nRF Connect SDK v2.0.0 nRF52833 direction finding - AOA mode 4 ants

[HSUAN]

I am currently conducting experiments on direction finding using two nRF52833, one TX  and the other as RX .

RX employs a 4PST (4-pole single-throw) RF switch for antenna switching.  The logic for controlling the RF switch is achieved by toggling between high and low voltage.

I saw the following configuration in the nrf52833.overlay file, and I understand that this configuration is intended for use with antenna arrays designed by Nordic Semiconductor.

I have 2 question:

1. Could I use the provided configuration to control my RF SWITCH for antenna switching? If yes, what configurations should I modify for control? If not, do I have alternative methods to control my SWITCH?

2. Using an antenna array with four antennas, do I need to make modifications to the beam pattern for the following?

static const uint8_t ant_patterns[] = { 0x2, 0x0, 0x5, 0x6, 0x1, 0x4,
					0xC, 0x9, 0xE, 0xD, 0x8, 0xA };
#endif /* CONFIG_BT_DF_CTE_RX_AOA */

thanks for your help!

[Kenneth]

Hello,

Looking at the picture you shared of your antennas I can see that this will not work well. It's very important that all antennas are 100% locked in distance and placement, so we recommend PCB antennas soldered directly to the PCB. Also, with only 4 antennas you will not get accurate results.

If you only have 4 antennas you need to set dfe-antenna-num to 4 (instead of 12), and you need to update the antenna pattern to fit with how the gpios can enable each individual antenna, ref: 
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/bluetooth/direction_finding_connectionless_rx/README.html#antenna-patterns

Kenneth

[HSUAN]

1.  Can I use gpio 3, 4, 28, 29, with two of them controlling my 4PST RF SWITCH, without the need to modify other settings? (other than set "dfe-antenna-num to 4")

2.  Does having four antennas mean I need more than four "antenna patterns"?

3.  Does each antenna pattern from 0 to F represent a specific beamforming direction?

thanks for your help!!

[Kenneth]

I suggest you sit and try out with different settings here. It should be easy to compile and observe the results on the pins in question, just make sure to do a pristine build (or delete build folder) when doing changes in the dts or overlay file, since the toolchain may not allways catch that these has changed since previous build. To answer your questions:

You can use whatever pins you want, I assume if you only have 4 antennas then 2 pins should be sufficient to choose any of the antenna: 0x0, 0x1, 0x2 and 0x3 will be the pin pattern used to select an antenna by the 2 pins in such case. 

Also check out: https://infocenter.nordicsemi.com/topic/nwp_036/WP/nwp_036/intro.html 

Kenneth