Delta Modulation

Delta Modulation :-

A delta modulation (DM or Δ-modulation) is an analog-to-digital and digital-to-analog signal conversion technique used for transmission of voice information where quality is not of primary importance.

Diagram :- 

Waveform  :-

What is Delta Modulation  :-

# Delta modulation has its roots in Differential pulse code modulation method. It is also known as the simplified form of Differential pulse code modulation. Delta modulation is a scheme to permit the use of a simple quantizing strategy for constructing the encoded signals which are over-sampled purposely, to increase the correlation between adjacent samples of the signal, as seen in Differential pulse code modulation method.

# This modulation is also called one bitter two-level version of Differential pulse code modulation. It provides a staircase approximation of over-sampled base-band signal. Here, the difference between the present sample and previous approximated sample is quantized into two levels i.e. ±δ.

# If the previous approximation is below the present sample value, then the error is quantized by +δ. If the approximation is above the present sample value then the error is quantized by -δ.

Applications  :- 

# Some of the applications of this modulation are given below –

# Voice transmission systems such as telephone and radio communications highly prefer this Modulation technique.

Delta Modulation is most useful in systems where timely data delivery at the receiver is more important than the data quality.

# This modulation is applied to ECG waveform for database reduction and real-time signal processing.

For analog-to-PCM encoding, this Modulation method is used.

Delta Modulation is applied in television systems.

Advantages :-

# Advantages of Delta Modulation

Some of the advantages of Delta Modulation in comparison with other digital modulation techniques are given below-

# It was found that at lower bit rates Delta Modulation is better than the standard PCM. In a Delta modulation system, operating on voice signals under optimum conditions, the SNR is increased by 9dB by doubling the bit rate.

# The increase of SNR with bit rate is much more dramatic for Pulse code modulation than for Delta modulation. Therefore this modulation is recommended only in certain special circumstances such as when it is necessary to reduce the bit rate below 40 kilobytes per second and limited voice quality is tolerable.

# This modulation method is used if extreme circuit simplicity is of over-riding importance and the accompanying use of a high-bit rate is acceptable.

Delta modulation works with lower channel bandwidth. This makes the system cost-effective and simple to implement. The feedback mechanism present in this Modulation system ensures the quick and robust delivery of data bits.

Drawbacks :-

# Delta modulation has two major drawbacks that are:-

# Slope overload distortion. This distortion arises because of large dynamic range of input signal. ...

# Granular noise. Granular noise occurs when step size is too large compared to small variations in the input signal.