Eckhard Denicke

Bio: Eckhard Denicke is an academic researcher from Leibniz University of Hanover. The author has contributed to research in topics: Radar & Antenna (radio). The author has an hindex of 10, co-authored 28 publications receiving 193 citations.

Compact Unfocused Antenna Setup for X-Band Free-Space Dielectric Measurements Based on Line-Network-Network Calibration Method

Abstract: This paper presents a compact free-space measurement system for the characterization of dielectric materials within the X-band based on the line-network-network (LNN) calibration method. Using a pair of dielectric-filled horn antennas with enhanced directivity, the setup exhibits a total length of 250 mm between the antenna apertures and is suitable for measurements of planar samples with transverse dimensions equal to or greater than 250 mm×250 mm. Based on 3-D field simulations and measurements, the assumptions of plane wave incidence on the sample and negligible diffraction effects at the sample edges are investigated. The scattering parameters of the sample are obtained according to the LNN calibration method. Remaining multipath propagation effects caused by reflections at the antennas and their fixtures are filtered out via time gating. The complex permittivity is finally calculated from the transmission scattering parameter using the Newton-Raphson method. Results for exemplary dielectrics are in good accordance with reference values.

The application of multiport theory for MIMO RFID backscatter channel measurements

Abstract: This contribution deals with channel measurements in multiple-input multiple-output radio-frequency identification systems (MIMO RFID). Herein, multiple antennas are applied at the reader and at the RFID tag as well. A method for the determination of the channel coefficients between all antennas is presented. The channel information is needed to apply MIMO techniques to enhance the data rate or the reliability or range of the backscatter link. Since no measurement can be conducted at the tag antenna ports the method is based on the theory of determining the scattering parameters of a multiport (n-port) with a reduced number of measurement ports. Herein, the load impedances within the RFID tag being normally used to transmit information via backscatter modulation are used as known reflection standards. An internal thru standard between the tag antenna ports is introduced to reduce phase ambiguities. The method could be applied in future generations of multi-antenna RFID tags or could be used to characterize the channel for MIMO RFID prototype systems to evaluate their performance limits e.g. by calculating the MIMO capacity. Measurement results for the proposed method for a system with two reader transmit and receive and two tag antennas (2×2×2) are presented (5 to 6 GHz).

Compact directional UWB antenna with dielectric insert for radar distance measurements

Abstract: A circular waveguide-fed UWB antenna for the frequency range from 8.5 to 10.5 GHz is presented, incorporating a dielectric insert mounted inside a short metallic excitation horn, yielding a significantly enlarged aperture efficiency compared to the same horn without dielectric insert and even to the theoretical limit of a conical horn antenna of infinite length having similar geometrical aperture restrictions. Regarding industrial radar level gauging, the maximum antenna dimensions are strictly limited due to standardized nozzle and flange diameters and thus compact directional antennas with low side lobe levels are needed allowing broadband radar operation and simultaneously suppressing signal distortions by unwanted scatterers. By utilizing a prototype setup of the proposed antenna, the anticipated performance gain is proved by measurement results validating the simulated characteristic antenna parameters as well as the improved radar distance measurement accuracy.

Antenna Impact on the Gauging Accuracy of Industrial Radar Level Measurements

Abstract: This paper deals with a systematic evaluation of the antenna impact on the gauging accuracy of industrial radar level measurements for process automation. By this means, a framework is provided by which the antenna parameters of major influence on the gauging accuracy can be identified. Guidelines are given to what extent an improvement of these parameters results in a measurable accuracy increase. Firstly, the radar system theory for monostatic level gauging and the emulation of such radar systems by software and hardware are briefly reviewed. Secondly, an analytical model of traveling-wave endfire antennas is introduced, allowing to separately study the influence of individual antenna parameters on the distance measurement accuracy. Thus, a direct relationship between characteristic antenna properties, such as the level of the pattern attenuation in the direction of a parasitic scatterer, and the gauging performance is obtained. The investigations are conducted for one specific pulse-based barycentric signal-processing scheme, which is predestined for industrial level gauging due to its low complexity and reliability. Finally, the results are verified by measurements within a compact radar test range.

Compact mode-matched excitation structures for radar distance measurements in overmoded circular waveguides

Abstract: . This contribution deals with guided radar level measurements of liquid materials in large metal tubes, so-called stilling wells, bypass or still pipes. In the RF domain these tubes function as overmoded circular waveguides and mode-matched excitation structures like waveguide tapers are needed to avoid higher order waveguide modes. Especially for high-precision radar measurements the multimode propagation effects need to be minimized to achieve submillimeter accuracy. Therefore, a still pipe simulator is introduced with the purpose to fundamentally analyze the modal effects. Furthermore, a generalized design criterion is derived for the spurious mode suppression of compact circular waveguide transitions under the constraint of specified accuracy levels. According to the obtained results, a promising waveguide taper concept will finally be presented.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

A dielectric lens-based antenna concept for high-precision industrial radar measurements at 24GHz

Abstract: A lens-based antenna with a solid dielectric ellipsoid PTFE lens for industrial tank level probing radar (TLPR) is presented. Due to limitations of the application, a high antenna gain at a limited size as well as a good matching were the main design goals. The presented antenna achieves a high gain of 25.9 dBi with a beamwidth of ≈ 8.4° at an outer diameter of 74mm in simulations, which is confirmed by measurements. Despite the lens surface reflections, a good input matching of ≈ −20 dB is achieved in the full wide frequency band from 23 GHz to 28 GHz, which enables monostatic radar operation even close to the antenna. A laboratory radar setup is used to confirm the accuracy impact on distance measurements in a scenario with disturbing reflectors.

A dielectric lens antenna with enhanced aperture efficiency for industrial radar applications

Abstract: A dielectric lens antenna for 25 GHz industrial radar measurements in industrial tanks is presented. Due to the limited diameter, the aperture efficiency is an important benchmark for these applications. The presented approach uses a massive PTFE lens body, which results in a measured aperture efficiency of 104% at a diameter of 74 mm. This corresponds to a gain of 25.9 dBi. The main lobe has a tight 3 dB angular width of 8.4°/ 8.6° with a side lobe level of −17.0 dB /−17.6 dB.

UWB Antennas for Communication Systems

Abstract: Since the U.S. Federal Communications Commission (FCC) opened the spectrum from 3.1 to 10.6 GHz for unlicensed radio applications with an EIRP of up to 41.3 dBm/MHz, numerous papers have been published on ultrawideband (UWB) antennas. Often the goal in these publications is to present an antenna, which has a satisfactory input reflection coefficient and a reasonable, constant radiation diagram versus frequency. However, in the case of UWB, there are numerous additional critical characteristics, which must be considered in the proper wireless system design. The publications, which treat this topic with sufficient proficiency, use such quantities as transient gain, group delay, ringing, dispersion, signal fidelity, polarization, efficiency, and the peak value of the transient response. For practical applications based on signals with an UWB instantaneous bandwidth occupation, all criteria are of vital importance, because they determine the sensor resolution, accuracy, or increase the bit error rate in communications systems. This paper gives an overview of UWB antenna designs together with their suitability for different applications with respect to the aforementioned critical characteristics. Additionally, UWB antenna array design, polarization diversity, and application in body area network (BAN) will be discussed. In nearly all cases the time-domain characteristics are taken into account, as they are more intuitive to interpret and very convenient for time-domain UWB system design.

Free-Space Time Domain Position Insensitive Technique for Simultaneous Measurement of Complex Permittivity and Thickness of Lossy Dielectric Samples

Abstract: A novel time domain measurement technique is proposed to facilitate the simultaneous measurement of electrical properties (complex relative permittivity) and geometrical parameters (thickness) of the material under test (MUT). The overall process is noninvasive and noncontacting, which uses the measured scattering data of the MUT in the equivalent time domain or spatial domain. The effective time domain scattering data are employed to detect the primary and secondary peaks of the overall reflection and transmission coefficients. To this end, a novel algorithm is proposed to obtain the complex permittivity and thickness of the MUT in terms of extracted reflection and transmission power peaks. From the practical point of view, the main advantage of the proposed scheme is that one avoids the complicated calibration procedure normally required to define the reference plane. For increasing the accuracy of the overall reconstruction process, an automated optimization procedure based on parameter sensitivity analysis is proposed, which uses standard time gating procedure to implement the corresponding direct problem. The proposed technique is validated by extracting the relative permittivity, the dielectric loss (effective conductivity), and the thickness of various standard materials, such as polyethylene, Plexiglas, PVC, mortar, nylon, and so on, and comparing the extracted data with their values available in the literature.