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Delta Modulation My Part

Delta modulation transmits one bit per sample by comparing the present sample value to the previous one and transmitting whether the amplitude increased or decreased. It approximates the input signal as a step signal with a fixed step size, leading to two major drawbacks: slope overload distortion from the modulator's inability to vary step size for high signal slopes, and granular noise from large step size changes compared to small input variations.

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Zeenat Khokhar
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39 views9 pages

Delta Modulation My Part

Delta modulation transmits one bit per sample by comparing the present sample value to the previous one and transmitting whether the amplitude increased or decreased. It approximates the input signal as a step signal with a fixed step size, leading to two major drawbacks: slope overload distortion from the modulator's inability to vary step size for high signal slopes, and granular noise from large step size changes compared to small input variations.

Uploaded by

Zeenat Khokhar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PPTX, PDF, TXT or read online on Scribd
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Working

• Delta modulation transmits only one bit per sample


• Present sample value is compared with the previous
sample value and this result whether the amplitude is
increased or decreased is transmitted.
• Input signal x(t) is approximated to step signal by the
delta modulator, this step size is kept fixed
DELTA MODULATION WAVEFORM
Error

The error between the sampled value of x(t) and


last approximated sample is given as:
e(nT)=x(nT)- x°(nT)
where, e(nT): error at present sample
x°(nT): sampled signal of x(t)
Delta Sign
This means that depending on the sign of error e(nT),
the sign of step size is decided:

I
if positive, then a binary '1' is transmitted and if
negative then a binary '0' is transmitted
Drawbacks

The delta modulation has two major drawbacks:


1. Slope Overload Distortion
2. Granular or Idle Noise
Slope distortion
• This distortion arises because of large dynamic range of
the input.
• To reduce this error, the step size must be increased
when slope of signal x(t) is high
• In delta modulator, step size remain fixed so its
maximum or minimum slopes occur along straight
lines, therefore this modulator is known as Linear Delta
Modulator (LDM)
Slope Overload Distortion
Granular Noise

• It occurs when the step size is too large compared to


small variation in the input signal
• For very small variations in the input signal, the
staircase signal is changed by large amount (A)
Granular Noise

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