Complete Communications Engineering

ATSC Digital Terrestrial TV Transmitter is a standard developed by the Advanced Television Systems Committee, Inc. for terrestrial digital television broadcasting. ATSC is an international, non-profit organization developing voluntary standards for digital television. ATSC Digital TV Standards include digital high definition television (HDTV), standard definition television (SDTV), data broadcasting, multichannel surround-sound audio, and satellite direct-to-home broadcasting.

ATSC Digital Terrestrial TV Transmitter is widely adopted in North America for 6 MHz terrestrial channels with a bitrate for the transmitted signal of 19.3 Mbit/sec. This standard is based on 8-VSB (Vestigial Sideband) modulation with pilot.

Fig 1 ATSC Digital Terrestrial TV Data Frame

The input video stream for the modulator is a set of 188-byte standard MPEG-2 data packets. There are two stages of FEC (forward error correction): Reed-Solomon encoding and Trellis encoding. The sequence of MPEG-2 data packets are encoded in Reed Solomon. The encoder adds 20 parity bytes for each data packet.

ATSC Digital Terrestrial TV Data Segment

Fig 2 ATSC Digital Terrestrial TV Data Segment

Next, the data is sent through an interleaver to be robust against bursts of impulse noise and encoded using a Trellis encoder to form the transmission data. Each transmission data frame consists of two fields, and each field consists of 313 data segments. The first segment of each field is a frame synchronization segment. Each segment consists of 832 one dimensional 8-level symbols. Each segment has a 4-symbol synchronizing signal that takes only two levels out of 8. The symbol rate for all digital VSB modes is 10.762 Msb/s.

Fig.3 ATSC 8-VSB transmitter block diagram
Fig.3 ATSC 8-VSB transmitter block diagram

The sequence of symbols are modulated in the VSB modulator to form an 8-VSB signal. After that the signal is moved in the spectral domain to RF band and then broadcast.

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