Forum: GNU Radio BASIC_RX complex sampling

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558c40b97bd1af8d912424757714bda9?d=identicon&s=25 Marcus D. Leech (Guest)
on 2009-04-16 20:23
(Received via mailing list)
Does the FPGA code for BASIC_RX support a Hilbert transform to convert
one of the real inputs into a complex stream?

--
Marcus Leech
Principal Investigator, Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
D0072e69d706bb3ca211d33a1b536e2c?d=identicon&s=25 Johnathan Corgan (Guest)
on 2009-04-16 20:43
(Received via mailing list)
On Thu, 2009-04-16 at 14:22 -0400, Marcus D. Leech wrote:

> Does the FPGA code for BASIC_RX support a Hilbert transform to convert
> one of the real inputs into a complex stream?

No, but if your signal of interest has a passband above DC, when you
"tune" the BasicRX, the complex mixer in the FPGA will still
down-convert it to a complex baseband I/Q signal.

Johnathan
558c40b97bd1af8d912424757714bda9?d=identicon&s=25 Marcus D. Leech (Guest)
on 2009-04-16 20:52
(Received via mailing list)
Johnathan Corgan wrote:
>
> Johnathan
>
>
>
>
Ah, fabulous.   So if I have a 10.7MHz IF coming out of a receiver in
real mode, I can just "tune" the BASIC_RX
  to 10.7, and it'll as-if-by-magic become a complex signal of +/-5Mhz?
Sweet.

--
Marcus Leech
Principal Investigator, Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
D0072e69d706bb3ca211d33a1b536e2c?d=identicon&s=25 Johnathan Corgan (Guest)
on 2009-04-16 20:59
(Received via mailing list)
On Thu, Apr 16, 2009 at 11:51 AM, Marcus D. Leech <mleech@ripnet.com>
wrote:

> Ah, fabulous.   So if I have a 10.7MHz IF coming out of a receiver in
> real mode, I can just "tune" the BASIC_RX
>  to 10.7, and it'll as-if-by-magic become a complex signal of +/-5Mhz?

Close.  You didn't mention USRP1 or 2, so I'm assuming USRP1, and
you'll get a baseband signal of a maximum +/-4MHz with decimation of
8.

It's not magic, it's math :-)

Johnathan
558c40b97bd1af8d912424757714bda9?d=identicon&s=25 Marcus D. Leech (Guest)
on 2009-04-16 21:36
(Received via mailing list)
Johnathan Corgan wrote:
> On Thu, Apr 16, 2009 at 11:51 AM, Marcus D. Leech <mleech@ripnet.com> wrote:
>
> Close.  You didn't mention USRP1 or 2, so I'm assuming USRP1, and
> you'll get a baseband signal of a maximum +/-4MHz with decimation of
> 8.
>
Yes, USRP1.
> It's not magic, it's math :-)
>
>
It's so much more fun to think of it as magic, but yes, it's math.
Coupla synthetic LOs, coupla multiplies, voila, a complex mixer.

I'll actually be using it at +/- 3.2MHz (decim=10).

--
Marcus Leech
Principal Investigator, Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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