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Introduction to SNG and ENG Microwave by Jonathan Higgins

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Digital modulation in SNG

Without going into heavy-duty theory, you need to appreciate that there are different types of modulation (we have already gone over the basics of this) and in digital modulation the predominant modulation is QPSK – a type of phase modulation. Other types of phase modulation are 8-PSK and 16QAM, but these are not commonly used in DSNG.

With QPSK, the carrier undergoes four changes in phase and can thus represent 4 bits of data, and every 2 bits in a QPSK modulated signal make up a ‘symbol’. We talk of a digital modulated signal in symbols per second, or mega (million) symbols per second (MSps).

We have talked about encoding in terms of compression and MPEG-2, but there is also an element of digital encoding within the ...

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