Philips 14AA3322/40B Guía de instalación descargar pdf (Pagina 122)

Generation of a transport stream for DVB and realisation of a HF-modulated DVB-signal

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If you don’t see anything press the magnifying glass button and check that the blue LEDs “T” and “D” are

switched on.

Figure 4. Promax’s Satellite/Terrestrial and Analog Digital buttons.

Also you will have to check the tuning frequency, it has to be the same at the StreamXpress and at the TV

EXPLORER.

NOTE: Only CBR Transport Streams are supported

Exercise1

Explain the differences between DVB-H, DVB-C and DVB-T.

DVB-H: is a modulation standard for terrestrial handheld broadcasting used by countries that adopted

DVB standards

DVB-T: is a modulation standard for terrestrial broadcasting used by countries that adopted DVB

standards.

DVB-C: is a modulation standard for cable TV used by countries that adopted DVB standards.

Exercise2

Explain the differences between QPSK, 16-QAM, 64-QAM constellations.

Both 16 and 64-QAM are divided in groups of bits, as many as are needed to generate the N modulation

states. That’s why we talk about N-QAM. In the 16-QAM case, every 4 entrance bits, which provide 16

different values (0 - 15), the amplitude and the phase of the carrier are altered to derivative 16 unique

modulated states.

With QPSK the difference is the distribution of the symbols. They are equally separated around a circle.

QPSK can code 2 bits per symbol and the bit assignment it’s made by Gray code which can achieve a less

bit error rate. It’s also used to duplicate the data rate keeping the same bandwidth of the signal.

Exercise3

What do you see when you change the constellation? Try with N-QAM and QPSK. Comment the

differences.

If the change it’s between N-QAM, the only difference we will notice it’s the modulation error rate. The

symbols will appear more scattered, but the image it’s barely the same, you won’t distinguish any

differences.

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Philips 14AA3322/40B Guía de instalación Pagina 122