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Original question:

CCS/LAUNCHXL-CC2640R2: How to integrate the BMI 160 sensor on CC2640R2 as AoA sender without using sensors booster pack.

LAUNCHXL-CC2640R2: Question regarding to ant1 vs. ant3 non-linear issue and the increase antenna spacing

Andy Yang78
Intellectual 380 points
Part Number: LAUNCHXL-CC2640R2

Dear Sir,

We will like to ask following two questions.

1. Non-linear issue b/w ant1 vs. ant3

When we measure antenna pair of the TI CC2540R2 SimpleLink™ Angle of Arrival BoosterPack, the measurement result of pair ant 1 and ant 2 is liner. the pair ant 2 and ant 3 is liner too. but not pair ant1 and ant3.

The measurement of pair ant1 and ant3 is not as liner as the other two pairs. is it unknown issue?

Plus, in the TI AoA project, the pair ant 1 and ant 3 isn't used in the angle calculation. is there any particular reason why not using it as part of angle calculation?

2. Increase antenna spacing (from 0.5 -> 0.6 waveform length)

We will like to increase the waveform length from 0.5 to 0.6.

For my understanding, we can achieve this goal by increase the distance between antenna pairs.

If this is the case, how could we calculate the distance between the antenna pair to get the 0.6 waveform length?

The TI AoA antenna pair is 3.5cm.

  • 0
    TI__Guru 56215 points
    1. It's not a known issue that v13 pair is not linear. The code we have provided is just example, and since we already observed that ant1 and ant2 pair angle gives good result, we did not use v13.
    2. All the theory for angle calculation can be found here:
    dev.ti.com/.../
    We are working on updating the AoA to have it coherent as our Q4 SDK release, but the theory is the same.
  • 0 in reply to Christin Lee
    Intellectual 380 points

    Hello Christin

    Thank you for the reply

    For the distance between each antenna patch, I couldn't find the relating calculation in the TI AoA receiver  sample code.

    In the AoA.c, function AOA_getPairAngles().

    I only see the following calculation for phase drift, phase difference, etc.

    Could you point out where the distance of each antenna patch is applied in the sample code for the angle calculation?

    // Calculate the phase drift across one antenna repetition (X * complex conjugate (Y))
    int16_t Paa_rel = AngleComplexProductComp(sample[r*numAnt*AOA_NUM_SAMPLES_PER_BLOCK + a*AOA_NUM_SAMPLES_PER_BLOCK + i].i,
    sample[r*numAnt*AOA_NUM_SAMPLES_PER_BLOCK + a*AOA_NUM_SAMPLES_PER_BLOCK + i].q,
    sample[(r-1)*numAnt*AOA_NUM_SAMPLES_PER_BLOCK + a*AOA_NUM_SAMPLES_PER_BLOCK + i].i,
    sample[(r-1)*numAnt*AOA_NUM_SAMPLES_PER_BLOCK + a*AOA_NUM_SAMPLES_PER_BLOCK + i].q);

    // Calculate phase difference between antenna a vs. antenna b
    int16_t Pab_rel = AngleComplexProductComp(sample[r*numAnt*AOA_NUM_SAMPLES_PER_BLOCK + a*AOA_NUM_SAMPLES_PER_BLOCK + i].i,
    sample[r*numAnt*AOA_NUM_SAMPLES_PER_BLOCK + a*AOA_NUM_SAMPLES_PER_BLOCK + i].q,
    sample[r*numAnt*AOA_NUM_SAMPLES_PER_BLOCK + b*AOA_NUM_SAMPLES_PER_BLOCK + i].i,
    sample[r*numAnt*AOA_NUM_SAMPLES_PER_BLOCK + b*AOA_NUM_SAMPLES_PER_BLOCK + i].q);

    // Add to averages
    // v-- Correct for angle drift / ADC sampling frequency error
    antenna_versus_avg[a][b] += Pab_rel + ((Paa_rel * abs(a-b)) / numAnt);
    antenna_versus_cnt[a][b] ++;

    Regards,

    Andy

  • 0 in reply to Andy Yang78
    TI__Guru 56215 points
    Please see the comment in this post.
    e2e.ti.com/.../773118
  • 0 in reply to Christin Lee
    Intellectual 380 points
    1. for the distance between each antenna pair
    The "e2e.ti.com/.../773118" post shows the calculation θ by arcsin() isn't applied.
    the distance between each antenna pair isn't applied as well?

    2. We found out the antenna measurement for pair 1~2 and 2~3 isn't linear, is there any thing we can check?
    measurement is done in the chamber, distance between sender and receiver is about 2.5m.
  • 0 in reply to Andy Yang78
    TI__Guru 56215 points

    1. Yes, the whole step 3 in SimpleLink Academy is not applied in our software example.

    2. That's weird, if you are using our software and hardware in antenna chamber, you should be able to reproduce the result in AoA Booster Pack page

  • 0 in reply to Christin Lee
    Intellectual 380 points
    1. got it
    2. we are using our own antenna, therefore, we will like to know, is there any factor will cause the non-liner measurement result.
  • 0 in reply to Andy Yang78
    TI__Guru 56215 points
    If you are using custom design, then you should apply step 3 mentioned in SimpleLink Academy first and check your result afterwards.