Problems with delta modulation.

1] The step size in delta modulation as well as sampling rate must be properly change

2] Assuming that i/p signal does not changes too rapidly from sample to sample, the stair case approximation remains within ? of the i/p s/g

3] Increasing step size increases quantitization noise. There are two major sources of quantitization noise in delta modulation.

a] Slope overload

b] Granular noise.

a] Slope overload : When the slope of analog s/g is greater than the delta modulator can maintain, it is called slope overload distortion. It is more prevalent in analog s/g that have steep slope or whose amplitude levels vary rapidly.

b] Granular noise: When the i/p analog s/g has relatively constant amplitude, the reconstructed has variations that were not present in the original s/g. this is called granular noise. Granular noise is more prevalent in analog s/g that have gradual slopes and whose amplitude levels vary only by a small amount. It is analogous to quantization noise in conventional PCM.

Other disadvantages of DM :

• Higher bit rate requirement, For same quantity of transmission, the bit rate needed for DM is much higher than in the code modulation.

• The bandwidth requirement is higher than PCM.

Remedy or disadvantages of DM :

• A decrease in the magnitude of the minimum size is required.

• A small resolution is required.

• It reduces Granular noise.

• An increase in the magnitude of the minimum step size is required.

• An increase in clock frequency.

• A large resolution is required.

• It reduces slope overload noise.