Forum: GNU Radio Intermediate frequency question

Announcement (2017-05-07): www.ruby-forum.com is now read-only since I unfortunately do not have the time to support and maintain the forum any more. Please see rubyonrails.org/community and ruby-lang.org/en/community for other Rails- und Ruby-related community platforms.
Mir A. (Guest)
on 2009-05-13 06:06
(Received via mailing list)
Hi,
If I am using RFX2400 then what is the IF frequency and can we change
this
to some other value? Correct me if the question I asked is wrong.

Thanks,
Ali
Jason U. (Guest)
on 2009-05-13 09:22
(Received via mailing list)
> If I am using RFX2400 then what is the IF frequency and can we change this
> to some other value? Correct me if the question I asked is wrong.

With the RFX2400, and most of the high frequency usrp daughtercards,
there is no IF frequency.  The samples you receive (or send) from the
usrp.source_x (or usrp.sink_x) are baseband I and Q values.

Jason
Mir A. (Guest)
on 2009-05-13 10:26
(Received via mailing list)
Yeah, I got it. I read in a tutorial and I understand now.

Thanks again.
Mohd adib S. (Guest)
on 2009-05-14 10:28
(Received via mailing list)
Mir A.-4 wrote:
>
> Yeah, I got it. I read in a tutorial and I understand now.
>
>
>

hi Ali,
  what tutorial do you read for this? hope it will be useful to others
especially to me =) tQ

Adib
--
View this message in context:
http://www.nabble.com/Intermediate-frequency-quest...
Sent from the GnuRadio mailing list archive at Nabble.com.
Brook L. (Guest)
on 2011-10-06 03:08
(Received via mailing list)
Hi All,

I am confused on this reply. The reply said that "With the RFX2400, and
most
of the high frequency usrp daughtercards,
there is no IF frequency". How is that possible? For RFX2400 the RF
range is
from 2.3GHz to 2.9GHz, the ADC rate for USRP1 is 64MS/s. If there is no
IF
frequency, the ADC rate is obviously too low. There must be RF front-end
on
the daughterboard to tune the RF to the IF. Right? If so, my question is
what the IF is? Obviously, f_IF = f_RF - f_LO. (1) Are we setting the
f_LO
when we tune the usrp by usrp.tune(self.u, 0, self.subdev, target_freq)?
(2)
How to figure out f_IF for different daughterboards?

Thanks in advance,
Brook



Jason U. wrote:
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> removed_email_address@domain.invalid
> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>

--
View this message in context:
http://old.nabble.com/Intermediate-frequency-quest...
Sent from the GnuRadio mailing list archive at Nabble.com.
Nick F. (Guest)
on 2011-10-06 03:12
(Received via mailing list)
By "no IF frequency" he meant the LO frequency is the same as the RF
frequency. This is called a zero-IF receiver, or direct conversion.

http://en.wikipedia.org/wiki/Direct-conversion_receiver

--n
Marcus D. Leech (Guest)
on 2011-10-06 03:46
(Received via mailing list)
On 10/05/2011 07:11 PM, Nick F. wrote:
> By "no IF frequency" he meant the LO frequency is the same as the RF
> frequency. This is called a zero-IF receiver, or direct conversion.
>
> http://en.wikipedia.org/wiki/Direct-conversion_receiver
>
> --n
>
More precisely, and completely, they use a direct-conversion, quadrature
(I + Q) signal format.

Without the I+Q bits, then the the two side-bands created from mixing
the RF with LO==RF would cause
   them to "fold about each other".  In the very, very, early days of
direct-conversion designs (way back near
   the start of the 20th century), the fact that the two side-bands
overlapped wasn't an issue, because the modulation
   mode was typically AM, which "doesn't care" about such things.  But
for anything else, you need to use
   a complex representation, in order to distinguish  (-bandwidth/2-DC)
from (DC-bandwidth/2).

--
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
This topic is locked and can not be replied to.