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EWOK > Day 1: Signal Design > Flashcards

Day 1: Signal Design Flashcards

1
Q

What is the process of converting analog signals to digital signals?

A

Sampling

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2
Q

Why do we convert digital to analog before transmitting?

A

It proprogates through space better

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3
Q

Identify

The method of putting information onto a carrier signal by changing one or more properties of the wave in a pre-determined pattern to represent data

A

Modulation

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4
Q

When we modulate, what are we changing?

A

Frequency, amplitude, and/or phase

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5
Q

Identify

A method of encoding digital information (bits) onto an analog carrier wave for transmission over media that does not support direct digital transmission

A

Digital Modulation

Most common is shift-keying

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6
Q

Identify

Presents digital data as variations in the amplitude of a carrier wave

Shift Keying

A

Amplitude Shift Keying

It is also relatively inexpensive.

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7
Q

Identify

Shifts the output frequency between predetermined waves

Shift Keying

A

Frequency Shift Keying

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8
Q

Changes the phase of a carrier wave

A

Phase Shift Keying

BPSK and QPSK most common mod scheme due to better efficiency; idea for video

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9
Q

Identify

  • Stands for In-phase and Quadrature
  • It represents two 90 degrees perpendicular components to each other

Constellation Diagrams

A

I/Q

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10
Q

Identify

Graphical representation showing possible symbol locations in I/Q space

Constellation Diagrams

A

Constellation Plots

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11
Q

What do constellation diagrams represent?

A

Amplitude (I) and phase (Q) of a signal

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12
Q

Identify

Uses 2 phase shifts 180 degrees apart

Modulation Scheme

A

BPSK

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13
Q

Identify

Less sensitive to phase noise than other types

Modulation Scheme

A

BPSK

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14
Q

Identify

Used when lower data rates are required or more robustness is required

Modulation Scheme

A

BPSK

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15
Q

Identify

2 bits per symbol

Modulation Scheme

A

QPSK

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16
Q

Identify

More susceptible to nosie than BPSK and QPSK

Modulation Scheme

A

8PSK

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17
Q

Identify

Less BW required than BPSK and QPSK

Modulation Scheme

A
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18
Q

Identify

Often used for digital video

Modulation Scheme

A

QAM

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19
Q

Identify

Combination of modulating amplitude and phase

Modulation Scheme

A

QAM

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20
Q

Expressed as a percentage (%) deviation of Rx’d symbol vs Reference Point

A

Error Vector Magnitude

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21
Q

Identify

Expressed as a percentage (%), deviation of Rx’d symbol from desired phase angle

A

Phase Shift Error (PSE)

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22
Q

Identify

The range of frequencies where the majority of the signal’s power resides

A

Occupied Bandwidth

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23
Q

The bandwidth actually used for transmitting data

A

Effective Bandwidth

Always narrower than occupied BW due to guard intervals and other factors (ex. roll off factor)

24
Q

How is effective bandwidth is closely related to symbol rate?

A

The faster symbols are transmitted (higher symbol rate), the more bandwidth is needed

25
Q

Identify

Intentional periods (time) where signals do not transmit to prevent interfering with themselves

A

Guard Intervals

26
Q

Identify

Unoccupied spaces between signals to prevent interfering with one another

A

Guard Bands

27
Q

Identify

The difference in frequency between the effective and occupied bandwidth

A

Roll-off factor

28
Q

Identify

Speed at which raw data is transmitted

A

Data rate

29
Q

Identify

Overall speed of all bits being transmitted, including raw data and any additional bits like error correction

A

Total Bit Rate

30
Q

Rate at which symbols (which can represent multiple bits) are transmitted (changes)

A

Symbol Rate

31
Q

Identify

Adds “gain” to the signal (computational/coding)

A

Forward Error Correction (FEC)

32
Q

Identify

Added in the MODEM (prior to Tx)

A

Forward Error Correction (FEC)

33
Q

Identify

The ability to detect the presence of errors caused by noise or other impairments during transmission between the transmitter to the receiver

FEC

A

Error detection

34
Q

Identify

The additional ability to reconstruct the original, error-free data

FEC

A

Error correction

35
Q

Identify

Non-data bit added to data bit stream that enables receiver to detect errors or to detect and correct errors

FEC

A

Parity bit

36
Q

Identify

The actual information (1s, 0s) you are attempting to send

FEC

A

Data bits

37
Q

Identify

The entire series of “ones” or “zeros” (data and parity)

FEC

A

Bit stream

38
Q

Identify

A radio technology allowing one-way communication from a transmitter to a receiver

Communication Protocols

A

Simplex

39
Q

Identify

Operation mode of a radio communication system in which each end can transmit and receive, but not simultaneously

Communication Protocols

A

Half-duplex RF systems

Ex. walkie-talkie, wireless keyboard, mouse

40
Q

Identify

Radio system in which each end can transmit and receive simultaneously

Communication Protocols

A

Full-duplex RFsystem

41
Q

Identify

Combining multiple signals into ONE signal (Analog or Digital)

A

Multiplexing

42
Q

Identify

The separation of combined signals

A

De-multiplexing

43
Q

What are the methods of multiplexing?

A
  • Frequency Division MUX (FDM)
  • Time Division MUX (TDM)
  • Code Division MUX (CDM)
44
Q

Identify

The process of two or more signals physically taking turns on a channel (frequency)

This enables efficient use of the available bandwidth

A

Time Division Multiplexing (TDM)

45
Q

Identify

Assigns non-overlapping frequency ranges to different signals or to each “user” of a medium

A

Frequency Division MUX (FDM)

46
Q

A data signal is sent over a range of frequencies in an assigned frequency spectrum using a pseudo-random spreading code

A

Code Division MUX (CDM)

Ex. cellular network

47
Q

Multiple access differs from multiplexing because it occurs ____________ transmission.

A

After

48
Q

What are the types of multiple access?

A
  • Frequency Division Multiple Access (FDMA)
  • Time Division Multiple Access (TDMA)
  • Code Division Multiple Access (CDMA)
49
Q

Identify

Users share the satellite simultaneously, but each user transmit at a single frequency

A

Frequency Division Multiple Access (FDMA)

50
Q

List

Frequency Division Multiple Access (FDMA) Advantages

A
  • Simplicity
  • Proven and reliable
51
Q

List

Frequency Division Multiple Access (FDMA) Disadvantages

A
  • Needs more BW as you add users
  • In-flexible, not easy to reconfigure
52
Q

Identify

Users share a single RF channel without interference by allocating different time slots to each user

A

Time Division Multiple Access (TDMA)

53
Q

Time Division Multiple Access (TDMA) Advantage

A

Efficient use of BW (user gets full BW during their time slot)

54
Q

Time Division Multiple Access (TDMA) Disadvantages

A
  • Needs to account for Tx delay for differing Earth Stations
  • Large Earth Segment investment (transmit equip/controllers)
  • Need for very precise time standards
  • Limited time slots
55
Q

Tx technique that employs a scheme that codes every digital packet it sends with a unique key to allow users to be multiplexed over the same frequency channel

A

Code Division Multiple Access (CDMA)

56
Q

List

Code Division Multiple Access (CDMA) Advantages

A
  • More resistant to jamming and interference than FDMA and TDMA
  • Resistant to interception
57
Q

Code Division Multiple Access (CDMA) Disadvantage

A

Equipment cost is much higher, along with the larger BW that is required

EWOK (22 decks)

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