NCS AOA: IQ sample data type.

[Harvey Zheng]

Hi,

I am using Zephyr3.0.0 to validate AOA CTE sampling. 

Firstly,  as below is the official data format. Nordic Semiconductor Radio peripheral provides 16 bit wide IQ samples and the first 4 bits are the sign bit extension.

Secondly, BT 5.3 Core specification Vol 4, Part E sectons 7.7.65.21 and 7.7.65.22 limit size of IQ samples to 8 bits. So in this commit, Zephyr right shift the data 4bits.

I printed out some IQ sample data as below.

This is my print information: 2112.df.zip

I have some questions about this. It seems to missing some valid bits of data?  How will the loss of these data bits affect the positioning accuracy? Or does the application need to do something special with these IQ datas such as left shift them 4 bits?

[Simonr]

Hi

The AoA direction finding solution we provide will only output the raw IQ data by default, as we don't provide the AoA algorithm necessary to make use of the data collected by the antenna array. There is no point in looking at the raw data as it needs to be converted into vector form to review it properly. You can check out this page for information on the various formulas used to translate IQ data between polar and rectangular form.

Best regards,

Simon

[swz_nordic]

how do you print the IQ sample？do you use the two nrf5340 boards?

my output  in Rx in here.

PER_ADV_SYNC[0]: [DEVICE]: 0B:2B:C5:4A:72:01 (random), tx_power 127, RSSI -69, CTE AOA, data length 0, data:

CTE[0]: samples count 45, cte type AOA, slot durations: 2 [us], packet status CRC OK, RSSI -690

PER_ADV_SYNC[0]: [DEVICE]: 0B:2B:C5:4A:72:01 (random), tx_power 127, RSSI -65, CTE AOA, data length 0, data:

CTE[0]: samples count 45, cte type AOA, slot durations: 2 [us], packet status CRC OK, RSSI -650

beside,what terminator do you use?thanks tor your reply.

[Harvey Zheng]

I use the LOG_HEXDUMP_INF macro to print the IQ sample.

[swz_nordic]

ok,thanks,could you please tell me the more information abouot LOG_HEXDUMP_INF?.

You have iq sample then use the algorithm to d=get the angle.

[Harvey Zheng]

Hi，

I noticed that by shifting right 4 bits, the data 0xFFC7 becomes 0xFFFC. It can be interpreted as low 4 bits are useless data?

Thanks.