Lecture 2

Question 1

sampling

Answer 1

the measurement of a signal intensity or signal’s amplitude at discrete time intervals

Question 2

what affects the rate of sampling

Answer 2

how much information is preserved from the original continuous signal

Question 3

adequate sampling

Answer 3

the highest frequency components of the continuous signal are preserved in the discrete signal

Question 4

aliases

Answer 4

samples (the intensity of a signal) with lower frequencies

Question 5

when does aliasing occur

Answer 5

undersampling a signal

Question 6

nyquist-shannon sampling theorem

Answer 6

dictates how to prevent aliasing

Question 7

how to prevent aliasing

Answer 7

make sure that at least 2 samples are taken from each sine wave and the sampling frequency is two times larger than the maximum frequency

fs > 2f max

Question 8

Nyquist rate

Answer 8

given the max frequency, the sampling frequency should be two times larger

fs > 2fmax

Question 9

oscillator

Answer 9

something that generates a tone

Question 10

what is a phasor

Answer 10

a way of representing a sinusoidal signal in time by a vector

Question 11

sinusoidal signal is defined by

Answer 11

magnitude (A)
phase (θ )
frequency (ω)

Question 12

Changing “A” in the phasor demo reflects in?

Answer 12

changing the magnitude (applitude) of a sine wave

Question 13

Changing the phase (θ theta) in the phasor demo reflects in?

Answer 13

changing the shift of the sine wave

Question 14

Changing ω in the phasor

Answer 14

changing the frequency

Question 15

the sampling rate is dependent on

Answer 15

how fast the signal fluctuates

Question 16

True or False

Humans are sensitive to spatial frequency

Answer 16

True

Question 17

space varying sampling

(think about the resolution of the retina)

Answer 17

captures the high model

Question 18

Sunflower-distribution

Answer 18

represents how the human visual system perceive the world

high frequencies in the center, low in the periphery

Question 19

Schwartz model

Answer 19

• Captures the variations between the sunflower distribution and the Stack model
• Log polar map of what is received on the retina to the cortex
• Reference point: fovea

Question 20

What is represented by the Stack model

(the pyramid of hectagones)

Answer 20

how we sample the world in different levels, how extensive the scope is depending on the resolution

lowest level: large extend
with lower resolution
(see the entire room)

highest level on the top: small in high resolution, examine something in detail
(reading a book)

Question 21

log-polar mapping

Answer 21

• Approximates how brain perceives images in a non-uniform way
• it’s a coordinate system in two dimensions

Question 22

What is aliasing
When does happen
How to prevent aliasing?

Answer 22

1. Aliasing are samples with lower frequencies
2. Occurs when we undersample a signal
3. Make sure that at least 2 samples are taken from each sine wave and the sampling frequency is two times larger than the maximum frequency

fs > 2f max