[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-t
From: |
Activecat |
Subject: |
Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back) |
Date: |
Sat, 15 Mar 2014 12:10:56 +0800 |
Dear Marcus,
On Sat, Mar 15, 2014 at 11:14 AM, Marcus D. Leech <address@hidden> wrote:
> The SBX does analog downconversion, nothing more. It knows nothing about
> the incoming signal, and doesn't demodulate it in any way.
Please be clarified what do you mean by "analog downconversion".
At the transmitter side, complex-based (I/Q) signal is fed into USRP.
Says, the signal is x(t) = I(t) + j.Q(t)
I think this is performed at transmitter SBX:
y(t) = I(t).cos(wt) - Q(t).sin(wt) where w = central frequency, t = time
here the y(t) is the output of SBX to the antenna.
Is this what you meant by "analog upconversion" ?
Whereas at the receiver side, the received signal from antenna is real
signal, says,
z(t) = c.y(t) = c.I(t).cos(wt) - c.Q(t).sin(wt) where c =
channel attenuation
The receiver SBX performs this:
Retrieved I(t) = LPS( z(t).cos(wt) ) where LPS = low pass filter
Retrieved Q(t) = LPS( z(t). sin(wt) )
With this process the receiver SBX is able to produce complex-based
(I/Q) signal from the real signal from antenna.
Is this what you meant by "analog downconversion"?
If not, please describe what you mean by "analog upconversion" and
"analog downconversion", because I have no idea of what you are trying
to explain. It is impossible that SBX only mix the incoming
complex-based signal with a central frequency and then send directly
to antenna for transmission, because the simple mixing (analog
upconversion) produces another complex-based signal which cannot be
transmitted through antenna. A physical antenna can only transmit
real signal, not complex-based signal.
Please clarify, thanks.
Regards,
Activecat
> That is what SDR is all about--the signals are represented as
> complex-baseband (i/Q) format for processing by computer algorithms.
>
> The SBX (or any other daughtercard) is simply doing downconversion (or,
> upconversion for TX).
> Frequency offset in a digital demodulator implemented in software generally
> drives a local correction--not the hardware. You achieve this by
> bringing in a bit more bandwidth than you actually need, and then applying
> frequency corrections in software.
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Johnathan Corgan, 2014/03/14
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Activecat, 2014/03/14
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Martin Braun, 2014/03/14
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Activecat, 2014/03/14
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Marcus D. Leech, 2014/03/14
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back),
Activecat <=
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Marcus D. Leech, 2014/03/15
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Activecat, 2014/03/15
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Sylvain Munaut, 2014/03/15
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Activecat, 2014/03/15
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Sylvain Munaut, 2014/03/15
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Activecat, 2014/03/15
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Attila Kinali, 2014/03/15
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Tom Rondeau, 2014/03/15
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Activecat, 2014/03/15
- Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back), Marcus D. Leech, 2014/03/15