analogue an digital signals internet.ppt
TRANSCRIPT
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Analogue an Digital Signals
01001011010011001001010010010010
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How many things use digital or analogue signals
• Digital Analogue
TV
Radio
Talking
vinyl
watch
Mp3 playerCamera
Orchestra
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Analogue TV
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How are digital television pictures sent?
The TV program is filmed,This is a real life analogue signal
It is converted to a Digital signal
The signal is transmitted using radio waves
It is received by your aerialand decoded at your house
Watch TV
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Make your own signal
0 = 01 = 12 = 103 = 114 = 1005 = 1016 = 1107 = 1118 = 10009 = 100110 = 1010
7
111 110
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0
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1 Sec
Sampled at 2 Hz
Signal Consisting of 1 Hz, 5 Hz and 10Hz
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Sampled at 5 Hz
Signal Consisting of 1 Hz, 5 Hz and 10Hz
Here we seem to obtain a good sin wave at a frequency which was not present in the original signal. This is called ‘Aliasing’.
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Sampled at 10 Hz
Signal Consisting of 1 Hz, 5 Hz and 10Hz
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Sampled at 20 Hz
Signal Consisting of 1 Hz, 5 Hz and 10Hz
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Sampled at 40 Hz
Signal Consisting of 1 Hz, 5 Hz and 10Hz
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A Noise Signal
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Analog Signal with Noise (Large Signal to Noise Ratio)
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Analog Signal with medium Signal to Noise Ratio
The signal can be recovered reasonably well by smoothing (but each time we do this the corruption is increased.)
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Analog Signal with small signal to noise Ratio
Even if we try to recover the signal by smoothing it is corrupted.
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0
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Digital Signal
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Digital Signal Signal with quite large signal to noise ratio.
The signal only consists of ‘1’s and ‘0’s so it can be recovered exactly.This can be done as many times as necessary.
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The advantages of digital signals
The disadvantages of digital
In pairs discuss
Unwanted noise
quality
Quantity of information
Unwanted errorsEasy to use
The advantages of analogue signals
The disadvantages of analogue
simple
complicated
Needs extra equipment
Difficult for humans to understand
Easy for computers to work with
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Write your own code and swap with your neighbour to decode
A 0 B 1C 10D 11E 100F 101G 110H 111I 1000J 1001K 1010L 1011M 1100N 1101
O 1110P 1111Q 10000R 10001S 10010T 10011U 10100V 10101W 10110X 10111Y 11000Z 11001
Put commas between the words to help the decoding
Encoding