BASIC_RX complex sampling


#1

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


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


#2

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


#3

Johnathan C. 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 L.
Principal Investigator, Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org


#4

On Thu, Apr 16, 2009 at 11:51 AM, Marcus D. Leech removed_email_address@domain.invalid
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 :slight_smile:

Johnathan


#5

Johnathan C. wrote:

On Thu, Apr 16, 2009 at 11:51 AM, Marcus D. Leech removed_email_address@domain.invalid 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 :slight_smile:

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 L.
Principal Investigator, Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org