Uploaded on

 

More in: Technology , Business
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
    Be the first to like this
No Downloads

Views

Total Views
208
On Slideshare
0
From Embeds
0
Number of Embeds
0

Actions

Shares
Downloads
0
Comments
0
Likes
0

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. Chapter 3 - Sampling Converting the Real World to the Digital World…
  • 2. We know that analogue signals constantly change and digital signals have a value of 1 or 0.
  • 3. So how do we get digital signals?
    • Digital signals are produced from the ‘real’ analogue waveform
    • Digital codes represent analogue signals and therefore have to be reconstructed back into analogue signals.
    Original Reconstructed 0110101100010101
  • 4. Sampling
    • The value of an analogue signal at a point is called a sample.
    Sample
  • 5. Variables in sampling
    • The following can be altered when sampling a analogue waveform:
      • Sampling frequency – this is how many times a sample is taken every second.
      • Resolution – the number of bits used to record the value of a sample
  • 6. Sampling Frequency
    • The number of times that a sample is taken per second will affect the quality of the digitised information. i.e….
  • 7. Sampling Frequency and Waveforms
    • The sampling rate needs to be more than double the highest frequency component of the waveform
    • If not, aliasing can occur – this means that the reconstructed wave is not representative of the original
  • 8.  
  • 9. Hearing Sampling…
  • 10. Resolution
    • The resolution is the number of ‘bits’ used to represent a value of a sample.
      • 1 bit has 2 values, 0 or 1 = 2 1
      • 2 bits has 4 values 0, 1, 2, 3 = 2 2
      • 3 bits has 8 values, 0, 1, 2, 3, 4, 5, 6, 7 = 2 3
    • The more values, the more accurate the digital sample. Note that 8 bits = a byte
    • Draw a table of Number of Bits, Number of Levels and power of 2 – see page 65 for help.
  • 11. 2 1 6 65536 16 … … … 2 9 512 9 2 8 256 8 2 7 128 7 2 6 64 6 2 5 32 5 2 4 16 4 2 3 8 3 2 2 4 2 2 1 2 1 2 n Number of Levels Number of Bits
  • 12. Redundancy
    • To prevent errors in sending digital signals, more information is sent.
    • This can be seen in a CD with a scratch or hole in it…
    Jarrow Sings the Blues MFI Records 1934