Active protection system with millimeter wave radar
Numerous deployment scenarios involve serious threats from hand-held anti-tank weapons which are now available in large quantities on the world market. One promising approach to counter this threat is the development and realization of active protection systems.
Due to the high impact force of armor-piercing projectiles and the present – almost hemispheric – threat situation, it is practically impossible to provide appropriate protection, especially for light, air-transportable vehicles, using conventional ballistic protection technologies. Hence, there is an urgent demand for active protection systems that are capable of detecting and combating an approaching projectile before it reaches its target. The efficiency of such a system depends on a number of factors: the reliability of detection (low false alarm rate), the quality of classification and three-dimensional localization, the processing speed of the measurement data as well as the initiation of appropriate countermeasures. The sensor, which detects the approaching threat, can also provide information on the type of the threat and supplies data which enables high-precision determination of the flight parameters (distance, flight direction, speed), plays a key role. This information must then be made available to fire control in real time. Due to its all-weather capability and its ability to penetrate dust and sand clouds, radar technology offers a number of advantages compared to other sensors (e.g. electro-optical or infrared).
Within the framework of the research project DUSIM (Dual Use Sensors in Medium Distance Range), a four-channel radar system was developed for active protection within a monitored range of between 8 m and 250 m. It operates at a frequency of 94 GHz with a low output emission of 100 mW. This makes the sensor almost undetectable for non-cooperative troops and harmless for persons in the immediate vicinity. The frequency-modulated continuous wave signal (FMCW) with a bandwidth of 1 GHz provides a high range resolution of 15 cm. The core of the DUSIM radar front end is the highly stable signal generation (Chirp Generation Board) which creates a linear frequency ramp at approx. 15.7 GHz. This is subsequently sextupled and amplified. Thanks to the four-channel receive system, the sensor can provide the precise location of the approaching projectile; here, use is made of the monopulse technique. The speed and flight direction of the projectile can also be determined using the Doppler effect. The immediate creation of a flight track after successful detection is the most important basis for targeted and precisely timed countermeasures. Clear classification lowers the false alarm rates as a distinction can be made between relevant and non-relevant targets. The front end shown in Fig. 1 measures 200 x 180 x 230 mm3 and weighs approx. 3 kg.
The system was successfully tested under realistic conditions in several measurement campaigns. Tests were carried out with small caliber ammunition as well as with armor-piercing projectiles (e.g. RPG 7). Examples of the results are presented in Figures 2 and 3. In 2016 and 2017, additional tests were carried out in the centrifuge facility of WTD 91 in Meppen.