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BOOSTXL-AOA: Why peak value of I and Q samples vary for different packets on a same single antenna

Akansha Verma
Expert 1220 points

Part Number: BOOSTXL-AOA

Hi,

I  observed the I and Q sample waveform on single antenna.

Why peak value of I and Q sample vary for different packet on a single antenna?

Here, i got 47 samples of one packet and took 3 packets and then plotted I waveform. Why peak value of I is varying?

If packets are sent by same slave to same slave and that too on one antenna, then ideally magnitude of Signal should be constant, but it is varying as shown below:

Magnitude of three packets on same antenna is plotted below:

Thanks

Akansha

  • 0
    TI__Genius 14845 points

    Hi Akansha, 

    Assigning an expert to comment. 

    Thanks, 
    Elin 

  • 0 in reply to Elin W
    TI__Guru** 101490 points

    Hi Akansha,

    Please have a look to the link provided in the thread you opened a couple days ago, it explains why the I Q data varies along the periods.

    By the way, you got nice data, we can clearly see the antenna switching :)

    Regards,

  • 0 in reply to Clément
    Expert 1220 points

    Hi,

    As i am calculating phase difference between antenna using I and Q samples. If IQ sample magnitude will be different for different packet from same slave at same position, then phase difference will also be different.

    But my doubt is that phase difference between antenna should be constant is slave is at same position as before.

    And the graph which i posted in query is I samples on one antenna, these are three packets' I samples plotted. There is no antenna switching.

    Please clear this doubt.

    Thanks

    Akansha 

  • 0 in reply to Akansha Verma
    TI__Guru** 101490 points

    Hi,

    Yes phase difference between the two antennas should be constant if the slave does not move and you are in a perfect environment. Don't forget that the environment can disturb the BLE signals and introduce multipath problems.

    To clear your doubts, simplify your problem by using known data or by using conducted waves instead of radiated waves (i.e. use a cable to conduct your waves from the slave to the passive to avoid to be disturbed by the environment).

    I hope this will help,

  • 0 in reply to Clément
    Expert 1220 points

    Thanks!

    I will perform this experiment

    Regards

    Akansha

  • 0 in reply to Akansha Verma
    Expert 1220 points

    Hi,

    I am attaching I samples' waveform for 5 packets incoming on single array (A1) and using antenna 1 and 2.

    Each packet provide 320 I samples.

    I observed that behavior of  I value graph is not constant in case of different packets. Thatswhy, i am getting different phase difference for different packet - which should be constant.

    Then how to get constant phase difference?

    Thanks

    Akansha