Germany's Hensoldt is presenting its “TwInvis” passive radar system for the first time in live operation during this year's ILA show in Berlin.

The TwInvis system, which can be integrated into an all-terrain vehicle or a van, does not emit its own signals to monitor air traffic, but simply analyses the echoes of signals from radio or TV stations.

Hensoldt CEO Thomas Müller says that newly developed, highly sensitive digital receivers now make it possible for a single TwInvis system to monitor up to 200 aircraft in 3D within a radius of 250km, opening up new options for civil and military applications, e.g. air defence and air traffic control.

Passive radar systems detect aircraft by analysing the signals that they reflect from existing third-party emissions. For military applications, systems cannot be located by the enemy and are very hard to jam; wide-area surveillance can be achieved using networked receivers.

Hensoldt's TwInvis system claims to offer a very precise picture of the airspace covered, by simultaneously analysing a large number of frequency bands. Up to 16 FM transmitters (analogue radio) plus 5 frequencies used by several DAB and DAB+ transmitters (digital radio), as well as DVB-T and DVB-T2 (digital, terrestrial television), can be simultaneously analysed.

Hensoldt says that two TwInvis demonstrators have already been delivered to potential customers in Europe.