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- 1. Digital Signal Processing Rohit Dhongde (B-41) Sushant Burde(B-48) Vaibhav Deshmukh(B- 52) Swapnil Dondal (B-49)
- 2. What is DSP? Converting a continuously changing waveform (analog) into a series of discrete levels (digital)
- 3. What is DSP? The analog waveform is sliced into equal segments and the waveform amplitude is measured in the middle of each segment The collection of measurements make up the digital representation of the waveform
- 4. What is DSP? 0 0.22 0.44 0.64 0.82 0.98 1.11 1.2 1.24 1.27 1.24 1.2 1.11 0.98 0.82 0.64 0.44 0.22 0 -0.22 -0.44 -0.64 -0.82 -0.98 -1.11 -1.2 -1.26 -1.28 -1.26 -1.2 -1.11 -0.98 -0.82 -0.64 -0.44 -0.22 0 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37
- 5. Binary Search The speed the binary search is accomplished depends on: The clock speed of the ADC The number of bits resolution Can be shortened by a good guess (but usually is not worth the effort)
- 6. How Does It Work? Faithful Duplication Now that we can slice up a waveform and convert it into digital form, let’s take a look at how it is used in DSP Draw a simple waveform on graph paper Scale appropriately “Gather” digital data points to represent the waveform
- 7. Starting Waveform Used to Create Digital Data
- 8. How Does It Work? Faithful Duplication Swap your waveform data with a partner Using the data, recreate the waveform on a sheet of graph paper
- 9. Waveform Created from Digital Data
- 10. How Does It Work? Faithful Duplication Compare the original with the recreating, note similarities and differences
- 11. How Does It Work? Faithful Duplication Once the waveform is in digital form, the real power of DSP can be realized by mathematical manipulation of the data Using EXCEL spreadsheet software can assist in manipulating the data and making graphs quickly Let’s first do a little filtering of noise
- 12. How Does It Work? Faithful Duplication Using your raw digital data, create a new table of data that averages three data points Average the point before and the point after with the point in the middle Enter all data in EXCEL to help with graphing
- 13. Noise Filtering Using Averaging Raw -150 -100 -50 0 50 100 150 0 10 20 30 40 Time Amplitude Ave before/after -150 -100 -50 0 50 100 150 0 10 20 30 40 Time Amplitude
- 14. How Does It Work? Faithful Duplication Let’s take care of some static crashes that cause some interference Using your raw digital data, create a new table of data that replaces extreme high and low values: Replace values greater than 100 with 100 Replace values less than -100 with -100
- 15. Modulation Discrete signals are rarely transmitted over long distances or stored in large quantities in their raw form. Signals are normally modulated to match their frequency characteristic to those of the transmission and/or storage media to minimize signal distortion, to utilize the available bandwidth efficiently, or to ensure that the signal have some desirable properties. Two application areas where the idea of modulation is extensively used are: 1. telecommunications
- 16. Three most commonly used digital modulation schemes for transmitting Digital data over bandpass channels are: Amplitude shift keying (ASK) Phase shift keying (PSK) Frequency shift keying (FSK) When digital data is transmitted over an all digital network a scheme known As pulse code modulation (PCM) is used.
- 17. Digital Signal Processing And Its Benefits By a signal we mean any variable that carries or contains some kind of information that can be conveyed, displayed or manipulated. Examples of signals of particular interest are: - speech, is encountered in telephony, radio, and everyday life - biomedical signals, (heart signals, brain signals) - Sound and music, as reproduced by the compact disc player - Video and image, - Radar signals, which are used to determine the range and bearing of distant targets
- 18. Attraction of DSP comes from key advantages such as : * Guaranteed accuracy: (accuracy is only determined by the number of bits used) * Perfect Reproducibility: Identical performance from unit to unit ie. A digital recording can be copied or reproduced several times with no loss in signal quality * No drift in performance with temperature and age * Uses advances in semiconductor technology to achieve: (i) smaller size (ii) lower cost (iii) low power consumption
- 19. Disadvantages of DSP * Speed and Cost DSP designs can be expensive, especially when large bandwidth signals are involved. ADC or DACs are either to expensive or do not have sufficient resolution for wide bandwidth applications. * DSP designs can be time consuming plus need the necessary resources (software etc) * Finite word-length problems If only a limited number of bits is used due to economic considerations serious degradation in system performance may result.
- 20. Key DSP Operations 1. Convolution 2. Correlation 3. Digital Filtering 4. Discrete Transformation 5. Modulation
- 21. Convolution Convolution is one of the most frequently used operations in DSP. Specially in digital filtering applications where two finite and causal sequences x[n] and h[n] of lengths N1 and N2 are convolved 0 ][][][][][][][ kk knxkhknxkhnxnhny where, n = 0,1,…….,(M-1) and M = N1 + N2 -1 This is a multiply and accumulate operation and DSP device manufacturers have developed signal processors that perform this action.
- 22. Correlation There are two forms of correlation : 1. Auto-correlation 2. Cross-correlation 1. The cross-correlation function (CCF) is a measure of the similarities or shared properties between two signals. Applications are cross-spectral analysis, detection/recovery of signals buried in noise, pattern matching etc. Given two length-N sequences x[k] and y[k] with zero means, an estimate of their cross-correlation is given by: ,...2,1,0 00 2 1 n rr nr n yyxx xy xy Where, rxy(n) is an estimate of the cross covarience
- 23. The cross-covarience is defined as 1 0 2 1 0 2 1 0 1 0 ][ 1 )0(,][ 1 )0( ,...2,1,0][][ 1 ,...2,1,0][][ 1 N k yy N k xx nN k nN k xy ky N rkx N r nkynkx N nnkykx Nnr
- 24. 2. An estimate of the auto-correlation of an length-N sequence x[k] with zero mean is given by ][nxx 2,1,0, ]0[ ][ ][ n r nr n xx xx xx
- 25. Application Areas Image Processing Instrumentation/Control Speech/Audio Military Pattern recognition spectrum analysis speech recognition secure communications Robotic vision noise reduction speech synthesis radar processing Image enhancement data compression text to speech sonar processing Facsimile position and rate digital audio missile guidance animation control equalization Telecommunications Biomedical Consumer applications Echo cancellation patient monitoring cellular mobile phones

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