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Re: [Discuss-gnuradio] How to show the internal clock on the flowgraph

From: Marcus Müller
Subject: Re: [Discuss-gnuradio] How to show the internal clock on the flowgraph
Date: Thu, 05 Mar 2015 16:55:03 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0

Hi Manuel,

On 03/05/2015 01:40 PM, Manuel David Lozano Amezquita wrote:

Hi Marcus,

Now I have another question, How can I estimate the time shift in fractional samples?, for example, I have a Cosine signal with amplitude of 1 v, and 1 kHz, and I configure my sample rate in 1 MHz. Then I transmit that signal, and some time later I receive it with another antenna, so How could I determine the time difference of both?.
That is a question that seems to be central to your problem. I have some approaches to answers, but explaining them in depth will take rather long, and not explaining them won't actually help you. Have a look at what a cross correlation is; you should be able to understand what you need to do rather quickly.

The objective is to measure the distance between the Tx antenna and the Rx antenna, And I know that distance=velocity/time, I know the velocity but I need the time that the signal spends from the Tx antenna to ]Rx antenna.
Yep, classical radio ranging problem; have a look at existing radar algorithms. Also bear in mind that the temporal resolution of your system is given by Nyquist's theorem, which leads you to $\delta t =
      \frac{1}{f_\text{sample}}$ in the complex case, to assess if your application is feasible at all.

All the advices or tips that you could give me, I will appreciatte it a lot.
In all honesty: what you're having are basic signal processing questions, and you should read a textbook on signal theory. GNU Radio has a suggested reading page, which might give you a start[1].


[1] https://gnuradio.org/redmine/projects/gnuradio/wiki/SuggestedReading
From: address@hidden
To: address@hidden; address@hidden
Subject: Re: [Discuss-gnuradio] How to show the internal clock on the flowgraph

Hi Manuel,

your signal is sampled with a sample rate. You can now estimate the time shift in (fractional) samples, and calculate the "wall clock" time difference by dividing by the sampling rate.
You, as a user, set the sampling rate that your device uses. The B210 is very flexible in respect to that.

Best regards,

On 03/02/2015 09:02 PM, Manuel David Lozano Amezquita wrote:

Hi Marcus

Thank you for your time,

I need to transmit a signal and then receive it, so I need the time difference between the two signals. I thought that I need a clock in both so I could compare in the same time scale the two signals. Thats why I need the clock.

Or how can I take the time between the 2 signals?

Thank you!

El mar 2, 2015 2:53 PM, =?ISO-8859-1?Q?Marcus_M=FCller?= <address@hidden> escribió:
Hi Manuel,
On 03/02/2015 08:38 PM, Manuel David Lozano Amezquita wrote:

Hi Marcus, I know that the clock of the USRP b210 is 62MHz, but I need to show it on the flowgraph to compare the phase of two signals.

I'm really confused. You *can* configure the master clock rate, which is the rate at which the signal is sampled, to be up to 61.44MHz, but that's neither the default nor 62MHz. There are several clocks in the B210, so maybe I'm missing something.

Where does that freuquency come from? What does it signify?
Why do you need it to compare phases? Of what?

Best regards,
Marcus Müller



El mar 2, 2015 2:26 PM, =?ISO-8859-1?Q?Marcus_M=FCller?= <address@hidden> escribió:
Hi Manuel,

could you explain what you mean with "internal clock of the board"?

Best regards,
Marcus Müller

On 03/02/2015 08:04 PM, Manuel David Lozano Amezquita wrote:
Hi everyone,

I'm using a USRP B210 board, and I don't know how to watch on the flowgraph the internal clock of the board, I need it to compare the time difference of two signals.

Please Help Meeeee.



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