The ATSC Terrestrial TV standard is based on an 8-VSB modulation with pilot insertion. The sequence of 8 level symbols with levels ±1, ±3, ±5 and ±7 is the input to the 8-VSB modulator. The symbol rate is 10.762 Msb/s. The modulator has to modulate these symbols using VSB modulation and form the VSB spectrum that fits within a terrestrial 6 MHz channel.
![8-VSB Signal Spectrum 8-VSB Signal Spectrum](https://vocal.com/wp-content/uploads/2015/04/8-vsb-signal-spectrum.png)
To form this spectrum, the 8-VSB modulator has to process symbols by real and imaginary VSB filters and create a complex 8-VSB spectrum. The real VSB filter is a bypass filter that is just a delay block. The pilot insertion happens by adding a constant value to the input filter. For ATSC the standard pilot value is 1.25. The rolloff of the spectrum and respectively of the imaginary filter has to be 0.115.
![8-VSB Modulator 8-VSB Modulator](https://vocal.com/wp-content/uploads/2015/04/8-vsb-modulator.png)
After modulation to the intermediate frequency fIF the signal is then shifted to radio frequency (RF).
![8-VSB Real and Imaginary filter frequency responses 8-VSB Real and Imaginary filter frequency responses](https://vocal.com/wp-content/uploads/2015/04/8-vsb-real-imaginary-filter-frequency-responses.png)
More Information
- ATSC Digital Terrestrial TV Transmitter
- ATSC Digital Terrestrial TV Receiver
- Video Streaming
- Video Codecs
- Video Design
- Video Reference Designs