the representation of a signal by a series of digital pulses firstly by sampling the signal, quantizing it and then encoding it.
The PCM signal itself is a succession of discrete, numerically encoded binary values derived from digitizing the analog signal.
PCM Steps
Sampling
– PAM
– Nyquist sampling rate theorem
Quantizing
– Uniform and non uniform
– A- Law and m- Law
Encoding
– Binary sequences.
Pulse Modulation Examples
Pulse-amplitude modulation (PAM)
Delta modulation (DM)
Pulse-width modulation (PWM)
Pulse-code modulation (PCM)
Pulse-position modulation (PPM)
ADVANTAGES OF PULSE MODULATION
Noise immunity
Inexpensive digital circuitry
Can be time-division multiplexed with other pulse modulated signals
Transmission distance is increased through the use of regenerative repeaters
Digital pulse streams can be stored.
Error detection and correction is easily implemented
DISADVANTAGES OF PULSE MODULATION
Require a much greater bandwidth to transmit and receive than its analog counterpart
Special encoding and decoding techniques may be necessary to increase transmission rates making the pulse stream more difficult to recover.
May require precise synchronization of clocks between the transmitting and the receiving stations