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DIGITAL COMMS > DIGITAL CARRIER LINE ENCODING > Flashcards

DIGITAL CARRIER LINE ENCODING Flashcards

REVIEWER

1
Q

Process of encoding digital data into digital signal.

A

Digital Line Encoding

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2
Q

Categories of Transmission Voltages.

A

Unipolar and Bipolar

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3
Q

Type of Data that is either a High Signal or a Low Signal.

A

Binary Data

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4
Q

This Transmission of Binary Data only utilizes a single nonzero voltage level.

A

Unipolar Transmission

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5
Q

This Transmission of Binary Data utilizes two nonzero voltage levels.

A

Bipolar Transmission

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6
Q

If the binary pulse is maintained for the entire bit time, this is called _____.

A

Non Return to Zero (NRZ)

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7
Q

If the binary pulse’s active time is less than 100%, it is called _____.

A

Return to Zero (RZ)

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7
Q

If the Transmission uses one non zero high value, and is using 100% of the active time?

A

Unipolar Non Return to Zero (UPNRMZ) Transmission

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8
Q

If the Transmission uses one non zero high value, and is not using 100% of the active time?

A

Unipolar Return to Zero (UPRZ) Transmission

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9
Q

If the Transmission uses two non zero high value, and using 100% of the active time?

A

Bipolar Non Return to Zero (UPNRZ) Transmission

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10
Q

If the Transmission uses two non zero high value, and is not using 100% of the active time?

A

Bipolar Return to Zero (BPRZ) Transmission

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11
Q

Define UPNRZ, UPRZ, BPRZ, BPNRZ.

A

Unipolar Non Return to Zero, Unipolar Return to Zero, Bipolar Return to Zero, Bipolar Non Return to Zero

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12
Q

_____ refers to the percentage of time during which a digital signal is in the high (1) state compared to the total time of a signaling period.

A

Duty Cycle

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13
Q

Average DC voltage of Bipolar Transmission assuming that there is an equal number of high and low signals.

A

0V

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14
Q

Average DC voltage of Unipolar Transmission Non Return to Zero assuming that there is an equal number of high and low signals.

A

V/2 (Half of the voltage value of High Signal)

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15
Q

Average DC voltage of Unipolar Transmission Return to Zero assuming that there is an equal number of high and low signals.

A

V/4 (Quarter of the voltage value of High Signal)

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16
Q

There are three voltage levels for Bipolar Transmissions, +V, 0, -V, what logic does -V represent?

A

Logic 0

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17
Q

For Return to Zero Transmission, how long are the pulses active with respect to the Bit Time?

A

50% of the Bit Time

18
Q

A type of Transmission where successive logic 1s are inverted in polarity from the previous logic 1.

A

Bipolar Return to Zero Alternate Mark Inversion (BPRZ-AMI) Transmission

19
Q

Distinct feature of Alternate Mark Inversion (AMI)?

A

It is bipolar, but its +V and -V both represent logic 1, while 0 represent logic 0. Another distinct feature is the fact that successive 1s are inverted in polarity to look like a sine wave in pulse format.

20
Q

Occurs when long string of either 1s or 0s causes the signal to lose its amplitude reference.

A

DC Wandering

21
Q

What happens in DC Wandering

A

Lose of amplitude reference making it hard to distinguish between high signals and low signals

22
Q

How do we solve DC wandering?

A

By applying transitions using Return to Zero (RZ) encoding or using techniques like Alternate Mark Inversion (AMI)

23
Q

What will cause the highest bandwidth requirement for Unipolar Non Return to Zero (UPNRZ) Transmission?

A

Alternate 1/0 Sequence

24
Q

What will cause the highest bandwidth requirement for Bipolar Non Return to Zero (BPNRZ) Transmission?

A

Alternate 1/0 Sequence

25
Q

What will cause the highest bandwidth requirement for Unipolar Return to Zero (UPRZ) Transmission?

A

Successive 1s sequence

26
Q

What will cause the highest bandwidth requirement for Bipolar Return to Zero (BPRZ) Transmission?

A

Successive 1s or 0s Sequence

27
Q

At worst case scenario what is the highest fundamental frequency for Non Return to Zero encoded Transmissions?

A

Equal to Bit rate (fb) / 2

(bit/epoch)/2
2bit (needed for NRZ cycle)
(2bit/2epoch)/2
4bit/2epoch
2bit/cycle (highest fundamental frequency, 1 cycle)

28
Q

At worst case scenario what is the highest fundamental frequency for Return to Zero encoded Transmissions?

A

Equal to Bit Rate (fb)

since they only consume 50% of the bit time when active, they are able to form a cycle in 1 bit time

29
Q

What will cause the highest bandwidth requirement for Bipolar Return to Zero Alternate Mark Inversion (BPRZ-AMI)?

A

Two or MORE consecutive 1s

30
Q

At worst case scenario what is the highest fundamental frequency for Bipolar Return to Zero Alternate Mark Inversion Transmissions?

A

bf/2

the only return to zero that requires two bit time to complete its cycle

31
Q

UPNRZ and BPNRZ are _____ for Clock Recovery. Explain why.

A

Inadequate. Because they do not return to zero and use all of their bit time to relay information. They don’t have any rooms for transitions.

32
Q

UPRZ and BPRZ-AMI are _____ for Clock Recovery. Explain why.

A

Adequate but not the best. Since they return to Zero, they have natural transition time. But the problem lies on not being able to code a transition time, since 0V are logic 0 for the two of them.

33
Q

_____ is the best for Clock Recovery. Explain why.

A

Bipolar Return to Zero (BPRZ). It’s the best for clock recovery because it returns to zero, meaning it has its natural transition time and its logic 1 and 0 are expressed by +V and -V respectively, allowing us to encode transition time into the line using 0V

34
Q

BPRZ-AMI is sufficient for clock recovery if and only if _____.

A

Long sequences of 0s are prevented.

35
Q

Best data line encoding technique in terms of error detection. Why?

A

Bipolar Return to Zero Alternate Mark Inversion (BPRZ-AMI). An error in any bit will result to Bipolar Violation (BPV).

36
Q

What is BPV?

A

Bipolar Violation is a type of coding error in BPRZ-AMI transmission where two consecutive 1s are coded with the same polarity.

37
Q

Which encoding technique has it’s own built in error detection mechanism?

A

Bipolar Return to Zero Alternate Mark Inversion (BPRZ-AMI)

38
Q

Best encoding technique for data line encoding?

A

Bipolar Return to Zero Alternate Mark Inversion (BPRZ-AMI)

39
Q

______ is a popular type of line encoding that produces a strong timing component for clock recovery and does not cause dc wandering.

A

Digital Biphase

40
Q

_____ is a type of encoding technique, where a bit time is divided into two, and logic 1 and 0 are expressed in terms of high voltages of opposite polarities. Give all three names.

A

Digital Biphase, Manchester Code or Biphase

41
Q

In Biphase, what represents a logic 1?

A

+V/-V in the same bit time

42
Q

What represents logic 0 in Manchester Code?

A

-V/+V in the same bit time

43
Q

What is the best feature of Manchester code?

A

It can’t be affected by DC wandering

DIGITAL COMMS (3 decks)

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