Lecture 1

Question 1

What is quantised boxcar

Answer 1

quantised but not sampled continous

Question 2

What is sampled data

Answer 2

sampled but not quantised

Question 3

What is the 3rd step of A2D conversion after sampling and quantising?

Answer 3

Coding- putting into binary

Question 4

Formula for quantisation width

Answer 4

(xmax - xmin)/(no. levels -1)

Question 5

For Ensemble recording what is the best amount of recordings needed?

Answer 5

many

Question 6

What is Ensemble recording

Answer 6

At each point work out the average from many trials

Question 7

Why is Median recording better than Ensemble recording?

Answer 7

It can deal with a smaller amount of samples as high noise samples wont throw it off

Question 8

How many trials do you need for moving average filtering

Answer 8

only one

Question 9

What is moving averaging filtering?

Answer 9

find average of points near eachother

Question 10

What do you need to be careful with with moving average filtering?

Answer 10

length will change so need to pad with zeros at end

Question 11

What kind of filter does moving average act like?

Answer 11

low pass

Question 12

In a moving average filter what is the comprise between order and distortion?

Answer 12

As order increases passband gets smaller (removes more of the noise) but also increases distortion (as removes part of the signal also)

Question 13

opposite of periodic

Answer 13

aperiodic

Question 14

What does a finite total energy signal mean for power?

Answer 14

zero power

Question 15

What does finite average power mean for energy?

Answer 15

infinite

Question 16

Power=

Answer 16

energy/time

Question 17

Reasons for incorrect sampling [3]

Answer 17

hardware problems
Cant sample that first
noise might cause highest frequency

Question 18

How to fix incorrect sampling [2]

Answer 18

Use a really high frequency
low pass in time domain before converting to frequency domain

Question 19

Difference between DFT and DTFT

Answer 19

DTFT has an infinite sum, frequency is continuous - DFT everything is discrete

Question 20

DFT symmetric?

Answer 20

magitude is symmetric around fs/2 and phase is anti symmetric

Question 21

With DFT what needs to be thought about in terms of sample size

Answer 21

big enough to carry a full cycle to get proper results.

Question 22

What is the picket fence effect?

Answer 22

If you want to know the value of X(m) that is between discrete values

Question 23

How do you solve picket fence effect?

Answer 23

Zero padding to increase the display of DFT

Question 24

When picking a cycle to do DFT what causes spectral leaking

Answer 24

the truncation if the signal doesn’t start and end at the same place- (as we are assuming its periodic but it doesn’t need to be)

Question 25

How do you solve spectral leaking?

Answer 25

Windowing

Question 26

Why the z transform?

Answer 26

can verify stability

Question 27

What is the region of convergence?

Answer 27

area where z transform is defined and it also has an impact on BIBO stability

Question 28

What is delay in z transform

Answer 28

z^-n (where n is delay)

Question 29

What is spectral filtering?

Answer 29

Keeping the components of the frequency that you want and removing undesired frequencies

Question 30

an ideal filter can do what?

Answer 30

pass signal components without any distortion

Question 31

When you are far from a pole zero pair what will h(w) do?

Answer 31

stay close to 1

Question 32

To emphasise signal components what do you need to do?

Answer 32

What poles very close to unit circle in this range

Question 33

To attenuate signal components what do you need to do?

Answer 33

Place zeros close to unit circle (notch filter)

Question 34

What is an IRR filter?

Answer 34

has current inputs, past inputs and past outputs

Question 35

What is a FIR filter?

Answer 35

current and past inputs only

Question 36

Which of IRR and FIR structure diagram have feedback

Answer 36

IRR

Question 37

Which of FIR and IRR only have zeros and therefore is always stable

Answer 37

FIR

Question 38

Out of FIR and IRR which one has finite impulse response

Answer 38

FIR

Question 39

Why do you sometimes filter in the time domain not the frequency domain?

Answer 39

Less computational time needed

Question 40

How can you make a sum filter better?

Answer 40

Using more than one in a cascade

Question 41

Why would you transport from analogue rather then straight to digital?

Answer 41

techniques highly advances, extensive tables

Question 42

In Butterworth what is omega c

Answer 42

cut off frequency i.e. frequency at -3db

Question 43

What is the window method

Answer 43

Truncate by N+1 then shift N/2 to keep causality

Question 44

What is the Gibbs phenomenon?

Answer 44

oscillatory behaviour caused by noise from using a rectangular window in FIR filtering

Question 45

what can Increasing N of FIR not decrease

Answer 45

ripple peak

Question 46

What can increasing N of FIR do?

Answer 46

sharpen transistion

Question 47

Which window has best transition

Answer 47

Hamming

Question 48

Which window has best ripple decrease

Answer 48

Blackman

Question 49

What is wc normally

Answer 49

wp+ws /2

Question 50

with SNR is higher or lower better

Answer 50

higher is better

Question 51

What is the fast Fourier Transform?

Answer 51

Same method but tried to reduce complexity so its quicker