Analogue and
digital signals
12 grade 1 term 3 week 5-6
LO
12.1.1.5 - recall the advantages of the transmission of data in
digital form, compared to the transmission of data in
analogue form;
12.1.1.6 - understand that the digital transmission of a signal
involves analogue-to-digital conversion (ADC) on
transmission and digital-to-analogue conversion (DAC) on
reception;
New topic
Analogue signal
Digital signal
Binary numbers
The transmission of a signal
Analogue and digital signals
Analogue signal - in nature is information (speech, music, picture)
A digital signal consists of a series of ‘highs’ and ‘lows’ with no values between the
‘high’ and ‘lows’
Binary numbers
The transmission of a signal
In analogue-digital converter analog signal must be converted into a digital signal.
LO: Understand that the digital
transmission of speech or
music involves analogue-todigital conversion (ADC) on
transmission and digital-toanalogue conversion (DAC) on
reception.
Keywords
analogue-to-digital conversion (ADC) –
Conversion of a continuous analogue signal
to discrete digital numbers
digital-to-analogue conversion (DAC) –
Conversion of a series of digital numbers
into a continuous analogue signal
Analogue signal
An information signal that has the same variations with time as the
information itself is known as an analogue signal.
For example, the voltage signal generated by a microphone is an analogue
signal
A digital signal is series of pulses between discrete levels.
Digital signal consists of a series of “0” and “1”.
Analogue-to-digital conversion (ADC) – Conversion
of a continuous analogue signal to discrete digital
numbers
Component of PCM
(Pulse Code Modulation)
SAMPLING
Sampling is the measurement of the analogue
signal at regular time intervals.
Digital to analogue conversion
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Digital-to-analog conversion is a process in which signals
having a few (usually two) defined levels or states (digital)
are converted into signals having a theoretically infinite
number of states (analog). ... The circuit that performs this
function is a digital-to-analog converter (DAC).
DAC to ADC Conversion
The transmission of a signal
In an analogue signal, such as speech or music, the generated voltage
signal varies continuously. For digital transmission, this analogue signal
must be converted into a digital signal. This is achieved using an
analogue-to-digital converter (ADC).
The digital transmission of speech may be represented by the block
diagram:
Principles involved in the analogue-to-digital conversion of the signal
and its transmission:
1) signal sampled at regular intervals
2) signal voltage converted to a digital number
3) transmitted as a series of groups of pulses
4) pulses could be IR pulses in optic fibre
Binary and Decimal Numbers
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Most numbers we are used to using are part of the
decimal system, in which counting is done on a basis of
10.
In the binary system, counting is done on the basis of 2,
since there are only two digits.
In the decimal system, 243 = 2 x 100 + 4 x 10 + 3 x 1
In the binary system, 111 = 1 x 4 + 1 x 2 + 1 x 1 = 7
Each digit in the binary system is known as a bit
The bit with the highest value is on the left hand side,
and is known as the most significant bit (MSB)
The bit with the lowest value is on the right hand side,
and is known as the least significant bit (LSB)
Converting binary and decimal numbers
Reflection
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On a scale of 1-5, how well do you understand
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ADC and CAD
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Binary numbers
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Sample rate
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The advantages of digital signals