A Review Paper on Synthetic Aperture Radar Engineering (original) (raw)

Special Issue “Synthetic Aperture Radar (SAR) Techniques and Applications”

Sensors

This editorial of the special issue titled “Synthetic Aperture Radar (SAR) Techniques and Applications”, reviews the nineteen papers selected for publication. The proposed studies investigate different aspects of SAR processing including signal modelling, simulation, image analysis, as well as some examples of applications. The papers are grouped according to homogeneous subjects, then objectives and methods are summarised, and the more relevant results are commented.

Introduction to Synthetic Aperture Radar (SAR

The synthetic aperture radar principle has been discovered in the early 50 th. Since then, a rapid development took place all over the world and a couple of air-and space-borne systems are operational today. Progress made in technology and digital signal processing lead to very flexible systems useful for military and civilian applications. Radar has proved to be valuable before, because of its day-and-night capability and the possibility to penetrate clouds and rain. Optical instruments however had great advantages in the interpretation of depicted objects. The great wavelength of radar signals limits the achievable resolution in cross range direction of real aperture radar systems. Thus, imaging cannot be realized using static radar systems 1. The idea of SAR was to transmit pulses and store the scene echoes along a synthetic aperture (i.e. the path of the SAR sensor) and to combine the echoes afterwards by the application of an appropriate focussing algorithm. The combination is carried out coherently. As we will see, it is quit easy to understand the basic idea of SAR. We will show also the hardware concept or a SAR system and give an idea for a processing algorithm. 1.0 GENERAL FACTS ABOUT SAR Today, synthetic aperture radar (SAR) plays an important role in military ground surveillance and earth observation. Since the late eighties a couple of SAR-systems have been developed for both space and airborne operation. The underlying radar principle offers advantages compared to competing sensors in infrared or visible spectral area. This chapter describes the field of applications where SAR can be used to gain valuable information. Physical conditions like propagation of electromagnetic waves and scene reflectivity affect the choice of several radar design parameters.

The Principles of Synthetic Aperture Radar

Processing of Synthetic Aperture Radar Images, 2008

Synthetic Aperture Radar (SAR) is an active microwave imaging method. It operates independently of Sun illumination and cloud coverage. Current spaceborne systems use wavelengths of 3 to 25 cm and achieve resolutions of 10 to 50 m. The paper attempts to explain the basic SAR imaging principles using a minimum of mathematics. Emphasis is put on the particular properties of SAR images that should be understood before interpreting these data.

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.

High Resolution Synthetic Aperture Radar

This manuscript first introduces the fundamentals of Synthetic Aperture radar (SAR), there including the principle of the high resolution imaging capability, the processing required to focus the images, with its constraints and the different acquisition modes. Thereafter, it shows the potential ways to increase the imaging capabilities based on the concept of distributed SAR. Specifically both multistatic and MIMO SAR are considered with both aims of increasing azimuth resolution and increasing the ground range swath. The formation of increased high resolution images by exploiting the distributed SAR concept is then described in details for a specific application: to increase the cross range resolution of ISAR images of rotating targets. This distributed ISAR technique is devised for two different cases: (i) MIMO case with each platform carrying an active radar, that transmits and receives RF waveforms, (ii) multistatic case with a single platform carrying an active radar (i.e. transmitting and receiving) and the remaining platforms equipped with passive sensors (i.e. receiving only). The processing chain required to focus the High Resolution distributed ISAR is shown, together with the results obtained against simulated ISAR data for both the MIMO and the multistatic cases. The performance analysis shows that the distributed approach is able to provide an increase of the cross range resolution up to the number of platforms in the multistatic case and even higher in the MIMO case, if the platforms are properly located. This is of great benefit in applications where the target rotation angle is insufficient to guarantee the desired resolution. A typical case is the imaging of ship targets with rotation induced by the sea swell structure under low sea state conditions.

Synthetic aperture radar imaging systems

IEEE Aerospace and Electronic Systems Magazine, 1995

This paper presents profiles of 12 airborne and spaceborne Synthetic Aperture Radar (SAR) imaging systems. This information is intended to help potential users evaluate the systems for specific applications. The systems profiled in this article can be used for commercial purposes; some have been built specifically for commercial use while others also serve as science and research tools. Both domestic and foreign systems designed for government agencies and private industry are profiled. Nine of these systems are currently operational; two systems are scheduled to begin service in the near future. A third system is no longer active, but archive data are commercially available.