[hpsdr] Horton (or other) gain distribution targets?

[John B. Stephensen]

Analog devices also limit long before IP3 is reached. ADCs behave somewhat
differently in that distortion products don't increase by the square of the
input signal level, but tend to remain at a relatively fixed level, varying
by only 10 dB or so with different input signal levels.  The equivalent
specifications for an ADC woud be two-tone dynamic range or intermodulation
distortion data specified two-tone input levels.

73,

John
KD6OZH

----- Original Message ----- 
From: "Ray Anderson" <ray.anderson at xilinx.com>
To: <hpsdr at hpsdr.org>
Sent: Wednesday, August 09, 2006 18:17 UTC
Subject: Re: [hpsdr] Horton (or other) gain distribution targets?


> ***** High Performance Software Defined Radio Discussion List *****
>
>
>
> >Hi Jim,
>
> >The ENOB of the AK ADC on the Janus board is 20. Given the max input of
> >1.5v p-p you can work out the MDS and hence the  gain required on each
> >band.
>
> >Gain will be required in the ISD but we may not need a preamp on
> 10/12m, we
> >will require one on 6m and above.
>
> >73's Phil...VK6APH
>
>
> Phil, can you go into a bit more detail on the AK ADC ENOB number?
>
> Since ENOB = (SINAD-1.76dB)/6.02 , we can say the SINAD =
> (6.02*ENOB)+1.76dB
>
> So for a ENOB of 20 then SINAD = 122.16 dB . So far, so good.
>
> Now looking at the AK5394a datasheet we find S/(N+D) in the 87dB to
> 110dB range (depending on the sampling freq and input level). Is S/(N+D)
> the same as SINAD ?
>
> I find a S/N (a-weighted) spec of 123dB typ or 117dB min, but this isn't
> the same as SINAD. (or is it ??)
>
> Could you elaborate a bit on the interpretation of the AK5394a specs?
> Thanks!
>
>
> One other related question. I notice in the calculation write-up on the
> Mercury Wiki page you talk about a IP3 for the ADC chip. Can you really
> talk about IP3 for a ADC since it doesn't gracefully compress when
> overloaded but acts as a hard limiter? Thanks again...
>
> 73 de Ray WB6TPU
>
>
>
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