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John Sokol Home Page, HDTV and Video Compression/Streaming Expert

ATSC(Advanced Television Systems Committee) Released the A/53 standard based on 8VSB modulation. A/53 can transport 18 different formats of information and A/53 is extensible, meaning the standard has the ability to expand and change as time goes by.

8-VSB is the 8-level Trellis coded Vestigial SideBand Modulation developed by Zenith and adopted for FCC and ATSC(Advanced Television Systems Committee) standard of DTV (Digital TeleVision) in the USA. HDTV uses this for terrestrial broadcast transmission. Other standards like DVB-S are used for Satellite transmissions..

Transmitted 8VSB HDTV signal on Spectrum analyser
	Horizontal is 2 Mhz / div Vertical is 10 dB / div Notice on the left side that spike on top, this is the ATSC Pilot signal use to accuraty tune in the DTV signal.
90% of the transmitted power falls within 5.39 MHz

Harris - What Exactly Is 8-VSB Anyway? (HTML) , (PDF) By David Sparano

There has been a continuing lobby for changing the modulation for ATSC to COFDM instead, the way DVB-T is transmitted in Europe, and ISDB-T in Japan. However, the FCC has continued to assert that 8VSB is the better modulation for use in U.S. digital television broadcasting.

FCC: DTV REPORT ON COFDM AND 8-VSB PERFORMANCE September 30, 1999

FCC's Digital Television (DTV) Regulatory Information

Analog Broadcast TV Frequencies in the US

Proposed Digital HDTV broadcast modulations

Excellent Paper on history of HDTV, PDF

FM - Frequency Modulated

Video technology Magazine Has More information on Digital Television

Mark Schubin digitaltelevision Memo Just ran across this by accident, but this guy is realy on top of the news

Zenith - ATSC TRANSMISSION SYSTEM: VSB TUTORIAL

Vestigial Sideband Modulation

Amplitude modulation typically produces a modulated output signal that has twice the bandwidth of the modulating signal, with a significant power component at the original carrier frequency. Single-sideband modulation improves this, at the cost of extra complexity.

The best way of thinking of SSB modulation is to first consider an amplitude modulated signal. This will have two frequency-shifted copies of the modulated signal (the lower one is frequency-inverted) on either side of the remaining carrier signal. These are known as sidebands.

To produce an SSB signal, apply a filter that will filter out one of the sidebands, and remove the carrier signal. What remains still contains the entire information content of the AM signal, using substantially less bandwidth and power, but cannot now be demodulated by a simple envelope detector.

When the 'wrong' sideband is only partially suppressed, the resulting modulation technique is known as vestigial-sideband modulation (VSB).

To recover the original signal from an SSB signal, the carrier must be replaced with an extra substitute carrier signal, sometimes called a "false carrier", prior to sending the signal to a standard envelope detector.

For this to work, the substitute carrier must be accurately adjusted to match the frequency of the original carrier. If the substitute carrier is mis-adjusted, the output signal will be frequency-shifted, making speech sound strange and 'Donald Duck'-like.

If the wrong substitute carrier is selected at IF conversion time, the audio signal will also be frequency inverted. This effect was used, in conjunction with other filtering techniques, during World War II as a method for speech encryption. Radio telephone conversations between the US and England were intercepted and 'decrypted' by the Germans; they included some early conversations between Roosevelt and Churchill. Today (2001), such simple 'inverter'-based speech encryption techniques are easily decrypted using simple techniques and are no longer regarded as secure.

SSB and VSB can also be regarded mathematically as special cases of quadrature amplitude modulation.