Re: [Discuss-gnuradio] (no subject)

[Marcus Müller]

Hi Vinay,

Really sorry for images sizes

Don't be sorry! A few hundred kilobyte won't break the mailing list, and it's always a good thing to illustrate your system well; I've spent much (too much?) time in university labs, and believe me, there's nothing more crucial about science and technological progress than to be able to communicate your knowledge; pictures are a very good way of doing that.

So: let's consider this:

Since we're talking about SDR with USRPs, there's two ways you can interpret this graphic, if it stands alone:

1. This is the equivalent baseband signal, or
2. This is the electrical signal as "seen" by the antenna (RF signal).
   

Considering the time axis, the first (0-2ns) slot has 1GHz of frequency, and the second period (4ns-6ns) has 2GHz. That means that (since there is no USRP with a >=2GHz sampling rate) this can only be interpreted as the antenna signal, so this is case 2.

This means that, yes, this is possible in principle, but not quite in the shape shown: you tune your USRP to frequency 1, and transmit  a constant baseband value (e.g. 1+0j) for your "dwell time"; then, you start tuning to the next frequency, and transmit 0's, and then another "dwell time" worth of constant value, and so on.

Aside from the obvious timing impossibility (the shown waveform has a tone duration of 2ns; that won't be possible with any USRP; our DAC/ADC don't exist in a 500MS/s variant so far), you cannot continue the wave at the same zero phase, so the phase of the wave at each transmission start won't be zero, but some other value. However, there are USRP/daughterboard combinations that allow for a fixed phase reconstruction at tuning. Hence my repeated question: What is your USRP, and if applicable, your daughterboard?¹

Then, you have a second picture, which I admittedly really do not understand:

I had the feeling that this was some kind of Y-over-X graph, but I really could not tell what the axis and the meaning of your line are, so could you please define ?1 and ?2, as well as explain what the graph means? What happens there?


Best regards,
Marcus

¹I really usually don't nitpick, but it's really hard to get the information out of you to help you, so I'm asking you explicitly: Please always answer all questions we ask so that we can actually help you!

On 15.12.2015 07:30, vingnu GNU wrote:

Hi,
This is the wave form I required to generate and Its a step frequency CW
starts from 1GHz and ends with 2GHz,constant incremental steps of 60MHz and
4KHz of dwell time. pic2 shows the waveform in frequency Vs time domain.
Really sorry for images sizes
[image: Inline image 1]

[image: Inline image 2]
Regards
Vinay


On Mon, Dec 14, 2015 at 6:01 PM, Kevin McQuiggin <address@hidden> wrote:

Hi Vingnu:

Perhaps you mean a swept frequency from 1 GHz to 2 GHz?  The group needs
further information.

Kevin

Sent from my iPad

On Dec 14, 2015, at 4:25 AM, Marcus Müller <address@hidden>

wrote:

Hi Vingnu,

so you mean that on one frequency, you want to have a CW tone, and one
the next frequency another etc, but not continuous phase across

frequencies.

** Do I understand that correctly? ** I'm confused because you then
mention "pulses", and that is a concept that is incompatible with CW

radar.

Hardware-wise, most USRPs (which one are you using) support timed
commands so that you can tune at a specific sample time. For those that
don't, you'll have to use some time buffers, but it's essentially what
the example probably does that you cite -- though you're not really
telling me which example exactly you're referring to.

All in all, please try to make your questions a little more precise, add
all the details that are important right from the start.

Best regards,
Marcus

On 14.12.2015 12:05, vingnu GNU wrote:
Hi ,
That is nothing but in examples of USRP they have used FMCW for target
simulator with frequency modulated CW here in my case I am going to use
unmodulated CW  .
My question was ,is it possible to increment this CW signal source

interms

of 60MHz step size and keeping 250usec of dwell time between 60MHz steps
and it should be upto  2GHz and repeating same in next cycle.
ex: first frequency is 1GHz it has to add 60MHz step size and keep

250usec

of dwell time i.e.,after 1.06GHz pulse it has to maintain 250usec dwell
time before next 60MHz pulse .

regards
vingnu

On Mon, Dec 14, 2015 at 3:44 PM, Marcus Müller <

address@hidden>

wrote:

Hi Vingnu,
that's all nice, but what does "continuous wave" _mean_?

Best regards,
Marcus

On 14.12.2015 10:02, vingnu GNU wrote:
Hi marcus,

Its like this : generating continuous wave of signal which starts from

1GHz

and it has to increase in steps of 250usec upto 2GHz.Then I wanted to

feed

it for Radar transmitter.Its like generating Step frequency continuous

wave

signal for radar transmitter. Is it possible from GNU radio and I am

having

USRP E310 right now.

regards
Vingnu

On Mon, Dec 14, 2015 at 2:06 PM, Marcus Müller <

address@hidden

wrote:

Hi Vingnu,

note that GNU Radio is software that handles sample streams, so yes,

any

signal that you can imagine in a given bandwidth can be generated;

the

question is whether you can realize that signal in the physical

world.

So:

* do you just want to simulate the signal or really transmit that?
 * if you want to transmit that, with which hardware?
* what exactly is "continuous wave" for you here? Continuous for a

single

frequency step, or continuous across multiple frequencies?

Best regards,
Marcus


On 14.12.2015 05:59, vingnu GNU wrote:

Hi every one,

Is this possible to generate step frequency continuous wave for

frequency

range of 2GHz to 4GHz in GNU radio and step size in range of 250micro
seconds(Dwell time).

regards
Vingnu




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