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Discussion Starter · #1 ·
I've put together a web page answering alot of the quesitons I seen here, and have had emailed to me. Let me know if there is anything confusing about it, or if I can add other information to make it better.

-Bill

Zektor

http://www.zektor.com/hds4/componentvideo.htm
 

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I guess I don't agree with using the Kell factor as

part of the equation. Let's take the case of the

6.75 MHz resolution pattern on Avia. It's alternating

pixels of digital values 16 and 235 in the horizontal

direction. For 480i scanning, the pixel time is:


1 / 29.97 fps / 525 lines / 858 pixels per line = 74.074 ns


So the video output signal while scanning the pattern

should ideally be a square wave at black for 74 ns

and white for 74ns which is equal to 6.75 MHz (hence

the name 6.75 MHz resolution pattern).


How does the Kell facter come into play in this example?


I do agree with the rule of thumb that you need 10x

the bandwidth for 0.1 dB flatness. That's excellent info.


The other way to think of this is the square wave example

I gave above. Since a square wave is composed of the

fundamental frequency and infinite odd harmonics, then

you must pass at least up to the 9th harmonic to have a

reasonable looking square wave.


Ron W6RZ
 

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Discussion Starter · #3 ·
The Kell factor is more of an adjustment factor for apparent vertical resolution, but it would also seem to me that the max bandwidth requirement would come from horizontal resolution, so the Kell factor would be ignored for finding the Max BW. However the Kell factor is commonly used throughout the industry for determining the bandwidth requirements, not just by Dallas/Maxim. It is something I am still researching.

-Bill
 

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Quote:
Originally posted by dr1394
I do agree with the rule of thumb that you need 10x

the bandwidth for 0.1 dB flatness.
I disagree. Why would you assume the response is any better than +/- 3 dB for any sub-band across the stated band? If it really was +/- 0.1 dB across a smaller bandwidth (the bandwidth that's actually important to you) don't you think they'd publish that spec? Something like:


+/- 3 dB to 50 MHz and +/- 0.1 db to 6 MHz
 

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