Re: [Discuss-gnuradio] Doppler simulator

[Marcus Müller]

Yes and no. The signal source just uses the information "sampling rate" to calculate the length of one period in samples. Other than that, nothing in GNU radio cares about sampling rate - that's a real world concept that only applies to real world devices (such as the USRP sink) but not to the digital signal processing. You should make sure to use the same nominal sampling rate that you used to generate the files with the signal in. For example, if you calculated the satellite signal based on a nominal rate of 1MS/s, and play it back at 5MS/s, everything will be frequency scaled with a factor of five.
Greetings,
Marcus

On December 22, 2014 11:51:34 AM CET, Carlos Alberto Ruiz Naranjo <address@hidden> wrote:

Ok. Signal and sine must have the same sample rate (5 MS/s), right?

2014-12-22 11:46 GMT+01:00 Marcus Müller <address@hidden>:

Yes and no: the shifting is done right; however, you should make sure to use a consistent sampling rate throughout the block.
The USRP sink interprets the samples that come into it as having a sample rate of 5MS/s, whereas the nominal sampling rate in the signal sources is set to 2MS/s.

On 12/22/2014 10:45 AM, Saul E. wrote:

First of all, I want to thank you for your answer.

Then, It is correct? (for a simple simulation of 1k, 2k and 3k Hz of doppler shift)

​

Thank you.

Saul E.

2014-12-22 10:26 GMT+01:00 Marcus Müller <address@hidden>:

Hi Saul,

a doppler shift is, mathematically speaking, nothing more than a multiplication with a complex sine, so use a multiply block and a signal source per simulated sattelite.

Now, you might want to update your doppler shift according to a simulated sattelite's position. I recommend having a look at PyEphem[1], which offers you calculational routines for such things, and writing your own python block[2] to generate the complex sine.

Greetings,
Marcus

[1] http://rhodesmill.org/pyephem/
[2] http://gnuradio.org/redmine/projects/gnuradio/wiki/Guided_Tutorials ; go through tutorials 1, 2, 3

On 12/22/2014 10:14 AM, Saul E. wrote:

Hi all!!

I am developing a SDR receiver and want to simulate the doppler of signal from several satellites.
Any suggestions?

Signal1, signal2 and signal3 are BPSK signals and I use a USRP N200.

​

Thank you very much in advance.

Saul E.

_______________________________________________
Discuss-gnuradio mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

_______________________________________________
Discuss-gnuradio mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

_______________________________________________
Discuss-gnuradio mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.