Why DW3120 measurement results are inaccurate?

I have two EVBs for DW3000, one for node and one for tag. Then, I used Decawave’s example and the measurement results are shown in the figure.

Node and tag face each other and Im not sure if that is 0° or 90°. I record data every 1.2m between node and tag.

The angles and distances measured are offset.

Are you using NucleoF429ZI , we are using DWM3000evb with it

If you are, can you share your e-mail with us because we are University students and we can’t connect with “DecaPDOARTLS” also with “DecaRanging”. So, we need some help about what we should do.


Hi Malan,

The antenna delays of the antenna elements / RF traces can be different, causing an offset in the PDoA measurement.

This can be accounted for by placing the tag in front of the node, preferably at a 1 meter distance, and clicking the “Calibrate” button. See section 4.1.3 Enabling the Correction Algorithm in DW3000_Arduino_Shield_QSG_STM.pdf or DW3000_Arduino_Shield_QSG_Nordic.pdf

The jumping in range could be explained by incorrect orientation of the devices. This can cause the RF traces to pick up the radio iof the antennas, causing the channel impulse analyzer to find incorrect first paths. See section 2 in the QSGs:


The devices are placed like this.

But PDoA is like this. The PDOA are almost 90° different from actual angle.

I tried to use Decaranging to change antenna delay to adjust PDOA, but the PDOA of Decaranging is 0°, is it my configuration wrong?


Hi @Malan
Im not familiar with the SW so I cant help you here. But try to move the nodes far away from your metal table (if it is metal). It could cause a lot of weird behavior. Also table corners could affect the measurement (reflection). Try to move it up by 20-30cm (use carboard box, plywood something and etc)

In general UWB is sensitive to any object (especially metallic) close to antenna.


I used a cable instead of antenna, and the PDOA still wrong, and then I check the circuit and found a short in an unremarkable place.

Now PDOA is better :wink:

Ranging can be adjusted by changing the antenna delay

Hi! JK

As you said, UWB is very sensitive to metals, so how can I install UWB in the car to make it less affected?

How does the iphone minimize the affect of metal case on UWB?


Hi @Malan
Im not an antenna guru. However position TN in car is not an easy task - I would try hang it on rear mirror or stick it to area behind back door.

Re iPhone) I dont have such experience (Im happy Android user) but from my knowledge the antennas on iPhone are more or less directional (you cannot get signal though the display area). From what I heard you need to hold/position the iPhone correct to make it work OK. So they bypassing the limits by antenna design and by instructing users how to work with it 8-).