Deck 6: Signalling 2 Flashcards

1
Q

The values that a digital signal can take depend on what?

A
  • Depend on the number of bits used.
  • A one bit signal can only take the values 0 and 1.
  • A one byte signal can take 256 different values.
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2
Q

What type of signals are not limited in the values they can take?

A

Analogue signals are not limited in the values they can take- they vary continuously.

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3
Q

Why is it much easier to reconstruct a digital signal rather than an analogue signal?

A
  • Because the number of values a digital signal can take is limited.
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4
Q

What is digitising?

A
  • Transforming an analogue signal into a digital signal.
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5
Q

How do you digitise a signal?

A
  • To digitise a signal, you take the value of the signal at regular time intervals, then find the nearest digital value.
  • Each digital value is represented by a binary number, so you can convert the analogue values to binary numbers.
  • The digital signal will not exactly the same.
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6
Q

How well a digital signal matches the original signal depends on what two factors?

A

1) The difference between the possible values(resolution)

2) The time taken from one sample to the next(sampling rate).

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7
Q

How can you calculate the maximum number of bits a digitised signal can have?

A

Maximum number of bits = log2(Vtotal/Vnoise)

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8
Q

What is the sampling rate?

A

When you digitise a signal, you record the value of (sample) the original signal at regular intervals. The rate at which you sample the signal is called the sampling rate.

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9
Q

What are the consequences of having a low sampling rate?

A
  • A low sampling rate can create low frequency signals- called aliases - that weren’t in the original signal at all.
  • Detail can be lost.
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10
Q

How is the minimum sampling rate calculated?

A

Minimum rate of sampling = 2 x maximum frequency of signal.

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11
Q

What are the four main advantages that digital signals have over analogue signals?

A
  • Digital signals can be sent, received and reproduced more easily than analogue signals because they can only take a limited number of values.
  • Digital signals are resistant to the effect of noise
  • Digital signals can be used to represent different kinds of information in the same way - for example, images and sounds can both be represented by a string of bits.]
  • Digital signals are easy to process using computers.
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