Lecture 6

Lecture 6

 

• Phase
  
  • 270 degrees = 3/2 pi
    
  • 360 degrees = 2 pi
    
  • 180 degrees = pi
    
  • 90 degrees = ½ pi
    
• Wavelength
  
  • Pi = vt
    
  • pi(f) = v
    
• periodic signals
  
  • with fundamental frequency of f₀ = 1/t Hz may be represented by the 'fourier series', defined as:
    
  • 
    
• Sampling
  
  • Obtain the value of signal every T seconds
    
    • Choice of T is determined b how fast a signal changes, it, the frequency of content of the signal
      
    • Nyquist sampling theorem says:
      
      • Sampling rate (1/T) >= maximum frequency in the signal
        
    • An analogue signal
      
      • Defined for all time can have any amplitude
        
    • Discrete time signal:
      
      • Defined for multiples of T can have any amplitude
        
      • Must be sure sampling rate is greater than maximum frequency of the signals
        
  • Quantization
    
    • Approximate signal to certain levels. Number of levels used to determine the resolution
      
    • Digital signal
      
      • Defined for multiples of T amplitude limited to a few levels