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IWR6843ISK: How to measure reflected signal's strength.

kisub Jung
Intellectual 930 points
Part Number: IWR6843ISK
Other Parts Discussed in Thread: IWR6843, AWR1642, AWR1843, AWR1843BOOST

Hi

I wonder whether we can measure or have TX RF signal strengh and paired RX RF signal strength. And you might call it signal amplitude.

You might call it "Reflection Coefficient" with assumption of IWR6843 EVM. Of course, you will know this reflection coefficient would be different per materials such as glass, carbon, stainless..etc.

if we can not have absolute value of it, can we measure relative value of RX signal strength, assuming that TX signal strength is 1.

We can assume that radar is located in front of 1cm away from subject.

Please guide me how to measure RX RF signal strength or estimation method.

 Best Regards,

kisub

  • 0
    Intellectual 930 points

    rlMonTxBallBreakRep_t Struct Reference

    This is the Monitoring report which RadarSS sends to the host, containing the measured TX reflection coefficient's magnitude values

    How can I see this value of measured TX reflection coefficient's magnitude values? Let's assume that I have a vitalsign project. I would like to see these values together.

    If I know how to read these value, I can put the variable value into TLV reserved area.

    Is it right? If so, how can I read it? Please show me the exact example so that I can try to dump it.

    Thanks in advance,

    Warm regards,

    kisub

  • 0 in reply to kisub Jung
    TI__Guru 50240 points

    Hi Kisub,

    I've asked an expert to look into this and we should have an answer for you later this week.

     

    Cheers,

    Akash

  • 0 in reply to Akash Gondalia
    TI__Mastermind 25835 points

    Hello Kisub,

         Typically Tx ball break monitoring is used in the safety critical applications, This provides rough TX reflection coefficient’s magnitude values, meant for detecting TX ball break, in case of any adverse scenarios in the application, From this information safety host could take appropriate actions in the safety critical system.

    Currently this API is not available in the device firmware; as it's not yet developed in the firmware.  In the future it is being planned (Approximately 2nd half of next year). 

    Thanks and regards,

    CHETHAN KUMAR Y.B.

  • 0 in reply to CHETHAN KUMAR Y.B.
    Intellectual 930 points

    Currently this API is not available in the device firmware.

    but, the documents shows it has it.

    rlTxBallbreakMonConf_t tx0BallBreakMonCfg =
    {
    .reportMode = MON_REPORT_MODE_PERIODIC_WITH_THRESHOLD_CHECK,
    .reserved0 = 0x0,
    .txReflCoeffMagThresh = -90,
    .reserved1 = 0x0,
    .reserved2 = 0x0,
    };

    Also, it does not work at all? If it does not rough values, can you let us know even it is rough value?

    We need it so deadly. also, if 6843aop is not available, what about other chips such as 1443, 1642, 12xx, 18xx? 

    Thanks for your fast feedback in advance,

    BR,

    kisub Jung

  • 0 in reply to kisub Jung
    Intellectual 930 points

    if firmware is not available, there must be a work-around to measure reflected signal strength comparing to transmitted signal strengh.

    Can you suggest a way for best way for now?

  • 0 in reply to kisub Jung
    TI__Guru 50240 points

    Hi Kisub,

    Our hardware expert is currently unavailable but we should have a response for you the week of 23 December.

     

     

    Cheers,

    Akash

  • 0 in reply to Akash Gondalia
    TI__Mastermind 25835 points

    Hello Kisub,

         For the ball break monitoring APIs are defined in IWR6843, However when APIs are issued underlying firmware present in the BIST processor would measure and reports the values. Currently for the IWR6843 this firmware yet to be developed. 

    If you really want to use this feature, you may want to explore Automotive family of devices AWR1642/AWR1843 devices which supports this feature as part of monitoring APIs.

    Thanks and regards,

    CHETHAN KUMAR Y.B.

  • 0 in reply to CHETHAN KUMAR Y.B.
    Intellectual 930 points

    Thanks Chethan,

    from doxygen, Doppler DPU document index.html file, I found it shows TX and RX signals.

    Q1. So, I can calculate Reflection Coefficient with this. Isn't it right?

    Reflection Coefficient = S'1/S1 (S'1 can be derived from S'a, S'b two fomulas)

    Q2. If it is right, is it possible to derive unwrapped Phase?

    cf) 

    BPM Scheme Antenna configuration

    BPM decoding
    Let S1 and S2 represent chirp signals from two TX antennas. In time slot zero a combined signal Sa=S1+S2 is transmitted. Similarly, in time slot one a combined signal Sb=S1-S2 is transmitted. Using the corresponding received signals, (S'a and S'b), at a specific received RX antenna, the components from the individual transmitters are separated out using

    S'1=(S'a+S'b)/2

    and

    S'2=(S'a-S'b)/2

    reflection coefficient = S’1/S1

    With simultaneous transmission on both TX antennas the total transmitted power per chirp interval is increased, and it can be shown that this translates to an SNR improvement of 3dB.

  • 0 in reply to kisub Jung
    TI__Mastermind 25835 points

    Hello Kisub,

          For the reflection coefficient power need to be measured at the at the RF ports (Received power and reflected power), It cannot be performed at the base-band level. Typically this is done by the BSS firmware and estimates the reflection coefficient and sends the Monitoring report to the host.  In IWR6843 firmware this monitoring API has not been developed yet. You may need to wait for Approximately 2nd half of next year. 

    Or you may explore Automotive family of devices where this API is supported.  

    Thanks and regards,

    CHETHAN KUMAR Y.B.

  • 0 in reply to CHETHAN KUMAR Y.B.
    Expert 1180 points

    We have AWR1843.

    We succeeded in measuring the reflection coefficient using mmwavelink and AWR1843boost.

    ...
    RL_RF_AE_MON_TX0_BALLBREAK_REPORT [0x1]
    RL_RF_AE_MON_TX1_BALLBREAK_REPORT [0x1]
    RL_RF_AE_MON_TX2_BALLBREAK_REPORT [0x1]
    ReflCoefVal: tx0 = 0xffffff98 tx1 = 0xffffff83 tx2 = 0xffffffffff88.
    ...

    However, the mmwavelink only runs one test.

    We want to know how to measure the reflection coefficient value continuously.

  • 0 in reply to chunghee cho
    TI__Mastermind 25835 points

    Hello Kisub,

        Glad to know you are able to succeed in getting the reflection coefficient value. 

    You could configure to get periodic monitoring report, Please refer below app-note "Self-Calibration in TI’s mmWave Radar Devices".

    http://www.ti.com/lit/an/spracf4/spracf4.pdf

    You need account for the minimum time needed for running the monitors and overhead for issuing the APIs. Above app-note provides more details with example for scheduling the calibration and monitoring. 

    Thanks and regards,

    CHETHAN KUMAR Y.B.

  • 0 in reply to CHETHAN KUMAR Y.B.
    TI__Mastermind 25835 points

    Hello Kisub,

        Could you please confirm we could close this thread? If you have additional questions please raise new thread and you could reference this thread.

    Thanks and regards,

    CHETHAN KUMAR Y.B.