Radio pattern

Wireless Connectivity Ultra-Wideband
1

Hello guys, I have a question related to the antenna radio pattern of dwm1001 device.
I already know that those antennas are vertically polarized, means that they obtain the “almost” omnidirectional pattern if vertically placed.
I installed a tripod on the ground and put on it an antenna which is more or less at 1 meter above the ground.
Now I have a drone that flies on the sky at altitude 10 meters.
I placed another antenna on the drone, vertically, but in a reverse way, since I thought that the uwb transceiver should have been positioned in such a way to have as much as possible free space.

Not consider that the antenna on the ground is positioned at the origin (0, 0) and that the drone start to fly on the sky at a fixed speed of 5 m/s. The drone continuously sends its actual GPS coordinates taken from its installed GPS module.
In order to do that, the drone converts the GPS coordinates into local (x, y) coordinates relatively to the origin (0, 0).
The antenna on the ground has the leds that look the “south” where the leds on the antenna on the ground look the “north” pole.
Just to better understand the meaning of north and south, north is towards a positive y-coordinate, south the opposite.

The drone starts from (-30, -100) and goes to (-30, +100), hence it runs “bottom-up”.
Checking the log, I saw that the drone “refreshes” its new local (x, y) position every 0.6-0.7 meters in average.

In the other side, the antenna on the ground registers the messages sent by the “drone”. If the sensor hears, for example, (30.45, 76.89), it “casts” the messages in (30, 76). In other words, I’m working on only integer values.
Every time that a sensor hears the same local position, it increases a variable (starting from 0).

However, I attached a plot that represent the messages hear by the antenna on the tripod.
In this figure, three scan have been reported, where a “scan” is simply a vertical line followed by the drone “bottom-up”.
The first scan is in -30, the second in 0, and the third in +30.

The strange thing is that the heard “line” on the left is different from the one heard at +30.
Why? I was expecting to have almost the same behavior.
Moreover, this occur always: repeating the experiment, changing the place, setting different speeds and altitudes…

Thanks.

2

The simple answer is that it’s doing that because that is what the radios are doing.

Predicting or modeling antenna patterns is a horribly complicated thing to try to do and the theory never quite matches the real world.
People can give you suggestions as to how to make things more symmetrical but ultimately with this sort of thing the only way to know for sure what’s going to happen is to test it.

Can you post photos of how things are mounted to the tripod and drone?

Does the orientation of the drone make a difference? e.g. if you fly north while facing south do you get a different result to flying north facing north? (Obviously if it’s a fixed wing drone this isn’t an option)

3

This summer I made a video about my research: https://www.youtube.com/watch?v=WqZtsQ3HyEY
I moreover set the orientation along the same axis, I mean, if east is 0 deg, north 90, west, 180, and so on, the ground antenna has a -90 (270 deg) and the drone 90 deg.

ps: as you can see, the drone goes towards 90 and then 270. But now we only have to consider when the drone goes north.
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I want to share other photos/figures that may help you.