AoA - Angle of Arrival Measurement

Angle-of-Arrival Measurement

At a glance

WiSmIt - localization, communication and identification

WiSmIt - localization, communication and identification

BlackFIR® is a technology based on a combination of angle-of-arrival measurement, i.e. the determination of the angles at which signals reach an antenna array, and time-of-flight techniques, which measure how far away a given tag is.

Based on the angle and distance determined, it is then possible to calculate the position of an object equipped with transmitters. Fusing the result with sensor data (from accelerometers, barometers, gyroscopes) helps refine the calculated position or determine its reliability.

BlackFIR® works in various frequency bands and can be adapted to a wide range of radio transmission standards, which means it is suitable for both indoor and outdoor use. Its robust infrastructure enables several hundred measurements per second and makes it possible to calculate the positions of moving objects with an accuracy of 0.5–1 m.

Technical description

Each BlackFIR® receiver unit comprises several antenna elements. Depending on their arrangement (one-dimensional linear array vs. two-dimensional array), it is possible to determine azimuth and/or elevation.

The signals received are mixed down to baseband by a multi-channel receiver and sampled by an analog-to-digital converter.

Once digitized, the data is filtered by an FPGA (field-programmable gate array) and downsampled.

Angles are calculated using common algorithms such as ESPRIT and MUSIC. Implemented on a digital signal processor, the algorithms offer high performance while also meeting strict real-time constraints.

For travel time measurement, BlackFIR® uses nanoLOC chips or systems developed by project partners.


Testing and Adaptation of Solutions in the Test- and Application Centre L.I.N.K.


The tracking system is designed to be incorporated into diverse types of technical products for both indoor and outdoor use. Application areas include the following:

  • Logistics and security systems
  • Rescue systems
  • Leisure and lifestyle
  • Automotive technology
  • Manufacturing
  • Telemetry and sensor networks
  • Robotics
  • Driver assistance systems
  • Work organization

Currently available:

A 2.45 GHz and an 868 MHz version of the system are currently available. Both can be used as a flexible basis for a range of applications. The tracking system has been trialed in various projects concerned with logistics and security.


To be able to meet diverse client requirements in terms of accuracy, time constraints, purpose of use, and cost, we offer a range of scalable tracking systems which can be adapted to the intended environment. As our partner you will benefit from first-rate information about both potential applications and the market. Strong technology partners with expert knowledge are a guarantee for substantial success in the marketplace. Think of us as an outsourced development department. We will be happy to share our tracking expertise with you.

Fraunhofer's BlackFIR® 2.4 Tracking Development Kit provides a platform that allows you to explore and trial a wide variety of tracking applications in your environment. The kit is easy to install and a user-friendly plug-and-play system makes it simple to test the technology under real-life conditions.


Cell-based tracking

Our cell-based tracking system comprises a number of BlackFIR® receivers and a network infrastructure. Angle and distance data is transmitted over the network to a central server, where it is used to calculate the position of the object being tracked. Wismit V3 base stations can additionally be used for greater accuracy.

Single Point Locators

BlackFIR® Single Point Locator

BlackFIR® Single Point Locator

BlackFIR® systems that apart from measuring angles can also determine how long a signal took to reach a given tag can be deployed as what we call Single Point Locators. In this case, one receiver unit is sufficient to locate objects up to approx. 100 meters away. Their positions can be calculated directly on the BlackFIR receiver unit. An advantage of this solution is that it requires very little instrumentation or configuration.

As part of the BlackFIR® 2.4-Development-Kit, Fraunhofer IIS has developed a Single Point Locator that allows you to explore implementing tracking technology in your specific environment.

Positioning at the object

BlackFIR® positioning at the object

BlackFIR® positioning at the object

For vehicle tracking in large environments such as warehouses, the vehicles to be tracked can be equipped with a BlackFIR® receiver unit while tags are distributed around the infrastructure to serve as landmarks.

This approach is also used for driver assistance systems and navigation, e.g. of forklift trucks in warehouses.

Fraunhofer IIS has been evolving three different BlackFIR technologies. One of them, BlackFIR® 2.4, is now available in the form of a development kit.

BlackFIR® 868

The BlackFIR® 868 technology is designed for use in large-scale infrastructures such as airports or production facilities as well as for tracking indoor movement from the outside, for instance when monitoring emergency responders inside a building. This is made possible through the use of the 868 MHz frequency band, which offers superior penetration characteristics.

This technology combines a one-dimensional array for angle-of-arrival measurement with inertial sensors. Additionally, the 868 MHz channel can be used for communication.


BlackFIR® 2.4

The BlackFIR® 2.4 technology combines angle measurement with a time-of-flight technique based on nanoLOC modules.

BlackFIR® 2.4 uses the Wismit µ tag for tracking and can be combined with the Wismit V3 base station.

Because BlackFIR® 2.4 is modular and uses the 2.4 GHz ISM band, the signal needed for angle measurement can be provided by tags based on Wi-Fi or Bluetooth rather than by Wismit µ tags. In that case, however, it is not possible to measure round-trip times.


BlackFIR® 5.9

BlackFIR® 5.9 is our latest technology. This system uses the 5.6-5.9 GHz band and is ideally suited to installation in vehicles on account of its small size. Thanks to its two-dimensional antenna array, it can determine both elevation and azimuth.

Possible uses include driver assistance systems and navigation of vehicles such as forklift trucks.