USRP problem ? used for Digital beacon receiver

GNU Radio
1

Hi everybody , I’m new for the gnuradio.Now my researching is about
digital beacon receiver.So what’s my problem is in the list below

  1. How do everybody set MUX? I tried to read the datasheet but It
    wasn’t make sense for me.So what I do is use the GRC and used the Usrp
    block so i know that my db BasicRx is on side B RXA and My WBX is on
    Side A Rx2 but if i want to set mux in the python program how do i do?

  2. I tried to find the signal’s phase,so i generated the signal
    about 1.5M from signal generator (just for test) directly to the Basic
    Rx Db. So what i expect is the IQ signal that show in the GRC Scope sink
    would be the constant(cosphi and sinphi) signal but It’s not ,the
    signal seem to be like the cycle(period). What do I misunderstanding?

  3. From the Question 2. How can I find the phase of the signal that i
    generate through the usrp.

Thank every one for yours advices

2
  1. How do everybody set MUX? I tried to read the datasheet but It
    wasn’t make sense for me.So what I do is use the GRC and used the Usrp
    block so i know that my db BasicRx is on side B RXA and My WBX is on
    Side A Rx2 but if i want to set mux in the python program how do i do?

This is the code for the grc usrp* blocks:
You can see how its set in <gnuradio_repo>/grc/grc_gnuradio/usrp/*.py

  1. I tried to find the signal’s phase,so i generated the signal
    about 1.5M from signal generator (just for test) directly to the Basic
    Rx Db. So what i expect is the IQ signal that show in the GRC Scope sink
    would be the constant(cosphi and sinphi) signal but It’s not ,the
    signal seem to be like the cycle(period). What do I misunderstanding?

What frequency did you tune the basic RX? Perhaps you are seeing an
offset between signal generator and DDC. Do the tones the FFT sink look
to be in the correct positions?

-Josh

3

Thank you very much Josh

but i have another question for more please

What frequency did you tune the basic RX? Perhaps you are seeing an
offset between signal generator and DDC. Do the tones the FFT sink look
to be in the correct positions?

Did you mean the tune frequency in the basic Rx same with the frequency
that i can set in the usrp source block ?

So if the same i set the frequency in the usrp source block(from my
understand is nco frequency ) equal 1.5Mhz

and the tones of the FFT sink seem like the product of the
multiplication of the input signal(1.5Mhz) and nco signal(1.5Mhz)

and showed only the input signal - nco signal ’ s frequency response
and i think it’s correct.

and i have another question that is the signal that come from usrp
source that show in the scope sink show the I and Q signal but if i
connect the usrp source with the FFT sink it’s show the frequncy
response only one graph So i’m not sure what was the FFT sink show(I and
Q , just I or Q only , or I +Q )

thank you very much for yours advice