Jens Klare

Fraunhofer Institute for High Frequency Physics and Radar Techniques FHR, Вахтберг, North Rhine-Westphalia, Germany

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Publications (44)30.56 Total impact

  • Vishal Riche · Jens Klare · D. Cerutti-Maori
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    ABSTRACT: One limitation of radar systems using multiple antennas is the waveform diversity available for the transmitters. Indeed, different properties for the transmitted signals, such as orthogonality, Doppler tolerance and low interference for imaging wide scenes are required in order to obtain good imaging quality with the radar system. This paper investigates the optimization of coded waveforms such as DFCW waveforms. First we describe DFCW signals and their properties, and then, an optimization procedure for the coding sequence is proposed and evaluated.
    No preview · Conference Paper · Sep 2014

  • No preview · Conference Paper · Aug 2014
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    ABSTRACT: This paper addresses signal reconstruction for future multiple-input multiple-output synthetic aperture radars (SARs) equipped with a multichannel antenna to enable wide-area high-resolution imaging. To image large swaths without range ambiguities, these high-resolution wide-swath (HRWS) SAR systems use a low pulse repetition frequency (PRF). Such a PRF, however, causes the radar echoes received by each channel to be strongly aliased. By introducing new techniques, this paper extends the theory of multichannel signal processing for reconstructing the SAR signal from the aliased signals. The reconstruction performances of the proposed processing methods in terms of signal-to-noise ratio, resolution, point target ambiguity ratio, peak-to-sidelobe ratio, and signal-to-ambiguity-plus-noise ratio are investigated according to the PRF and compared with each other for an exemplary HRWS SAR system.
    No preview · Article · Jul 2014 · IEEE Transactions on Geoscience and Remote Sensing
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    ABSTRACT: This paper compares the imaging quality of several multichannel processing methods that have been proposed for high-resolution wide-swath (HRWS) synthetic aperture radar (SAR) systems. A review of the different reconstruction methods is performed and their imaging performances are investigated for an exemplary multi-channel HRWS SAR.
    No preview · Conference Paper · Jul 2014
  • Oliver Biallawons · Jens Klare · Olaf Saalmann
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    ABSTRACT: This paper presents the technical realization of the multiple-input multiple-output (MIMO) radar MIRA-CLE Ka (MIMO radar-configurable in Ka-band). This system is a stationary imaging radar without any mechanical moving parts. It is highly portable, ready to use in only a couple of minutes, and it is able to process one radar image per second during continuous radar measurements in the current stage of development. In addition to the image processing, it is possible to detect changes in range of 0.1 mm in the illuminated scene. The MIMO system operates in Ka band and consists of 16 receive and 16 transmit elements, so that 256 virtual elements are generated during signal processing. The size of the antenna's frontend is about 80 cm in width. Owing to its compact size, flexibility, and realtime capability, the system offers a wide field of applications.
    No preview · Article · Jun 2014 · International Journal of Microwave and Wireless Technologies
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    ABSTRACT: The present paper gives an overview of recent developments in Active Electronically Scanned Arrays and advancement of radar processing techniques at the Fraunhofer-Institute for High Frequency Physics and Radar Techniques FHR. Among others, demonstrator systems currently developed in the fields of Space Situational Awareness, Airborne Surveillance, and Maritime Navigation Radar are described.
    No preview · Conference Paper · Apr 2014
  • V. Riche · J. Klare · D. Cerutti-Maori
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    ABSTRACT: One limitation of MIMO imaging radar systems is the waveform diversity available for the transmitters. Indeed, different properties for the transmitted signals, such as orthogonality and Doppler tolerance, are required in order to obtain good imaging quality with the radar system. This paper investigates the optimization of coded waveforms such as the OFDM and DFCW waveforms. First we demonstrate that DFCW is suitable to be used for radar imaging application, then an optimization procedure for the coding sequence is proposed for a MIMO imaging radar application.
    No preview · Article · Mar 2014
  • Jens Klare · Olaf Saalmann · Oliver Biallawons
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    ABSTRACT: MIRA-CLE Ka is a stationary imaging radar system without moving parts which uses 16 transmit and 16 receive antennas to form 256 virtual antenna elements during signal processing. The system is intended to be used as a mobile imaging, change detection and live sign detection radar for risk monitoring and disaster management. Particular the observation of instable hillsides nearby villages and infrastructures and also the work hillsides and boundary hillsides in daylight mining benefits from a 24/7 weather independent monitoring system. In cases of disasters and catastrophes, MIRA-CLE Ka can be used to secure search and rescue teams to warn for sliding debris and possible collapsing ruins. Also injured people can be detected and localized by the small motion of their chest due to breathing. The benefit of this system is to reduce the complexity, weight, and cost of a fully electronically multi mode radar system compared to common phased-array systems. In this paper we present first proof-of-concept imaging and change detection results obtained with MIRA-ClE Ka.
    No preview · Conference Paper · Nov 2013
  • G. El-Arnauti · O. Saalmann · J. Klare
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    ABSTRACT: MIRA-CLE Ka (MIMO radar-configurable in Ka-band) is a MIMO (Multiple Input Multiple Output) radar system in Ka-band for various applications like change detection with an accuracy of about 1 mm. The requirements for the signal generation, in terms of spurious suppression, amplitude ripple, and phase variation are very critical for this system. Designing appropriate filters is one of the major challenges for up-converting a signal to higher frequencies. The extraction of the phase information required for the system calibration is a critical part too, since a non-linear frequency translating system is used. This paper presents the design and construction of an up-converter, in addition to the characterization of the MIRA-CLE Ka transmit path.
    No preview · Conference Paper · Jan 2013
  • O. Biallawons · J. Klare · O. Saalmann
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    ABSTRACT: This paper presents the technical realization of the MIMO (Multiple Input Multiple Output) radar MIRA-CLE Ka (MIMO radar-configurable in Ka-band). This system is a stationary imaging radar without any mechanical moving parts. It is highly portable, ready to use in only a couple of minutes, and it is able to process one radar image per second in the current stage of development. The MIMO system operates in Ka band and consists of 16 receive and 16 transmit elements so that 256 virtual elements are generated. The size of the antenna frontend is about 80 centimeters in width and only a bit larger than the real array. Due to its compact size the system offers a wide field of applications.
    No preview · Conference Paper · Jan 2013
  • J. Klare · O. Saalmann · O. Biallawons
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    ABSTRACT: Stationary imaging radars can be used for a large range of applications like environmental monitoring, industrial inspection, and security monitoring. Radar systems using the Multiple Input Multiple Output (MIMO) principle benefit from a drastically reduced number of antenna elements compared to fully filled phased array systems. With a special arrangement of the transmit and receive antenna elements one can almost double the azimuth resolution with respect to phased array systems. This paper presents first imaging and change detection results of the stationary MIMO radar configurable in Ka band (MIRA-CLE Ka).
    No preview · Article · Jan 2013
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    ABSTRACT: The acquisition of Synthetic Aperture Radar (SAR) data in a bistatic forward-looking configuration offers many new capabilities for a broad spectrum of remote sensing applications. A radar system in an aircraft could image the runway during the landing approach to improve landing safety, particularly in poor visibility conditions. First experiments and imaging results demonstrate the feasibility of forward-looking bistatic radar imaging even with a very low elevation angle to the receiver, which is in the order of four degrees for a typical landing approach. The paper presents the challenges of imaging in forward direction and shows experimental results with a moving ground-based transmitter and an approaching aircraft. The experiments have been conducted to demonstrate the suitability of forward-looking SAR to improve the safety of aircrafts landing under low visibility conditions.
    No preview · Conference Paper · Jul 2012
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    ABSTRACT: This paper concentrates on the Doppler spectrum characteristics of hybrid bistatic SAR experiments, i.e., TerraSAR-X/PAMIR where TerraSAR-X was steered as the illuminator in the sliding spotlight mode, and PAMIR, mounted on a Transall C-160, operated in the inverse sliding spotlight mode. The bistatic Double Sliding Spotlight (DSS) experiment has been successfully performed in March 2009. For the DSS mode, the total azimuth signal bandwidth would cover several Pulse Repetition Frequency (PRF), which will result in the azimuth spectrum aliasing. In this paper, we will emphasize the signal, signal characteristics in double sliding spotlight mode, and use the azimuth chirp filtering method to address the spectrum aliasing.
    Full-text · Conference Paper · Jan 2012
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    ABSTRACT: This paper presents a new bistatic point target reference spectrum. It is derived by using the 2-D principle of stationary phase which is first applied in the synthetic aperture radar (SAR) community. The spectrum contains two hyperbolic range-azimuth coupling terms and thus is very similar to the monostatic spectrum. It shows the characteristic of the conventional monostatic SAR besides an additional azimuth scaling term. Therefore, it makes the common Doppler-based monostatic processing algorithms readily suitable to handle the Bistatic SAR (BiSAR) data in the moderate-squint azimuth-variant configurations with two moving platforms. Based on the spectrum, two Doppler-based monostatic imaging algorithms [i.e., range-Doppler algorithm (RDA) and chirp-scaling algorithm (CSA)] are readily implemented to deal with the moderate-squint azimuth-variant BiSAR data. Compared to the processing procedure for the monostatic SAR, the RDA and CSA for the BiSAR need only the adjustment of Doppler parameters. Finally, the potential and limitation of the spectrum are analyzed, and the real raw data in the spaceborne/airborne configurations are used to validate the proposed spectrum and processing methods.
    Full-text · Article · Nov 2011 · IEEE Transactions on Geoscience and Remote Sensing
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    ABSTRACT: This paper presents a new bistatic point target ref- erence spectrum. It is derived by using the 2-D principle of stationary phase which is first applied in the synthetic aperture radar (SAR) community. The spectrum contains two hyperbolic range-azimuth coupling terms and thus is very similar to the monostatic spectrum. It shows the characteristic of the conven- tional monostatic SAR besides an additional azimuth scaling term. Therefore, it makes the common Doppler-based monos- tatic processing algorithms readily suitable to handle the Bistatic SAR (BiSAR) data in the moderate-squint azimuth-variant con- figurations with two moving platforms. Based on the spec- trum, two Doppler-based monostatic imaging algorithms (i.e., range-Doppler algorithm (RDA) and chirp-scaling algorithm (CSA)) are readily implemented to deal with the moderate-squint azimuth-variant BiSAR data. Compared to the processing proce- dure for the monostatic SAR, the RDA and CSA for the BiSAR need only the adjustment of Doppler parameters. Finally, the potential and limitation of the spectrum are analyzed, and the real raw data in the spaceborne/airborne configurations are used to validate the proposed spectrum and processing methods. Index Terms—Bistatic point target reference spectrum (BPTRS), bistatic synthetic aperture radar (SAR) (BiSAR), chirp-scaling algorithm (CSA), 2-D principle of stationary phase (2DPSP).
    Full-text · Article · Oct 2011 · IEEE Transactions on Geoscience and Remote Sensing
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    ABSTRACT: Forward-looking radar imaging continues to gain in significance due to a variety of convenient applications, like landing assistance for aircraft in poor visibility conditions. Synthetic aperture radar (SAR) techniques are typically used to achieve a high azimuth resolution, but conventional monostatic SAR is not applicable in forward direction because of azimuth ambiguities and poor Doppler resolution. To improve the Doppler resolution and to avoid azimuth ambiguities, bistatic SAR configurations can be used to obtain high-resolution radar images. This is demonstrated for the first time in a spaceborne-airborne SAR experiment by using TerraSAR-X as the illuminator and the Phased Array Multifunctional Imaging Radar as the receiver. For convenience, the receiver's SAR antenna was mounted on the aircraft's loading ramp and looked backward. Due to identical image properties and the same challenges for forward- and backward-looking sensors, this configuration also demonstrates the feasibility of forward-looking bistatic SAR. This letter describes the experimental setup, analyzes the performance, and presents the imaging results.
    No preview · Article · Aug 2011 · IEEE Geoscience and Remote Sensing Letters

  • No preview · Article · Jan 2011
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    ABSTRACT: Bistatic SAR experiments using a ground-based transmitter and a forward- looking airborne receiver have been conducted in June 2011. These experiments are supposed to demonstrate the suitability of forward-looking SAR for an improvement of aircrafts' landing safety in conditions of low visibility. The feasibility of airborne bistatic forward-looking SAR was already demonstrated experimentally by the authors in 2009. This paper gives a short introduction to forward-looking radar imaging, explains the problems of monostatic SAR to image in forward direction and presents and analyzes bistatic sensor configurations as a suitable solution for high resolution imaging in for- ward direction.
    No preview · Article · Jan 2011
  • J. Klare · O. Saalmann
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    ABSTRACT: The research field of MIMO radar offers a bunch of new opportunities for various applications. Imaging MIMO radars can be used as a significant supplement to usual SAR and phased array radars and can extend the common applications for radar. MIRA-CLE X is an X-band MIMO radar consisting of 16 transmit and 14 receive antennas. During signal processing, 224 virtual antenna elements are generated to enable 2D radar imaging. This paper presents the radar system, the signal processing approach as well as a detailed analysis of first imaging results.
    No preview · Conference Paper · Nov 2010
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    ABSTRACT: The spatial separation of the transmitter and the receiver in bistatic synthetic aperture radar (SAR) enables a variety of data acquisition geometries to achieve benefits like the increased information content of bistatic SAR data. In the case of hybrid bistatic SAR constellations where the transmitter is spaceborne and the receiver is onboard an aircraft, one has to deal with a huge discrepancy between platform velocities. This paper presents bistatic spaceborne/airborne SAR experiments, where the radar satellite TerraSAR-X is used as a transmitter and the airborne SAR sensor Phased Array Multifunctional Imaging Radar (PAMIR) of the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR) is used as a receiver. Both sensors are equipped with phased-array antennas, which offer the possibility of beam steering and could be used for the first time for the “double sliding spotlight mode.” In this mode, the space- and airborne sensors operate with different sliding factors (ratio between footprint and platform velocity). The performance of two different experiments is analyzed, and the novel double sliding spotlight mode is presented. This paper describes the experimental setups, the synchronization system, and the data acquisition. The image results were processed by a modified backprojection algorithm and a frequency-domain algorithm. The analysis of the final bistatic images comprises the spatial resolution and the scattering behavior of selected objects. Parts of the bistatic SAR images are compared with the corresponding monostatic images of PAMIR and TerraSAR-X. It will be shown that hybrid bistatic SAR is a worthwhile and helpful addition to current monostatic SAR.
    Full-text · Article · Sep 2010 · IEEE Transactions on Geoscience and Remote Sensing