Ultra Wide Band Illumination

A very exciting application of ultra-wideband technology is the exact positioning of objects at distances of up to 250m. It is currently attracting great interest not only from automotive manufacturers. In the following we describe the special challenges of position determination from the point of view of the antennas used.

Imagine that your car could automatically hitch up a trailer without you having to do anything yourself: Your car reverses the last few meters toward the trailer, the trailer hitch comes out from under the rear of the car and safely couples the trailer. Certainly, this is still a long way off, but thanks to UWB technology, the position of the trailer coupling can be determined precisely.

At least two antennas, similar to RF-ID technology, are used to determine the exact position between the vehicle and the trailer: one antenna is fixed (anchor), and another is not fixed in position (tag). In the trailer coupling example, the anchor is on the vehicle and the tag is on the trailer. Both antennas must be developed to suit the respective application. In particular, the radiation characteristics (pattern) are crucial for reliable reception and positional accuracy.The transmitting or receiving range of both antenna modules is first determined without application on our measuring station and allows statements on the field homogeneity (determination of the minimum number of anchors), the 3D beam angle (illumination range), the course of the power (among other things for energy optimization) as well as the areas in which no reception will be possible. Also difficulties caused by runtime errors can not only be detected but also determined.

These parameters give the developer excellent possibilities to analyze the system comprehensively and to characterize, monitor and optimize it in all development stages from the early design process up to the production state (here installation in the vehicle). Let’s stay with the example of the trailer coupling and also consider a gesture control, e.g. to open or close the trunk. If a wave is given with the vehicle key or the cell phone as a gesture in the direction of the trunk, the trunk lid opens or closes automatically. In this case, several anchors are needed on the vehicle to detect the gesture in three dimensions. Due to vehicle geometry, the anchor placements on the motor vehicle as well as unknown objects located around the vehicle, safe reception may be disturbed. A high-quality statement about the reliable recognition of gestures is not only possible with this system test at vehicle level, but also allows reproducible results.

Figure 1: Test Setup.

As a final example, we address use cases within the car. Examples here are the automatic check of whether an existing child seat is safely and accurately positioned and where the vehicle key is currently located in the car. Here, too, we offer precise position determination by measuring the interior precisely and comparing it with the values from the UWB system. The deviation between both measurement methods is evaluated in the report and thus allow a qualitative assessment depending on the particular application.Our measuring station can measure and visualize individual antennas as well as the interaction of all installed anchors and tags. Weak points in the system can thus be identified at an early stage and improvements can be made immediately on site, so that development time is significantly reduced and development steps are simplified. The measurement capabilities available to us allow the desired exact position determination and thus a tolerance determination between the real distance and the distance detected by the UWB system.

Figure 2: Polar Plot - Sky View.