8 level VSB modulation-Vestigial Sideband Amplitude Modulation
This page describes 8 level VSB modulation. VSB is the short form of Vestigial Sideband Amplitude Modulation.
It is the modulation scheme used in Digital TV. In this modulation, carrier is suppressed. It carries only upper sideband for transmission. The serial data is passed to DAC where in 3 bit group is converted into a discrete voltage level.
The system encodes 3 bits per symbol. This increases data rate within the channel. The example is depicted in the figure above. As shown each 3 bit group is converted into relative level of -7, -5, -3, -1, +1, +3, +5 or +7. This is the signal which is used to modulate on the RF carrier.
This results into symbol rate of about 10800 symbols per second. This gets translated into 3 x 10800 = 32.4 Mbps.
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