35 research outputs found
Modular Ka-band switch matrices using two RF MEMS technologies
No full textThis paper presents the design and measurement of two different switch matrix modules based on Radio Frequency Microelectromechanical System (RF MEMS) switches. The operational frequency range is between 25.5 GHz and 26.5 GHz for data links between a Geostationary Earth Orbit (GEO) relay satellite and Low Earth Orbit (LEO) satellites. The switch matrix implements a key functionality for tracking the incident signals of the LEO satellites on the receive feed antenna array of the GEO satellite's reflector antenna. Two different technologies are used to build simplified switch matrix modules suitable for realizing the full functionality switching matrix. Rogers RT/Duroid 5880 with commercially available RF MEMS is used to build the first module, while EADS in house RF MEMS are integrated in Rogers Ultralam 3850 Liquid Crystal Polymer (LCP) for the second module. Maximum insertion losses of 8.5 dB and 10.2 dB have been measured for the Rogers RT/Duroid 5880 and the LCP module, respectively. Isolation is higher than 45 dB and a minimum return loss of 15 dB is shown. Finally, the measured losses in the LCP module are analyzed and suitable improvements are discussed
Multifunctional and compact 3D FMCW MIMO radar system with rectangular array for medium-range applications
No full textMiralles-Navarro, E.; Multerer, T.; Ganis, A.; Schoenlinner, B.; Prechtel, U.; Meusling, A.; Mietzner, J.... (2018). Multifunctional and compact 3D FMCW MIMO radar system with rectangular array for medium-range applications. IEEE Aerospace and Electronic Systems Magazine. 33(4):46-54. https://doi.org/10.1109/MAES.2018.160277S465433
A system concept for a 3D real-Time OFDM MIMO radar for flying platforms
No full textIn this paper a new system concept for a low cost, miniaturized and real-time imaging radar system for flying platforms is presented. The proposed solution is based on the MIMO radar architecture, orthogonal signals for simultaneous transmit capabilities and highly integrated SiGe chipsets. Using beamforming techniques at the receiver together with radar processing techniques, a 3D sensing of the range, azimuth, elevation and Doppler information for an arbitrary number of objects can be estimated through a simultaneous transmission and with real-time hardware implementable FFT processing techniques. A top-level system concept and a complete parametrization is proposed for a radar system which is intended for obstacle warning for helicopters and to enhance flight safety in approach, landing and take-off phases of flight even in degraded visual conditions. The full OFDM MIMO Radar system has been implemented and tested in a MATLAB environment and simulation results are here presented. This paper is the first step towards the implementation of a compact and real-time radar system demonstrator
A Portable 3-D Imaging FMCW MIMO Radar Demonstrator With a 24x24 Antenna Array for Medium-Range Applications
No full textMultiple-input multiple-output (MIMO) radars have been shown to improve target detection for surveillance applications thanks to their proven high-performance properties. In this paper, the design, implementation, and results of a complete 3-D imaging frequency-modulated continuous-wave MIMO radar demonstrator are presented. The radar sensor working frequency range spans between 16 and 17 GHz, and the proposed solution is based on a 24-transmitter and 24-receiver MIMO radar architecture, implemented by time-division multiplexing of the transmit signals. A modular approach based on conventional low-cost printed circuit boards is used for the transmit and receive systems. Using digital beamforming algorithms and radar processing techniques on the received signals, a high-resolution 3-D sensing of the range, azimuth, and elevation can be calculated. With the current antenna configuration, an angular resolution of 2.9° can be reached. Furthermore, by taking advantage of the 1-GHz bandwidth of the system, a range resolution of 0.5 m is achieved. The radio-frequency front-end, digital system and radar signal processing units are here presented. The medium-range surveillance potential and the high-resolution capabilities of the MIMO radar are proved with results in the form of radar images captured from the field measurements
An overview of atmospheric deposition chemistry over the Alps: present status and long-term trends
No full textSeveral research programs monitoring atmospheric deposition have been launched in the Alpine countries in the last few decades. This paper uses data from previous and ongoing projects to: (i) investigate geographical variability in wet deposition chemistry over the Alps; (ii) assess temporal trends of the major chemical variables in response to changes in the atmospheric emission of pollutants; (iii) discuss the potential relationship between the status of atmospheric deposition and its effects on forest ecosystems in the alpine and subalpine area, focusing particularly on nitrogen input. We also present results of studies performed at a local level on specific topics such as long-term changes in lead deposition and the role of occult deposition in total nitrogen input. The analysis performed here highlights the marked geographical variability of atmospheric deposition in the Alpine region. Apart from some evidence of geographically limited effects, due to local sources, no obvious gradients were identified in the major ion deposition. The highest ionic loads were recorded in areas in the foothills of the Alps, such as the pre-alpine area in North-Western Italy and the area of Canton Ticino, Switzerland. Trend analysis shows a widespread decrease in the acidity of precipitation in the last 15–20 years as a consequence of the reduced emission of S compounds. On the other hand, nitrate concentrations in rain have not changed so much, and ammonium has decreased significantly only at the Austrian sampling sites. The deposition of N is still well above the estimated critical loads of nutrient N at some forest sites in the alpine and subalpine areas, thus confirming the critical situation of both terrestrial and aquatic ecosystems regarding N inputs. Existing data highlights the importance of continuously monitoring atmospheric deposition chemistry in the Alpine area, taking account of acidifying elements, nutrients and other pollutants such as heavy metals and organic compounds. There is also a need for unifying sampling and analytical methods in order to obtain comparable data from the different regions of the Alps
An Automated Approach for Detection of Shallow Landslides from LiDAR Derived DEM Using Geomorphological Indicators in a Tropical Forest
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