Chapter 3

Chapter 3 – Signalling with Electromagnetic Waves How Signals are Sent…

We know that analogue signals constantly change and digital signals have a value of 1 or 0.

2 1 6 65536 16 … … … 2 9 512 9 2 8 256 8 2 7 128 7 2 6 64 6 2 5 32 5 2 4 16 4 2 3 8 3 2 2 4 2 2 1 2 1 2 n Number of Levels Number of Bits

Redundancy ,[object Object],[object Object],Jarrow Sings the Blues MFI Records 1934

So how do we get digital signals? ,[object Object],[object Object],Original Reconstructed 0110101100010101 How does this get sent??

Electromagnetic Radiation ,[object Object],[object Object],[object Object]

What is a Signal ,[object Object],[object Object],[object Object]

Signal Properties ,[object Object],[object Object],[object Object],[object Object],[object Object]

Calculating Frequency ,[object Object],[object Object]

Calculating Frequency ,[object Object],[object Object],[object Object],[object Object]

Calculating Frequency Frequency = 1 / Period Period = 6.6 ms Amplitude = 4V Frequency = 1/6.6ms = 150Hz

Frequency Spectrum ,[object Object],[object Object],Contains frequencies around 50Hz only

Frequency Spectrum ,[object Object],Contains frequencies around 150Hz only

What about complex signals ,[object Object],[object Object],This is made up of several different frequencies – see how a wave can be made up…

Draw these waves onto graph paper. Draw the combined waveform.

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