The detection and tracking of UAV’s is a critical task for public and military security. The main are the low flight height and the small radar cross section (RCS). The problems increase in an urban environment with many high buildings, especially when tall buildings block the line of sight. A new concept of distributed radar sensors was developed to close this gap. To reduce the impact of radar shadows in urban canyons, a surveillance grid of optical and radar sensors is necessary which covers the complete urban environment. The radar sensors build up different security sectors and monitor all access routes for attacking UAVs. Sophisticated cameras which offer night vision capabilities complete the sensor network to reduce the false alarm rate through these regular, declared UAV flights. Cameras allow the integration of a man in the loop which has the final responsibility to define a target as a threat or not. The system supports the operator with a database which based on optical and radar signature of most commercially available UAV’s.
Letter bombs are an increasing problem for public authorities, companies and public persons. Nowadays every big company uses in his headquarters inspection system to check the incoming correspondence. Generally x-ray systems are used to inspect complete baskets or bags of letters. This concept which works very fine in big company with a large postal center is not usable for small companies or private persons. For an office environment with a small number of letters x-ray systems are too expensive and oversized. X-ray systems visualize the wires and electric circuits inside the envelope. If a letter contains no metallic components but hazard materials or drugs, the dangerous content is invisible for the most low-cost x-ray systems. Millimeter wave imagining systems offer the potential to close this gap.
A high resolution imaging millimetre wave SAR delivers three key parameters important for precision farming
applications, namely range, reflectivity and polarization state. The reflectivity gives information upon the type of crop
and its humidity. Especially in the millimeter wave region young growing green plants exhibit a considerably higher
reflectivity than older, dry leaves. Dependent on the transmit-receive polarization also indications are given upon the
humidity of the underlying soil. Polarimetry also allows to judge the ripeness of the grain as the geometry of the ear is
changing during the ripening process.
Propagation of electromagnetic waves through canopies of wood are of interest for he choice of operating frequencies for microwave based sensors of different kind. It is known that in general the propagation properties become worse with higher frequency. Especially the upper millimeterwave bands are severely attenuated by leaves.
Measurements were conducted during a period in spring on a transmission path through an apple tree. The measurement period covered states of the tree ranging from leave-less over blooming to fully developed leaves on the branches. Three frequency bands were covered, namely 10 GHz, 35 GHz and 94 GHz. To allow a concise judgment of the data, meteorological measurements were done in parallel.
It is well known that radar sensors are capable to propagate through smoke and dust with only very little attenuation. The
higher the operating frequency, the smaller is the necessary antenna diameter for a required geometrical resolution on the
ground. Consequently millimeter waves would be the choice for this type of sensor system. For an optimum system
design the question of atmospheric attenuation at different bands within the millimeter wave region due to losses by dust
and sand has to be answered. As only little data exist on this topic, respective measurements were done under
reproducible laboratory conditions. Different approaches were used to cover a broad range of sand and dust types.
The contribution describes the experimental set-ups and gives typical results for calibrated samples of sand and dust,
which were derived from the lab measurements. A perspective is given for further investigations upon this topic.
The characterization of materials in the millimeter wave frequency range offer many new applications for quality control and security applications. This paper shows results for different applications with a real aperture scanning system in the frequency range between 75 GHz - 325 GHz in amplitude and phase.
The paper describes different technological efforts to demonstrate the usefulness of millimeter wave sensors for security applications. The scope of the work covers a miniature radar in a portal geometry using a near field SAR approach for passenger control and the same radar hardware with a slightly modified scanning approach for luggage inspection employing a three dimensional SAR algorithm.
Another approach to detect concealed weapons and explosives is by using radiometric systems. In principle, a scanner using this technique measures the thermal noise of the radiation reflected by the body. This is equivalent to the temperature on the surface of the body. The main difficulty with this technique is the realization of a fast scanning algorithm.
The status of both approaches is surveyed and typical results are discussed.
In this paper two RCS prediction codes were investigated with respect to their applicability at millimeterwave radar bands. Two classes of land-targets, anti-tank mines and a jeep, were measured at two frequencies and afterwards the RCS calculations with the facet models of the objects, partly simplified, were done under the same conditions. The paper describes the experimental set-up and the simulation methods used. Furthermore the output of the simulations is compared with the experimental results. The importance of the comparison for simulations at millimeter-wavelengths is discussed.