Quiz 2. Digital Signals

Question 1

Analog vs Digial

Answer 1

ANALOG SIGNALS:
 In theory have
infinite resolution
– Any small change is
detectable
• Value is know at all
times
– Continuous signal
• In reality noise and
interference limits
resolution

DIGITAL SIGNALS
• Inherently have
limited resolution
• Value is only known
at sample time
– Discrete signal
• Less susceptible to
noise and bandwidth
limits

Question 2

sample rate

Answer 2

• Quicker sampling we can reconstruct the signal
• Nyquist = 2x Highest Frequency of desired signal
• Rule of Thumb – 10x Highest Frequency

Question 3

what are the steps you should do in sampling:?

Answer 3

determine the frequencies of the signal you are interested in

put the signal through a high pass filter, say 2-5X higher than highest wanted frequency

then sample at rate at least twice (10x!) the highest frequency

Question 4

why has digital become so popular?

Answer 4

– Transistor – miniaturization, cost and speed
– It can be minimized with billions on one simple
chip.

Question 5

what does a transistor have to do with it???

Answer 5

– It is a switch – it has two states on or off

Question 6

all a computer knows is On or Off, or more correctly, high voltage and low voltage

Answer 6

– Called binary – High = 1 and Low = 0

Question 7

computers use _________-

Answer 7

binary digits

Question 8

why know binary?q

Answer 8

• Due to transistors it has become very easy and
low cost to implement
• Now very fast and sampling very close
approximation to analog
• Less susceptible to noise and interference
(more robust)
– Each digital level represents a range of voltages so
effectively ignores noise in that range
“0”  0-2V and “1”  3-5V

Question 9

Resolution in general:

Answer 9

– More bits means better resolution
– More bits increase costs (becomes exponential
increase at higher levels)
– Each digital level represents a smaller analog input
voltage range
– If we have x bits