POLARIS: ESA's airborne ice sounding radar front-end design, performance assessment and first results
Tech. Univ. of Denmark, Lyngby, DenmarkDOI: 10.1109/MWSYM.2009.5165716 Conference: Microwave Symposium Digest, 2009. MTT '09. IEEE MTT-S International
Source: IEEE Xplore
This paper addresses the design, implementation and experimental performance assessment of the RF front-end of an airborne P-band ice sounding radar. The ice sounder design comprises commercial-of-the-shelf modules and newly purpose-built components at a centre frequency of 435 MHz with 20% relative bandwidth. The transmitter uses two amplifiers combined in parallel to generate more than >128 W peak power, with system >60% PAE and 47 dB in-band to out-of-band signal ratio. The four channel receiver features digitally controlled variable gain to achieve more than 100 dB dynamic range, 2.4 dB noise figure, 160 ns receiver recovery time and -46 dBc 3rd order IMD products. The system comprises also, a digital front-end, a digital signal generator, a microstrip antenna array and a control unit. All the subsystems were integrated, certified and functionally tested, and in May 2008 a successful proof-of-concept campaign was organized in Greenland. The system detected the bedrock under 3 km of ice, and internal layers were mapped up to 1.3 km.
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ABSTRACT: In this paper, the design of a single-chip RF Pulse-Width Modulator and Driver (PWMD) aimed at exciting a 80 W class-E GaN high-power stage at 435 MHz is described. For the required buffer size, avoiding potential ringing of the pulses within the buffer structure presents a major challenge in the design process. Therefore, a smaller chip capable of driving capacitive loads of up to 5 pF was initially designed, fabricated and tested. An approach based on 3D EM simulations was used to validate the test results. Based on the presented results, an enlarged chip able to drive a 80 W GaN high-power stage is currently being designed.
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ABSTRACT: Exhaustive investigations of the ice sheet subsurface can be carried out by analyzing the information contained in the huge archives of radargrams acquired by dedicated radar sounder (RS) instruments. The analysis can be done by using properly designed automatic techniques for a quantitative, objective, and reliable extraction of information from radargrams. Unfortunately, the definition and development of such automatic techniques have only been marginally addressed in the literature. In this paper, we propose a novel and efficient system for the automatic classification of ice subsurface targets present in radargrams. The core of the system is represented by the extraction of a set of features for target discrimination. The features are based on both the specific statistical properties of the RS signal and the spatial distribution of the ice subsurface targets. Such features are then provided as input to an automatic classifier based on support vector machine. Experimental results obtained on two real-world data sets acquired by airborne-mounted RSs in large regions of Antarctica confirm the robustness and effectiveness of the proposed classification system.
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