Adaptive delta modulation is a technique that makes the step size adaptive to variations in the input signal in order to overcome quantization errors from slope overload and granular noise. It works by increasing the step size in sections of the signal where it is changing rapidly and decreasing it where the signal is changing slowly. The transmitter uses adaptive logic to continuously or discretely change the step size based on the one-bit quantizer output. The receiver reproduces the step size and uses an accumulator and low-pass filter to reconstruct the original signal from the transmitted bit sequence and adaptively changing step sizes. Adaptive delta modulation provides better signal-to-noise ratio, wider dynamic range, and more efficient bandwidth utilization than regular delta modulation.

1. Adaptive Delta Modulation
Unit -2
Presented by
Mrs. M.P.Sasirekha

2. Reasons to use Adaptive Delta
Modulation
• In order to overcome the quantization errors due to slope
overload and granular noise, the step size (Δ) is made adaptive
to variations in the input signal x(t).
• Particularly in the step segment of the signal x(t), the step size
is increased. And the step is decreased when the input is
varying slowly.
• This method is known as Adaptive Delta Modulation (ADM).
• The adaptive delta modulators can take continuous changes in
step size or discrete changes in step size.

3. Transmitter

4. Transmitter
• The logic for step size control is added in the diagram.
• The step size increases or decreases according to a specified
rule depending on one bit quantizer output.
• For an example, if one bit quantizer output is high (i.e., 1), then
step size may be doubled for next sample.
• If one bit quantizer output is low, then step size may be reduced
by one step.
• Fig.2 shows the staircase waveforms of adaptive delta
modulator and sequence of bits to be transmitted.

5. Transmitter

6. Receiver

7. Receiver
• The receiver has two portions. The first portion produces the
step size from each incoming bit. Exactly the same process is
followed as that in transmitter.
• The previous input and present input decide the step size.
• It is then applied to the second portion i.e., an accumulator
which builds up staircase waveform.
• The low pass filter then smoothens out the staircase waveform
to reconstruct the original signal.

8. Advantages of Adaptive Delta Modulation
• Adaptive delta modulation has certain advantages over delta
modulation as under :
1.The signal to noise ratio of ADM is better than that of DM
because of the reduction in slope overload distortion and idle
noise.
2.Because of the variable step size , the dynamic range of
ADM is wider than DM.
3.Utilization of bandwidth is better in ADM than DM.

10. Thank you