A Short Range Synthetic Aperture Imaging Radar with Rotating Antenna (original) (raw)
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A Rotating Synthetic Aperture Radar Imaging Concept for Robot Navigation
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Synthetic aperture radar (SAR) is a powerful remote-sensing tool that can operate independent of solar illumination to produce radar images at night and under cloudy conditions. Using signal-processing techniques to generate high-resolution radar images, SAR systems operate from airborne platforms and spacecraft. Their operating frequency can be customized to enhance target characteristics. For example, low-frequency SAR can penetrate vegetation and dry soils, while high-frequency SAR emphasizes vegetation. Unfortunately, the complexity and high costs of SAR systems often preclude them from applications requiring long-term monitoring or frequent revisiting. Moreover, large size and power requirements have limited SAR to large and expensive platforms. There is a need for small, lowcost, high-resolution SAR systems designed for operation on small unmanned aerial vehicles (UAVs).
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2013 IEEE International Geoscience and Remote Sensing Symposium - IGARSS, 2013
Synthetic Aperture Radar (SAR) is a multipurpose sensor that can be operated in all-weather and day-night time. Recently, the SAR sensor is operated in linear polarization (HH, V V and its combination) with limited retrieved information. The characteristic of the conventional SAR sensor is bulky, high power, sensitive to Faraday rotation effect etc. Recently, we are developing the Circularly Polarized Synthetic Aperture Radar (CP-SAR) onboard Microsatellite (µSAT CP-SAR) to retrieve the physical information of Earth surface, especially to monitor the cryosphere, global vegetation and disaster area in the future. In this research, the CP-SAR sensor is developed to radiate and receive circularly polarized wave. The sensor is designed as a low cost, simple, light, strong, low power, low profile configuration to transmit and receive left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP), where the transmission (Tx) and reception (Rx) are working in RHCP and RCHP+LCHP, respectively. Then these circularly polarized waves are employed to generate the axial ratio image (ARI). This sensor is not depending to the platform posture, and it is available to avoid the effect of Faraday rotation during the propagation in ionosphere. Therefore, the high precision and low noise image is expected to be obtained by the CP-SAR. This satellite platform is composed by RCHP and LHCP antennas for CP-SAR sensor subsystem, telemetry subsystem that constructed by S band telemetry and X band transponder to transmit CP-SAR signal to ground station, and some altitude controller subsystem. This satellite planned to be launched in 2014 with altitude between 500 km and 700 km. This sensor is operated with center frequency on L band (1.27 GHz) and 10 MHz of chirp pulse bandwidth. The gain in main beam is set higher than 30 dBic to obtain received signal higher than −20 dB (equivalent backscattered noise level). The axial ratio is set lower than 3 dB to obtained ideal circular polarization. The antenna size (inflatable antenna) is 4 m and 8 m for range and azimuth directions, respectively. The center of off-nadir angle and swap width are set 29 • and 50 km, respectively. The ARI is expected to retrieve various physical information of Earth surface accurately and high precision. i.e., up-lift and subsidence, biomass, vegetation height and age, soil and snow physical characteristics based on the relationship between axial ratio and each characteristic. In the near future, CP-SAR is expected to improve the characteristics of conventional SAR system, especially to extract some new physical information on the Earth surface.
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A Review Paper on Synthetic Aperture Radar Engineering
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Comparison of 10–18 GHz SAR and MIMO-based short-range imaging radars
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A Tutorial on Synthetic Aperture Radar
IEEE Geoscience and Remote Sensing Magazine, 2013
Synthetic Aperture Radar (SAR) has been widely used for Earth remote sensing for more than 30 years. It provides high-resolution, day-and-night and weather-independent images for a multitude of applications ranging from geoscience and climate change research, environmental and Earth system monitoring, 2-D and 3-D mapping, change detection, 4-D mapping (space and time), security-related applications up to planetary exploration. With the advances in radar technology and geo/bio-physical parameter inversion modeling in the 90s, using data from several airborne and spaceborne systems, a paradigm shift occurred from the development driven by the technology push to the user demand pull. Today, more than 15 spaceborne SAR systems are being operated for innumerous applications. This paper provides first a tutorial about the SAR principles and theory, followed by an overview of established techniques like polarimetry, interferometry and differential interferometry as well as of emerging techniques (e.g., polarimetric SAR interferometry, tomography and holographic tomography). Several application examples including the associated parameter inversion modeling are provided for each case. The paper also describes innovative technologies and concepts like digital beamforming, Multiple-Input Multiple-Output (MIMO) and bi-and multi-static configurations which are suitable means to fulfill the increasing user requirements. The paper concludes with a vision for SAR remote sensing.