DOA using MUSIC Algorithm

[sayyar]

Hello all!

I have gone through the example provided by NI:

https://decibel.ni.com/content/docs/DOC-25716

Now I want to Implement it using only two array elements so that I can bypass the process of synchronization. Is it possible to estimate DOA using two antennas (array elements) and one source test signal. I am using USRP-2940 for reception of signals (CH0 RX2 and CH1 RX2) and USRP N200 for transmitting test target signal. Can any one guide me step wise. I have also gone through a lot of MUSIC literature.

I am not understanding how to move from theory towards implementation.

Matlab codes available already feed DOA of source signals and then plot MUSIC spectrum showing peaks at the given DOAs where as in practical case DOA is an unknown to be estimated.

Kindly help me out if some body have already tried it.

Thanks!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[AgentAstronaut]

I'm not certain how you would do this with two antennas. If you think about the way that MUSIC works using phase differences to detect the angle, then you can reason why it wouldn't be possible. Basically, if you have an antenna array and only have the difference between the phases of the signal coming into the two antennas, then may be able to tell the source's distance from the center, but you would not be able to determine on which of the center that signal is coming from.

Additionally, I'm not certain how you would get away with not synchronizing. Can you explain your rational to me? You would still need to ensure that the two receiving antennas are synchronized to each other.

We also have another Angle of Arrival article that could be helpful for you. This one requires a single USRP 2945 or 2955.

https://forums.ni.com/t5/Software-Defined-Radio/USRP-2945-and-USRP-2955-Direction-Finding/ta-p/35857...

[sayyar]

Dear AgentAstronaut !

Thanks for your kind reply!

I have no background in DOA estimation, Antenna arrays and communication, however, I am an Electronic Engineer.

I think Synchronization is required when we are using multi usrps for receiving signal but in my case I want to utilize two antennas of the same usrp.

To understand the music spectrum I took two IQ signals with no phase difference (Assuming one coming from antenna 1 and another from 2) and applied the simple music algorithm. It showed a peak at 90 degree. I am attaching the VI kindly have a look and put a guideline for me if you have time.

I am going through your provided link.

Thanks!

[sayyar]

KINDLY OPEN SCREENSHOT FIRST

How to simulate these steps in LABVIEW by using the inside functions only (not using USRPS) what these Matrices are in actual. Lets assume we have target signal=1 and Array elements=4 (Uniform Linear Array)

what is X(k)?

How to get Rxx?

Similarly till step 5.

[sayyar]

What do we mean by Phase Calibration here any literature????

[AgentAstronaut]

Responding to each:

Thanks for your kind reply!

I have no background in DOA estimation, Antenna arrays and communication, however, I am an Electronic Engineer.

I think Synchronization is required when we are using multi usrps for receiving signal but in my case I want to utilize two antennas of the same usrp.

To understand the music spectrum I took two IQ signals with no phase difference (Assuming one coming from antenna 1 and another from 2) and applied the simple music algorithm. It showed a peak at 90 degree. I am attaching the VI kindly have a look and put a guideline for me if you have time.

I am going through your provided link.

Thanks!

This is fine when the two signals are aligned. Try using the attached VI, which is just a modified version of your VI. I added the ability to add a phase difference between the two signals. You will see that the MUSIC Algorithm falls apart when using two elements.

KINDLY OPEN SCREENSHOT FIRST

How to simulate these steps in LABVIEW by using the inside functions only (not using USRPS) what these Matrices are in actual. Lets assume we have target signal=1 and Array elements=4 (Uniform Linear Array)

what is X(k)?

How to get Rxx?

Similarly till step 5.

---

This is literally the MUSIC algorithm in the Mathscript code, just implement it that way since it already seems to work.

What do we mean by Phase Calibration here any literature????

---

Since the alogrithm is reliant on phase alignment of the antennas, you will need share an LO between all of the USRPs and compensate for the differences in their phase. I do not have any literature on it unfortunately.

[sayyar]

Dear AgentAstronaut!

Your provided VI is not running in my Labview version as mine is 2015 version.

Thanks for your help.

[AgentAstronaut]

I resaved it for 2015

[sayyar]

Dear AgentAstronaut!

I have gone through it. Can I have the relation of phase difference with DOA so that I can find the Phase Difference numerically for known DOAs and can verify the Algorithm before jumping into practical implementation?

Thanks!!!!!

[AgentAstronaut]

Hi Sayyar,

NI does not have that information, you will have to look for that on your own.

Cheers