Digital Coding of Analog Signal

1. Digital Coding of Analog Signal Electronics Engineering Department, Sardar Vallabhbhai National Institute of Technology, Surat-395007. Prepared By: Amit Degada Teaching Assistant

2. Goal of Today’s lecture. • Prediction Filter • Delta Modulation • Delta Modulation De-merits • Solution of De-merits • Adaptive delta Modulation

3. Pq How Prediction Helps • Correlation between two samples. • We can exploit for our case. • Fewer bits are required to encode.

4. How can we predict? • Ideally predicted value must be close to real value of message signal. At the receiver we can generate message signal Prediction filter at both side i.e. TX and RX, must be identical

5. Approach to signal Prediction • Prediction of the future is mysterious stuff. • We can summon Taylor, Maclaurin & Weiner to help us • A signal m(t) has all derivative of t then, ………..(1) If Ts is very small then, ………..(2) From the Knowledge of Derivative we can predict sample at t+Ts instant

6. Approach to signal Prediction But So equation 2 is simplifies to ………..(3) In general ………..(4) The above equation is for Nth order. Larger the N better is the Prediction

7. Approach to signal Prediction The above equation reduces to For 1st Order

8. DPCM Transmitter and Receiver

9. Delta Modulation • Its same as DPCM. Signal Is sampled at 4 times the Nyquist Frequency.

10. Analysis of delta Modulation ………..(5) Hence ………..(6) Above equation (5) becomes

11. Analysis of delta Modulation • Finally we can say for mq(0)=0 (Assuming Zero Initial Condition)

12. Why the Name Delta? • It Transmits the Difference, hence the name is Delta. • If the Difference is Positive, A Positive pulse is transmitted, Vice Versa.

13. Analysis of delta Modulation

14. Practical Implementation Transmitter

15. Practical Implementation

16. Delta Modulation Waveform

17. Delta Modulation Error

18. Thank You