[hpsdr] New RF Digitizer

Tue Nov 14 06:14:09 PST 2006

Nyall,

That's a great explanation. The SDR-IQ uses the AD9245 with an SN of 72.7dB 
to nyquist. The chose this part for the current draw. It had to be powered 
from USB.

Regards,

Pieter

>From: "Nyall Davies" <nyalldavies at ukonline.co.uk>
>To: "Ahti Aintila" <oh2rz.sdr at gmail.com>,"Lyle Johnson" 
><kk7p at wavecable.com>
>CC: High Performance Software Defined Radio Discussion List 
><hpsdr at hpsdr.org>
>Subject: Re: [hpsdr] New RF Digitizer
>Date: Tue, 14 Nov 2006 10:01:21 -0000
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>***** High Performance Software Defined Radio Discussion List *****
>
>
>COMPARISON OF SDR-IQ with HPSDR
>The signal noise ratio of the fast AD converters does not allow the full 
>use
>of all the bits. The extra bits in the AD should mean that the quantization
>loss in the AD can be ignored - it should provide its own dither noise.
>
>The picture of the SDR-IQ shows that it uses the AD6620 which comprises the
>digital mixer and set of CIC filters. The processing gain the AD6620 is 
>such
>that 23 bits are required at its output
>I cannot see what AD it uses but we have to assume that it is the AD6645.
>This part has a S/N ratio around 74dB
>It states that the sampling is done at 67MHz (the max spec of the AD6620)
>If we are using the LTC2207 sampling at 100MHz - it has a quoted S/N of 
>78.2
>dB so we are better due to the AD SN by 4.2dB
>If we sample at 100 MHz we gain 10 log(100/67) dB of processing gain =1.739
>dB
>
>So we can expect a performance 4.2 +1.7 = 5.9dB better than the SDR-IQ
>
>It has been suggested to me that we Linear tech can supply a device to
>sample at higher rates say 150MHz so we may, depending on the S/N of this
>device, be able to gain another 1.7dB
>
>Nyall G8IBR
>
>----- Original Message -----
>From: "Ahti Aintila" <oh2rz.sdr at gmail.com>
>To: "Lyle Johnson" <kk7p at wavecable.com>
>Cc: "High Performance Software Defined Radio Discussion List"
><hpsdr at hpsdr.org>
>Sent: Tuesday, November 14, 2006 5:23 AM
>Subject: Re: [hpsdr] New RF Digitizer
>
>
> > ***** High Performance Software Defined Radio Discussion List *****
> >
> > On 14/11/06, Lyle Johnson <kk7p at wavecable.com> wrote:
> >> ***** High Performance Software Defined Radio Discussion List *****
> >>
> >> This from RF Space, the guys that make the SDR-14:
> >>
> >> <http://www.rfspace.com/sdriq.html>
> >>
> >> A sort-of Ozy+Mercury, albeit with fewer bits and a lower sampling 
>rate.
> >>
> >> 73,
> >>
> >> Lyle KK7P
> >
> > Not bad and very compact! I hope that our heavy-weight champion
> > Atlas+Ozy+Mercury combination can put the dynamic range at least 20 dB
> > better. Am I asking too much?
> >
> > 73, Ahti OH2RZ
> >
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