AIM:To study the delta modulation process by comparing the present signal with the previous signal of the given modulating signal.
APPARATUS:1. Delta modulation trainer kit
2..Dual trace CRO
3.Digital multi meter
4.CRO probes and set of patch cards
THEORY:
Delta modulation is a differential PCM technique in witch the difference signal between two successive samples is encoded into a single bit code . The process of encoding is as follows .The comparator compares the in put signal m(t) and r(t) .
If m(t) >r(t) logic 1 is generated at the out put of the comparator. Otherwise a logic 0 is generated. the value of logic 1 or logic 0 is termed as ∆(t) is held for the bit duration by the sample and hold current to generate So(t) , the delta modulated out put .
This out put So(t) is fed to the 8bit binary up/down counter to control its count direction . A logic’1’ at the mode control in put increases the count value by one And a logic ‘0’ decrements the count value by one . All the eight out puts of the counter are given to DAC to reconstruct the original signal .In essence the counter and decoder forms the delta modulation in the feed back loop of the comparator .Thus if the input signal is higher then the reconstructed signal the counter increments at each step so as to enable the DAC out put to reach to the input signal values.Similarly the in put signal m(t) is lower then the reconstructed signal r(t) , the counter decrements at each step and the DAC output gets reduced to reach a value m(t) .
PROCEDURE:
1.Verify the circuit as per circuit diagram .
2. connect clock signal to the delta modulator .
3. Connect modulating signal to the input of delta modulator and observe the same on channel one .
4.Observe the delta modulation out put on channel 2.
5.Connect this delta modulator out put to the demodulator.
6.Also connect the clock signal to de modulator .
7.Observe the de modulator out put with and without RC filter on CRO.
PRECAUTIONS:
RESULT:
VIVA VOICE:1.What is the aim of the experiment?
2.What is delta modulation ?
3. What is demodulation ?
4. Why we need modulation ?
5. What is the use of modulation ?
Posted By 225-╰»мαηιкυмαя Y
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