[opendtv] Re: Samsung Prototype ATSC Receiver Test Report
- From: Eory Frank-p22212 <Frank.Eory@xxxxxxxxxxxxx>
- To: "'opendtv@xxxxxxxxxxxxx'" <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 13 Oct 2005 02:13:19 -0700
Al Limberg wrote:
>The inability of the receivers to reject short-delay echoes is probably
>because they use synchronous equalizers in which tap
>spacing is equal to the reciprocal of symbol rate. Eventually, the industry
>may gravitate towards fractional equalizers in
>which tap spacing is equal to the reciprocal of twice symbol rate.
>U.S. patent No. 6,377,312 titled "ADAPTIVE FRACTIONALLY SPACED EQUALIZER FOR
>RECEIVED RADIO TRANSMISSIONS WITH DIGITAL CONTENT, >SUCH AS DTV SIGNALS" is on
>point, describing how such equalizers can accommodate data slicing in the IIR
>filtering. The patent >issued 23 April 2002 to Dr. C. B. Patel and me. Samsung
>is the assignee.
>Al Limberg
C'mon Al, T/2 equalizers are as old as the hills. I studied them in college
almost 2 decades ago and have built several in the intervening years. Not all
8-VSB receivers use symbol-spaced equalizers, as we discussed 5 years ago in
the ATSC ad-hoc group. So naturally, not all of them have problems rejecting
short-delay echoes. "Delay" never was and still is not a real "problem" for
equalizers in ATSC receivers -- delay, aka equalizer tap spacing and total
equalizer span, is just a matter of hardware, which is a cost issue, and one
that is exacerbated by the ATSC's foolish decision to use a one-dimensional
modulation (VSB) when a quadrature modulation would have done just as well
(actually better) and would have been cheaper to build.
Glad to see you and C.B. are still bombarding the PTO office with applications,
and I mean no disrespect. I'm just sitting here chuckling at the DTV
transmission issues that never seem to end or be completely solved. I've been
away from OpenDTV for awhile, but it looks like I could pick up right where I
left off way back when on these receiver discussions! I don't think the recent
news of "progress" bodes well for all those poor suckers who will be forced to
buy ATSC receivers in their new TV sets.
-- Frank
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