Keynote Speaker



On-Site Measurements of Terrestrial Navigation and Radar Signals using Drones and a Research Aircraft

By Dr. Thorsten Schrader, Director and Professor, Head of Division Mechanics and Acoustics, Physikalisch-Technische Bundesanstalt (PTB), The National Metrology Institute of Germany
With contributions from Jochen Bredemeyer, Thomas Kleine-Ostmann, Jens Werner, Jens Wellhausen, and Heyno Garbe

In order to validate the functionality of terrestrial navigation aids and radars as well as their signal integrity in airspace, on-site measurements of these signals are essential. In particular, the question of whether and to what extent wind turbines alter the signals and thus lead to a safety risk has gained great importance due to the expansion of wind turbines in recent years.This question was investigated in the WERAN and WERAN PLUS projects for a number of navigation and radar systems between 500 kHz and 9.3 GHz. Drones were used to measure signals of airport surveillance radars, air surveillance radars and weather radars, localizer and glide path of instrument landing systems as well as very high frequency omnidirectional radio range (VOR). Horizontal beamwidths, side lobe suppression, front-to-back ratio, and near-ground radar coverage can be readily acquired and studied using drones. The flight measurement platforms (FMP) in use are RC octocopters with a flight range of 1 km, an RC hybrid variant copter/airplane (VTOL) with a range of about 100 km, and a Touring Motor Glider research aircraft with a range of over 1000 km. All the necessary data from RF frontends and flight position is synchronized in time and recorded on a SSD.

The measurements in the airspace represent the electromagnetic fields present at a distinct location and their signal structure. This measurement data can be compared well with, for example, numerical full-wave simulations of the fields and signals of VOR, since the same physical quantity is recorded here. A post-processing of this data on a mainframe computer allows one to calculate the target quantity (here the bearing angle error).

The FMP were calibrated on the reference open area test site (OATS) of PTB in Braunschweig using a reflector dipole antenna. Its simulated radiation pattern was measured in several virtual planes at increasing distances with the octocopter. At a distance of 2 km from the OATS and at an altitude of 600 m, it was thus possible to calibrate "real" aircraft or to validate their antenna pattern. Another goal was to develop a simple prediction method for the bearing angle error of Doppler-VOR caused by wind turbines, which runs on a simple PC and delivers the result in a few minutes. This prediction is backed up and validated by on-site measurements and full-wave simulations.

Examples of the available data will be shown and discussed


Thorsten Schrader Thorsten Schrader (SM'11) was born in Braunschweig, Germany, in 1967. He received the Dipl.-Ing. and Dr.-Ing. Degrees in electrical engineering from the Technical University of Braunschweig, Braunschweig, in 1992 and 1997, respectively. In 1998, he was with EMC Test Systems, L.P., Austin, Texas (now ETS-Lindgren, Cedar Park, Texas).  In 1999, Dr. Schrader joined the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig, Germany. He started in the working group "High Frequency Measurement Techniques". In 2000, he served the Presidential Staff Office. In 2004, he became head of the working group "Electromagnetic Fields and Electromagnetic Compatibility";. From 2006 to 2011, he was responsible for the Working Group "Antenna Measuring Techniques". In 2019, he became head of the working group "Non-Linear High-Frequency Metrology for Digitalization". Between 2005 and 2020 he directed the department "High Frequency and Electromagnetic Fields". Since May 2020, he is head of the division "Mechanics and Acoustics".

Dr. Schrader has supervised 19 externally funded research projects since 2006. He currently holds six patents in the area of high frequency measurements and communications. In 2015, he received the IEEE Transactions on the THz Science and Technology Best Paper Award of the Microwave Theory and Techniques Society for the contribution "Field Exposure and Dosimetry in the THz Frequency Range," Vol. 4, No.1, pp. 12-25, January 2014.

The Physikalisch-Technische Bundesanstalt, Germany’s national metrology institute, is a scientific and technical higher federal authority falling under the competence of the Federal Ministry for Economic Affairs and Energy.  It is Germany’s highest authority when it comes to correct and reliable measurements.

Founded in 1887, PTB was the first metrology institute worldwide.  With its almost 2000 staff members, it is the largest institute in Europe and one of the fifth largest of this type worldwide. Research and development work amounts to 70% of PTB’s activities.

Nearly all sectors of Physics are covered to support the International System of Units (realization and dissemination of the physical units), legal metrology, and measurement science. PTB is also providing calibration services for industry to help traceability (several thousand calibrations per year).