HPEM detection system FORDES – development, performance and application

Robust measurement system for high-power interference signals

Research at Fraunhofer INT into interference in electronic devices under the influence of high-power electromagnetic signals (HPEM, High Power Electromagnetics) has a history stretching back decades. The phenomena investigated have in common that the affected target objects often exhibit malfunctions such as system crashes or hardware defects, which can also occur during normal operation due to instabilities or wear and tear. The deliberate external influence of the actual cause often escapes human perception. For this reason, Fraunhofer INT has for many years been pursuing the basic idea of a measurement system that is itself robust against interference, but is still capable of detecting high-performance interference signals.

Since deliberate interference tests usually operate at electric field strengths that are at least an order of magnitude higher than the civilization background caused by radio, television and mobile communications, a simple warning device could initially indicate the exceeding of a critical threshold at its location. However, more precise detection of parameters such as signal strength and, depending on the signal form, carrier frequency and modulation characteristics, is required to perform a risk assessment of potential damage and source forensics.

Development goals at Fraunhofer INT

The aim of the development efforts at Fraunhofer INT was to reflect the dynamic range, measurement accuracy and frequency bandwidth of common laboratory measuring devices as comprehensively as possible in a compact, robust and energy-efficient detection system. The aim was to significantly reduce the device volume and lower the acquisition costs by around one order of magnitude. A particular challenge here is the broad spectrum of possible interference signals to be detected. Thanks to its compact design and integrated battery module, the HPEM detector FORDES, developed at Fraunhofer INT, can be installed as a stationary device in a data center or control room, for example, or used as a mobile device in the field for special situations.

Differentiation from standard market solutions

Due to the basic risk described above, detection solutions that tackle the measurement problem with different focuses have been discussed in the research community for several years and are now also available on the market. The broadband detection of interference signal amplitudes up to ten gigahertz carrier frequencies with the required measurement dynamics remains a challenge. In contrast to simple warning or measurement solutions, FORDES was developed as an FPGA-based system capable of detecting narrowband interference over an effective dynamic range of at least four orders of magnitude and also measuring its carrier frequency. This enables frequency response corrections for an accurate reconstruction of the electromagnetic fields present on site and thus a well-founded risk assessment in the event of an incident. An ongoing patent application is also based on the implementation of this unique selling point. Together with a recording of the signal envelopes on time scales of a few nanoseconds, basic source forensics is thus also possible for pulsed signals, which allows conclusions to be drawn about the originator of the respective interference.

Possible applications

The battery installed in the current FORDES laboratory demonstrator enables the system to monitor the field load at any location for more than ten hours and to record fault events. Using a separately hardened power supply unit, a permanent power supply is also possible in stationary operation, for example, at key systems in critical infrastructure. The system can be controlled and read out from a computer via a web interface using an interference-resistant optical network connection.

The FORDES HPEM-detector is also increasingly being used in a military context, as the systems used are becoming more complex and electromagnetic means of action are constantly being developed further. Due to the increasing relevance of interference tests, efforts are currently underway to instrument FORDES as an HPEM-sensor for a military land vehicle. This requires mechanical and technical adaptations in terms of installation location and on-board electronics as well as the IT connection to the modern NGVA (NATO Generic Vehicle Architecture) standard.