Re: [Discuss-gnuradio] QT scope block?

[Marcus Müller]

Hi Numeric,

have you tried my constellation sink approach? Pretty sure it works well [1].

By the way, the USRPs are not calibrated measurement equipment, which means that you will have to calibrate the amplitude response at each frequency/gain/sampling rate/master clock rate combination you want to use yourself first, for both channels. The second problem is that after every tuning, the phase relationship between the TX and the RX LO will be random.

Best regards,
Marcus

[1] http://imgur.com/a/YjF25#0

On 06/29/2015 02:27 AM, numeric wrote:

Hello Marcus, thank you for your suggestion.
A QT scope capable of displaying Lissajous patterns would solve my problem. 

Hardware analogy:
Most hardware scopes can be set up in an XY mode without difficulty. In my
case a hardware scope with two inputs to display the complex input ( Y axis
) and a third channel for the X axis, would work. I even have a 4 channel
scope that would work nicely in the hardware world. However I prefer to
solve the scope function using the GNU radio companion. 

My objective is to create a vector network analyzer using the Ettus b200
USRP board. It can provide a sweep rf output and simultaneously receive the
in phase and quadrature phase reflection component. While it is possible to
trigger the X axis; I would prefer to use the actual sweep waveform for the
X axis.
 
Rob  



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