19-10-2012, 12:46 PM
Digital Signal Processing (DSP) Fundamentals
Digital Signal Processing Fundamentals.ppt (Size: 2.48 MB / Downloads: 126)
Overview
What is DSP?
Converting Analog into Digital
Electronically
Computationally
How Does It Work?
Faithful Duplication
Resolution Trade-offs
What is DSP?
Converting a continuously changing waveform (analog) into a series of discrete levels (digital)
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
Converting Analog into DigitalElectronically
The device that does the conversion is called an Analog to Digital Converter (ADC)
There is a device that converts digital to analog that is called a Digital to Analog Converter (DAC)
The simplest form of ADC uses a resistance ladder to switch in the appropriate number of resistors in series to create the desired voltage that is compared to the input (unknown) voltage
The output of the resistance ladder is compared to the analog voltage in a comparator
When there is a match, the digital equivalent (switch configuration) is captured
Converting Analog into DigitalComputationally
The analog voltage can now be compared with the digitally generated voltage in the comparator
Through a technique called binary search, the digitally generated voltage is adjusted in steps until it is equal (within tolerances) to the analog voltage
When the two are equal, the digital value of the voltage is the outcome
The binary search is a mathematical technique that uses an initial guess, the expected high, and the expected low in a simple computation to refine a new guess
The computation continues until the refined guess matches the actual value (or until the maximum number of calculations is reached)
The following sequence takes you through a binary search computation
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
Swap your waveform data with a partner
Using the data, recreate the waveform on a sheet of graph paper
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