Digital modulation quiz

Digital modulation quiz#

Symbols#

Exercise 103

Which is/are correct about symbols?

  1. A symbol always represents exactly one bit of information.

  2. In sign language, every sign can be considered a symbol.

  3. A symbol can be either -1 or 1.

  4. A symbol can be either 0 or 1.

  5. Symbols must always be square waves to maximize spectral efficiency.

Wireless symbols#

Exercise 104

Which is/are true?

  1. We can transmit a -1 Hz signal with an antenna but not with cable.

  2. We can transmit 0 Hz signal with a cable but not with an antenna.

  3. It is not possible to transmit square waves with an antenna.

  4. An FM radio signal that your car radio receives is a square wave.

  5. The concept of a symbol in an analog radio signal transmission like FM does not make significant sense, because we don’t define individual symbols but send continuous analog data like voice.

ASK#

Exercise 105

Look at the following figure:

https://github.com/777arc/PySDR/blob/master/_images/ethernet.svg?raw=1

Fig. 72 One of the Ethernet modulation schemes.#

Source M. Lichtman | License: CC BY-NC-SA 4.0

Which property/properties are varied in the signal above?

  1. Value

  2. Amplitude

  3. Frequency

  4. Phase

  5. Modulation

  6. Skew

  7. Spectral efficiency

PSK#

Exercise 106

Which is/are true?

  1. PSK stands for phase shift keying.

  2. BPSK defines two symbols that differ in their amplitude

  3. BPSK defines four symbols that differ in their amplitude

  4. BPSK defines two symbols that differ in their phase

  5. BPSK defines four symbols that differ in their phase

IQ Plots/constellations#

Exercise 107

Which is/are true?

  1. IQ plot displays amplitude and phase information

  2. IQ plot displays amplitude and frequency information

  3. IQ plot displays phase and frequency information

  4. IQ plot is useful for visualizing received symbols

  5. A constellation plot shows the symbols defined in a modulation scheme.

  6. A constellation plot with four points shows a modulation scheme with four symbols.

QAM#

Exercise 108

Which is/are true?

  1. 16-QAM uses 16 symbols.

  2. 16-QAM uses 4 symbols.

  3. 16-QAM uses 4-bit symbols.

  4. 16-QAM uses 16-bit symbols.

  5. QAM varies amplitude compared to ASK.

  6. QAM varies frequency compared to ASK.

FSK#

Exercise 109

Which is/are true?

  1. FSK varies frequency compared to QAM.

  2. FSK varies amplitude compared to QAM.

  3. In FSK, each frequency is an individual symbol.

  4. A typical carrier frequency for the frequencies 1.15, 1.20, 1.05, 1 MHz could be 1.1 MHz.

Differential coding#

Exercise 110

Which is/are true?

  1. If we encode nine BPSK symbols using differential coding, then we get at most nine bits.

  2. Differential coding transmits the differences between the transmitted symbols.

  3. The differences between the symbols of BPSK can be -1, 0 or 1, so a sequence of -1, 0 or 1s are transmitted.

  4. Differential coding can also be applied to QPSK.

  5. Differential coding helps to solve phase ambiguity in a received symbol.

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