Slope Overload Distortion and Granular Noise (Idle Noise)
Slope overload distortion and granular noise (idle noise) are the two major drawbacks of delta modulation.So here we are going to discuss both of these drawbacks of delta modulation-
Slope Overload Distortion and Granular Noise (Idle Noise) Video
Slope Overload Distortion
This distortion is caused due to large dynamic range of the input signal. Because When the input signal rising rate is very high, then the staircase signal cannot approximate it correctly.So it creates large error between the original input signal X(t) and the staircase approximated signal. This noise (error) is known as slope overload distortion.
Solution of Slope Overload Distortion
The step size must be increased, when the input signal has high Slope. Therefore we use Adaptive Delta Modulation technique where the step size is increased when large dynamic variations are present in the signal X(t), to reduce the quantization errors present in delta modulation.Granular Noise (Idle Noise)
This noise (error) occurs when the step size is too large in comparison to small variations in the input signal.So because of large step size in comparison to the signal having very small variations or constant; error is introduced between the input signal and the approximated staircases signal. This error is known as the granular or idle noise.
Solution of the Granular Noise (Idle Noise)
We can overcome the problem of granular noise by keeping the step size small.We use this in adaptive delta modulation technique, where the step size is reduced as per the small signal value to reduce the difference between the signal and its approximation (staircase waveform).
Now observe the image shown below-
This image shows the quantisation errors in Delta modulation (slope overload distortion and granular noise).
Slope Overload Distortion and Granular Noise in Delta Modulation |
As you can see in the image that the shaded part in red color shows the slope overload distortion present in Delta modulation while the shaded region in green color represents the granular noise which is also known as idle noise. Both of these errors (noises) are quantization errors and are present in Delta modulation.