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Re: aliasing with X310 BasicRX (higher order Nyquist zone) ?

From: Marcus D. Leech
Subject: Re: aliasing with X310 BasicRX (higher order Nyquist zone) ?
Date: Mon, 20 Jul 2020 11:40:59 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

On 07/20/2020 11:29 AM, jean-michel.friedt@femto-st.fr wrote:
Indeed second Nyquist zone before decimation.
My thought was
143.05 MHz -> transpose by 100 MHz using the DDC (NCO at 100 MHz considering the
200 MHz sampling rate) to reach 43.05, and after transposition, decimating to 
8 MS/s (I do have Epcos B3607 SAW filters 140+/-3 MHz frontend to select only 
signal I am interested in).
It is in the decimation process that I was thinking of being in the third
Nyquist zone after decimation, which is incorrect because 8 MS/s is -4 to +4, 
so that
43.05 is in the 6th Nyquist zone after decimation (\in[36:44] MHz).

Thanks, JM

The signal will be coming out of the ADC at 56.5Mhz, which you should be able to just ask the DDC to pick off and give you your desired 8MHz
   of bandwidth--I think it's as uncomplicated as that.

The BASIC_RX implementation still accepts tuning requests, and those just direct the DDC to do the right thing. This should "just work", unless
  there's breakage in the BASIC_RX implementation...

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