signals Flashcards
signals
variations of a physical quantity that encode information
continuous
their level is known always and everywhere
analog
their level is a infinite-precision real number
period signal properties
volume
duration
period
frequency
DC component or mean value
speech
1D continuous analog time signal
attenuation
gradual reduction of the amplitude of a signal
image
2D continuous time signal
digitisation
sampling + quantisation
sampling
process of measuring a continuous signal at isolated, equally spaced moments in time
quantisation
representing real numbers with a finite number of bits
digital signal
non-continuous, changes in individual steps, takes discrete values
ADC
device that preforms digitisation
DAC
device that preforms reconstruction; needed for controlling the actuators
reconstruction
reassembling an analog signal from the digital samples
A/D resolution
refers to the number of bits used to represent the amplitude of an analog signal in a digital form after analog-to-digital conversion, determines the number of possible outputs
N=2^R, R-bits
sampling frequency
number of samples per second
vin
input analog voltage
vref
analog reference voltage
pixel
a discrete point in 2D space
spatial reosolution
number of pixels per each direction
colour reoslution
number of bits used to express the colour of a pixel
binary image
one bit per pixel
gray scale image
8 bits per pixel
RGB
24 bits per pixel
The Nyquist-Shannon sampling theorem
minimal sampling rate is 2fmax-the Nyquist sampling frequency
for a good reconstruction it is recommended to use _________
10fmax
aliasing
effect of undersampling, can lead to the misinterpretation or distortion of the signal
alias frequencies
false frequencies resulted after reconstruction
oversampling
bigger storage requirements
