TVRX question

GNU Radio
1

Hi all

For some reason I always thought that the TVRX daughterboards support
IQ sampling. Turns out I was wrong. How do I modify my applications
for I sampling? Can I just wire up a whole IQ chain, save files in IQ
format, use read_complex_binary.m to read it in and discard the Q
part? How do I setup the USRP to only have an I path on the inside?
Do I just use usrp_source_s and then read saved files using
read_float_binary.m?

Thanks in advance.

Sebastiaan

–
Sebastiaan H.
Radar Remote Sensing Group, University of Cape Town, South Africa
Tel: +27 83 305 5667

2

On Sun, 2009-06-21 at 15:15 +0200, Sebastiaan H. wrote:

Hi all

For some reason I always thought that the TVRX daughterboards support
IQ sampling. Turns out I was wrong.
You are only partly wrong.
The TVRX is only sampled in I.
But the usrp firmware transforms this into IQ samples at the stage which
converts the signal from the IF to baseband.

The samples you get in the PC are IQ samples.
You don’t have to modify your processing chain in your application.

You only have to take care of the I sampling at the place where you set
the ADC mux (only sample the I part of the IF using only one ADC).

Greetings,
Martin

3

Martin

Thanks for the reply. How do I set the mux then? Is 0xf2f0f2f0
correct when I have 2 TV tuner modules and 0xf0f0f0f0 correct when I
have only one?

Just to recap, in case you can’t remember what the mux, etc. looks
like. ADC 0 and 1 are on the first IC and ADC 2 and 3 are on the
second IC. The mux bits look as follows.

Chan3 Chan2 Chan1 Chan0
Q I Q I Q I Q I

So 0xf2f0f2f0 connects ADC0 to the I of Chan0, a zero to the Q of
Chan0, ADC2 to the I of Chan1 and a zero to the Q of Chan1. Is this
fine? Then I just use a deinterlever on the PC and connect Chan0 and
Chan1 to separate file sinks?

Thanks

Sebastiaan

4

On Sun, Jun 21, 2009 at 08:34:51PM +0200, Sebastiaan H. wrote:

Martin

Thanks for the reply. How do I set the mux then? Is 0xf2f0f2f0
correct when I have 2 TV tuner modules and 0xf0f0f0f0 correct when I
have only one?

Correct, assuming that in the single case the board is on the A side.

Eric