[USRP-users] Configuration Simulink

Jorge Miguel jmiggal at gmail.com
Wed Nov 10 16:35:38 EST 2010


Hi Mike,

More feedback about your comments which I find extremely useful, many thanks
!

Why only try? Is there any case we are not allowed to run in rapid accelerator
> mode?
>
>
>
> In some cases, scopes do not plot data in Rapid Accelerator (RA) mode.
> That could be a reason to avoid RA.  Also, it’s always better to use good
> modeling techniques to speed up your model, and not simply rely on RA.  That
> being said, RA is a very useful technique that you should take advantage of
> if you can.
>

Are the techniques to speed a model you refer to based on the Real Time
workshop?
>From your words I understand that the real workshop is not much better
compared with the rapid accelerator method since the advantage if of being
still in Simulink has to be taken into consideration as well.


> A couple of thoughts:
>
> 1.       Are you simply receiving data from the USRP?  Are you processing
> it at all?
>
> 2.       Store the Spectrum Scope input data into a workspace variable and
> do some post-processing in MATLAB.  Try some histogramming to see if the
> signal has anything besides the DC component.
>
> 3.       What is your input data?  A sine wave?  If so, it is possible
> that the frequency offset of your USRP2 LO is erroneously landing the sine
> wave at 0 Hz.  We have seen phenomena like that before.
>

As I said in other post, this is what is happening to me. I connect a single
tone from a signal generator and no matter the frequency it lands at
baseband. (I explain it in the post "Flat response from a signal generator")

However I will focus on the XCVR2450.

As I told you I want to build a pulse radar application. Since the XCVR2450
is not full-duplex I need to switch between TX and RX periodically. that is,
transmit a signal (pulse) and switch to RX mode as soon as possible to
listen received echoes.

My first thought was to place the USRP2 TX inside one subsystem and the
USRP2 RX in another subsystem both with enable inputs controlled by the same
pulse which has to be transmitted. Are the transmission/reception from the
USRP blocks triggered/stopped just by enabling/disabling this enable input
subsystems? I have the impression that when disabled they do not stop the
USRP.

My second thought is about going lower into the code and modify it. Is it
feasible to create a new block (that implements both TX and RX code) with an
extra input which executes either the TX code or the RX code. Which parts of
the code I have to focus into? (the ones that trigger TX and RX)

How can it be achieved? It is necessary to modify code of the Matlab blocks?
Write new code?

Many thanks in advance,
Jorge.



Many thanks in advance,
Jorge
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