What is Delta Modulation : Advantages and Disadvantages

Delta modulation is a digital signal encoding technique that transmits only the difference between successive signal samples rather than absolute values. It simplifies analog to digital conversion and reduces hardware complexity. Advantages include simple implementation and low bandwidth requirements, while disadvantages include slope overload distortion and granular noise.

Delta Modulation Block Diagram

It is also known as Delta Pulse Code Modulation or DPCM.

Unlike PCM, here the difference between m(t) and m^(t) is actually transmitted. Hence, it is known as delta modulation.

In delta modulation, a multi-bit difference value is stored or transmitted as per requirements.

Delta Modulation

As shown in the block diagram, we do not transmit D(t) but transmit only its polarity as determined at each sampling rate. Here P0(t) is obtained by multiplying input pulse train Pi(t) by +1 or by -1 depending on polarity only and not magnitude of D(t).

In Delta modulation, we have applied D(t) in place of m(t) as used in PCM. This kind of system is feasible to implement.

Benefits or Advantages of Delta Modulation

Following are the benefits or advantages of Delta Modulation:

1. In Delta modulation, the electronic circuit requirement for modulation at the transmitter and for demodulation at the receiver is substantially simpler compared to PCM.
2. In delta modulation, the amplitude of the speech signal does not exceed the maximum sinusoidal amplitude.
3. PCM has a sampling rate higher than the Nyquist rate. The encoded signal contains redundant information. DPCM can efficiently remove this redundancy.
4. DPCM needs less number of quantization levels, and hence, less number of bits are needed to represent them.
5. The signaling rate and bandwidth of DPCM or delta modulation are less than the PCM technique.

Drawbacks or Disadvantages of Delta Modulation

Following are the drawbacks or disadvantages of Delta Modulation:

1. If changes in the signal are less than the step size, then the modulator no longer follows the signal, thus producing a train of alternating positive and negative pulses.
2. The modulator overloads when the slope of the signal is too high.
3. High bit rate.
4. It requires a predictor circuit and hence it is very complex.
5. Its practical usage is limited.

Summary

Delta modulation digitizes signals by transmitting incremental changes between samples. Advantages include simplicity and efficiency, while disadvantages include noise and distortion issues.