# Application for using the 2 RX channels simultaneously

**URL:** <https://discourse.myriadrf.org/t/application-for-using-the-2-rx-channels-simultaneously/1852>\
**Category:** LimeSDR\
**Created:** [17 October 2017 08:12 UTC](https://discourse.myriadrf.org/t/application-for-using-the-2-rx-channels-simultaneously/1852 "2017-10-17T08:12:32Z")\
**Posts on this page:** 1\
**Showing post:** 127

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**Author:** ![DamirRakhimov](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/damirrakhimov/32/3180_2.png) [@DamirRakhimov](https://discourse.myriadrf.org/u/DamirRakhimov)\
**Post date:** [2 January 2020 11:24 UTC](https://discourse.myriadrf.org/t/application-for-using-the-2-rx-channels-simultaneously/1852/127 "2020-01-02T11:24:33Z")

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Hi,  
We are developing array processing algorithms and we would like to use LimeSDR-USB as a hardware platform.  
I tried to check the time allignment and the phase coherence between Rx0 and Rx1.  
For this purpose the following experiment was performed:  
During one run a sequence of chirp waveforms [Fc-Fdev, Fc+Fdev] was sent from Tx0.  
Then, based on the received signals from Rx0 and Rx1, the phase difference between channels for different frequencies was evaluated.  
The experiment was performed several times (several runs) to collect statistics about the behaviour of evaluated parameters.  
In the end, I have obtained the following results

 ![checkRxPhaseAlign_2019-12-29_164754_hist_Fc%3D900M%2CFs%3D4M%2CFdev%3D2M%2CT%3D2%2CNstat%3D600](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/1/10a0f0ccc0ca246a37d960ecad9e68b07524cf99.png)  
This is collection of histograms of phase differences vs frequency. As I understand, the results shows the presence of the time offset between ADCs,  
 ![checkRxPhaseAlign_2019-12-29_164754_offset_Fc%3D900M%2CFs%3D4M%2CFdev%3D2M%2CT%3D2%2CNstat%3D600](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/d/d5971d984a637017f118416e4dbadad90827d9b9.png)  
histogram of time offsets in terms of fraction numbers of the sampling interval,  
 ![checkRxPhaseAlign_2019-12-30_104330_drift_Fc%3D900M%2CFs%3D1M%2CFdev%3D500k%2CT%3D60%2CNstat%3D100](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/0/0e09d39d90462e14fca14c72466f55dd46c010a0.png)  
histogram of drift of phase between channels with time for one run - no questions.

System configuration for the experiment:

- T = 2s or 60s - Total time
- Fc = 900MHz - Carrier frequency
- Fs = 2MHz - Sampling rate
- Fdev = 500kHz - Deviation frequency of the chirp
- Nstat = 100 or 600 - Number of runs

I used Matlab to write the test program. You can find it by the link:  
[https://github.com/RakhDamir/LimeSDR-Matlab/tree/master/\_testbenches](https://github.com/RakhDamir/LimeSDR-Matlab/tree/master/_testbenches)  
Library was compiled using source code from the LimeSuite master branch from 05.12.19.

I would like to ask, if there way to fix this time offset for Rx channels?  
Thank you in advance for your help!

Best regards,  
Damir

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