CC2642R: the AOA data vibrate badly

Hi Yanpo,

Assigning a team member to look into your questions.

Hi,

Now I have use the rtls_ala_iq_log.py   to get several IQ sample data files. What I found is, sometimes there is no any discontinuity after index 32 point while sometimes it just looks like as the picture in "Valid I/Q Samples For Angle Calculation" (docs/ble5stack/ble_user_guide/html/ble-stack-5.x-guide/localization-index-cc13x2_26x2.html#valid-i-q-samples-for-angle-calculation). I guess the discontinuity matters with the path between passive and slave. if there is no any obstacle between them, then the IQ plot is fluent , and if there is some obstacle between them, then the bigger the obstacle is ,the worse of the discontinuity is. SO is this right or not?

Besides, if I want to print the signalstrength_A1 out, is it the amplitude of the antenna A1? or it is just left for future. And I need to calculate the amplitude myself? Thanks.

Yanpo, Li

Hi,

When you are performing your test, do you have a phase difference between the signal coming from the two antennas? (If you do not have a phase difference then you will not observe the discontinuity). You can provoke a phase difference by having a non-zero angle between the passive and the slave. I assume that the obstacle might provoke a phase difference also (however it is not the recommended approach).

Regarding the second part of your message, you can get the signal strength through the RSSI. The structure AoA_AntennaResult has a field (named rssi) holding this information. You can basically retrieve this information and display it. (note: there is a function AOA_postProcess() that might help you)

Best regards,

Hi,

Now the AOA value vibrate ±5 degree when the slave keeps its position. However, it only works in a few range, like ±20 degree, when the slave move out this area, the AOA angle will not discontinue. Is this normal or not.? if it is abnormal, where is the possible wrong point? 

By the way, how big the AOA range is?   Thank you.

best regards,

Yanpo, li

Hi,

Can you verify if both antennas arrays are activated?

With both antennas arrays the theoretical AoA range is 270 degrees. I invite you to consult the chapter "AoA performance" of the following page: http://dev.ti.com/tirex/content/tirex-product-tree/cc26xx_devtools/.metadata/.tirex/project0_boostxl_aoa_bp/landing_page_index.html

Regards,

Hi,

I test the switch I/O signal in the oscilloscope,  both the two antenna work. Now during ±25°， it works very well, just as expected. But when  the slave moves out of this range, the AOA degree is not right.

I do not know why. in the linked web set of the launchpadXL, it says the range is ±50°，I do not know why I get only half the range.

Besides, when changed to two antennas , the following need to be changed or not?

const int16_t AoA_A1 = ((antA1Result->pairAngle[0] + antA1Result->pairAngle[1]) / 2)+ 45 + antA1Result->channelOffset[antA1Result->ch];// the original sentence

const int16_t AoA_A1 = antA1Result->pairAngle[0]  + antA1Result->channelOffset[antA1Result->ch];// the changed sentence

if not, where other place that affect the effective angle range?

thank you

Yanpo, li

Hi Yanpo,

Regarding the fact you are getting bad results when the angle is over ±25°. If you are getting data completely wrong, then I would suggest you to verify that nothing is disturbing your signals when you are over 25° (i.e. something reflecting the signals). You can also try to have the slave closer to the passive to limit the multipath possibilities. On the contrary, if you are having results that are not totally accurate, this might be the sign that you need to have a better treatment-algorithm or use different channel-offsets over a certain angle. 

Regarding the way to compute the angle, I confirm, with only two antennas you have to change the content of RTLSCtrl_estimateAngle() in rtls_ctrl_aoa.c:  

// const int16_t AoA_A1 = ((antA1Result->pairAngle[0] + antA1Result->pairAngle[1]) / 2)+ 45 + antA1Result->channelOffset[antA1Result->ch];

const int16_t AoA_A1 = antA1Result->pairAngle[0] + 45 + antA1Result->channelOffset[antA1Result->ch];

Note: The offset +45 only depends on where you want to have the reference.

I hope this will help,

Regards,

Hi,

there is no obstacle between passive and slave. their distance is 1.5 meter, not far. they are tested in a open room. the result a got is like the following picture. the y axis is the degree. the x axis is time.  the picture shows when slave moves from -60 degree to 60 degree. Only -30-25 degree is right.

thank you.

Yanpo, li