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Background Microcalcifications within the fibrous cap of the arteriosclerotic plaques lead to the accrual of plaque-destabilizing mechanical stress. New techniques for plaque screening with small detectors and the ability to differentiate between the smooth and hard elements of plaque formation are necessary. Method Vascular plaque formations are characterized as calcium phosphate containing structures organized as hydroxylapatite resembling the mineral whitlockite. In transmission and reflexion studies with a simple millimeter wave (mm-wave)–demonstrator, we found that there is a narrow window for plaque detection in arterial vessels because of the tissue water content, the differentiation to fatty tissue, and the dielectric property of air or water, respectively. Result The new sensor is based on a sensing oscillator working around 27 GHz. The open-stub capacitance determines the operating frequency of the sensor oscillator. The capacitance depends on the dielectric properties of the surrounding material. The sensor components were completely built up in surface mount technique. Conclusion Completed with a catheter, the sensor based on microwave technology appears as a robust tool ready for further clinical use.

A reflectarray concept which allows electronic beam-steering by using a binary phase approximation is presented. The proposed antenna element works at 24 GHz and is comprised of an aperture-coupled patch antenna with an open-ended microstrip line on the backside to obtain the proper phase distribution on the reflectarray aperture. Electronic beam-steering is achieved by applying PIN diodes on the individual reflectarray elements. To simplify the control process of the antenna, the elements function as one-bit phase shifters either reflecting with a 0° or 180° phase shift. The reflectarray element is verified by measurements obtained with a prototype in a waveguide simulator setup.

In this contribution a MIMO radar concept based on a hexagonal configuration of antenna elements is presented. The concept has been designed for a radar system with 7 transmitting and 7 receiving antenna elements and has been compared to a common two dimensional MIMO arrangement. It is shown that the presented hexagonal setup improves the side lobe suppression by 3 dB while enhancing the angular resolution to 13.8°. Furthermore a thinning method for the hexagonal arrangement is presented. Finally, radar measurements have been performed in order to compare the performance of the concepts in a close range scenario.

This contribution shows a sensor design for the intravascular differentiation of vulnerable and calcified plaques. A measurement concept based on the reflection of an oblique incident electromagnetic wave at the dielectric interface between blood and plaque is discussed. Therefore, the indispensable dielectric properties of both materials are presented. For a catheter embedded solution the sensor is optimized with respect of small geometries and a smooth cylindrical shape. The optimization and verification are performed by means of 3D electromagnetic wave simulations. Furthermore, a broadband measurement concept is presented, which provides additional information for the plaque type differentiation.

In this contribution, a Frequency Modulated Continuous Wave (FMCW) radar system, working in the 75 to 85 GHz frequency range, for level measurement of liquids in tanks is presented. The realized radar antenna has been specially designed to cope with the given harsh environmental conditions (high pressure, high temperature, explosion protection requirements, etc.) in industrial applications. The basic design concept of the antenna is to utilize a dielectric lens as ‘barrier element’ between the tank and the radar electronics module, and especially for high-pressure applications, a cylindrical glass element is included into the lens system. Different configurations of dielectric lens antennas (different biconvex and plano-convex lenses with 45 mm diameter), also in versions including a glass barrier element with 20 mm thickness, have been evaluated by means of electromagnetic field simulations and measurements. A circular waveguide with 2.6 mm inner diameter equipped with a conical horn with 4.8 mm diameter and 3 mm length is used as feeding structure. Results demonstrate a range pulse width (−6 dB) of 30 mm with the full bandwidth of 10 GHz of the system. As expected, the best antenna performance is given with the biconvex lens antenna without the glass barrier element. Nevertheless, a reasonably good performance in the case of equipping the glass barrier with plano-convex dielectric lenses at its front and rear sides can be achieved.

In this contribution, a two-dimensional radar simulator, which is used to determine the specifications and to predict the accuracy of a scanning radar system for filling volume measurement of bulk solids in silos, is presented. The simulator is based on a simple scattering model using polar coordinates in order to achieve an efficient implementation. Additionally, a detection algorithm based on a speckle filter has been tested for an exemplarily bulk solid scenario, and the influence of the penetration depth of the bulk solid, the antenna beam width, and the filling level on the measurement error has been analyzed.With a minimum signal to noise ratio of 10 dB, a measurement error smaller 2 m has been obtained for the given scenario.

In this contribution, a novel measuring method for the differentiation of intra vascular plaque types is presented. The proposed method operates contact free because of the mm-wave based approach. Fundamentals concerning material properties of blood and plaque, and electromagnetic barrier reflections are discussed. Furthermore, a test setup consisting of a miniaturized sensor setup is introduced that clarifies the measuring concept. Additionally, results of 3D electromagnetic field simulations as well as first measurements ex situ performed on non-human genetic materials are shown and discussed in detail.

In this contribution a dielectric hemispherical antenna allowing wide range beam steering for 24 GHz radar applications is presented. A feeding concept for a hemispherical lens is developed using the geometrical-optical lens approach, therewith a high gain of 24 dBi is achieved with a lens radius of 90 mm. The lens is fed by a corrugated horn antenna to provide a low side lobe level up to a steering angle of 50°. 3D-electromagnetic field simulations and measurements confirm the antenna performance in the chosen scenario.