RE: we want to use nRF52833 as BLE5.1 AOA/DOA locator

Dmitry — Fri, 03 Apr 2020 13:03:43 GMT

Hi,

Concerning first question, I'm not an expert in antenna design, maybe somebody with better experience could answer. Just notice that I can't see any difference in two pictures..

RE: we want to use nRF52833 as BLE5.1 AOA/DOA locator

Athos.Zhang — Fri, 03 Apr 2020 03:06:42 GMT

Hi Sir：

two more question:

1. If we design 4 pieces of antenna element, For the antenna position, which arrangement is better? Antenna is on the one side of PCB?like this:

Or on the tow side of PCB? like this:

2. i can't open this link:http://www.diva-portal.org/smash/get/diva2:1317231/FULLTEXT01.pdf

can you help to share the PDF file in another way ?

RE: we want to use nRF52833 as BLE5.1 AOA/DOA locator

Dmitry — Fri, 27 Mar 2020 09:14:42 GMT

Hi,

[quote userid="89085" url="~/f/nordic-q-a/59578/we-want-to-use-nrf52833-as-ble5-1-aoa-doa-locator"]How many antennas are needed for direction finding/positioning? Is 6 enough? What are the maximum and minimum numbers of antennas supported?[/quote]

Depends on your case. Two antennas can cover a 90-degree sector, if you need 360-degree coverage, you need at least four antennas. More antennas can improve accuracy with a good algorithm.

Maximum controlled GPIO lines is 8 - with SP4T switches, you can easy connect 16 antennas.

[quote userid="89085" url="~/f/nordic-q-a/59578/we-want-to-use-nrf52833-as-ble5-1-aoa-doa-locator"]What are the requirements for isolation, polarization, and cross-polarization isolation between antennas?[/quote]

IMHO absolute polarization doesn't matter, as tags may have any orientation - two sets of differently polarized antennas would improve distance but increases complexity a lot. Of course, each two antennas involving in one measurement should have equal polarization.

[quote userid="89085" url="~/f/nordic-q-a/59578/we-want-to-use-nrf52833-as-ble5-1-aoa-doa-locator"]What is the fundamental theory of the direction finding/positioning algorithm? Is there a ready-made algorithm that we can use?[/quote]

http://www.diva-portal.org/smash/get/diva2:1317231/FULLTEXT01.pdf gives a good overview of principles with the real evaluation.

[quote userid="89085" url="~/f/nordic-q-a/59578/we-want-to-use-nrf52833-as-ble5-1-aoa-doa-locator"]Should the phase delay of each RF path be consistent? Are the amplitudes required to be consistent? What about phase error and amplitude error index ?[/quote]

Not necesary, but you should account phase difference in your algorithm. With equal antennas, amplitudes should be near equal (amplitude difference can give you a hint about mixing with reflected signal).

[quote userid="89085" url="~/f/nordic-q-a/59578/we-want-to-use-nrf52833-as-ble5-1-aoa-doa-locator"]Can all GPIO ports be configured to switch antenna paths?[/quote]

Any GPIO that is not marked as "low drive, low frequency I/O only" in product specification.