Size and feed structure are some of the important constraints for using antenna-elements in multi-element two-dimensional arrays, where easy planar integration and appropriate matching with transceiver chips are essential. This applies especially when differential signaling and adaptable polarization are required. Based on a balanced-fed patch-excited cavity-backed horn antenna (hybrid antenna), feeding concepts, and approaches to reduce size are discussed and evaluated in this paper. The influence of the substrate-integrated cavity is analyzed and methods to overcome the restrictions are presented, together with simulated and measured results. The antenna elements are evaluated with regard to their use in multistatic and polarimetric sparse arrays, which will be briefly introduced. The optimized antennas achieve 10 dB return loss, a gain of more than 5 dBi as well as symmetric and homogeneous radiation patterns in amplitude and phase with low cross-polarization in the desired frequency-band of operation between 70 and 80 GHz.

In this paper, an approach to differentiate between various dielectric threat objects in security applications is investigated. The scattering information in form of the Sinclair matrix of relevant scenarios is gained from a fully polarimetric, synthetic aperture radar. Both monostatic and multistatic array configurations are examined. A possible polarimetric calibration procedure is presented. The radar data are processed with the H-α decomposition algorithm. The H-α scattering characteristics of threat objects are analyzed in terms of a weighted averaging. It is shown that an object classification is possible even for threat objects conceiled under thick layers of clothing. Measurement results are presented to illustrate the topic.

Radar sensors are used widely in modern driver assistance systems. Available sensors nowadays often operate in the 77 GHz band and can accurately provide distance, velocity, and angle information about remote objects. Increasing the operation frequency allows improving the angular resolution and accuracy. In this paper, the technical feasibility to move the operation frequency beyond 100 GHz is discussed, by investigating dielectric properties of radome materials, the attenuation of rain and atmosphere, radar cross-section behavior, active circuits technology, and frequency regulation issues. Moreover, a miniaturized antenna at 150 GHz is presented to demonstrate the possibilities of high-resolution radar for cars.

ADS-B provides convenient means of air traffic control (ATC) for its low cost and simple ground station hardware. In a low percentage of cases, aircraft positions transmitted via ADS-B are error prone due to e.g. faulty wiring with onboard navigation systems. In the proposed approach, direction of arrival (DOA) estimation is used to verify ADS-B airborne positions. The potential positioning error of ADS-B is thereby evaluated by comparing DOA estimates to DOA values calculated from ADS-B references and the sensor position and orientation. To prove the accuracy of the applied DOA estimation sensor, an additional measurement campaign using a dedicated measurement aircraft has been conducted.

In this contribution, fundamental design considerations for a novel metallization technique to realize millimeter-wave microstrip structures are presented. This hot embossing technology is a fast and economic process originating from the production of three-dimensional molded interconnect devices. Conductive structures are coated onto plastic parts or plastic foils using a heated stamp. This approach shows high potential and therefore will be investigated for the fabrication of low-cost printed antennas at millimeter-wave frequencies. The focus of this contribution is on design guidelines considering process parameters and interactions with substrate and copper foil characteristics derived from the fabrication and measurement of single microstrip patch antenna prototypes for radar applications in the industrial, scientific and medical (ISM) band at 24 GHz. Far-reaching potential lies in the utilization of the three-dimensional manufacturing technology for the construction of conformal integrated antenna systems based on the thermoforming capabilities of polymer substrates.